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  • C Programming - My program is good enough for my assignment but I know its not good

    - by Joe
    Hi there I'm just starting an assignment for uni and it's raised a question for me. I don't understand how to return a string from a function without having a memory leak. char* trim(char* line) { int start = 0; int end = strlen(line) - 1; /* find the start position of the string */ while(isspace(line[start]) != 0) { start++; } //printf("start is %d\n", start); /* find the position end of the string */ while(isspace(line[end]) != 0) { end--; } //printf("end is %d\n", end); /* calculate string length and add 1 for the sentinel */ int len = end - start + 2; /* initialise char array to len and read in characters */ int i; char* trimmed = calloc(sizeof(char), len); for(i = 0; i < (len - 1); i++) { trimmed[i] = line[start + i]; } trimmed[len - 1] = '\0'; return trimmed; } as you can see I am returning a pointer to char which is an array. I found that if I tried to make the 'trimmed' array by something like: char trimmed[len]; then the compiler would throw up a message saying that a constant was expected on this line. I assume this meant that for some reason you can't use variables as the array length when initialising an array, although something tells me that can't be right. So instead I made my array by allocating some memory to a char pointer. I understand that this function is probably waaaaay sub-optimal for what it is trying to do, but what I really want to know is: 1. Can you normally initialise an array using a variable to declare the length like: char trimmed[len]; ? 2. If I had an array that was of that type (char trimmed[]) would it have the same return type as a pointer to char (ie char*). 3. If I make my array by callocing some memory and allocating it to a char pointer, how do I free this memory. It seems to me that once I have returned this array, I can't access it to free it as it is a local variable. Many thanks in advance Joe

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  • Run Linux command as predefined user

    - by vijay.shad
    Hi all, I have created a shell script to start a server program. startup.sh start When above command will executes, it will try starts the server as adminuser. To achieve this my script has written like this. SUBIT="su - adminuser -c " SERVER_BOX_COMMAND_A="Server" ############## # Function to start cluster function start(){ $SUBIT "$SERVER_BOX_COMMAND_A" } When i execute the command it asks for password. Is there any other way to do this so, it will not ask for password.

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  • No bean named 'springSecurityFilterChain' is defined

    - by michaeljackson4ever
    When configs are loaded, I get the error SEVERE: Exception starting filter springSecurityFilterChain org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'springSecurityFilterChain' is defined My sec-config: <http use-expressions="true" access-denied-page="/error/casfailed.html" entry-point-ref="headerAuthenticationEntryPoint"> <intercept-url pattern="/" access="permitAll"/> <!-- <intercept-url pattern="/index.html" access="permitAll"/> --> <intercept-url pattern="/index.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/history.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/absence.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/search.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/employees.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/employee.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/contract.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/myforms.html" access="hasAnyRole('HLO','OPISK')"/> <intercept-url pattern="/vacationmsg.html" access="hasAnyRole('ROLE_USER')"/> <intercept-url pattern="/redirect.jsp" filters="none" /> <intercept-url pattern="/error/**" filters="none" /> <intercept-url pattern="/layout/**" filters="none" /> <intercept-url pattern="/js/**" filters="none" /> <intercept-url pattern="/**" access="isAuthenticated()" /> <!-- session-management invalid-session-url="/absence.html"/ --> <!-- logout logout-success-url="/logout.html"/ --> <custom-filter ref="ssoHeaderAuthenticationFilter" before="CAS_FILTER"/> <!-- CAS_FILTER ??? --> </http> <authentication-manager alias="authenticationManager"> <authentication-provider ref="doNothingAuthenticationProvider"/> </authentication-manager> <beans:bean id="doNothingAuthenticationProvider" class="com.nixu.security.sso.web.DoNothingAuthenticationProvider"/> <beans:bean id="ssoHeaderAuthenticationFilter" class="com.nixu.security.sso.web.HeaderAuthenticationFilter"> <beans:property name="groups"> <beans:map> <beans:entry key="cn=lake,ou=confluence,dc=utu,dc=fi" value="ROLE_ADMIN"/> </beans:map> </beans:property> </beans:bean> <beans:bean id="headerAuthenticationEntryPoint" class="com.nixu.security.sso.web.HeaderAuthenticationEntryPoint"/> And web.xml <context-param> <param-name>contextConfigLocation</param-name> <param-value> /WEB-INF/applicationContext.xml /WEB-INF/sec-config.xml /WEB-INF/idm-config.xml /WEB-INF/ldap-config.xml </param-value> </context-param> <display-name>KeyCard</display-name> <context-param> <param-name>webAppRootKey</param-name> <param-value>KeyCardAppRoot</param-value> </context-param> <context-param> <param-name>log4jConfigLocation</param-name> <param-value>/WEB-INF/log4j.properties</param-value> </context-param> <!-- Reads request input using UTF-8 encoding --> <filter> <filter-name>characterEncodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> <init-param> <param-name>forceEncoding</param-name> <param-value>true</param-value> </init-param> </filter> <filter> <filter-name>springSecurityFilterChain</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> </filter> <filter-mapping> <filter-name>characterEncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <filter-mapping> <filter-name>springSecurityFilterChain</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener> <listener> <!-- this is for session scoped objects --> <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class> </listener> <listener> <listener-class>org.springframework.security.web.session.HttpSessionEventPublisher</listener-class> </listener> <!-- Handles all requests into the application --> <servlet> <servlet-name>KeyCard</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet> <servlet-name>tiles</servlet-name> <servlet-class>org.apache.tiles.web.startup.TilesServlet</servlet-class> <init-param> <param-name> org.apache.tiles.impl.BasicTilesContainer.DEFINITIONS_CONFIG </param-name> <param-value> /WEB-INF/tilesViewContext.xml </param-value> </init-param> <load-on-startup>2</load-on-startup> </servlet> <servlet-mapping> <servlet-name>KeyCard</servlet-name> <url-pattern>*.html</url-pattern> </servlet-mapping> <session-config> <session-timeout> 120 </session-timeout> </session-config> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <!-- error-page> <exception-type>java.lang.Exception</exception-type> <location>/WEB-INF/error/error.jsp</location> </error-page --> </web-app> What's wrong?

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  • Using the erlang mysql module, how is a database connection closed?

