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  • Why does appending "" to a String save memory?

    - by hsmit
    I used a variable with a lot of data in it, say String data. I wanted to use a small part of this string in the following way: this.smallpart = data.substring(12,18); After some hours of debugging (with a memory visualizer) I found out that the objects field smallpart remembered all the data from data, although it only contained the substring. When I changed the code into: this.smallpart = data.substring(12,18)+""; ..the problem was solved! Now my application uses very little memory now! How is that possible? Can anyone explain this? I think this.smallpart kept referencing towards data, but why? UPDATE: How can I clear the big String then? Will data = new String(data.substring(0,100)) do the thing?

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  • Writing a Servlet that checks to see if JSP's exist and forwards to another JSP if they aren't

    - by Omar Kooheji
    I've beeb tasked with writing a servlet that intercepts a call to and JSP in a specific directoy, check that the file exists and if it does just forwarding to that file, if if doesn't I'm to forward to a default JSP. I've setup the web.xml as follows: <servlet> <description>This is the description of my J2EE component</description> <display-name>This is the display name of my J2EE component</display-name> <servlet-name>CustomJSPListener</servlet-name> <servlet-class> ... CustomJSPListener</servlet-class> <load-on-startup>1</load-on-startup> </servlet> ... <servlet-mapping> <servlet-name>CustomJSPListener</servlet-name> <url-pattern>/custom/*</url-pattern> </servlet-mapping> And the doGet method of the servlet is as follows: public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { logger.debug(String.format("Intercepted a request for an item in the custom directory [%s]",request.getRequestURL().toString())); String requestUri = request.getRequestURI(); // Check that the file name contains a text string if (requestUri.toLowerCase(Locale.UK).contains("someText")){ logger.debug(String.format("We are interested in this file [%s]",requestUri)); File file = new File(requestUri); boolean fileExists = file.exists(); logger.debug(String.format("Checking to see if file [%s] exists [%s].",requestUri,fileExists)); // if the file exists just forward it to the file if (fileExists){ getServletConfig().getServletContext().getRequestDispatcher( requestUri).forward(request,response); } else { // Otherwise redirect to default.jsp getServletConfig().getServletContext().getRequestDispatcher( "/custom/default.jsp").forward(request,response); } } else { // We aren't responsible for checking this file exists just pass it on to the requeseted jsp getServletConfig().getServletContext().getRequestDispatcher( requestUri).forward(request,response); } } This seems to result in an error 500 from tomcat, I think this is because the servlet is redirecting to the same folder which is then being intercepted again by the servlet, resulting in an infinite loop. Is there a better way to do this? I'm lead to believe that I could use filters to do this, but I don't know very much about them.

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  • best way to pick a random subset from a collection?

    - by Tom
    I have a set of objects in a Vector from which I'd like to select a random subset (e.g. 100 items coming back; pick 5 randomly). In my first (very hasty) pass I did an extremely simple and perhaps overly clever solution: Vector itemsVector = getItems(); Collections.shuffle(itemsVector); itemsVector.setSize(5); While this has the advantage of being nice and simple, I suspect it's not going to scale very well, i.e. Collections.shuffle() must be O(n) at least. My less clever alternative is Vector itemsVector = getItems(); Random rand = new Random(System.currentTimeMillis()); // would make this static to the class List subsetList = new ArrayList(5); for (int i = 0; i < 5; i++) { // be sure to use Vector.remove() or you may get the same item twice subsetList.add(itemsVector.remove(rand.nextInt(itemsVector.size()))); } Any suggestions on better ways to draw out a random subset from a Collection?

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  • simpledateformat parsing date with 'Z' literal

    - by DanInDC
    I am trying to parse a date that looks like this: 2010-04-05T17:16:00Z This is a valid date per http://www.ietf.org/rfc/rfc3339.txt. The 'Z' literal "imply that UTC is the preferred reference point for the specified time." If I try to parse it using SimpleDateFormat and this pattern: yyyy-MM-dd'T'HH:mm:ss It will be parsed as a Mon Apr 05 17:16:00 EDT 2010 SimpleDateFormat is unable to parse the string with these patterns: yyyy-MM-dd'T'HH:mm:ssz yyyy-MM-dd'T'HH:mm:ssZ I can explicitly set the TimeZone to use on the SimpleDateFormat to get the expected output, but I don't think that should be necessary. Is there something I am missing? Is there an alternative date parser?

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  • What can I access in Androids Native libraries? And How?

