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  • How do JVM's implicit memory barriers behave when chaining constructors

    - by Joonas Pulakka
    Referring to my earlier question on incompletely constructed objects, I have a second question. As Jon Skeet pointed out, there's an implicit memory barrier in the end of a constructor that makes sure that final fields are visible to all threads. But what if a constructor calls another constructor; is there such a memory barrier in the end of each of them, or only in one being called from outside? That is, when the "wrong" solution is: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } And the correct one would be a factory method version: public class SafeListener { private final EventListener listener; private SafeListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public static SafeListener newInstance(EventSource source) { SafeListener safe = new SafeListener(); source.registerListener(safe.listener); return safe; } } Would the following work too, or not? public class MyListener { private final EventListener Listener; private MyListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public MyListener(EventSource source) { this(); source.register(listener); } }

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  • How to detect a pending JDO transaction?

    - by Stevko
    I believe I am getting JDO commit Exceptions due to the transactions nesting although I'm not sure. Will this detect the situation where I am starting a transaction when another is pending? PersistenceManager pm = PersistenceManagerFactory.get().getPersistenceManager(); assert pm.currentTransaction().isActive() == false : "arrrgh"; pm.currentTransaction().begin(); Is there a better or more reliable way?

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  • What design pattern will you choose ?

    - by MemoryLeak
    I want to design a class, which contains a procedure to achieve a goal. And it must follow some order to make sure the last method, let's say "ExecuteIt", to behave correctly. in such a case, what design patter will you use ? which can make sure that the user must call the public method according some ordering. If you really don't know what I am saying, then can you share me some concept of choosing a design patter, or what will you consider while design a class?

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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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  • 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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  • Why does Hibernate 2nd level cache only cache within a session?

    - by Synesso
    Using a named query in our application and with ehcache as the provider, it seems that the query results are tied to the session. Any attempt to access the value from the cache for a second time results in a LazyInitializationException We have set lazy=true for the following mapping because this object is also used by another part of the system which does not require the reference... and we want to keep it lean. <class name="domain.ReferenceAdPoint" table="ad_point" mutable="false" lazy="false"> <cache usage="read-only"/> <id name="code" type="long" column="ad_point_id"> <generator class="assigned" /> </id> <property name="name" column="ad_point_description" type="string"/> <set name="synonyms" table="ad_point_synonym" cascade="all-delete-orphan" lazy="true"> <cache usage="read-only"/> <key column="ad_point_id" /> <element type="string" column="synonym_description" /> </set> </class> <query name="find.adpoints.by.heading">from ReferenceAdPoint adpoint left outer join fetch adpoint.synonyms where adpoint.adPointField.headingCode = ?</query> Here's a snippet from our hibernate.cfg.xml <property name="hibernate.cache.provider_class">net.sf.ehcache.hibernate.SingletonEhCacheProvider</property> <property name="hibernate.cache.use_query_cache">true</property> It doesn't seem to make sense that the cache would be constrained to the session. Why are the cached queries not usable outside of the (relatively short-lived) sessions?

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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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  • Webview can't type in, is that because of missing setting?

    - by Pentium10
    I have an Android application that connects to Facebook to request authorization of an Application. I use the following setting in the WebView, but once the view is loaded, I can't type in login details. What I am missing? WebView webview; webview = (WebView) findViewById(R.id.facebookview); webview.getSettings().setJavaScriptEnabled(true); webview.setWebViewClient(new FacebookWebViewClient()); webview .loadUrl("http://www.connect.facebook.com/login.php?return_session=1&nochrome=1&fbconnect=1&extern=2&connect_display=popup&api_key=" + FConnect.API_KEY + "&v=1.0&next=" + FConnect.SUCCESS_URL + "%3Ffb_login%26fname%3D_opener&cancel_url=" + FConnect.CANCEL_URL + "%23fname%3D_opener%26%257B%2522t%2522%253A3%252C%2522h%2522%253A%2522fbCancelLogin%2522%252C%2522sid%2522%253A%25220.741%2522%257D&channel_url=" + FConnect.XD_RECEIVER);

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  • Creating 3DES key from bytes