    - by Dan
    In using the erlang mysql module the exposed external functions are: %% External exports -export([start_link/5, start_link/6, start_link/7, start_link/8, start/5, start/6, start/7, start/8, connect/7, connect/8, connect/9, fetch/1, fetch/2, fetch/3, prepare/2, execute/1, execute/2, execute/3, execute/4, unprepare/1, get_prepared/1, get_prepared/2, transaction/2, transaction/3, get_result_field_info/1, get_result_rows/1, get_result_affected_rows/1, get_result_reason/1, encode/1, encode/2, asciz_binary/2 ]). From the this this, it is not apparent how to close a connection. How a connection closed?

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  • How can we stop a running java process through windows cmd?

    - by Wing C. Chen
    I am a newbie in cmd, so please allow me to ask a stupid question: How can we stop a running java process through windows cmd? For example, if we start jetty(a mini web server) with the following cmd: start javaw -jar start.jar How do we find the process and stop it later? Obviously the following cmd does not work: stop javaw -jar start.jar

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  • How to define a predicate as a function argument

    - by devoured elysium
    I want to be able to write something as void Start(some condition that might evaluate to either true or false) { //function will only really start if the predicate evaluates to true } I'd guess it must be something of the form: void Start(Predicate predicate) { } How can I check inside my Start function whenever the predicate evaluated to true or false? Is my use of a predicate correct? Thanks

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  • How do i convert a string to a JSON object in JQuery?

    - by Rob
    I have a string in my db I want to pull into my page and convert to a json object. [ {id: 1,title: "Long Event", start: new Date(2009, 5, 6, 14, 0),end: new Date(2009, 5, 11)}, {id: 2,title: "Repeating Event", start: new Date(2009, 5, 2)}, {id: 3,title: "Meeting", start: new Date(2009, 5, 20, 9, 0)}, {id: 4,title: "Click for Facebook", start: new Date(2009, 5, 27, 16),end: new Date(2009, 5, 29), url: "http://facebook.com/"} ] How can I do this using JQuery?

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  • Unit Testing - not testable code converted to testable code

    - by imak
    I have read so many places is that if your code is not test-able that mean code is not well written. So that makes me start writing a code that is test-able and to start using some unit testing framework. With this though I start looking for some example with piece of code that is not testable and gradually converted to a testable code. I find tons of examples on unit testing but if someone can provide an example like above it probably can jump start things for me. TIA

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  • HttpsCookieFilter - IllegalStateException: getOutputStream() has already been called for this response

    - by Mat Banik
    Following exception is thrown every once in a while and it shows up in localhost log file in tomcat log directory. If anyone know how to get rid of it, all help would be appreciated. BTW the filter is working fine I just don't know why this exception is happening. Stack trace: java.lang.IllegalStateException: getOutputStream() has already been called for this response at org.apache.catalina.connector.Response.getWriter(Response.java:611) at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198) at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112) at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:366) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:283) at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:233) at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:167) at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250) at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:65) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:176) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:145) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:92) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:381) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:368) at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109) at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:119) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:57) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.access.channel.ChannelProcessingFilter.doFilter(ChannelProcessingFilter.java:109) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:109) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380) at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:169) at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237) at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) //Here is the servlet I suspect is trowing the exception. at package.HttpsCookieFilter.doFilter(HttpsCookieFilter.java:38) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11NioProcessor.process(Http11NioProcessor.java:886) at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:721) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:2256) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:717) The HttpsCookieFilter class: public class HttpsCookieFilter implements Filter { private static Logger log = Logger.getLogger(HttpsCookieFilter.class); @Override public void destroy() { } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { final HttpServletRequest req = (HttpServletRequest) request; final HttpServletResponse res = (HttpServletResponse) response; final HttpSession session = req.getSession(false); if (session != null) { setCookie(req, res); } try{ chain.doFilter(request, response); // <- Exception thrown from here }catch (IllegalStateException e){ log.warn("HttpsCookieFilter redirect problem! ", e); } } @Override public void init(FilterConfig arg0) throws ServletException { } private void setCookie( HttpServletRequest request, HttpServletResponse response) { Cookie cookie = new Cookie("JSESSIONID", request.getSession(false).getId()); cookie.setMaxAge(-1); cookie.setPath(getCookiePath(request)); cookie.setSecure(false); response.addCookie(cookie); } private String getCookiePath(HttpServletRequest request) { String contextPath = request.getContextPath(); return contextPath.length() > 0 ? contextPath : "/"; } } web.xml <?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd"> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <listener> <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class> </listener> <listener> <listener-class>org.springframework.security.web.session.HttpSessionEventPublisher</listener-class> </listener> <filter> <filter-name>httpsCookieFilter</filter-name> <filter-class>com.iteezy.server.web.servlet.HttpsCookieFilter</filter-class> </filter> <filter-mapping> <filter-name>httpsCookieFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <filter> <filter-name>filterChainProxy</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> </filter> <filter-mapping> <filter-name>filterChainProxy</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> ... The reason for integrating this filter comes from Spring security FAQs: I'm using Tomcat (or some other servlet container) and have enabled HTTPS for my login page, switching back to HTTP afterwards. It doesn't work - I just end up back at the login page after authenticating. This happens because sessions created under HTTPS, for which the session cookie is marked as “secure”, cannot subsequently be used under HTTP. The browser will not send the cookie back to the server and any session state will be lost (including the security context information). Starting a session in HTTP first should work as the session cookie won't be marked as secure.

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  • Why do sockets not die when server dies? Why does a socket die when server is alive?

    - by Roman
    I try to play with sockets a bit. For that I wrote very simple "client" and "server" applications. Client: import java.net.*; public class client { public static void main(String[] args) throws Exception { InetAddress localhost = InetAddress.getLocalHost(); System.out.println("before"); Socket clientSideSocket = null; try { clientSideSocket = new Socket(localhost,12345,localhost,54321); } catch (ConnectException e) { System.out.println("Connection Refused"); } System.out.println("after"); if (clientSideSocket != null) { clientSideSocket.close(); } } } Server: import java.net.*; public class server { public static void main(String[] args) throws Exception { ServerSocket listener = new ServerSocket(12345); while (true) { Socket serverSideSocket = listener.accept(); System.out.println("A client-request is accepted."); } } } And I found a behavior that I cannot explain: I start a server, than I start a client. Connection is successfully established (client stops running and server is running). Then I close the server and start it again in a second. After that I start a client and it writes "Connection Refused". It seems to me that the server "remember" the old connection and does not want to open the second connection twice. But I do not understand how it is possible. Because I killed the previous server and started a new one! I do not start the server immediately after the previous one was killed (I wait like 20 seconds). In this case the server "forget" the socket from the previous server and accepts the request from the client. I start the server and then I start the client. Connection is established (server writes: "A client-request is accepted"). Then I wait a minute and start the client again. And server (which was running the whole time) accept the request again! Why? The server should not accept the request from the same client-IP and client-port but it does!