    - by Donal Rafferty
    I am completely new to the NDK. I have done a couple of the tutorials including the hello from jni one and another one that calculates the sum of two numbers. They involved using cygwin and the ndk to create the library so file and I have a bit of a grasp on how to insert my own libraries into the libraries layer of Android. I have now been asked to access the native libraries on Android and see what I can use them for. My question is can I do this? The STABLE-APIS.txt document is a bit vague and mentions the following as Stable C++ API's in Android 1.5 cstddef new utility stl_pair.h Does that mean I can access them? If so then how do I go about it? I dont think that following the tutorials I have already done would be any help? Any pointers on how to do this or links to tutorials etc.. would be greatly appreciated

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  • Parsing complex string using regex

    - by wojtek_z
    My regex skills are not very good and recently a new data element has thrown my parser into a loop Take the following string "+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write" Previously I had the following for my regex : [+\\-/] Which would turn the result into USER=Bob Smith GROUP=Admin FUNCTION=Read FUNCTION=Write FUNCTION=Read But now I have values with dashes in them which is causing bad output New string looks like "+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write/FUNCTION=Read-Write" Which gives me the following result , and breaks the key = value structure. USER=Bob Smith GROUP=Admin FUNCTION=Read FUNCTION=Write FUNCTION=Read Write Can someone help me formulate a valid regex for handling this or point me to some key / value examples. Basically I need to be able to handle + - / signs in order to get combinations.

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  • JBoss ignores @RemoteBinding annotation

    - by tputkonen
    I would like to specify JNDI name for an EJB3 bean using annotation, but JBoss 5.1.0 GA seems to ignore the annotation completely. Bean's annotations are: @Remote(Foobar.class) @Stateless(name = "Foobar") @TransactionManagement(TransactionManagementType.BEAN) @RemoteBinding(jndiBinding="ejb/Foobar") public class FoobarBean implements Foobar { ... I tested deploying also using @RemoteBindings annotation, but the result was same: @RemoteBindings({@RemoteBinding(jndiBinding="ejb/Foobar")}) The bean does not get bound to JNDI with the specified name, and the log file doesn't give any clues.

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  • Javas Math.sin() produces NaN all the time

    - by milan1612
    Forgive me if this is a dumb beginners problem, but I really don't get it. I have a member variable declared like so: public Double Value; When I assign 3.14159265 to Value and try to compute the sine of it, this happens: system.out.println(Value.toString()); //outputs 3.14159265 Value = Math.sin(Value); system.out.println(Value.toString()); //outputs NaN In fact, this happens with every single value I tried - even with 0! Math.sin() seems to always produce NaN as a result, regardless of the arguments value. The docs say: If the argument is NaN or an infinity, then the result is NaN. But my argument is clearly not NaN or infinity! What the heck is happening there?

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  • Why aren't APT generated classes being compiled by Eclipse?

    - by yamsha
    In my Eclipse project I'm using a third-party annotation processor, Hibernate Metamodel Generator to be exact. The annotation processor works as expected and generates files as specified by the spec. These files are generated inside the directory of the Eclipse project under a "gen" folder. In the project properties this is correctly reflected since two source folders exist - "src" and "gen." However, when the project is built for some reason all the [generated] sources under "gen" are not compiled (checking the "bin" directory I only see .class file from the "src" directory). Does anyone know why this is happening?

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  • Hibernate: Dirty Checking and Only Update of Dirty Attributes?

    - by jens
    Hello Experts, in "good old JDBC days" I wrote a lot of SQL Queries that did very targeted updates of only the "attributes/members" that were actually changed: For Example having an object with the following members: public String name; public String address; public Date date; If only date was changed in some Business Method I would only issue an SQL UPDATE for the date member. ==It seems however (thats my "impression" of hibernate) that when working with a standard Hibernate mapping (mapping the full class), even updates of only one single member lead to a full update of the object in SQL Statements generated by Hibernate. My Questions are: 1.) Is this observation correct, that hibernate DOES NOT intelligently check (in a fully mapped class), what member(s) where changed and then only issue updates for the specific changed members, but rather always will update (in the generated SQL Update Statement) all mapped members (of a class), even if they were not changed (in case the object is dirty due to one member being dirty...) 2.) What can I do to make Hibernate only update those members, that have been changed? I am searching for a solution to have hibernate only update the member that actually changed. (I know hibernate does some big work on doing dirty-checking, but as far as I know this dirtychecking is only relevant to identify if the object as whole is dirty, not what single member is dirty.) Thank you very much! Jens

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  • SLF4J, Common Logging, console output

    - by Mauricio Scheffer
    I have this 3rd party library that has: slf4j-api-1.5.5.jar slf4j-jdk14-1.5.5.jar jcl-over-slf4j-1.5.5.jar I want to write some tests against this library and see its log output, and I don't want to add any more logging libraries (no log4j or anything else). I understand that SLF4J and Common Logging are both logging abstractions so I probably need to write my own simple concrete logger (or maybe not, since jcl-over-slf4j includes org.apache.commons.logging.impl.SimpleLog?). If so, what interfaces should I implement, and more importantly, how do I set up SL4J/Common Logging to use my logger in my test? I read in the SLF4J docs that I have to modify the StaticLoggerBinder class... does that really mean that I actually have to download SLF4J sources, modify the class and recompile it?

