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  • Logic for controll concurrent in block/method

    - by Hlex
    1)My environment is web application, I develop servlet to receive request. A) In some block/method i want to control concurrent to not greater than 5 B) if there are 5 request in that block , the new coming must wait up to 60 second then throws error C) if there are sleep/waiting request more then 30, the 31th request will be throwed an error How I do this? 2)(Optional Question) from above I have to distribute control logic to all clustered host. I plan to use hazelcast to share the control logic (e.g. current counter) I see they provide BlockingQueue & ExectorService but I have no idea how to use in my case. Please recommend if you have idea.

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  • using internationalization on list data

    - by singh
    i am using Struts2 in application. <s:iterator value="listObject"> <s:component template="abc.vm"> <s:param name="text" value="listValue" /> <s:param name="prefix" value="listIndex" /> </s:component> </s:iterator> listValue is a values of list. i am using iterator to traverse the list. now on listValue, i want to put here internationalization concept.so that all the list value can be display based on Locale which store in a list. please suggest!

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  • Antlr MismatchedSetException During Interpretation

    - by user1646481
    I am new to Antlr and I have defined a basic grammar using Antlr 3. The grammar compiles and ANTLRWorks generates the Parser and Lexer code without any problems. The grammar can be seen below: grammar i; @header { package i; } module : 'Module1'| 'Module2'; object : 'I'; objectType : 'Name'; filters : EMPTY | 'WHERE' module; table : module object objectType; STRING : ('a'..'z'|'A'..'Z')+; EMPTY : ' '; The problem is that when I interpret the table Parser I get a MismatchedSetException. This is due to having the EMPTY. As soon as I remove EMPTY from the grammar, the interpretation works. I have looked on the Antlr website and some other examples and the Empty space is ' '. I am not sure what to do. I need this EMPTY. As soon as I change the EMPTY to be the following: EMPTY : ''; instead of: EMPTY : ' '; It actually interprets it. However, I am getting the following Exception: Interpreting... [10:57:23] problem matching token at 1:4 NoViableAltException(' '@[1:1: Tokens : ( T__4 | T__5 | T__6 | T__7 | T__8 | T__9 | T__10 | T__11 | T__12 | T__13 | T__14 | T__15 | T__16 );]) [10:57:23] problem matching token at 1:9 NoViableAltException(' '@[1:1: Tokens : ( T__4 | T__5 | T__6 | T__7 | T__8 | T__9 | T__10 | T__11 | T__12 | T__13 | T__14 | T__15 | T__16 );]) When I take out the EMPTY, there are no problems at all. I hope you can help.

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  • Getting the instance when Constructor#newInstance throws?

    - by Shtééf
    I'm working on a simple plugin system, where third party plugins implement a Plugin interface. A directory of JARs is scanned, and the implementing classes are instantiated with Constructor#newInstance. The thing is, these plugins call back into register* methods of the plugin host. These registrations use the Plugin instance as a handle. My problem is how to clean up these registrations if the constructor decides to fail and throw halfway through. InvocationTargetException doesn't seem to have anything on it to get the instance. Is there a way to get at the instance of an exception throwing constructor? P.S.: It's typically strongly advised to users that the constructor not do anything, but in practice people are doing it any ways.

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  • How to avoid repetition when working with primitive types?

    - by I82Much
    I have the need to perform algorithms on various primitive types; the algorithm is essentially the same with the exception of which type the variables are. So for instance, /** * Determine if <code>value</code> is the bitwise OR of elements of <code>validValues</code> array. * For instance, our valid choices are 0001, 0010, and 1000. * We are given a value of 1001. This is valid because it can be made from * ORing together 0001 and 1000. * On the other hand, if we are given a value of 1111, this is invalid because * you cannot turn on the second bit from left by ORing together those 3 * valid values. */ public static boolean isValid(long value, long[] validValues) { for (long validOption : validValues) { value &= ~validOption; } return value != 0; } public static boolean isValid(int value, int[] validValues) { for (int validOption : validValues) { value &= ~validOption; } return value != 0; } How can I avoid this repetition? I know there's no way to genericize primitive arrays, so my hands seem tied. I have instances of primitive arrays and not boxed arrays of say Number objects, so I do not want to go that route either. I know there are a lot of questions about primitives with respect to arrays, autoboxing, etc., but I haven't seen it formulated in quite this way, and I haven't seen a decisive answer on how to interact with these arrays. I suppose I could do something like: public static<E extends Number> boolean isValid(E value, List<E> numbers) { long theValue = value.longValue(); for (Number validOption : numbers) { theValue &= ~validOption.longValue(); } return theValue != 0; } and then public static boolean isValid(long value, long[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } public static boolean isValid(int value, int[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } Is that really much better though? Any thoughts in this matter would be appreciated.