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  • Problem with list slice syntax in python

    - by Dingle
    The extended indexing syntax is mentioned in python's doc. slice([start], stop[, step]) Slice objects are also generated when extended indexing syntax is used. For example: a[start:stop:step] or a[start:stop, i]. See itertools.islice() for an alternate version that returns an iterator. a[start:stop:step] works as described. But what about the second one? How is it used?

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  • Why sockets does not die when server dies? Why socket dies when server is alive?

    - by Roman
    I try to play with sockets a bit. For that I wrote very simple "client" and "server" applications. Client: import java.net.*; public class client { public static void main(String[] args) throws Exception { InetAddress localhost = InetAddress.getLocalHost(); System.out.println("before"); Socket clientSideSocket = null; try { clientSideSocket = new Socket(localhost,12345,localhost,54321); } catch (ConnectException e) { System.out.println("Connection Refused"); } System.out.println("after"); if (clientSideSocket != null) { clientSideSocket.close(); } } } Server: import java.net.*; public class server { public static void main(String[] args) throws Exception { ServerSocket listener = new ServerSocket(12345); while (true) { Socket serverSideSocket = listener.accept(); System.out.println("A client-request is accepted."); } } } And I found a behavior that I cannot explain: I start a server, than I start a client. Connection is successfully established (client stops running and server is running). Then I close the server and start it again in a second. After that I start a client and it writes "Connection Refused". It seems to me that the server "remember" the old connection and does not want to open the second connection twice. But I do not understand how it is possible. Because I killed the previous server and started a new one! I do not start the server immediately after the previous one was killed (I wait like 20 seconds). In this case the server "forget" the socket from the previous server and accepts the request from the client. I start the server and then I start the client. Connection is established (server writes: "A client-request is accepted"). Then I wait a minute and start the client again. And server (which was running the whole time) accept the request again! Why? The server should not accept the request from the same client-IP and client-port but it does!

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  • problem with presentModalViewController

    - by pbcoder
    If my iPad is in Landscape mode and presentModalViewController is called the view automatically turns into portrait mode. Any solutions? UIViewController * start = [[UIViewController alloc]initWithNibName:@"SecondView" bundle:nil]; start.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; start.modalPresentationStyle = UIModalPresentationFormSheet; [self presentModalViewController:start animated:YES]; In SecondView I've already added: - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; }

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  • How do I change the color of a Cocos2d MenuItem?

    - by Rob Sawyer
    [MenuItemFont setFontSize:20]; [MenuItemFont setFontName:@"Helvetica"]; //I'm trying to change the color of start (below item) MenuItem *start = [MenuItemFont itemFromString:@"Start Game" target:self selector:@selector(startGame:)]; MenuItem *help = [MenuItemFont itemFromString:@"Help" target:self selector:@selector(help:)]; Menu *startMenu = [Menu menuWithItems:start, help, nil]; [startMenu alignItemsVertically]; [self add:startMenu];

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  • C - What is the proper format to allow a function to show an error was encountered?

    - by BrainSteel
    I have a question about what a function should do if the arguments to said function don't line up quite right, through no fault of the function call. Since that sentence doesn't make much sense, I'll offer my current issue. To keep it simple, here is the most relevant and basic function I have. float getYValueAt(float x, PHYS_Line line, unsigned short* error) *error = 0; if(x < line.start.x || x > line.end.x){ *error = 1; return -1; } if(line.slope.value != 0){ //line's equation: y - line.start.y = line.slope.value(x - line.start.x) return line.slope.value * (x - line.start.x) + line.start.y; } else if(line.slope.denom == 0){ if(line.start.x == x) return line.start.y; else{ *error = 1; return -1; } } else if(line.slope.num == 0){ return line.start.y; } } The function attempts to find the point on a line, given a certain x value. However, under some circumstances, this may not be possible. For example, on the line x = 3, if 5 is passed as a value, we would have a problem. Another problem arises if the chosen x value is not within the interval the line is on. For this, I included the error pointer. Given this format, a function call could work as follows: void foo(PHYS_Line some_line){ unsigned short error = 0; float y = getYValueAt(5, some_line, &error); if(error) fooey(); else do_something_with_y(y); } My question pertains to the error. Note that the value returned is allowed to be negative. Returning -1 does not ensure that an error has occurred. I know that it is sometimes preferred to use the following method to track an error: float* getYValueAt(float x, PHYS_Line line); and then return NULL if an error occurs, but I believe this requires dynamic memory allocation, which seems even less sightly than the solution I was using. So, what is standard practice for an error occurring?

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  • access Elf section header table

    - by idealistikz
    Assume I have the following: Elf_FIle_Header *fileHeader //struct pointer, points to start of the Elf file header fileHeader->offset //byte offset from start of file to section headers Elf_Section_Header *sectionHeader = (Elf_Section_Header *)(char *)fileHeader + fileHeader->offset Why doesn't the above line point me to the start of the section header table? How do I point to the start of the section header table?

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  • SQL: Is there a more efficient way to calculate elapsed hours, minutes, seconds?

    - by hamlin11
    I'm using Computed Columns to provide me with the following information: Hours, Minutes, and Seconds between a Start DateTime and Finish DateTime (Where Minutes and Seconds are between 0 and 59 and Hours can be any value 0 or greater) Computed Column for Seconds: datediff(second,[Start],[Finish]) % 60 Computed Column for Minutes: floor(datediff(second,[Start],[Finish]) / 60.0) % 60 Computed Column for Hours: floor(datediff(second,[Start],[Finish]) / 3600.0) Here's the table for reference Note: I'm also calculating TotalElapsedSeconds, TotalElapsedMinutes, and TotalElapsedHours in other computed columns, but those are easy. I just feel like I might be missing out on a nice built in function in SQL.

