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  • What is design principle behind Servlets being Singleton

    - by Sandeep Jindal
    A servlet container "generally" create one instance of a servlet and different threads of the same instance to serve multiple requests. (I know this can be changed using deprecated SingleThreadModel and other features, but this is the usual way). I thought, the simple reason behind this is performance gain, as creating threads is better than creating instances. But it seems this is not the reason. On the other hand, creating instances have little advantage that developers never have to worry about thread safety. I am trying to understand the reason for this decision over the trade-off of thread-safety.

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  • How to override j_security_check in glassfish?

    - by Alex B
    I'm currently using FORM based authentication in glassfish v2.1 to log users in and it works fine. I want to switch to ProgrammaticLogin and I want to be able to get the initially requested URL (i.e. before redirecting to login page) and use it in my programmatic login code so that the user is redirected back to the requested page after authentication. I've seen the source code for j_security_check - in my case that's FormAuthenticator (catalina codebase) and it saves the initial request in a SavedRequest object in the session but that session is a StandardSession rather than HttpSession so there's no direct way to access it. Or should I change the authentication mechanism from FORM to something else? Thanks!

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  • J2ME TextField Exception

    - by Bob
    When I instantiate a textField, I have a number in it that I want to be the default text. The problem is, I can't seem to be able to place that value into the textfield without getting an error. The strange thing about it is that the same TextField is what I use to set the value of the variable containing the number. TextField myTF = new TextField("Number", value, 10, TextField.NUMERIC); When I run this code, I receive an exception stating that value doesn't match the constraints of TextField.NUMERIC. However, when I check the vale of the value of the variable, I get the following output: value = 1234567890 value.length() = 10 The value is set by the same TextField, saved to the phone that I am working on, and when loaded from the phone's settings, throws an exception.

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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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  • Can't run jUnit with Eclipse

    - by KimKha
    I use new Eclipse. Create demo test with jUnit (I added default jUnit library built-in Eclipse). Then I write this code: import junit.framework.*; import org.junit.Test; public class SimpleTest extends TestCase { public SimpleTest(String name) { super(name); } public final void main(String method){ } @Test public final void testSimpleTest() { int answer = 2; assertEquals((1+1), answer); } } But it doesn't run. In the Debug tab: org.eclipse.jdt.internal.junit.runner.RemoteTestRunner at localhost:52754 Thread [main] (Suspended (exception ClassNotFoundException)) URLClassLoader$1.run() line: not available [local variables unavailable] AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method] Launcher$AppClassLoader(URLClassLoader).findClass(String) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available Launcher$AppClassLoader.loadClass(String, boolean) line: not available Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available How can I solve this?

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  • Android Lightweight HTML Template Engine

    - by Anthoni Gardner
    Hello, I am after a very lightweight template engine that supports / can be embedded inside Android programs. I've looked at the MiniTemplator (I think that is how you spell it) and that looks great but it loads in only from file and I need to load templates from string and I am not fully confident in changing that code lol. Can anyone recommend a very lightweight (preferably no jars, single source files etc) that I can use ? I do not need it to parse XML or anything like, just normal HTML files with keywords embedded into them betwee %% tags etc. Regards Anthoni

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  • Traceroute comparison and statistics

    - by ben-casey
    I have a number of traceroutes that i need to compare against each other but i dont know the best way to do it, ive been told that hash maps are a good technique but i dont know how to implement them on my code. so far i have: FileInputStream fstream = new FileInputStream("traceroute.log"); // Get the object of DataInputStream DataInputStream in = new DataInputStream(fstream); BufferedReader br = new BufferedReader(new InputStreamReader(in)); String strLine; // reads lines in while ((strLine = br.readLine()) != null) { System.out.println(strLine); } and the output looks like this: Wed Mar 31 01:00:03 BST 2010 traceroute to www.bbc.co.uk (212.58.251.195), 30 hops max, 40 byte packets 1 139.222.0.1 (139.222.0.1) 0.873 ms 1.074 ms 1.162 ms 2 core-from-cmp.uea.ac.uk (10.0.0.1) 0.312 ms 0.350 ms 0.463 ms 3 ueaha1btm-from-uea1 (172.16.0.34) 0.791 ms 0.772 ms 1.238 ms 4 bound-from-ueahatop.uea.ac.uk (193.62.92.71) 5.094 ms 4.451 ms 4.441 ms 5 gi0-3.norw-rbr1.eastnet.ja.net (193.60.0.21) 4.426 ms 5.014 ms 4.389 ms 6 gi3-0-2.chel-rbr1.eastnet.ja.net (193.63.107.114) 6.055 ms 6.039 ms * 7 lond-sbr1.ja.net (146.97.40.45) 6.994 ms 7.493 ms 7.457 ms 8 so-6-0-0.lond-sbr4.ja.net (146.97.33.154) 8.206 ms 8.187 ms 8.234 ms 9 po1.lond-ban4.ja.net (146.97.35.110) 8.673 ms 6.294 ms 7.668 ms 10 bbc.lond-sbr4.ja.net (193.62.157.178) 6.303 ms 8.118 ms 8.107 ms 11 212.58.238.153 (212.58.238.153) 6.245 ms 8.066 ms 6.541 ms 12 212.58.239.62 (212.58.239.62) 7.023 ms 8.419 ms 7.068 ms what i need to do is compare this trace against another one just like it and look for the changes and time differences etc, then print a stats page.