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  • How can I pipe a large amount of data as a runtime argument?

    - by Zombies
    Running an executable JAR on a linux platform here. The program it self works on a somewhat large amount of data, basically a list of URLs... could be up to 2k. Currently I get this from a simple DB call. But I was thinking that instead of creating a new mode and writing SQL to get a new result set and having to redploy everytime, I could just make the program more robust by passing in the result set (the list of URLs) that need to be worked on... so, within a linux environment, is there a pain-free/simple way to get the result set and pass it in dynamically? I know file i/o is one, but it doesn't seem to be effecient because each file has to be named, as well more logic to handle grabbing the correct file, creating a file with a unique name, etc.

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  • Scaling an Image in GWT

    - by Daniel
    Changing the size of an Image Widget in GWT changes the size of the image element, but does not rescale the image on the screen. Therefore, the following will not work: Image image = new Image(myImageResource); image.setHeight(newHeight); image.setWidth(newWidth); image.setPixelSize(newWidth, newHeight); This is because GWT implements its Image widget by setting the background-image of the HTML <img... /> element as the image, using CSS. How does one get the actual image to resize?

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  • How to log all sql going through JBoss datasource with log4j

    - by Ichorus
    I've looked at log4jdbc (which does not support datasources), p6spy which seems to be what I am looking for but it has not been updated since 2003 which makes me nervous and lists only JBoss 3.x (we use JBoss 5), and JAMon which seems heavyweight for what I am trying to accomplish (a simple log of all SQL statements running through a JBoss application server). I was hoping that JBoss itself would have a switch to log all the sql (as Websphere does) but I cannot find any documentation for it so that functionality might not exist.

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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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  • Using Comparable to compare objects and sorting them in a TreeMap

    - by arjacsoh
    II cannot understand how should the natural ordering of class be "consistent with equals" when implementing the Comparable interface. I deteted a flaw in my program and therefore I deteced that in the documentantion of the interface Comparable. My problem is that although two Objects are considered as distinct on the base of equals method, the TreeMap structure treats them as equal and consequently does not accept the second insert. The sample code is: public class Car implements Comparable<Car> { int weight; String name; public Car(int w, String n) { weight=w; name=n; } public boolean equals(Object o){ if(o instanceof Car){ Car d = (Car)o; return ((d.name.equals(name)) && (d.weight==weight)); } return false; } public int hashCode(){ return weight/2 + 17; } public String toString(){ return "I am " +name+ " !!!"; } public int compareTo(Car d){ if(this.weight>d.weight) return 1; else if(this.weight<d.weight) return -1; else return 0; } /*public int compareTo(Car d){ return this.name.compareTo(d.name); }*/ } public static void main(String[] args) { Car d1 = new Car(100, "a"); Car d2 = new Car(110, "b"); Car d3 = new Car(110, "c"); Car d4 = new Car(100, "a"); Map<Car, Integer> m = new HashMap<Car, Integer>(); m.put(d1, 1); m.put(d2, 2); m.put(d3, 3); m.put(d4, 16); for(Map.Entry<Car, Integer> me : m.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); TreeMap<Car, Integer> tm = new TreeMap<Car, Integer>(m); System.out.println("After Sorting: "); for(Map.Entry<Car, Integer> me : tm.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); } The output is : I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am c !!! 2 That is, that the object c has replaced (somewhat) object b. If I comment the original equals method and uncomment the second equals method, which compares the objects according name, the output is the expected: I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am b !!! 2 I am c !!! 3 Why does it come around in this way and what should I alter in order to insert and sort different objects with some attributes of equal value in a TreeMap?

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  • Safe to pass objects to C functions when working in JNI Invocation API?