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  • finding a solution to a giving maze txt.file

    - by alberto
    how can i fix this program, the problem is when it print out the coordinate it give me a 7 for the start and finish, i would appreciated you help, thanks start = (len(data)) finish = (len(data)) pos= [] for i in range(len(pos)): for j in range(len(pos[i])): if pos[i][j] == "S": start=(i,j) elif pos[i][j] == "F": finish=(i,j) print "S found in",start, print "\nF found in",finish,"\n"

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  • compacting line of code

    - by dlee313
    Assume I have the following: unsigned int *start; unsigned int total; #define OFF_MASK (1 << 31) #define ON_MASK (~(1 << 31)) if (!(*start & OFF_MASK) && ((*start & ON_MASK) >= total))) How do I change the above if statement so that it makes just one comparison like this: if (*start >= total)

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  • How to handle error on other thread?

    - by markattwood
    Hi, I'm trying to handle errors that have occurred on other threads the .NET CF program is like below: static void Main() { Thread t = new Thread(Start); t.Start(); ... } void Start() { ... Exception here } In my situation, putting try catch in the Start method is impossible. How can I handle it in the global code?

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  • --log-slave-updates is OFF but some updates are still logged to the slave binary log?

    - by quanta
    MySQL version 5.5.14 According to the document, by the default, slave does not log to its binary log any updates that are received from a master server. Here are my config. on the slave: # egrep 'bin|slave' /etc/my.cnf relay-log=mysqld-relay-bin log-bin = /var/log/mysql/mysql-bin binlog-format=MIXED sync_binlog = 1 log-bin-trust-function-creators = 1 mysql> show global variables like 'log_slave%'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | log_slave_updates | OFF | +-------------------+-------+ 1 row in set (0.01 sec) mysql> select @@log_slave_updates; +---------------------+ | @@log_slave_updates | +---------------------+ | 0 | +---------------------+ 1 row in set (0.00 sec) but slave still logs the some changes to its binary logs, let's see the file size: -rw-rw---- 1 mysql mysql 37M Apr 1 01:00 /var/log/mysql/mysql-bin.001256 -rw-rw---- 1 mysql mysql 25M Apr 2 01:00 /var/log/mysql/mysql-bin.001257 -rw-rw---- 1 mysql mysql 46M Apr 3 01:00 /var/log/mysql/mysql-bin.001258 -rw-rw---- 1 mysql mysql 115M Apr 4 01:00 /var/log/mysql/mysql-bin.001259 -rw-rw---- 1 mysql mysql 105M Apr 4 18:54 /var/log/mysql/mysql-bin.001260 and the sample query when reading these binary files with mysqlbinlog utility: #120404 19:08:57 server id 3 end_log_pos 110324763 Query thread_id=382435 exec_time=0 error_code=0 SET TIMESTAMP=1333541337/*!*/; INSERT INTO norep_SplitValues VALUES ( NAME_CONST('cur_string',_utf8'118212' COLLATE 'utf8_general_ci')) /*!*/; # at 110324763 Did I miss something? Reply to @RolandoMySQLDBA: If replication brought this over, then the same query has to be in the relay logs. Please go find the relay log that has the INSERT query with the same TIMESTAMP (1333541337). There is no such query with the same TIMESTAMP in the relay logs. If you cannot find it in the relay logs, then look and see if Infobright is posting the INSERT query. In that instance, the INSERT should be recorded in the binary logs of the Slave. Looking more deeply into the binary logs, I see that almost of the queries are CREATE/INSERT/UPDATE/DROP "temporary" tables, something like this: # at 123873315 #120405 0:42:04 server id 3 end_log_pos 123873618 Query thread_id=395373 exec_time=0 error_code=0 SET TIMESTAMP=1333561324/*!*/; SET @@session.pseudo_thread_id=395373/*!*/; CREATE TEMPORARY TABLE `norep_tmpcampaign` ( `campaignid` INTEGER(11) NOT NULL DEFAULT '0' , `status` INTEGER(11) NOT NULL DEFAULT '0' , `updated` DATETIME, KEY `campaignid` (`campaignid`) )ENGINE=MEMORY /*!*/; # at 123873618 #120405 0:42:04 server id 3 end_log_pos 123873755 Query thread_id=395373 exec_time=0 error_code=0 SET TIMESTAMP=1333561324/*!*/; DROP TABLE IF EXISTS `norep_tmpcampaign1` /* generated by server */ "temporary" here means that they are dropped after calculation is done. I also tells the slave not to replicate any statement matches the norep_ wildcard pattern: replicate-wild-ignore-table=%.norep_% But there is an exception table in the binary logs: # at 123828094 #120405 0:37:21 server id 3 end_log_pos 123828495 Query thread_id=395209 exec_time=0 error_code=0 SET TIMESTAMP=1333561041/*!*/; INSERT INTO sessions (SessionId, ApplicationName, Created, Expires, LockDate, LockId, Timeout, Locked, SessionItems, Fla gs) Values('pgv2exo4y4vo4ccz44vwznu0', '/', '2012-04-05 00:37:21', '2012-04-05 00:57:21', '2012-04-05 00:37:21', 0, 20, 0, 'AwAAAP////8IdXNlcm5hbWUGdXNlcmlkCHBlcm1pdGlkAgAAAAQAAAAGAAAAAQABAAEA', 0) /*!*/; Description: mysql> desc reportingdb.sessions; +-----------------+------------------+------+-----+---------------------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------------------+-------+ | SessionId | varchar(64) | NO | PRI | | | | ApplicationName | varchar(255) | NO | | | | | Created | timestamp | NO | | 0000-00-00 00:00:00 | | | Expires | timestamp | NO | | 0000-00-00 00:00:00 | | | LockDate | timestamp | NO | | 0000-00-00 00:00:00 | | | LockId | int(11) unsigned | NO | | NULL | | | Timeout | int(11) unsigned | NO | | NULL | | | Locked | bit(1) | NO | | NULL | | | SessionItems | varchar(255) | YES | | NULL | | | Flags | int(11) | NO | | NULL | | +-----------------+------------------+------+-----+---------------------+-------+ I'm sure all these queries are posting by MySQL, not Infobright: $ mysql-ib -u root -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 48971 Server version: 5.1.40 build number (revision)=IB_4.0.5_r15240_15370(ice) (static) Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select * from information_schema.tables where table_name='sessions'; Empty set (0.02 sec) I've been trying some INSERT/UPDATE queries with testing tables on the master, it is copied to the relay logs, not binary logs on slave: # at 311664029 #120405 0:15:23 server id 1 end_log_pos 311664006 Query thread_id=10458250 exec_time=0 error_code=0 use testuser/*!*/; SET TIMESTAMP=1333559723/*!*/; update users set email2='[email protected]' where id=22 /*!*/; Pay attention to the server id, in the relay logs, server id is master's (1) and in the binary log, server id is slave's (3 in this case). Reply to @RolandoMySQLDBA: Thu Apr 5 10:06:00 ICT 2012 Run CREATE DATABASE quantatest; on the Master now, please. Tell me if CREATE DATABASE quantatest; showed up in the Slave's Binary Logs. As I said above: I've been trying some INSERT/UPDATE queries with testing tables on the master, it is copied to the relay logs, not binary logs and you can guess, IO thread copied it to the relay logs, not binary logs. #120405 10:07:25 server id 1 end_log_pos 347573819 Query thread_id=10480775 exec_time=0 error_code=0 SET TIMESTAMP=1333595245/*!*/; /*!\C latin1 *//*!*/; SET @@session.character_set_client=8,@@session.collation_connection=8,@@session.collation_server=8/*!*/; create database quantatest /*!*/; The question must probably change to: why some update queries still logged to the slave binary logs althrough --log-slave-updates is disabled? Where they come from? Here are few last: /*!*/; # at 27492197 #120405 10:12:45 server id 3 end_log_pos 27492370 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595565/*!*/; CREATE TEMPORARY TABLE norep_SplitValues ( value VARCHAR(1000) NOT NULL ) ENGINE=MEMORY /*!*/; # at 27492370 #120405 10:12:45 server id 3 end_log_pos 27492445 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595565/*!*/; BEGIN /*!*/; # at 27492445 #120405 10:12:45 server id 3 end_log_pos 27492619 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595565/*!*/; INSERT INTO norep_SplitValues VALUES ( NAME_CONST('cur_string',_utf8'119577' COLLATE 'utf8_general_ci')) /*!*/; # at 27492619 #120405 10:12:45 server id 3 end_log_pos 27492695 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595565/*!*/; COMMIT /*!*/; # at 27492918 #120405 10:12:46 server id 3 end_log_pos 27493115 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595566/*!*/; SELECT `reportingdb`.`selfserving_get_locationad`(_utf8'3' COLLATE 'utf8_general_ci',_utf8'' COLLATE 'utf8_general_ci') /*!*/; # at 27493199 #120405 10:12:46 server id 3 end_log_pos 27493353 Query thread_id=410353 exec_time=0 error_code=0 SET TIMESTAMP=1333595566/*!*/; /*!\C utf8 *//*!*/; SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=8/*!*/; DROP TEMPORARY TABLE IF EXISTS `norep_SplitValues` /* generated by server */ /*!*/;

