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  • Recommendations for an in memory database vs thread safe data structures

    - by yx
    TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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  • MySQL best usage in Tomcat?

    - by mabuzer
    Which one is better way of using MySQL in Tomcat : A) assign a DB connection for user as long as it's session is valid. [OR] B) open connection to DB, on every request come to server and when it's done close that. ?

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  • Sharing beans from contextListener -- dispatcher servlet

    - by Ernest
    Hello! ok, i have another question now. I have a bunch of beans loaded succesfully in applicationContext.xml, which loads from web.xml: contextConfigLocation applicationContext.xml org.springframework.web.context.ContextLoaderListener Here are is the bean defined in applicationContext.xml that i want to share: it loads other beans (DAOs) which are initialized with hibernet. I need to acces catalogFacadeTarget from the dispatcherServlet, declared in web.xml: dispatcher org.springframework.web.servlet.DispatcherServlet 1 <servlet-mapping> <servlet-name>dispatcher</servlet-name> <url-pattern>*.htm</url-pattern> </servlet-mapping> and configured dispatcher-servlet.xml like this: welcome There! in the property called catalogFacadeImpl. If you need the entire applicationCOntext.xml, web.xml, and dispatcher-servlet.xml please let me know. From what i read, i should be able to share beans if i declared them in the contextConfigLocation configuration file. Thank you very much in advance.

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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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  • Nhibernate fires SQL commands

    - by Chris
    Hi all, when updating an entity A, NHibernate also send an SQL update command for some other entity B. A and B are not related. Just before saving entity A, the parent of entity B is loaded via a SQLQuery. Then, when accessed, B is lazy loaded (part of a collection). If I save entity A an update statement for entity B is generated as well. How can that be, that when saving an entity, another entity loaded before but is not related to the entity saved, is updated as well?! Can I somehow track where the update comes from? Btw. I am using an save event listener. Could it be that this is always triggered for entity loaded, even though they are not saved explicitly? public class EntitySaveEventListener : NHibernate.Event.Default.DefaultSaveEventListener { protected override object PerformSaveOrUpdate(SaveOrUpdateEvent e) { //auditing return base.PerformSaveOrUpdate(e); } } Update (sorry for providing not enough info): I tracked it down a bit. A select stateement on a entity called address is executed (is it lazy loaded by a parent). Then I create a new entity called Request. Right before saving this entity a session flush is called which updates the address, even though I did not call save or update on the address. Address is a collection within Request. <class name="Request" table="Request"> <bag name="addresses" access="field" cascade="all-delete-orphan" where="IsDeleted = 0"> <key column="RequestId"/> <one-to-many class="Address"/> </bag> ... // address is fetched only NHibernate.SQL: 2010-02-17 11:47:21,306 [21] DEBUG NHibernate.SQL [(null)] - SELECT addresses0_.RequestId as ServiceP8_3_, .... // session flushed here // address is updated NHibernate.SQL: 2010-02-17 11:47:34,306 [21] DEBUG NHibernate.SQL [(null)] - Batch commands: command 0:UPDATE Address SET Street = @p0, ..... Would the address be updated automatically when it is manipulated somehow even though it is not explicitly saved via it's parent (cascade)?

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  • What's the best way to retrieve two pieces of data from an XML file?

    - by Morinar
    I've got an XML document that is in either a pre or post FO transformed state that I need to extract some information from. In the pre-case, I need to pull out two tags that represent the pageWidth and pageHeight and in the post case I need to extract the page-height and page-width parameters from a specific tag (I forget which one it is off the top of my head). What I'm looking for is an efficient/easily maintainable way to grab these two elements. I'd like to only read the document a single time fetching the two things I need. I initially started writing something that would use BufferedReader + FileReader, but then I'm doing string searching and it gets messy when the tags span multiple lines. I then looked at the DOMParser, which seems like it would be ideal, but I don't want to have to read the entire file into memory if I could help it as the files could potentially be large and the tags I'm looking for will nearly always be close to the top of the file. I then looked into SAXParser, but that seems like a big pile of complicated overkill for what I'm trying to accomplish. Anybody have any advice? Or simple implementations that would accomplish my goal? Thanks.

