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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • Why do I get empty request from the Jakarta Commons HttpClient?

    - by polyurethan
    I have a problem with the Jakarta Commons HttpClient. Before my self-written HttpServer gets the real request there is one request which is completely empty. That's the first problem. The second problem is, sometimes the request data ends after the third or fourth line of the http request: POST / HTTP/1.1 User-Agent: Jakarta Commons-HttpClient/3.1 Host: 127.0.0.1:4232 For debugging I am using the Axis TCPMonitor. There every things is fine but the empty request. How I process the stream: StringBuffer requestBuffer = new StringBuffer(); InputStreamReader is = new InputStreamReader(socket.getInputStream(), "UTF-8"); int byteIn = -1; do { byteIn = is.read(); if (byteIn > 0) { requestBuffer.append((char) byteIn); } } while (byteIn != -1 && is.ready()); String requestData = requestBuffer.toString(); How I send the request: client.getParams().setSoTimeout(30000); method = new PostMethod(url.getPath()); method.getParams().setContentCharset("utf-8"); method.setRequestHeader("Content-Type", "application/xml; charset=utf-8"); method.addRequestHeader("Connection", "close"); method.setFollowRedirects(false); byte[] requestXml = getRequestXml(); method.setRequestEntity(new InputStreamRequestEntity(new ByteArrayInputStream(requestXml))); client.executeMethod(method); int statusCode = method.getStatusCode(); Have anyone of you an idea how to solve these problems? Alex

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  • When do instance variables get initialized and values assigned?

    - by AKh
    When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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  • ArrayList<String> NullPointerException

    - by Carlucho
    Am trying to solve a labyrinth by DFS, using adj List to represent the vertices and edges of the graph. In total there are 12 nodes (3 rows[A,B,C] * 4 cols[0,..,3]). My program starts by saving all the vertex labels (A0,..C3), so far so good, then checks the adjacent nodes, also no problems, if movement is possible, it proceeds to create the edge, here its where al goes wrong. adjList[i].add(vList[j].label); I used the debugger and found that vList[j].label is not null it contains a correct string (ie. "B1"). The only variables which show null are in adjList[i], which leads me to believe i have implemented it wrongly. this is how i did it. public class GraphList { private ArrayList<String>[] adjList; ... public GraphList(int vertexcount) { adjList = (ArrayList<String>[]) new ArrayList[vertexCount]; ... } ... public void addEdge(int i, int j) { adjList[i].add(vList[j].label); //NULLPOINTEREXCEPTION HERE } ... } I will really appreaciate if anyone can point me on the right track regrading to what its going wrong... Thanks!

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  • PropertyPlaceholderConfigurer vs Filters -- Spring Beans

    - by John
    Hi there. I've got a question regarding the difference between PropertyPlaceholderConfigurer (org.springframework.beans.factory.config.PropertyPlaceholderConfigurer) and normal filters defined in my pom.xml. I've been looking at examples, and it seems that even though filters are defined and marked to be active by default in the pom.xml they still make use of PropertyPlaceholderConfigurer in Spring's applicationContext.xml. This means that the pom.xml has a reference to a filter-LOCAL.properties while applicationContext.xml has a reference to application.properties and they both contain the same settings. Why is that? Is that how it is supposed to be done? I'm able to run the goal mvn jetty:run without the application.properties present, but if I add settings to the application.properties that differ from the filter-LOCAL.properties they don't seem to override. Here's an example of what I mean: pom.xml <profiles <profile <idLOCAL <activation <activeByDefaulttrue </activation <properties <envLOCAL </properties </profile </profiles applicationContext.xml <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" <property name="locations" <list <valueclasspath:application.properties </list </property <property name="ignoreResourceNotFound" value="true"/ </bean <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" <property name="driverClassName" value="${jdbc.driver}"/ <property name="url" value="${jdbc.url}"/ <property name="username" value="${jdbc.username}"/ <property name="password" value="${jdbc.password}"/ </bean an example of the content of application.properties and filters-LOCAL.properties jdbc.driver=org.postgresql.Driver jdbc.url=jdbc:postgresql://localhost/shoutbox_dev jdbc.username=tester jdbc.password=tester Can I remove the propertyConfigurer from the applicationContext, create a PROD filter and disregard the application.properties file, or will that give me issues when deploying to the production server?

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  • How to access a variable in other class?