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  • Jetty interprets JETTY_ARGS as file name

    - by Lena Schimmel
    I'm running Jetty (version "null 6.1.22") on Ubuntu 10.04. It's running fine until I need JSP support. According to several blog posts I need to set the JETTY_ARGS to OPTIONS=Server,jsp. However, if I put this into /etc/default/jetty: JETTY_ARGS=OPTIONS=Server,jsp and restart Jetty via /etc/init.d/jetty stop && /etc/init.d/jetty start, it reports success, but does not accept connections. I notices that it logs something to /usr/share/jetty/logs/out.log: 2012-09-11 11:19:05.110:WARN::EXCEPTION java.io.FileNotFoundException: /var/cache/jetty/tmp/OPTIONS=Server,jsp (No such file or directory) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(FileInputStream.java:137) at java.io.FileInputStream.<init>(FileInputStream.java:96) at sun.net.www.protocol.file.FileURLConnection.connect(FileURLConnection.java:87) at sun.net.www.protocol.file.FileURLConnection.getInputStream(FileURLConnection.java:178) at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:630) at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(XMLVersionDetector.java:189) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:776) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:741) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123) at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1208) at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:525) at javax.xml.parsers.SAXParser.parse(SAXParser.java:392) at org.mortbay.xml.XmlParser.parse(XmlParser.java:188) at org.mortbay.xml.XmlParser.parse(XmlParser.java:204) at org.mortbay.xml.XmlConfiguration.<init>(XmlConfiguration.java:109) at org.mortbay.xml.XmlConfiguration.main(XmlConfiguration.java:969) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.mortbay.start.Main.invokeMain(Main.java:194) at org.mortbay.start.Main.start(Main.java:534) at org.mortbay.jetty.start.daemon.Bootstrap.start(Bootstrap.java:30) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177) That is, whatever I put into JETTY_ARGS, it inteprets is as a filename inside /var/cache/jetty/tmp/ and tries to parse that file as XML (or does it parse some other XML and tries to read that file as a DTD? I'm not sure.). This doesn't seem to make any sense to me, especially since that directory is entirely empty. I've verified this with several other Strings, not only OPTIONS=Server,jsp.

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  • How to auto advance a PowerPoint slide after an exit animation is over?

    - by joooc
    PowerPoint entrance animation set up with "Start: With Previous" starts right when a new slide is advanced. However, if you set up an exit animation in the same way, it doesn't start with a slide ending sequence. Instead, the "Start: On Click" trigger needs to be used and after your exit animation is over you still need one extra click just to advance to the next slide. Workarounds to this are obvious: create a duplicate slide, make your ending animations from the original slide being your starting animations on the duplicate slide and let them be followed with whatever you want or create a transition slide with those ending animations only and set up "Change Advance slide - Automatically after - [the time it takes your animations to finish]". These workarounds will make it work for your audience, visually. However, it has an impact on slide numbers you might need to adjust accordingly and/or duplicate content changes. If you are the only one creating and using your presentation, this might be just fine. But if you are creating a presentation in collaborative mode with three other people and don't even know who will be the presenter at the end, you can mess things up. Let's be specific: most of my slides have 0.2s fly in entrance animation applied to blocks of content coming from right, bottom or left. Advancing to the next slide I want them to fly out in another 0.2s exit animation being followed by new slide 0.2s fly in entrance animation of the new blocks. The swapping of the blocks should be triggered while advancing to the next slide, as usually. As mentioned, I'm not able to achieve this without one extra click between the slides. I wrote a VBA script that should start together with an exit animation and will auto advance a slide after 0.3s when the exit animation is over. That way I should get rid of those extra clicks which are needed right now. Sub nextslide() iTime = 0.3 Start = Timer While Timer < Start + iTime DoEvents Wend With SlideShowWindows(1).View .GotoSlide (ActivePresentation.SlideShowWindow.View.Slide.SlideIndex + 1) End With End Sub It works well when binded on a box, button or another object. But I can't make it run on a single click (anywhere on the slide) so that it could start together with the exit animation onclick trigger. Creating a big transparent rectangular shape over the whole slide and binding the macro on it doesn't help either. By clicking it you only get the macro running, exit animation is not triggered. Anyway, I don't want to bind the macro to any other workaround object but the slide itself. Anyone knows how to trigger a PowerPoint VBA script on slide onclick event? Anyone knows a secret setting that will make the exit animation work as expected i.e. animating right before exiting a slide while transitioning to the next one? Anyone knows how to beat this dragon? Thank you!