    - by bubbadoughball
    I am coding up something using the JNI Invocation API. A C program starts up a JVM and makes calls into it. The JNIenv pointer is global to the C file. I have numerous C functions which need to perform the same operation on a given class of jobject. So I wrote helper functions which take a jobject and process it, returning the needed data (a C data type...for example, an int status value). Is it safe to write C helper functions and pass jobjects to them as arguments? i.e. (a simple example - designed to illustrate the question): int getStatusValue(jobject jStatus) { return (*jenv)->CallIntMethod(jenv,jStatus,statusMethod); } int function1() { int status; jobject aObj = (*jenv)->NewObject (jenv, aDefinedClass, aDefinedCtor); jobject j = (*jenv)->CallObjectMethod (jenv, aObj, aDefinedObjGetMethod) status = getStatusValue(j); (*jenv)->DeleteLocalRef(jenv,aObj); (*jenv)->DeleteLocalRef(jenv,j); return status; } Thanks.

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  • Commercial Website architecture question

    - by Maxime ARNSTAMM
    Hello everyone, I have to write an architecture case study but there are some things that i don't know, so i'd like some pointers on the following : The website must handle 5k simultaneous users. The backend is composed by a commercial software, some webservices, some message queues, and a database. I want to recommend to use Spring for the backend, to deal with the different elements, and to expose some Rest services. I also want to recommend wicket for the front (not the point here). What i don't know is : must i install the front and the back on the same tomcat server or two different ? and i am tempted to put two servers for the front, with a load balancer (no need for session replication in this case). But if i have two front servers, must i have two back servers ? i don't want to create some kind of bottleneck. Based on what i read on this blog a really huge charge is handle by one tomcat only for the first website mentionned. But i cannot find any info on this, so i can't tell if it seems plausible. If you can enlight me, so i can go on in my case study, that would be really helpful. Thanks :)

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  • JPA joined column allow every value...

    - by Fabio Beoni
    I'm testing JPA, in a simple case File/FileVersions tables (Master/Details), with OneToMany relation, I have this problem: in FileVersions table, the field "file_id" (responsable for the relation with File table) accepts every values, not only values from File table. How can I use the JPA mapping to limit the input in FileVersion.file_id only for values existing in File.id? My class are File and FileVersion: FILE CLASS @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="FILE_ID") private Long id; @Column(name="NAME", nullable = false, length = 30) private String name; //RELATIONS ------------------------------------------- @OneToMany(mappedBy="file", fetch=FetchType.EAGER) private Collection <FileVersion> fileVersionsList; //----------------------------------------------------- FILEVERSION CLASS @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="VERSION_ID") private Long id; @Column(name="FILENAME", nullable = false, length = 255) private String fileName; @Column(name="NOTES", nullable = false, length = 200) private String notes; //RELATIONS ------------------------------------------- @ManyToOne(fetch=FetchType.EAGER) @JoinColumn(name="FILE_ID", referencedColumnName="FILE_ID", nullable=false) private File file; //----------------------------------------------------- and this is the FILEVERSION TABLE CREATE TABLE `JPA-Support`.`FILEVERSION` ( `VERSION_ID` bigint(20) NOT NULL AUTO_INCREMENT, `FILENAME` varchar(255) NOT NULL, `NOTES` varchar(200) NOT NULL, `FILE_ID` bigint(20) NOT NULL, PRIMARY KEY (`VERSION_ID`), KEY `FK_FILEVERSION_FILE_ID` (`FILE_ID`) ) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=latin1

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  • Testing REST webservices

    - by anjanb
    HI There, My organization is working on building RESTful webservices on JBoss appserver. The QA team is used to testing SOAP webservices so far using SoapUI. SoapUI has a new version that has REST capabilities. We're considering using that. 1) Are there any publicly available RESTful services available on the net for free that someone could test ? 2) What tools are available(and used) for testing RESTful web services ? Thank you in Advance, BR, ~A

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  • Redirecting to a Facelet is not working when extending FaceletViewHandler

    - by Abel Morelos
    I'm overriding the handleRenderResponse method defined in com.sun.facelets.FaceletViewHandler: protected void handleRenderException(FacesContext context, Exception ex) I'm overriding this method so I can redirect the user to a custom error page (which contain the desired look and feel and other stuff). This is the way I'm trying to String errorPage = "/error.xhtml"; String contextPath = context.getExternalContext().getRequestContextPath(); String errorPagePath = contextPath+errorPage; context.getExternalContext().redirect(errorPagePath); The previous code is what I'm using to perform the redirect to this custom error page. Anyway, when I perform the redirect I'm prompted with a download dialog (this is with Internet Explorer, in Firefox the page does not display properly or as I would expect). I tried changing "/error.xhtml" to "/error.jsf" but in that case I get a 404 error. Somehow I think that the XHTML file is not being handled to the Facelets ViewHandler after the redirect, if I open the downloaded xhtml file I can see that the EL expressions were not resolved and the the ui tags were not handled. I don't have problems with other pages in my application, only when doing the redirect programatically. Important data from my web.xml: facelets.VIEW_MAPPINGS is set to *.xhtml javax.faces.DEFAULT_SUFFIX is set to .xhtml servlet-mapping for the "Faces Servlet" is ".jsf" and "/faces/"