    - by Christine
    Hi! I've problem regarding GUI with one Menu and one Order Class. I've created a variable to store how many items have been selected in the Menu Class. private int totalSelected; The var totalSelected is live updated. It can be changed anytime depending on actionPerformed() function.(Exp: totalSelected will add up all the selected items) In the Order Class, how can I access to the live update variable totalSelected in order to retrieve the live update value? When I invoke getTotalSelected() function inside the Menu Class, I will only obtain a 0 value. Thanks for your help ^^! Please allow me to specify my question clearer. public class MenuTab extends JPanel { private JLabel display; private int totalSelected; public MenuTab() { .... } } public getTotalSelected(){ return totalSelected; } private class SelectedListener implements ActionListener { public void actionPerformed() { ....... //Assume that totalSelected has been updated! display = new JLabel("Total: " + totalSelected); // OK to display totalSelected live value here. } } // A new class is the confirmation of order public class OrderConfirmedTab extends JPanel{ private JLabel displayTotal; private MenuTab order = new MenuTab(); public OrderConfirmedTab() { ...... int totalSelected = order.getTotalSelected(); displayTotal = new JLabel("Total: " + totalSelected); // Problem to display totalSelected live value here. // Will obtain 0; // How can I obtain the live updated value from class MenuTab? Thanks! } }

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  • How to reverse a string?

    - by WM
    Example : hi how are you; output : you are how hi; but wrote this code and im stuck not knowing how to put a string into an array and reverse it..? public class Reverse { public static void main(String[] args) { Scanner text = new Scanner(System.in); System.out.print("Enter your Text : "); String input = text.nextLine(); Scanner text2 = new Scanner(text.nextLine()); String[] array = new String[] ; int i; for(i = 0; i < input.length(); i++) { array[i] = input;

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  • Properly removing an Integer from a List<Integer>

    - by Yuval A
    Here's a nice pitfall I just encountered. Consider a list of integers: List<Integer> list = new ArrayList<Integer>(); list.add(5); list.add(6); list.add(7); list.add(1); Any educated guess on what happens when you execute list.remove(1)? What about list.remove(new Integer(1))? This can cause some nasty bugs. What is the proper way to differentiate between remove(int index), which removes an element from given index and remove(Object o), which removes an element by reference, when dealing with lists of integers? The main point to consider here is the one @Nikita mentioned - exact parameter matching takes precedence over auto-boxing.

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  • How to allow for modular development while still running in same JVM?

    - by Marcus
    Our current app runs in a single JVM. We are now splitting up the app into separate logical services where each service runs in its own JVM. The split is being done to allow a single service to be modified and deployed without impacting the entire system. This reduces the need to QA the entire system - just need to QA the interaction with the service being changed. For interservice communication we use a combination of REST, an MQ system bus, and database views. What I don't like about this: REST means we have to marshal data to/from XML DB views couple the systems together which defeats the whole concept of separate services MQ / system bus is added complexity There is inevitably some code duplication between services You have set up n JBoss server configurations, we have to do n number of deployments, n number of set up scripts, etc, etc. Is there a better way to structure an internal application to allow modular development and deployment while allowing the app to run in a single JVM (and achieving the associated benefits)?

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  • Many returned records cause stackoverflow with Hibernate

    - by mimi law
    If there are many return records from DB. It will get stackoverflow problem. User is a class, which has a one to many relationship (to 3 other classes). When I print out the SQL, i found that the system runs the same query many time to get the data from DB. Does anyone know what the problem is? result.addAll(getCurrentSession().createCriteria(User.class) .add(Restrictions.ilike("name", "tom", MatchMode.ANYWHERE)) .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY) .list());

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  • Catch FileNotFoundException in AsyncTask method

    - by Musterknabe
    I'm getting the favicon of a website with a method. Of course not every website has a favicon. So I want to catch it. The app doesn't crash if the website doesn't have a favicon but I still get an FileNotFoundException in the LogCat. The problem I'm encountering is that I can't catch it When I add `catch (FileNotFoundException f) to my try-catch block it tells me Unreachable catch block for FileNotFoundException. This exception is never thrown from the try statement body. The options I have is to remove it or to add a throws declaration to the doInBackground-method. The latter is not possible. This is the whole Try-Catch try{ String baseURL = getBaseURL ( sourceURLArr[i] ); System.out.println(baseURL + "/favicon.ico"); Bitmap favicon = getBitmapFromURL( baseURL + "/favicon.ico"); Drawable fv = new BitmapDrawable(getResources(), Bitmap.createScaledBitmap(favicon, 20, 20, true)); source [i].setCompoundDrawablesWithIntrinsicBounds(fv, null, null, null); } catch(NullPointerException e){ } catch(FileNotFoundException f){ } I already tried to switch the FileNotFoundException with the NullPointerException but it was the same error. When I add the throws to the asynctask do in background method I get Exception FileNotFoundException is not compatible with throws clause in AsyncTask<Void,Void,Void>.doInBackground(Void[]) How can I now catch the FileNotFoundException?