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  • Using HTML 5 SessionState to save rendered Page Content

    - by Rick Strahl
    HTML 5 SessionState and LocalStorage are very useful and super easy to use to manage client side state. For building rich client side or SPA style applications it's a vital feature to be able to cache user data as well as HTML content in order to swap pages in and out of the browser's DOM. What might not be so obvious is that you can also use the sessionState and localStorage objects even in classic server rendered HTML applications to provide caching features between pages. These APIs have been around for a long time and are supported by most relatively modern browsers and even all the way back to IE8, so you can use them safely in your Web applications. SessionState and LocalStorage are easy The APIs that make up sessionState and localStorage are very simple. Both object feature the same API interface which  is a simple, string based key value store that has getItem, setItem, removeitem, clear and  key methods. The objects are also pseudo array objects and so can be iterated like an array with  a length property and you have array indexers to set and get values with. Basic usage  for storing and retrieval looks like this (using sessionStorage, but the syntax is the same for localStorage - just switch the objects):// set var lastAccess = new Date().getTime(); if (sessionStorage) sessionStorage.setItem("myapp_time", lastAccess.toString()); // retrieve in another page or on a refresh var time = null; if (sessionStorage) time = sessionStorage.getItem("myapp_time"); if (time) time = new Date(time * 1); else time = new Date(); sessionState stores data that is browser session specific and that has a liftetime of the active browser session or window. Shut down the browser or tab and the storage goes away. localStorage uses the same API interface, but the lifetime of the data is permanently stored in the browsers storage area until deleted via code or by clearing out browser cookies (not the cache). Both sessionStorage and localStorage space is limited. The spec is ambiguous about this - supposedly sessionStorage should allow for unlimited size, but it appears that most WebKit browsers support only 2.5mb for either object. This means you have to be careful what you store especially since other applications might be running on the same domain and also use the storage mechanisms. That said 2.5mb worth of character data is quite a bit and would go a long way. The easiest way to get a feel for how sessionState and localStorage work is to look at a simple example. You can go check out the following example online in Plunker: http://plnkr.co/edit/0ICotzkoPjHaWa70GlRZ?p=preview which looks like this: Plunker is an online HTML/JavaScript editor that lets you write and run Javascript code and similar to JsFiddle, but a bit cleaner to work in IMHO (thanks to John Papa for turning me on to it). The sample has two text boxes with counts that update session/local storage every time you click the related button. The counts are 'cached' in Session and Local storage. The point of these examples is that both counters survive full page reloads, and the LocalStorage counter survives a complete browser shutdown and restart. Go ahead and try it out by clicking the Reload button after updating both counters and then shutting down the browser completely and going back to the same URL (with the same browser). What you should see is that reloads leave both counters intact at the counted values, while a browser restart will leave only the local storage counter intact. The code to deal with the SessionStorage (and LocalStorage not shown here) in the example is isolated into a couple of wrapper methods to simplify the code: function getSessionCount() { var count = 0; if (sessionStorage) { var count = sessionStorage.getItem("ss_count"); count = !count ? 0 : count * 1; } $("#txtSession").val(count); return count; } function setSessionCount(count) { if (sessionStorage) sessionStorage.setItem("ss_count", count.toString()); } These two functions essentially load and store a session counter value. The two key methods used here are: sessionStorage.getItem(key); sessionStorage.setItem(key,stringVal); Note that the value given to setItem and return by getItem has to be a string. If you pass another type you get an error. Don't let that limit you though - you can easily enough store JSON data in a variable so it's quite possible to pass complex objects and store them into a single sessionStorage value:var user = { name: "Rick", id="ricks", level=8 } sessionStorage.setItem("app_user",JSON.stringify(user)); to retrieve it:var user = sessionStorage.getItem("app_user"); if (user) user = JSON.parse(user); Simple! If you're using the Chrome Developer Tools (F12) you can also check out the session and local storage state on the Resource tab:   You can also use this tool to refresh or remove entries from storage. What we just looked at is a purely client side implementation where a couple of counters are stored. For rich client centric AJAX applications sessionStorage and localStorage provide a very nice and simple API to store application state while the application is running. But you can also use these storage mechanisms to manage server centric HTML applications when you combine server rendering with some JavaScript to perform client side data caching. You can both store some state information and data on the client (ie. store a JSON object and carry it forth between server rendered HTML requests) or you can use it for good old HTTP based caching where some rendered HTML is saved and then restored later. Let's look at the latter with a real life example. Why do I need Client-side Page Caching for Server Rendered HTML? I don't know about you, but in a lot of my existing server driven applications I have lists that display a fair amount of data. Typically these lists contain links to then drill down into more specific data either for viewing or editing. You can then click on a link and go off to a detail page that provides more concise content. So far so good. But now you're done with the detail page and need to get back to the list, so you click on a 'bread crumbs trail' or an application level 'back to list' button and… …you end up back at the top of the list - the scroll position, the current selection in some cases even filters conditions - all gone with the wind. You've left behind the state of the list and are starting from scratch in your browsing of the list from the top. Not cool! Sound familiar? This a pretty common scenario with server rendered HTML content where it's so common to display lists to drill into, only to lose state in the process of returning back to the original list. Look at just about any traditional forums application, or even StackOverFlow to see what I mean here. Scroll down a bit to look at a post or entry, drill in then use the bread crumbs or tab to go back… In some cases returning to the top of a list is not a big deal. On StackOverFlow that sort of works because content is turning around so quickly you probably want to actually look at the top posts. Not always though - if you're browsing through a list of search topics you're interested in and drill in there's no way back to that position. Essentially anytime you're actively browsing the items in the list, that's when state becomes important and if it's not handled the user experience can be really disrupting. Content Caching If you're building client centric SPA style applications this is a fairly easy to solve problem - you tend to render the list once and then update the page content to overlay the detail content, only hiding the list temporarily until it's used again later. It's relatively easy to accomplish this simply by hiding content on the page and later making it visible again. But if you use server rendered content, hanging on to all the detail like filters, selections and scroll position is not quite as easy. Or is it??? This is where sessionStorage comes in handy. What if we just save the rendered content of a previous page, and then restore it when we return to this page based on a special flag that tells us to use the cached version? Let's see how we can do this. A real World Use Case Recently my local ISP asked me to help out with updating an ancient