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  • How do I determine whether I am going "forward" or "backward" through my History in GWT?

    - by Stephen Cagle
    I am looking at History and History JavaDocs in GWT and I notice that there is no way to tell whether the forward or backward button was pressed (either pragmatically or by the user). The "button press" is handled by your registered addValueChangeHandler, but the only thing passed to the handler is a string on your history stack. There is no indication as to whether the "History" is moving "back" (using the back arrow button) or "forward" (using the right arrow button). Is there any way to determine this?

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  • Autocompletion in Eclipse for Roo project

    - by niklassaers
    Hi guys, I've got a Roo project where I've made a couple of entities, and when I load up the project in Eclipse it loads up fine, but if I i.e. make an instance MyEntity entity and then write entity. I don't get any of my properties (i.e. getMyField) in the autocompletion list. If I write entity.getMyField() it compiles fine, that is taken care of by the aspects. How do I enable autocompletion for functions generated by the aspects? Cheers Nik

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  • i have some problem with left join JPQL

    - by Dora
    there is something wrong with ths way i use left join, and i dont understand what am i doing wrong. can you see it? select distinct r.globalRuleId, r.ruleId, sv.validFrom, pm.moduleId, nvl(min(rai.failedOnRegistration),0) from TRules r, TSlaVersions sv, TModuleFormulas mv, TPendingModule pm, left join TRulesAdditionalInfo rai on r.ruleId = rai.ruleId where r.slaVersionId = sv.slaVersionId and r.formulaId = mv.pk.formulaId and mv.pk.moduleId = pm.moduleId group by r.globalRuleId, r.ruleId, sv.validFrom, pm.moduleId order by pm.moduleId

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  • Getting a nicely formatted timestamp without lots of overhead?

    - by Brad Hein
    In my app I have a textView which contains real-time messages from my app, as things happen, messages get printed to this text box. Each message is time-stamped with HH:MM:SS. Up to now, I had also been chasing what seemed to be a memory leak, but as it turns out, it's just my time-stamp formatting method (see below), It apparently produces thousands of objects that later get gc'd. For 1-10 messages per second, I was seeing 500k-2MB of garbage collected every second by the GC while this method was in place. After removing it, no more garbage problem (its back to a nice interval of about 30 seconds, and only a few k of junk typically) So I'm looking for a new, more lightweight method for producing a HH:MM:SS timestamp string :) Old code: /** * Returns a string containing the current time stamp. * @return - a string. */ public static String currentTimeStamp() { String ret = ""; Date d = new Date(); SimpleDateFormat timeStampFormatter = new SimpleDateFormat("hh:mm:ss"); ret = timeStampFormatter.format(d); return ret; }

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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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  • JPA Entity Manager resource handling