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  • Display values inside a JList -

    - by sharon Hwk
    I have a method that returns a HashMap, and is defined as follows; public HashMap<Integer, Animal> allAnimal(){ return returnsAHashMap; } Animal will have the following values in its class: public Animal{ int animalID; String animalName; // i have declared getters/setters } I have a GUI screen which has a JList and it's defined as: l = new JList(); l.setModel(new AbstractListModel() { String[] v = new String[] {"animal id 1", "2", "3"}; public int getSize() { return v.length; } public Object getElementAt(int index) { return v[index]; } }); What I want to do is to display the AnimalID's in the JList. I need to find a way to call the allAnimal() method and display all its Animal Id's in the JList. How can i do this ?

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  • How to get parent node in Stanford's JavaNLP?

    - by roddik
    Hello. Suppose I have such chunk of a sentence: (NP (NP (DT A) (JJ single) (NN page)) (PP (IN in) (NP (DT a) (NN wiki) (NN website)))) At a certain moment of time I have a reference to (JJ single) and I want to get the NP node binding A single page. If I get it right, that NP is the parent of the node, A and page are its siblings and it has no children (?). When I try to use the .parent() method of a tree, I always get null. The API says that's because the implementation doesn't know how to determine the parent node. Another method of interest is .ancestor(int height, Tree root), but I don't know how to get the root of the node. In both cases, since the parser knows how to indent and group trees, it must know the "parent" tree, right? How can I get it? Thanks

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  • Arrays of different types

    - by Tyler
    Hi - Is it possible to have an array that contains two different types of data? I want to have an array that contains a double and also a string. I attempted: ArrayList<double><String> array; But that didn't work. Sorry for the silly question, but it has been a while since I have used something like this.. Can you refresh my memory on how would I declare and populate such an array? And then to take it a step further, I would like to sort the array by the double if possible? Thanks!

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  • Is javac enough to build an OSGi bundle?

    - by Chatanga
    To produce a bundle from source using a tool such as javac, you need to provide it with a linear classpath. Unfortunately, it won't work in some situations still perfectly legal from an OSGi point of view: dependencies with embedded JAR in them; same packages contained by different dependencies. Since javac doesn't understand OSGi metadata, I won't be able to simply but the dependencies in a classpath. A finer package grained approach seems necessary. How this problem is addressed by people using OSGi in an automated process (continuous integration)? Strangely, there is a lot of resources on the web on how to create bundle JAR (creating the metadata, creating the JAR) provided you have the classes/inner JAR to put inside, but very few things on how actually get theses classes compiled.

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  • How to reference another project in Eclipse with Google appengine project?

    - by virsir
    I am trying to extract some common classes out to be a common jar, and I want to reference it by the appengine project in Eclipse. It compiles well but could not run. The console just told that some classes from the common jar project could not be found. I know I can just export the project into a jar, but I may want to change it sometimes, so I prefer keep it dynamic. And I know maven may be an option but there is no official maven support for appengine, and I will not try to learn it. Then how can I make it work?

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  • Pageview implementation

    - by The Elite Gentleman
    Hi everyone I want to add a pageview feature on my current web application. This page view is based on the count of user viewing the page. It must be unique, i.e. I must not view a person's page 10000 times and record it as 10000 views, just record 1 view instead. My question is, should I base my pageview count on IP address? If not, what is/are the best approach in doing this? I know that if the person has logged in to my system, I can simply use the user id stored in the session and check on the record if the user has/hasn't viewed the page and update accordingly. But for "anonymous" viewers, what is the best approach? Thanks. PS How does Youtube does it?

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  • Can I close and reopen a socket?

    - by Roman
    I learned an example of usage of sockets. In this example a client sends a request to a server to open a socket and then the server (listening to a specific port) opens a socket and everything is fine, socket is "opened" from both sides (client and server). But it is still not clear to me how flexible is this stuff. For example, is it possible for the client to close an opened (from both ends) socket and to reopen it again (under condition that the server keeps the socket opened). Is it possible for the server to "know" that a socket was closed on the client side? Is it possible for the client to know that a socket was closed on the server side?

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