classifieds application. They had a very busy, local classifieds app that was originally an ASP classic application. The old app was - wait for it: frames based - and even though I lobbied against it, the decision was made to keep the frames based layout to allow rapid browsing of the hundreds of posts that are made on a daily basis. The primary reason they wanted this was precisely for the ability to quickly browse content item by item. While I personally hate working with Frames, I have to admit that the UI actually works well with the frames layout as long as you're running on a large desktop screen. You can check out the frames based desktop site here: http://classifieds.gorge.net/ However when I rebuilt the app I also added a secondary view that doesn't use frames. The main reason for this of course was for mobile displays which work horribly with frames. So there's a somewhat mobile friendly interface to the interface, which ditches the frames and uses some responsive design tweaking for mobile capable operation: http://classifeds.gorge.net/mobile  (or browse the base url with your browser width under 800px)   Here's what the mobile, non-frames view looks like:   As you can see this means that the list of classifieds posts now is a list and there's a separate page for drilling down into the item. And of course… originally we ran into that usability issue I mentioned earlier where the browse, view detail, go back to the list cycle resulted in lost list state. Originally in mobile mode you scrolled through the list, found an item to look at and drilled in to display the item detail. Then you clicked back to the list and BAM - you've lost your place. Because there are so many items added on a daily basis the full list is never fully loaded, but rather there's a "Load Additional Listings"  entry at the button. Not only did we originally lose our place when coming back to the list, but any 'additionally loaded' items are no longer there because the list was now rendering  as if it was the first page hit. The additional listings, and any filters, the selection of an item all were lost. Major Suckage! Using Client SessionStorage to cache Server Rendered Content To work around this problem I decided to cache the rendered page content from the list in SessionStorage. Anytime the list renders or is updated with Load Additional Listings, the page HTML is cached and stored in Session Storage. Any back links from the detail page or the login or write entry forms then point back to the list page with a back=true query string parameter. If the server side sees this parameter it doesn't render the part of the page that is cached. Instead the client side code retrieves the data from the sessionState cache and simply inserts it into the page. It sounds pretty simple, and the overall the process is really easy, but there are a few gotchas that I'll discuss in a minute. But first let's look at the implementation. Let's start with the server side here because that'll give a quick idea of the doc structure. As I mentioned the server renders data from an ASP.NET MVC view. On the list page when returning to the list page from the display page (or a host of other pages) looks like this: https://classifieds.gorge.net/list?back=True The query string value is a flag, that indicates whether the server should render the HTML. Here's what the top level MVC Razor view for the list page looks like:@model MessageListViewModel @{ ViewBag.Title = "Classified Listing"; bool isBack = !string.IsNullOrEmpty(Request.QueryString["back"]); } <form method="post" action="@Url.Action("list")"> <div id="SizingContainer"> @if (!isBack) { @Html.Partial("List_CommandBar_Partial", Model) <div id="PostItemContainer" class="scrollbox" xstyle="-webkit-overflow-scrolling: touch;"> @Html.Partial("List_Items_Partial", Model) @if (Model.RequireLoadEntry) { <div class="postitem loadpostitems" style="padding: 15px;"> <div id="LoadProgress" class="smallprogressright"></div> <div class="control-progress"> Load additional listings... </div> </div> } </div> } </div> </form> As you can see the query string triggers a conditional block that if set is simply not rendered. The content inside of #SizingContainer basically holds  the entire page's HTML sans the headers and scripts, but including the filter options and menu at the top. In this case this makes good sense - in other situations the fact that the menu or filter options might be dynamically updated might make you only cache the list rather than essentially the entire page. In this particular instance all of the content works and produces the proper result as both the list along with any filter conditions in the form inputs are restored. Ok, let's move on to the client. On the client there are two page level functions that deal with saving and restoring state. Like the counter example I showed earlier, I like to wrap the logic to save and restore values from sessionState into a separate function because they are almost always used in several places.page.saveData = function(id) { if (!sessionStorage) return; var data = { id: id, scroll: $("#PostItemContainer").scrollTop(), html: $("#SizingContainer").html() }; sessionStorage.setItem("list_html",JSON.stringify(data)); }; page.restoreData = function() { if (!sessionStorage) return; var data = sessionStorage.getItem("list_html"); if (!data) return null; return JSON.parse(data); }; The data that is saved is an object which contains an ID which is the selected element when the user clicks and a scroll position. These two values are used to reset the scroll position when the data is used from the cache. Finally the html from the #SizingContainer element is stored, which makes for the bulk of the document's HTML. In this application the HTML captured could be a substantial bit of data. If you recall, I mentioned that the server side code renders a small chunk of data initially and then gets more data if the user reads through the first 50 or so items. The rest of the items retrieved can be rather sizable. Other than the JSON deserialization that's Ok. Since I'm using SessionStorage the storage space has no immediate limits. Next is the core logic to handle saving and restoring the page state. At first though this would seem pretty simple, and in some cases it might be, but as the following code demonstrates there are a few gotchas to watch out for. Here's the relevant code I use to save and restore:$( function() { … var isBack = getUrlEncodedKey("back", location.href); if (isBack) { // remove the back key from URL setUrlEncodedKey("back", "", location.href); var data = page.restoreData(); // restore from sessionState if (!data) { // no data - force redisplay of the server side default list window.location = "list"; return; } $("#SizingContainer").html(data.html); var el = $(".postitem[data-id=" + data.id + "]"); $(".postitem").removeClass("highlight"); el.addClass("highlight"); $("#PostItemContainer").scrollTop(data.scroll); setTimeout(function() { el.removeClass("highlight"); }, 2500); } else if (window.noFrames) page.saveData(null); // save when page loads $("#SizingContainer").on("click", ".postitem", function() { var id = $(this).attr("data-id"); if (!id) return true; if (window.noFrames) page.saveData(id); var contentFrame = window.parent.frames["Content"]; if (contentFrame) contentFrame.location.href = "show/" + id; else window.location.href = "show/" + id; return false; }); … The code starts out by checking for the back query string flag which triggers restoring from the client cache. If cached the cached data structure is read from sessionStorage. It's important here to check if data was returned. If the user had back=true on the querystring but there is no cached data, he likely bookmarked this page or otherwise shut down the browser and came back to this URL. In that case the server didn't render any detail and we have no cached data, so all we can do is redirect to the original default list view using window.location. If we continued the page would render no data - so make sure to always check the cache retrieval result. Always! If there is data the it's loaded and the data.html data is restored back into the document by simply injecting the HTML back into the document's #SizingContainer element:$("#SizingContainer").html(data.html); It's that simple and it's quite quick even with a