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  • Spring transaction demarcation causes new Hibernate session despite use of OSIV

    - by Kelly Ellis
    I'm using Hibernate with OpenSessionInViewInterceptor so that a single Hibernate session will be used for the entire HTTP request (or so I wish). The problem is that Spring-configured transaction boundaries are causing a new session to be created, so I'm running into the following problem (pseudocode): Start in method marked @Transactional(propagation = Propagation.SUPPORTS, readOnly = false) Hibernate session #1 starts Call DAO method to update object foo; foo gets loaded into session cache for session #1 Call another method to update foo.bar, this one is marked @Transactional(propagation = Propagation.REQUIRED, readOnly = false) Transaction demarcation causes suspension of current transaction synchronization, which temporarily unbinds the current Hibernate session Hibernate session #2 starts since there's no currently-existing session Update field bar on foo (loading foo into session cache #2); persist to DB Transaction completes and method returns, session #1 resumes Call yet another method to update another field on foo Load foo from session cache #1, with old, incorrect value of bar Update field foo.baz, persist foo to DB foo.bar's old value overwrites the change we made in the previous step Configuration looks like: <bean name="openSessionInViewInterceptor" class="org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor" autowire="byName"> <property name="flushModeName"> <value>FLUSH_AUTO</value> </property> </bean> <bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="myDataSource" /> </bean> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="useTransactionAwareDataSource" value="true" /> <property name="mappingLocations"> <list> <value>/WEB-INF/xml/hibernate/content.hbm.xml</value> </list> </property> <property name="lobHandler"> <ref local="oracleLobHandler" /> </property> <!--property name="entityInterceptor" ref="auditLogInterceptor" /--> <property name="hibernateProperties" ref="HibernateProperties" /> <property name="dataSource" ref="myDataSource" /> </bean> I've done some debugging and figured out exactly where this is happening, here is the stack trace: Daemon Thread [http-8080-1] (Suspended (entry into method doUnbindResource in TransactionSynchronizationManager)) TransactionSynchronizationManager.doUnbindResource(Object) line: 222 TransactionSynchronizationManager.unbindResource(Object) line: 200 SpringSessionSynchronization.suspend() line: 115 DataSourceTransactionManager(AbstractPlatformTransactionManager).doSuspendSynchronization() line: 620 DataSourceTransactionManager(AbstractPlatformTransactionManager).suspend(Object) line: 549 DataSourceTransactionManager(AbstractPlatformTransactionManager).getTransaction(TransactionDefinition) line: 372 TransactionInterceptor(TransactionAspectSupport).createTransactionIfNecessary(TransactionAttribute, String) line: 263 TransactionInterceptor.invoke(MethodInvocation) line: 101 ReflectiveMethodInvocation.proceed() line: 171 JdkDynamicAopProxy.invoke(Object, Method, Object[]) line: 204 $Proxy14.changeVisibility(Long, ContentStatusVO, ContentAuditData) line: not available I can't figure out why transaction boundaries (even "nested" ones - though here we're just moving from SUPPORTS to REQUIRED) would cause the Hibernate session to be suspended, even though OpenSessionInViewInterceptor is in use. When the session is unbound, I see the following in my logs: [2010-02-16 18:20:59,150] DEBUG org.springframework.transaction.support.TransactionSynchronizationManager Removed value [org.springframework.orm.hibernate3.SessionHolder@7def534e] for key [org.hibernate.impl.SessionFactoryImpl@693f23a2] from thread [http-8080-1]

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  • Play framework 1.x on Tomcat - httpOnly cookies

    - by aishwarya
    I'm setting application.session.httpOnly=true in the application.conf and generating a war file and deploying on tomcat. I still see the cookie generated as HttpOnly=No and it is editable. This is an issue with play 1.x running on tomcat 6 (i.e. servlet api 2.x). Apparently, http only flag for cookies was only introduced in servlet 3.0 and so is only available in tomcat 7+ has anybody identified a workaround for this so far (so I could have http only cookies for play 1.x on tomcat 6.x ) ? the httpOnly flag on context in tomcat only works for tomcat's jsessionid cookie... also, can I run a play 1.x app on servlet 3.0 ? PS: This was also posted on the play framework's google groups but we did not receive a response and so posting on SO.

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  • BlazeDS StreamingAMF: How to detect when flex client closes the connection?