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  • Drag and drop + custom drawing in Android

    - by Rich
    I am working on something that needed custom drag-and-drop functionality, so I have been subclassing View, doing a bunch of math in response to touch events, and then rendering everything manually through code on the canvas in onDraw. Now, the more functionality I add, the more the code is growing out of control and I find myself writing a ton more code than I would expect to write in a high level environment like Android. Is this how it's done, or am I missing something? If I'm not doing anything fancy in the UI, the framework handles the majority of my interactions. Built-in controls handle the touches and drags, and my code is pretty much limited to business logic and data. Is there a way to leverage the power of some of the UI controls and things like animations while also doing some of it manually in the onDraw canvas? Is there an accepted standard of when to use one or the other (if indeed the two approaches can be mixed)?

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  • Lan Chatting system [closed]

    - by jay prakash singh
    Possible Duplicate: LAN chating system or LAN chat server displaying list of user to all the user window my code is i m use RMI so this is the interface declaration public void sendPublicMessage(String keyword, String username, String message) throws RemoteException; public void sendPrivateMessage(String keyword, String username, String message) throws RemoteException; public ArrayList getClientList() throws RemoteException; public void connect(String username) throws RemoteException; public void disconnect(String username) throws RemoteException; } chat Server here connectedUser is the HasMap object we use the follo0wing code for connection here ChatImpl is the stub try { InetAddress Address = InetAddress.getLocalHost(); ChatImpl csi = new ChatImpl(this); Naming.rebind("rmi://"+Address.getHostAddress()+":1099/ChatService", csi); } public ArrayList getClientList() { ArrayList myUser = new ArrayList(); Iterator i = connectedUser.keySet().iterator(); String user = null; while(i.hasNext()) { user = i.next().toString(); myUser.add(user); } return myUser; } public void addClient(Socket clientSocket) throws RemoteException { connectedUser.put(getUsername(), clientSocket); sendPublicMessage(ONLINE, getUsername(), "CLIENT"); } this is the client side code for array list public void updateClient(ArrayList allClientList) throws RemoteException { listClient.clear(); int i = 0; String username; for(i=0; i<allClientList.size(); i++) { username = allClientList.get(i).toString(); listClient.addElement(username); } }

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  • Jpa subclass mapping

    - by Roy Chan
    I am making a POS like system. I wonder how to map subclass using JPA (this is for my DAO). Product class has product details and OrderProduct class has information about the Product and details about the order. @Entity @Table(name="products") public class Product implements Serializable{ @Id @Column(name="id") @GeneratedValue(strategy = GenerationType.AUTO public int getId(){ return id;} /** Other get/set methods */ } @Entity @Table(name="order_products") public class OrderProduct extends Product{ @Id @Column(name="id") @GeneratedValue(strategy = GenerationType.AUTO) public int getId(){ return id;} /** Other get/set methods */ } I got complain about duplicate @Id. But OrderProduct class really need another id than the product one. How should I map this? DB is something like this Table products id int name varchar(32) Table order_product id int quantity int productid int fk referencing product table Would @IdClass or @AttributeOverride help?

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  • simple process rollback question

    - by OckhamsRazor
    hi folks! while revising for an exam, i came across this simple question asking about rollbacks in processes. i understand how rollbacks occur, but i need some validation on my answer. The question: my confusion results from the fact that there is interprocess communication between the processes. does that change anything in terms of where to rollback? my answer would be R13, R23, R32 and R43. any help is greatly appreciated! thanks!

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  • Checkbox values to varchar via Spring

    - by iowatiger08
    I am trying to get a varchar message from a database to display the selected values of a checkbox field in a jsp for patient's medication's dosage frequency. The possible values will be saved in comma-delimited string in the varchar. For most form fields there is simply a one form value to one database field ratio, but in this case, I am needing to merge the values that would come as a string[] into the comma-delimited string and then when retrieving that record for that medication of that patient, display the selected values from the comma-delimited string as selected from the selectableDosageFrequencyList. You assistance in this is greatly appreciated as I am not sure what I am missing here. In the application context, I created the list of possible values as part of the ServiceBean. <property name="selectableDosageFrequencyList"> <set> <value>On an empty stomach</value> <value>Every other day</value> <value>4 times daily</value> <value>3 times daily</value> <value>Twice daily</value> <value>At bedtime</value> <value>With meal</value> <value>As needed</value> <value>Once daily</value> </set> </property> This is set up in the flow as requestscope. <view-state id="addEditMedication" model="medication"> <on-render> <set name="requestScope.selectableDosageFrequencyList" value="memberService.buildSelectableDosageFrequencyList(patient)" /> </on-render> ... <transition on="next" to="assessment" > <evaluate expression="memberService.updateMedication(patient, medication)" /> </transition> </view-state> I have helper methods in the memberService that need to be executed when the form is init and then when the form is completed. //get the form fields selected and build the new string for db public String setSelectedDosageFrequency(String [] dosageFrequencies){ String frequencies = null; if (dosageFrequencies != null){ for (String s : dosageFrequencies){ frequencies = frequencies + "," + s; } } return frequencies; } //get value from database and build selected Set public LinkedHashSet<String> getSelectedDosageFrequencyList(String dosageFrequency){ String copyOfDosages =dosageFrequency;//may not need to do this LinkedHashSet<String> setofSelectedDosageFrequency = new LinkedHashSet<String> (); while (copyOfDosages!= null && copyOfDosages.length()>0){ for (String aFrequency: selectableDosageFrequencyList){ if (copyOfDosages.contains(aFrequency)){ setofSelectedDosageFrequency.add(aFrequency); if (!copyOfDosages.equals(aFrequency) && copyOfDosages.endsWith(aFrequency)){ copyOfDosages.replaceAll(","+aFrequency, ""); }else if (!copyOfDosages.equals(aFrequency) && copyOfDosages.contains(aFrequency=",")){ copyOfDosages.replaceAll(aFrequency+",", ""); }else copyOfDosages.replaceAll(aFrequency, ""); copyOfDosages.trim(); } } } return setofSelectedDosageFrequency; } The Medication class that backs the form will have a variable for dosage-frequency as a string. private String dosageFrequency; The jsp I currently am doing this. <div class="formField"> <form:label path="dosageFrequency">Dosage Frequency</form:label> <ul class="multi-column double" style="width: 550px;"> <form:checkboxes path="dosageFrequency" items="${selectableDosageFrequencyList}" itemLabel="${selectableDosageFrequencyList}" element="li" /> </ul> </div>