fully loaded list of additional items and on a phone. The actual HTML data is stored to the cache on every page load initially and then again when the user clicks on an element to navigate to a particular listing. The former ensures that the client cache always has something in it, and the latter updates with additional information for the selected element. For the click handling I use a data-id attribute on the list item (.postitem) in the list and retrieve the id from that. That id is then used to navigate to the actual entry as well as storing that Id value in the saved cached data. The id is used to reset the selection by searching for the data-id value in the restored elements. The overall process of this save/restore process is pretty straight forward and it doesn't require a bunch of code, yet it yields a huge improvement in the usability of the site on mobile devices (or anybody who uses the non-frames view). Some things to watch out for As easy as it conceptually seems to simply store and retrieve cached content, you have to be quite aware what type of content you are caching. The code above is all that's specific to cache/restore cycle and it works, but it took a few tweaks to the rest of the script code and server code to make it all work. There were a few gotchas that weren't immediately obvious. Here are a few things to pay attention to: Event Handling Logic Timing of manipulating DOM events Inline Script Code Bookmarking to the Cache Url when no cache exists Do you have inline script code in your HTML? That script code isn't going to run if you restore from cache and simply assign or it may not run at the time you think it would normally in the DOM rendering cycle. JavaScript Event Hookups The biggest issue I ran into with this approach almost immediately is that originally I had various static event handlers hooked up to various UI elements that are now cached. If you have an event handler like:$("#btnSearch").click( function() {…}); that works fine when the page loads with server rendered HTML, but that code breaks when you now load the HTML from cache. Why? Because the elements you're trying to hook those events to may not actually be there - yet. Luckily there's an easy workaround for this by using deferred events. With jQuery you can use the .on() event handler instead:$("#SelectionContainer").on("click","#btnSearch", function() {…}); which monitors a parent element for the events and checks for the inner selector elements to handle events on. This effectively defers to runtime event binding, so as more items are added to the document bindings still work. For any cached content use deferred events. Timing of manipulating DOM Elements Along the same lines make sure that your DOM manipulation code follows the code that loads the cached content into the page so that you don't manipulate DOM elements that don't exist just yet. Ideally you'll want to check for the condition to restore cached content towards the top of your script code, but that can be tricky if you have components or other logic that might not all run in a straight line. Inline Script Code Here's another small problem I ran into: I use a DateTime Picker widget I built a while back that relies on the jQuery date time picker. I also created a helper function that allows keyboard date navigation into it that uses JavaScript logic. Because MVC's limited 'object model' the only way to embed widget content into the page is through inline script. This code broken when I inserted the cached HTML into the page because the script code was not available when the component actually got injected into the page. As the last bullet - it's a matter of timing. There's no good work around for this - in my case I pulled out the jQuery date picker and relied on native <input type="date" /> logic instead - a better choice these days anyway, especially since this view is meant to be primarily to serve mobile devices which actually support date input through the browser (unlike desktop browsers of which only WebKit seems to support it). Bookmarking Cached Urls When you cache HTML content you have to make a decision whether you cache on the client and also not render that same content on the server. In the Classifieds app I didn't render server side content so if the user comes to the page with back=True and there is no cached content I have to a have a Plan B. Typically this happens when somebody ends up bookmarking the back URL. The easiest and safest solution for this scenario is to ALWAYS check the cache result to make sure it exists and if not have a safe URL to go back to - in this case to the plain uncached list URL which amounts to effectively redirecting. This seems really obvious in hindsight, but it's easy to overlook and not see a problem until much later, when it's not obvious at all why the page is not rendering anything. Don't use <body> to replace Content Since we're practically replacing all the HTML in the page it may seem tempting to simply replace the HTML content of the <body> tag. Don't. The body tag usually contains key things that should stay in the page and be there when it loads. Specifically script tags and elements and possibly other embedded content. It's best to create a top level DOM element specifically as a placeholder container for your cached content and wrap just around the actual content you want to replace. In the app above the #SizingContainer is that container. Other Approaches The approach I've used for this application is kind of specific to the existing server rendered application we're running and so it's just one approach you can take with caching. However for server rendered content caching this is a pattern I've used in a few apps to retrofit some client caching into list displays. In this application I took the path of least resistance to the existing server rendering logic. Here are a few other ways that come to mind: Using Partial HTML Rendering via AJAXInstead of rendering the page initially on the server, the page would load empty and the client would render the UI by retrieving the respective HTML and embedding it into the page from a Partial View. This effectively makes the initial rendering and the cached rendering logic identical and removes the server having to decide whether this request needs to be rendered or not (ie. not checking for a back=true switch). All the logic related to caching is made on the client in this case. Using JSON Data and Client RenderingThe hardcore client option is to do the whole UI SPA style and pull data from the server and then use client rendering or databinding to pull the data down and render using templates or client side databinding with knockout/angular et al. As with the Partial Rendering approach the advantage is that there's no difference in the logic between pulling the data from cache or rendering from scratch other than the initial check for the cache request. Of course if the app is a  full on SPA app, then caching may not be required even - the list could just stay in memory and be hidden and reactivated. I'm sure there are a number of other ways this can be handled as well especially using  AJAX. AJAX rendering might simplify the logic, but it also complicates search engine optimization since there's no content loaded initially. So there are always tradeoffs and it's important to look at all angles before deciding on any sort of caching solution in general. State of the Session SessionState and LocalStorage are easy to use in client code and can be integrated even with server centric applications to provide nice caching features of content and data. In this post I've shown a very specific scenario of storing HTML content for the purpose of remembering list view data and state and making the browsing experience for lists a bit more friendly, especially if there's dynamically loaded content involved. If you haven't played with sessionStorage or localStorage I encourage you to give it a try. There's a lot of cool stuff that you can do with this beyond the specific scenario I've covered here… Resources Overview of localStorage (also applies to sessionStorage) Web Storage Compatibility Modernizr Test Suite© Rick Strahl, West Wind Technologies, 2005-2013Posted in JavaScript  HTML5  ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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