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  • readObject() vs. readResolve() to restore transient fields

    - by Joonas Pulakka
    According to Serializable javadoc, readResolve() is intended for replacing an object read from the stream. But is it OK to use it for restoring transient fields, like so: private Object readResolve() { transientField = something; return this; } as opposed to using readObject(): private void readObject(ObjectInputStream s) { s.defaultReadObject(); transientField = something; } Is there any reason to choose one over other, when used to just restore transient fields?

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  • jpa @version optimistic locking

    - by cometta
    I loaded same entity record on 2 separate browser window then press submit (hibernate template.merge), version number incremented for both browser window, but never caught any problem with optimistic lock.. so how to test this? my save() look like this hibernatetemplate().merge(..); setJPAObject(null); //reset after save

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  • Detecting client disconnect in tomcat servlet?

    - by Seth
    How can I detect that the client side of a tomcat servlet request has disconnected? I've read that I should do a response.getOutputStream().print(), then a response.getOutputStream().flush() and catch an IOException, but is there a way I can detect this without writing any data?

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  • RSA encryption/ Decryption in a client server application

    - by user308806
    Hi guys, probably missing something very straight forward on this, but please forgive me, I'm very naive! Have a client server application where the client identifies its self with an RSA encrypted username & password. Unfortunately I'm getting a "bad padding exception: data must start with zero" when i try to decrypt with the public key on the client side. I'm fairly sure the key is correct as I have tested encrypting with public key then decrypting with private key on the client side with no problems at all. Just seems when I transfer it over the connection it messses it up somehow?! Using PrintWriter & BufferedReader on the sockets if thats of importance. EncodeBASE64 & DecodeBASE64 encode byte[] to 64base and vice versa respectively. Any ideas guys?? Client side: Socket connectionToServer = new Socket("127.0.0.1", 7050); InputStream in = connectionToServer.getInputStream(); DataInputStream dis = new DataInputStream(in); int length = dis.readInt(); byte[] data = new byte[length]; // dis.readFully(data); dis.read(data); System.out.println("The received Data*****************************************"); System.out.println("The length of bits "+ length); System.out.println(data); System.out.println("***********************************************************"); Decryption d = new Decryption(); byte [] ttt = d.decrypt(data); System.out.print(data); String ss = new String(ttt); System.out.println("***********************"); System.out.println(ss); System.out.println("************************"); Server Side: in = connectionFromClient.getInputStream(); OutputStream out = connectionFromClient.getOutputStream(); DataOutputStream dataOut = new DataOutputStream(out); LicenseList licenses = new LicenseList(); String ValidIDs = licenses.getAllIDs(); System.out.println(ValidIDs); Encryption enc = new Encryption(); byte[] encrypted = enc.encrypt(ValidIDs); byte[] dd = enc.encrypt(ValidIDs); String tobesent = new String(dd); //byte[] rsult = enc.decrypt(dd); //String tt = String(rsult); System.out.println("The sent data**********************************************"); System.out.println(dd); String temp = new String(dd); System.out.println(temp); System.out.println("*************************************************************"); //BufferedWriter bf = new BufferedWriter(OutputStreamWriter(out)); //dataOut.write(ValidIDs.getBytes().length); dataOut.writeInt(ValidIDs.getBytes().length); dataOut.flush(); dataOut.write(encrypted); dataOut.flush(); System.out.println("********Testing**************"); System.out.println("Here are the ids:::"); System.out.println(licenses.getAllIDs()); System.out.println("**********************"); //bw.write("it is working well\n");

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  • Unique task queue task names only for active duration

    - by antony.trupe
    I want to guarantee that a task is not in a task queue more then once, so I generate a unique name based on it's payload. But, that task name is reserved for up to 7 days, which is not what I want; I only want it reserved for the duration the task is queued; it could be immediately re-queued. Once a Task with name N is written, any subsequent attempts to insert a Task named N will fail. Eventually (at least seven days after the task successfully executes), the task will be deleted and the name N can be reused. Is there a way to check if the named task is already in the queue then add it if it's not? Or a totally different approach?