    - by Adrian Pirvulescu
    Hello, I have a Flex application that connects to a BlazeDS server using the StreamingAMF channel. On the server-side the logic is handled by a custom adapter that extends ActionScriptAdapter and implements FlexSessionListener and FlexClientListener interfaces. I am asking how can I detect which "flex-client" has closed a connection when for example the user is closing the browser? (so I can clean some infos inside the database) I tried using the following: 1. To manually manage the command messages: @Override public Object manage(final CommandMessage commandMessage) { switch (commandMessage.getOperation()) { case CommandMessage.SUBSCRIBE_OPERATION: System.out.println("SUBSCRIBE_OPERATION = " + commandMessage.getHeaders()); break; case CommandMessage.UNSUBSCRIBE_OPERATION: System.out.println("UNSUBSCRIBE_OPERATION = " + commandMessage.getHeaders()); break; } return super.manage(commandMessage); } But the clientID's are always different from the ones that came. 2. Listening for sessionDestroyed and clientDestroyed events @Override public void clientCreated(final FlexClient client) { client.addClientDestroyedListener(this); System.out.println("clientCreated = " + client.getId()); } @Override public void clientDestroyed(final FlexClient client) { System.out.println("clientDestroyed = " + client.getId()); } @Override public void sessionCreated(final FlexSession session) { System.out.println("sessionCreated = " + session.getId()); session.addSessionDestroyedListener(this); } @Override public void sessionDestroyed(final FlexSession session) { System.out.println("sessionDestroyed = " + session.getId()); } But those sessionDestroyed and clientDestroyed methods are never called. :(

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  • Checking if date parsing is correct

    - by Javi
    Hello, I have this code for checking whether the Date is OK or not, but it's not ckecking all the cases. For example when text="03/13/2009" as this date doesn't exist in the format "dd/MM/yyyy" it parses the date as 03/01/2010. Is there any way to change this behaviour and getting an exception when I try to parse a Date which is not correct? What's the best way to do this validation? public static final String DATE_PATTERN = "dd/MM/yyyy"; public static boolean isDate(String text){ SimpleDateFormat formatter = new SimpleDateFormat(DATE_PATTERN); ParsePosition position = new ParsePosition(0); formatter.parse(text, position); if(position.getIndex() != text.length()){ return false; }else{ return true; } } Thanks.

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  • Integrating Tomcat7 and Eclipse Helios on Snow Leopard

    - by ktm5124
    I am trying to write a "Hello World" web application using Tomcat and Eclipse, in order to familiarize myself with building Tomcat projects. So far I've gleaned from Google searches that I need to install Eclipse Web Tools Platform (WTP) to go ahead with it. But when I go to Help-Install New Software I can't find any software update site that is hosting WTP. My default "Available Software Sites" are Helios, Mylyn for Eclipse Helios, and the Eclipse Project Updates. Do I need to add a new software update site to install WTP? If so, what is the URL? If not, where can I find WTP? Thanks in advance.

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  • Has anybody use javafx on CDC J9?

    - by 4NDR01D3
    Is that possible?? I mean, I have an already working project that runs in windows mobile using the J9 virtual machine for CDC. My user interface there is using AWT and it works fine and it looks OK, but been honest it doesn't take real advantage of the devices were is running... So I start reading about JavaFX and that looks really cool, but all that I see about mobiles there is applied to CLDC, MIDP, etc. but my application is already running on CDC J9 and I can't change this cause I'm using a Derby database on it. So, my plan is to code the GUI again, but keeping the logic of the application. So do you guys think javafx is the way to go? or, am I wasting my time learning javafx for this project. Thanks in advance, Gustavo.

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  • How to increase detail band height dynamically

    - by Chandu
    Hi All, I am using ireport. My requirement is to increase the detail band height dynamically when the text field has more data , are there any settings to increase to it? I am using one textfield in the detail band when it has more information(words), it is displaying only some information.i.e the words are being cut off. Depending on the detail band height the words are displaying.I would like to increase the band hieght dynamically when the text field has more data. Please advice me on this regard. Regards, Chandu

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  • Unexpected JAXB error

    - by Mark Lewis
    Hello, From the documentation it's clear I need to use the following to get a simple unmarshalling to occur from my XML file/schema: JAXBContext jc = JAXBContext.newInstance("PackageName"); where PackageName is my package name. I've looked on google for a bit to no avail, to find out why I'm then getting this runtime error: Line:Col[2:142]:cvc-elt.1: Cannot find the declaration of element 'myconfig'. Line:Col[2:142]:unexpected element (uri:"http://www.w3.org", local:"myconfig"). Expected elements are <{}myconfig> Caught UnmarshalException This occurs at the top of all my class files, including the ones the XJC plugin for eclipse created for me (which I then moved out of PackageName.PackageName which it automatically created): package PackageName; so why is this error occurring?

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