    - by AO
    I create a triple DES key from the a byte array ("skBytes") but when calling getEncoded on the triple DES key ("sk") and comparing it to the byte array, they differ! They are almost the same if you look at the console output, though. How would I create a triple DES key that is exactly as "skBytes"? byte[] skBytes = {(byte) 0x41, (byte) 0x0B, (byte) 0xF0, (byte) 0x9B, (byte) 0xBC, (byte) 0x0E, (byte) 0xC9, (byte) 0x4A, (byte) 0xB5, (byte) 0xCE, (byte) 0x0B, (byte) 0xEA, (byte) 0x05, (byte) 0xEF, (byte) 0x52, (byte) 0x31, (byte) 0xD7, (byte) 0xEC, (byte) 0x2E, (byte) 0x75, (byte) 0xC3, (byte) 0x1D, (byte) 0x3E, (byte) 0x61}; DESedeKeySpec keySpec = new DESedeKeySpec(skBytes); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DESede"); SecretKey sk = keyFactory.generateSecret(keySpec); for(int i = 0; i < skBytes.length; i++) { System.out.println("(sk.getEncoded()[i], skBytes[i]) = (" + sk.getEncoded()[i] +", " + skBytes[i] + ")"); } Console output: (sk.getEncoded()[i], skBytes[i]) = (64, 65) (sk.getEncoded()[i], skBytes[i]) = (11, 11) (sk.getEncoded()[i], skBytes[i]) = (-15, -16) (sk.getEncoded()[i], skBytes[i]) = (-101, -101) (sk.getEncoded()[i], skBytes[i]) = (-68, -68) (sk.getEncoded()[i], skBytes[i]) = (14, 14) (sk.getEncoded()[i], skBytes[i]) = (-56, -55) (sk.getEncoded()[i], skBytes[i]) = (74, 74) (sk.getEncoded()[i], skBytes[i]) = (-75, -75) (sk.getEncoded()[i], skBytes[i]) = (-50, -50) (sk.getEncoded()[i], skBytes[i]) = (11, 11) (sk.getEncoded()[i], skBytes[i]) = (-22, -22) (sk.getEncoded()[i], skBytes[i]) = (4, 5) (sk.getEncoded()[i], skBytes[i]) = (-17, -17) (sk.getEncoded()[i], skBytes[i]) = (82, 82) (sk.getEncoded()[i], skBytes[i]) = (49, 49) (sk.getEncoded()[i], skBytes[i]) = (-42, -41) (sk.getEncoded()[i], skBytes[i]) = (-20, -20) (sk.getEncoded()[i], skBytes[i]) = (47, 46) (sk.getEncoded()[i], skBytes[i]) = (117, 117) (sk.getEncoded()[i], skBytes[i]) = (-62, -61) (sk.getEncoded()[i], skBytes[i]) = (28, 29) (sk.getEncoded()[i], skBytes[i]) = (62, 62) (sk.getEncoded()[i], skBytes[i]) = (97, 97)

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  • How would I set up this enum to return the image I want?

    - by Justen
    I'm trying to set up this enum so that it has the ability to return the correct image, though I'm struggling with a way to incorporate the context since it is in a separate class. public enum CubeType { GREEN { public Drawable getImage() { return Context.getResources().getDrawable( R.drawable.cube_green ); } }; abstract public Drawable getImage(); } The error I'm getting is: Cannot make a static reference to the non-static method getResources() from the type Context

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  • pluto or jetspeed on google app engine?

    - by Patrick Cornelissen
    I am trying to build something "portlet server"-ish on the google app engine. (as open source) I'd like to use the JSR168/286 standards, but I think that the restrictions of the app engine will make it somewhere between tricky and impossible. Has anyone tried to run jetspeed or an application that uses pluto internally on the google app engine? Based on my current knowledge of portlets and the google app engine I'm anticipating these problems: A war file with portlets is from the deployment standpoint more or less a complete webapp (yes, I know that it doesn't really work without a portal server). The war file may contain it's own web.xml etc. This makes deployment on the app engine rather difficult, because the apps are not visible to each other, so all portlet containing archives need to be included in the war file of the deployed "app engine based portal server". The "portlets" are (at least in liferay) started as permanent servlet processes, based on their portlet.xmls and web.xmls which is located in the same spot for every portlet archive that is loaded. I think this may be problematic in the app engine, because everything is in one big "web app", so it may be tricky to access the portlet.xmls from each archive. This prevents a 100% compatibility in my opinion. Is here anyone who has any experience with the combination of portlets and the app engine? Do you think it's feasible to modify jetspeed, pluto or any other portlet container to be able to run it on the app engine?

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  • How can I find out if two arguments are instances of the same, but unknown class?

    - by Ingmar
    Let us say we have a method which accepts two arguments o1 and o2 of type Object and returns a boolean value. I want this method to return true only when the arguments are instances of the same class, e.g.: foo(new Integer(4),new Integer(5)); Should return true, however: foo(new SomeClass(), new SubtypeSomeClass()); should return false and also: foo(new Integer(3),"zoo"); should return false. I believe one way is to compare the fully qualified class names: public boolean foo(Object o1, Object o2){ Class<? extends Object> c1 = o1.getClass(); Class<? extends Object> c2 = o2.getClass(); if(c1.getName().equals(c2.getName()){ return true;} return false; } An alternative conditional statement would be : if (c1.isAssignableFrom(c2) && c2.isAssignableFrom(c1)){ return true; } The latter alternative is rather slow. Are there other alternatives to this problem?