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  • Help in debugging the string concatenation code

    - by mithun1538
    I have a code to concatenate strings. However, for some reason, the final string is not a combination of the required strings. Consider the following code : //cusEmail is of type String[] String toList = ""; for(i=0; i < cusEmail.length - 1; i++) { toList.concat(cusEmail[i]); toList.concat("; "); System.out.println(cusEmail[i]); } toList.concat(cusEmail[i]); System.out.println(toList); The first sout statement displays the strings in cusEmail[i] correctly. However, once concatenated, the second sout displays a blank / empty. Any reason for this? Am i concatenating it correctly?

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  • Resolve naming conflict in included XSDs for JAXB compilation

    - by Jason Faust
    I am currently trying to compile with JAXB (IBM build 2.1.3) a pair of schema files into the same package. Each will compile on it's own, but when trying to compile them together i get a element naming conflict due to includes. My question is; is there a way to specify with an external binding a resolution to the naming collision. Example files follow. In the example the offending element is called "Common", which is defined in both incA and incB: incA.xsd <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/" xmlns:tns="http://www.example.org/" elementFormDefault="qualified"> <complexType name="TypeA"> <sequence> <element name="ElementA" type="string"></element> </sequence> </complexType> <!-- Conflicting element --> <element name="Common" type="tns:TypeA"></element> </schema> incB.xsd <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/" xmlns:tns="http://www.example.org/" elementFormDefault="qualified"> <complexType name="TypeB"> <sequence> <element name="ElementB" type="int"></element> </sequence> </complexType> <!-- Conflicting element --> <element name="Common" type="tns:TypeB"></element> </schema> A.xsd <?xml version="1.0" encoding="UTF-8"?> <schema targetNamespace="http://www.example.org/" elementFormDefault="qualified" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.example.org/"> <include schemaLocation="incA.xsd"></include> <complexType name="A"> <sequence> <element ref="tns:Common"></element> </sequence> </complexType> </schema> B.xsd <?xml version="1.0" encoding="UTF-8"?> <schema targetNamespace="http://www.example.org/" elementFormDefault="qualified" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.example.org/"> <include schemaLocation="incB.xsd"></include> <complexType name="B"> <sequence> <element ref="tns:Common"></element> </sequence> </complexType> </schema> Compiler error when both are compiled from one evocation of xjb: [ERROR] 'Common' is already defined line 9 of file:/C:/temp/incB.xsd [ERROR] (related to above error) the first definition appears here line 9 of file:/C:/temp/incA.xsd (For reference, this is a generalization to resolve an issue with compiling the OAGIS8 SP3 package)

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  • Vector ArrayIndexOutOfBounds

    - by Esmond
    I'm having an ArrayIndexOutofBounds exception with the following code. The exception is thrown at the line where Node nodeJ = vect.get(j) but it does not make sense to me since j is definitely smaller than i and Node nodeI = vect.get(i) does not throw any exception. any help is appreciated. public static Vector join(Vector vect) throws ItemNotFoundException { Vector<Node> remain = vect; for (int i = 1; i < vect.size(); i++) { Node nodeI = vect.get(i); for (int j = 0; j < i; j++) {//traverse the nodes before nodeI Node nodeJ = vect.get(j); if (nodeI.getChild1().getSeq().equals(nodeJ.getSeq())) { nodeI.removeChild(nodeJ); nodeI.setChild(nodeJ); remain.remove(j); } if (nodeI.getChild2().getSeq().equals(nodeJ.getSeq())) { nodeI.removeChild(nodeJ); nodeI.setChild(nodeJ); remain.remove(j); } } } return remain; }

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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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  • Changing order of children of an SWT Composite