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  • Closing Connections on asynchronous messaging in JMS

    - by The Elite Gentleman
    Hi Everyone! I have created a JMS wrapper (similar to Springs JmsTemplate since I'm not using Springs) and I was wondering: If I setup asynchronous messaging, when is a good time to close connections and JMS relates resources (so that the Connection Factory in the Resource Pool can be available)? Thanks Here's the source code for receiving JMS messages public Message receive() throws JMSException { QueueConnection connection = null; QueueSession session = null; QueueReceiver consumer = null; try { // TODO Auto-generated method stub connection = factory.createQueueConnection(); if (connection != null && getExceptionListener() != null) { connection.setExceptionListener(getExceptionListener()); } session = connection.createQueueSession(isSessionTransacted(), getAcknowledgeMode()); consumer = session.createReceiver(queue); if (getMessageListener() != null) { consumer.setMessageListener(getMessageListener()); } //Begin connection.start(); if (getMessageListener() == null) { return null; } return receive(session, consumer); } catch (JMSException e) { // TODO: handle exception logger.error(e.getLocalizedMessage(), e); throw e; } finally { JMSUtil.closeMessageConsumer(consumer); JMSUtil.closeSession(session, false); //false = don't commit. JMSUtil.closeConnection(connection, true); //true = stop before close. } As you can see, if getMessageListener() != null then apply it to the MessageConsumer. Am I doing this correctly? The same approach has also been taken for JMS Topic.

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  • Logic for controll concurrent in block or funciton

    - by Hlex
    1)My environment is web application, I accept large request from selvets. 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 most then 30,throws 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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  • PPR in tr:selectOneChoice does not work

    - by Nhut Le
    Hi, I have a simple testing page that test my PPR on a selectOneChoice component. when select a value from selectOnechoice 1, the selected value will display on a output label and also reset the selected value and the other selectOneChoice. However, it prints the selected values to the label correctly but it can't set the selected value for the other selectOneChoice. and Here are my page and my value change event method. <tr:form id="nhutForm"> <tr:selectOneChoice id="one" value="#{nhutTestBean.one}" autoSubmit="true" immediate="true" valueChangeListener="#{nhutTestBean.onMyValueChanged}"> <tr:selectItem label="0" value="0"/> <tr:selectItem label="1" value="1"/> <tr:selectItem label="2" value="2"/> <tr:selectItem label="3" value="3"/> </tr:selectOneChoice> <tr:selectOneChoice id="two" value="#{nhutTestBean.two}" partialTriggers="one"> <f:selectItems value="#{nhutTestBean.myList}"/> </tr:selectOneChoice> <tr:outputText id="nhutTextBox" value="hello: #{nhutTestBean.output}" partialTriggers="one"/></tr:form> and my valueChangeEvent method: public void onMyValueChanged(ValueChangeEvent event) { this.setOutput((String)event.getNewValue()); this.setTwo((String)event.getNewValue()); } One thing I realize is that it calls my setTwo twice, the first the set the correct values, but the second time set it to null so that nothing would be selected for the two drop down box. please help. thank you so much.