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  • NoSuchMessageException: No message found

    - by adisembiring
    Hi .... I try to learn Spring MVC 3.0 validation. but I got NoSuchMessageException: No message found under code 'name.required' for locale 'en_US' error message when form submted. I have create message.properties in src/message.properties and the content of that file is: name.required = User Name is required password.required = Password is required gender.required = Gender is required I have set ResourceBundleMessageSource in my app-servlet.xml <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource" p:basename="messages" /> My validator code is: @Component("registrationValidator") public class RegistrationValidator implements Validator { @Override public boolean supports(Class<?> clazz) { return RegistrationCommand.class.isAssignableFrom(clazz); } @Override public void validate(Object target, Errors errors) { RegistrationCommand registrationCommand = (RegistrationCommand) target; ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "name.required"); ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "password.required"); ValidationUtils.rejectIfEmpty(errors, "gender", "gender.required"); ValidationUtils.rejectIfEmpty(errors, "country", "country.required"); //ValidationUtils.rejectIfEmpty(errors, "community", "community.required"); ValidationUtils.rejectIfEmptyOrWhitespace(errors, "description", "description.required"); if (registrationCommand.getCommunity().length == 0) { errors.rejectValue("community", "community.required"); } } } and JSP Page is: <form:form commandName="registrationCommand"> <p class="name"> <label for="name">Name</label> <form:input path="name" /> <form:errors path="name" cssClass="error"></form:errors> </p> <p class="password"> <label for="password">Password</label> <form:password path="password" /> <form:errors path="password" cssClass="error"></form:errors> </p> <p class="gender"> <label>Gender</label> <form:radiobutton path="gender" value="M" label="M" /> <form:radiobutton path="gender" value="F" label="F" /> <form:errors path="gender" cssClass="error"></form:errors> </p> <p class="submit"> <input type="submit" value="Submit" /> </p> </form:form>

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  • JavaEE Application Server or Lightweight Container?

    - by Jeff Storey
    Let me preface this by saying this is not an actual situation of mine but I'm asking this question more for my own knowledge and to get other people's inputs here. I've used both Spring and EJB3/JBoss, and for the smaller types of applications I've built, Spring (+Tomcat when needed) has been much simpler to use. However, when scaling up to larger applications that require things like load balancing and clustering, is Spring still a viable solution? Or is it time to turn to a solution like EJB3/JBoss when you start to get big enough to need that? I'm not sure if I've scoped the problem well enough to get a good answer, so please let me know. Thanks, Jeff

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  • How to set the email protocol in JavaMail

    - by Dusk
    If I need to get inbox messages by passing request from servlets to javamail API , how can I know the protocol in which to retrieve inbox messages? Do I have to state the protocol in request URL? I've already checked in gmail, where they haven't stated any protocol, then How can I get inbox messages based on particular protocol like: POP3 or IMAP

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  • OpenCMS - Best approach for showing rotating references

    - by user197127
    Hi, I would like to add on the right column of my site a rotating references section. Each reference would have some text + name of person + company name. It does not need to be structured (open text is also ok). I would then want opencms to rotate between 20 difference references each time a page is displayed. I can keep a session scope counter holding which reference we last showed. I need a way to manage the references (users not programmers) over time. My question is which would be the best way to do so? Thanks

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  • Security when using GWT RPC

    - by gerdemb
    I have an POJO in Google Web Toolkit like this that I can retrieve from the server. class Person implements Serializable { String name; Date creationDate; } When the client makes changes, I save it back to the server using the GWT RemoteServiceServlet like this: rpcService.saveObject(myPerson,...) The problem is that the user shouldn't be able to change the creationDate. Since the RPC method is really just a HTTP POST to the server, it would be possible to modify the creationDate by changing the POST request. A simple solution would be to create a series of RPC functions like changeName(String newName), etc., but with a class with many fields would require many methods for each field, and would be inefficient to change many fields at once. I like the simplicity of having a single POJO that I can use on both the server and GWT client, but need a way to do it securely. Any ideas?

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  • JPA getSingleResult() or null

    - by Eugene Ramirez
    Hi. I have an insertOrUpdate method which inserts an Entity when it doesn't exist or update it if it does. To enable this, I have to findByIdAndForeignKey, if it returned null insert if not then update. The problem is how do I check if it exists? So I tried getSingleResult. But it throws an exception if the public Profile findByUserNameAndPropertyName(String userName, String propertyName) { String namedQuery = Profile.class.getSimpleName() + ".findByUserNameAndPropertyName"; Query query = entityManager.createNamedQuery(namedQuery); query.setParameter("name", userName); query.setParameter("propName", propertyName); Object result = query.getSingleResult(); if(result==null)return null; return (Profile)result; } but "getSingleResult" throws an exception. Thanks

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  • How can I give a variable to an action listener?

    - by Roman
    I have a static variable partner in the class. And I want to set a value of these variable whenever a radio button is pressed. This is the code I tried to use: for (String playerName: players) { option = new JRadioButton(playerName, false); option.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partner = playerName; } }); partnerSelectionPanel.add(option); group.add(option); } The problem here is that the actionPerformed does not see the variable playerName created in the loop. How can I pass this variable to the actionListener?

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  • Difference between try-finally and try-catch

    - by Vijay Kotari
    What's the difference between try { fooBar(); } finally { barFoo(); } and try { fooBar(); } catch(Throwable throwable) { barFoo(throwable); // Does something with throwable, logs it, or handles it. } I like the second version better because it gives me access to the Throwable. Is there any logical difference or a preferred convention between the two variations? Also, is there a way to access the exception from the finally clause?

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