    - by Alexey Romanov
    In my case I have two children of a SashForm, but the question applies to all Composites and different layouts. class MainWindow { Sashform sashform; Tree child1 = null; Table child2 = null; MainWindow(Shell shell) { sashform = new SashForm(shell, SWT.NONE); } // Not called from constructor because it needs data not available at that time void CreateFirstChild() { ... Tree child1 = new Tree(sashform, SWT.NONE); } void CreateSecondChild() { ... Table child2 = new Table(sashform, SWT.NONE); } } I don't know in advance in what order these methods will be called. How can I make sure that child1 is placed on the left, and child2 on the right? Alternately, is there a way to change their order as children of sashform after they are created? Currently my best idea is to put in placeholders like this: class MainWindow { Sashform sashform; private Composite placeholder1; private Composite placeholder2; Tree child1 = null; Table child2 = null; MainWindow(Shell shell) { sashform = new SashForm(shell, SWT.NONE); placeholder1 = new Composite(sashform, SWT.NONE); placeholder2 = new Composite(sashform, SWT.NONE); } void CreateFirstChild() { ... Tree child1 = new Tree(placeholder1, SWT.NONE); } void CreateSecondChild() { ... Table child2 = new Table(placeholder2, SWT.NONE); } }

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  • Resized image degrades in quality.

    - by Venkats
    I resized an image using Java2D Graphics class. But it doesn't look right. BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type); Graphics2D g = resizedImage.createGraphics(); g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null); g.dispose(); Is it possible to scale an image without introducing artifacts?

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  • Is there a useDirtyFlag option for Tomcat 6 cluster configuration?

    - by kevinjansz
    In Tomcat 5.0.x you had the ability to set useDirtyFlag="false" to force replication of the session after every request rather than checking for set/removeAttribute calls. <Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster" managerClassName="org.apache.catalina.cluster.session.SimpleTcpReplicationManager" expireSessionsOnShutdown="false" **useDirtyFlag="false"** doClusterLog="true" clusterLogName="clusterLog"> ... The comments in the server.xml stated this may be used to make the following work: <% HashMap map = (HashMap)session.getAttribute("map"); map.put("key","value"); %> i.e. change the state of an object that has already been put in the session and you can be sure that this object still be replicated to the other nodes in the cluster. According to the Tomcat 6 documentation you only have two "Manager" options - DeltaManager & BackupManager ... neither of these seem to allow this option or anything like it. In my testing the default setup: <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> where you get the DeltaManager by default, it's definitely behaving as useDirtyFlag="true" (as I'd expect). So my question is - is there an equivalent in Tomcat 6? Looking at the source I can see a manager implementation "org.apache.catalina.ha.session.SimpleTcpReplicationManager" which does have the useDirtyFlag but the javadoc comments in this state it's "Tomcat Session Replication for Tomcat 4.0" ... I don't know if this is ok to use - I'm guessing not as it's not mentioned in the main cluster configuration documentation.

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  • jQuery, get table cell at specific index

    - by Jarek Waliszko
    Hello, I know that I can get first or last table cell (ex for last row) using jquery expression like below: first cell: $('#table tr:last td:first') or last cell: $('#table tr:last td:last') Can I get cell at specific index, for example index 2, using similliar expression: ex: $('#table tr:last td:[2]')... Regards.

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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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  • How to set an empty value using XPath?

    - by Ricardo
    Using this xml example: <templateitem itemid="5"> <templateitemdata>%ARN%</templateitemdata> </templateitem> <templateitem itemid="6"> <templateitemdata></templateitemdata> </templateitem> I am using XPath to get and set Node values. The code I am using to get the nodes is: private static Node ***getNode***(Document doc, String XPathQuery) throws XPathExpressionException { XPath xpath = XPathFactory.newInstance().newXPath(); XPathExpression expr = xpath.compile(XPathQuery); Object result = expr.evaluate(doc, XPathConstants.NODESET); NodeList nodes = (NodeList) result; if(nodes != null && nodes.getLength() >0) return nodes.item(0); throw new XPathExpressionException("No node list found for " + XPathQuery); } To get %ARN% value: "//templateitem[@itemid=5]/templateitemdata/text()" and with the getNode method I can get the node, and then call the getNodeValue(). Besides getting that value, I would like to set templateitemdata value for the "templateitem[@itemid=6]" since its empty. But the code I use can't get the node since its empty. The result is null. Do you know a way get the node so I can set the value?