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  • Paypal - DoExpressCheckoutPayment null pointer

    - by user969894
    String nvpstr = "&TOKEN=" + token + "&PAYERID=" + payerID + "&PAYMENTREQUEST_0_PAYMENTACTION=" + paymentType + "&PAYMENTREQUEST_0_AMT=" + finalPaymentAmount + "&PAYMENTREQUEST_0_CURRENCYCODE=" + currencyCodeType + "&IPADDRESS=" + serverName; Having done an earlier call to SetExpressCheckout, I had to change a few parameter names because Paypal had changed it in the documentation but not in the code from the integration wizard. Now for DoExpressCheckoutPayment I've modified a few but I get a null pointer at strAck: HashMap nvp = httpcall("DoExpressCheckoutPayment", nvpstr); String strAck = nvp.get("ACK").toString(); if (strAck.equalsIgnoreCase("Success")) { return nvp; } Not sure what is wrong, any suggestions for debugging this or possible solutions?

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  • Method return type

    - by sarah xia
    Hi, In my company, a system is designed to have 3 layers. Layer1 is responsible for business logic handling. Layer3 is calling back end systems. Layer2 sits between the two layers so that layer1 doesn't need to know about the back end systems. To replay information from layer3, layer2 needs to define interface to layer1. For example, layer1 wants to check if a PIN from user is correct. It calls layer2 checkPin() method and then layer2 calls the relevant back end system. The checkPin() results could be: correctPin, inCorrectPin and internalError. At the moment, we defined the return type 'int'. So if layer2 returns 0, it means correctPin; if 1 is returned, it means inCorrectPin; if 9 is returned it means internalError. It works. However I feel a bit uneasy about this approach. Are there better ways to do it? For example define an enum CheckPinResult{CORRECT_PIN,INCORRECT_PIN,INTERNAL_ERROR}, and return CheckPinResult type? Thanks, Sarah

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  • Why does my JButton look differently of different computers?

    - by Roman
    I use JButtons in my application. They need to have different colors. First I used that btn.setBackground(col);. It works on my computer and on another computer my button just gray (not red, as it's supposed to be). Trying to solve this problem I decided to use images. I do it in the following way: tmp = new JButton(newIcon); Again, it works fine on my computer and on another computer I see just gray buttons. Does anybody have any ideas what can be the reason of the problem and how it can be solved? I heard it can be related to "look-and-feel of the native system". But I do not know what it means and what should I do if it is the case? Can anybody pleas, help me with that?

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  • Hibernate orm for a view

    - by EugeneP
    How do you ORM a view? Is there any difference with a table in terms of reverse engineering? In my case, I have a whole pile of joined tables that will be read-only in an application. So, if I need sort of a 1 Object with all collections in proper order, instead of long chains of relationships - collection with another etc, it'll be simpler. What do you think and how do you accomplish this?

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  • Deploy maven generated site on Google Code svn?

    - by xamde
    Using a google code svn as a basic maven repository is easy. However, using mvn site:deploy efficiently on google code seems hard. So far, I found only these solutions: * Deploy to a local file:/// and use a PERL script to delete the old and copy the new * Use wagen-svn to deploy. This is very slow (hours!) and does not delete old files * Plus all mime-types are wrong I am looking for a solution that allows new developers in my projects to check out the current source and just use it, without requiring to install PERL or learn weird steps to perform or wait hours.

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  • Webapp: safetly update a shared List/Map in the AppContext

    - by al nik
    I've Lists and Maps in my WebAppContext. Most of the time these are only read by multiple Threads but sometimes there's the need to update or add some data. I'm wondering what's the best way to do this without incurring in a ConcurrentModificationException. I think that using CopyOnWriteArrayList I can achieve what I want in terms of - I do not have to sync on every read operation- I can safety update the list while other threads are reading it. Is this the best solution? What about Maps?

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  • Using JLabels as pseudo buttons.

    - by FreeThinker
    Currently I am developing a small todo list manager and would like to use labels in place of buttons on the 'context' bar. If any one could provide me with information on how I could go about doing this I would appreciate it greatly.

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  • How do these user/userParam references relate to the Customer and Account lookups?

    - by marmalade
    In the following code example how do the user/userParam references relate to the Customer and Account lookups and what is the relationship between Customer and Account? // PersistenceManager pm = ...; Transaction tx = pm.currentTransaction(); User user = userService.currentUser(); List<Account> accounts = new ArrayList<Account>(); try { tx.begin(); Query query = pm.newQuery("select from Customer " + "where user == userParam " + "parameters User userParam"); List<Customer> customers = (List<Customer>) query.execute(user); query = pm.newQuery("select from Account " + "where parent-pk == keyParam " + "parameters Key keyParam"); for (Customer customer : customers) { accounts.addAll((List<Account>) query.execute(customer.key)); } } finally { if (tx.isActive()) { tx.rollback(); } }

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