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  • App Engine datastore does not support operator OR

    - by JohnIdol
    I am trying to query the google datastore for something like (with pm -- persistanceManager): String filters = "( field == 'value' || field == 'anotherValue' )"; Query query = pm.newQuery(myType.class, filters); When I execute - I am getting back: App Engine datastore does not support operator OR. What's the best approach in people experience for this kind of queries? Any help appreciated!

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  • Why are only some of my attributes shown in the response xml of jaxws?

    - by Andreas
    I created a jaxws webservice, but it returns only some of the attributes of my objects in the response xml. E.g. public class MyObject { private String attribute1; private String attribute2; //getter and setter } But the returned XML only contains <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <ns2:getVariantsResponse xmlns:ns2="mynamespace"> <myObject> <attribute1>stringcontent</attribute1> </myObject> ....

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  • swing gui improving

    - by radi
    hi all , i am looking for some methods to improve swing gui for example i want to know about new components libraries , new methods to enhance swing performance , new methods to add special effect to swing gui and new plaf for swing . please i want to know how to use this topics and where to find some tutorials about it . thanks.

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  • Why does Joda time change the PM in my input string to AM?

    - by Tree
    My input string is a PM time: log(start); // Sunday, January 09, 2011 6:30:00 PM I'm using Joda Time's pattern syntax as follows to parse the DateTime: DateTimeFormatter parser1 = DateTimeFormat.forPattern("EEEE, MMMM dd, yyyy H:mm:ss aa"); DateTime startTime = parser1.parseDateTime(start); So, why is my output string AM? log(parser1.print(startTime)); // Sunday, January 09, 2011 6:30:00 AM

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  • Netbeans Error: "Could not add one or more tag libraries"

    - by JJ4UC
    I am using Netbeans 6.1 and Tomcat 6.0.1.6. I made some very minor changes to a project that had been working and now I am getting the following error: com.sun.rave.web.ui.appbase.ApplicationException: org.apache.jasper.JasperException: Could not add one or more tag libraries. The only change I made was to a backing bean method, no new UI components, jsp, etc. Any direction would be greatly appreciated. Thanks!

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  • Tower of Hanoi, stop sliding

    - by ArtWorkAD
    Hi, I developed a solution for the Tower of Hanoi problem: public static void bewege(int h, char quelle, char ablage, char ziel) { if(h > 0){ bewege(h - 1, quelle, ziel, ablage); System.out.println("Move "+ h +" from " + quelle + " to " + ziel); bewege(h - 1, ablage, quelle, ziel); } } It works fine. Now i want to limit the number of slides and throw an exception if a certain limit is reached. I tried it with a counter but it does not work: class HanoiNK{ public static void main(String args[]){ Integer n = Integer.parseInt(args[0]); Integer k = Integer.parseInt(args[1]); try{ bewege(k, n, 'A', 'B', 'C'); }catch(Exception e){ System.out.println(e); } } public static void bewege(int c, int h, char quelle, char ablage, char ziel) throws Exception{ if(h > 0){ if(counter != 0){ bewege(c, h - 1, quelle, ziel, ablage); c--; System.out.println("Move "+ h +" from " + quelle + " to " + ziel); bewege(c, h - 1, ablage, quelle, ziel); c--; }else{ throw new Exception("stop sliding"); } } } } The exception is never thrown. Any ideas?

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