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  • Update database settings in properties file in Spring

    - by mvg
    Hi all, I am trying to create a Database Manager page which shows the database details on page load and updates the database settings when the user press submit I followed this tutorial and set the database settings in properties file. I managed to update the database settings in properties file programmatically. When I retrieved the database settings using the following code DriverManagerDataSource databaseSource = (DriverManagerDataSource)context.getBean("dataSource"); databaseSource.getUsername(); I managed to get the old value and unable to get the new value This is the mapping in applicationContext.xml file <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"> <value>classpath:/bundle/database.properties</value> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="${jdbc.driverClassName}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean> I checked the properties file and found it to be updated with the latest input. What am I missing? Thanks in advance P.S I am using JSF1.2 with Spring 3 Update Just making my requirement simple. I am creating a setparate dbsettings page, so that when user wishes to connect to different database he/she can just enter the details in dbsettings page and connect

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  • OPTICS Clustering algorithm. How to get the best epsilon

    - by Marco Galassi
    I am implementing a project which needs to cluster geographical points. OPTICS algorithm seems to be a very nice solution. It needs just 2 parameters as input(MinPts and Epsilon), which are, respectively, the minimum number of points needed to consider them as a cluster, and the distance value used to compare if two points are in can be placed in same cluster. My problem is that, due to the extreme variety of the points, I can't set a fixed epsilon. Just look at the image below. The same points structure but in a different scale would result very different. Suppose to set MinPts=2 and epsilon = 1Km. On the left, the algorithm would create 2 clusters(red and blue), but on the right it would create one single cluster containing all of the points(red), but I would like to obtain 2 clusters even on the right. So my question is: is there any kind of way to calculate dynamically the epsilon value to get this result? Thank you very much and excuse my for my poor english. Marco

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  • 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } The code that is executing is really simple and basically just this class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful! Well, the design is arguably flawed. The threads implement Genetic-Programming or GP, a type of learning algorithm. Each thread analyzes advanced trends makes predictions. If the thread ever completes, the learning is lost. That said, I was hoping that sleep() would allow me to share some of the resources while one thread isn't "learning"

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  • How do I execute a sequence of servlets?

    - by Legend
    I have some servlets that act as individual URLs for populating a database for some dummy testing. Something of the form: public class Populate_ServletName extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { resp.setContentType("text/plain"); //Insert records //Print confirmation } } I have about 6 such servlets which I want to execute in a sequence. I was thinking of using setLocation to set the next page to be redirected but was not sure if this is the right approach because the redirects should happen after the records have been inserted. Specifically, I am looking for something like this: public class Populate_ALL extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { resp.setContentType("text/plain"); //Call Populate_1 //Call Populate_2 //Call Populate_3 //... } } Any suggestions?

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  • What tool/framework to use for technical documentation?

    - by Pangea
    We develop products and frameworks to be used with in our organization. I am looking for programmer friendly documentation tools. I have researched on few options sometime back but couldn't decide which one to use. I am looking for suggestions from the people who already used these tools. docbook: springframework and hibernate use this format and this looks good. but I believe they have customized the default xslt/stylesheet. Can I copy and use their xslt and css (ofcourse with colors and images changed). Can I integrate the doc generation using maven? wiki: this is not friendly to the technical document writers and the documentation doesn't look professional. versioning is also not possible I believe word docs: this is what we use currently but it is hard to link and reuse common documents. DITA?

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