    - by chiragshahkapadia
    Every time I call JPA method its creating entity and binding query. My persistence properties are: <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/> <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.SingletonEhCacheProvider"/> <property name="hibernate.cache.use_second_level_cache" value="true"/> <property name="hibernate.cache.use_query_cache" value="true"/> And I am creating entity manager the way shown below: emf = Persistence.createEntityManagerFactory("pu"); em = emf.createEntityManager(); em = Persistence.createEntityManagerFactory("pu").createEntityManager(); Is there any nice way to manage entity manager resource instead create new every time or any property can set in persistence. Remember it's JPA. See below binding log every time : 15:35:15,527 INFO [AnnotationBinder] Binding entity from annotated class: * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: * = * 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [QueryBinder] Binding Named query: 15:35:15,527 INFO [EntityBinder] Bind entity com.* on table * 15:35:15,542 INFO [HibernateSearchEventListenerRegister] Unable to find org.hibernate.search.event.FullTextIndexEventListener on the classpath. Hibernate Search is not enabled. 15:35:15,542 INFO [NamingHelper] JNDI InitialContext properties:{} 15:35:15,542 INFO [DatasourceConnectionProvider] Using datasource: 15:35:15,542 INFO [SettingsFactory] RDBMS: and Real Application Testing options 15:35:15,542 INFO [SettingsFactory] JDBC driver: Oracle JDBC driver, version: 9.2.0.1.0 15:35:15,542 INFO [Dialect] Using dialect: org.hibernate.dialect.Oracle10gDialect 15:35:15,542 INFO [TransactionFactoryFactory] Transaction strategy: org.hibernate.transaction.JDBCTransactionFactory 15:35:15,542 INFO [TransactionManagerLookupFactory] No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recomm ended) 15:35:15,542 INFO [SettingsFactory] Automatic flush during beforeCompletion(): disabled 15:35:15,542 INFO [SettingsFactory] Automatic session close at end of transaction: disabled 15:35:15,542 INFO [SettingsFactory] JDBC batch size: 15 15:35:15,542 INFO [SettingsFactory] JDBC batch updates for versioned data: disabled 15:35:15,542 INFO [SettingsFactory] Scrollable result sets: enabled 15:35:15,542 INFO [SettingsFactory] JDBC3 getGeneratedKeys(): disabled 15:35:15,542 INFO [SettingsFactory] Connection release mode: auto 15:35:15,542 INFO [SettingsFactory] Default batch fetch size: 1 15:35:15,542 INFO [SettingsFactory] Generate SQL with comments: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL updates by primary key: disabled 15:35:15,542 INFO [SettingsFactory] Order SQL inserts for batching: disabled 15:35:15,542 INFO [SettingsFactory] Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory 15:35:15,542 INFO [ASTQueryTranslatorFactory] Using ASTQueryTranslatorFactory 15:35:15,542 INFO [SettingsFactory] Query language substitutions: {} 15:35:15,542 INFO [SettingsFactory] JPA-QL strict compliance: enabled 15:35:15,542 INFO [SettingsFactory] Second-level cache: enabled 15:35:15,542 INFO [SettingsFactory] Query cache: enabled 15:35:15,542 INFO [SettingsFactory] Cache region factory : org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge 15:35:15,542 INFO [RegionFactoryCacheProviderBridge] Cache provider: net.sf.ehcache.hibernate.SingletonEhCacheProvider 15:35:15,542 INFO [SettingsFactory] Optimize cache for minimal puts: disabled 15:35:15,542 INFO [SettingsFactory] Structured second-level cache entries: disabled 15:35:15,542 INFO [SettingsFactory] Query cache factory: org.hibernate.cache.StandardQueryCacheFactory 15:35:15,542 INFO [SettingsFactory] Statistics: disabled 15:35:15,542 INFO [SettingsFactory] Deleted entity synthetic identifier rollback: disabled 15:35:15,542 INFO [SettingsFactory] Default entity-mode: pojo 15:35:15,542 INFO [SettingsFactory] Named query checking : enabled 15:35:15,542 INFO [SessionFactoryImpl] building session factory 15:35:15,542 INFO [SessionFactoryObjectFactory] Not binding factory to JNDI, no JNDI name configured 15:35:15,542 INFO [UpdateTimestampsCache] starting update timestamps cache at region: org.hibernate.cache.UpdateTimestampsCache 15:35:15,542 INFO [StandardQueryCache] starting query cache at region: org.hibernate.cache.StandardQueryCache

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  • How to specify a parameter as part of every web service call?

    - by LES2
    Currently, each web service for our application has a user parameter that is added for every method. For example: @WebService public interface FooWebService { @WebMethod public Foo getFoo(@WebParam(name="alwaysHere",header=true,partName="alwaysHere") String user, @WebParam(name="fooId") Long fooId); @WebMethod public Result deletetFoo(@WebParam(name="alwaysHere",header=true,partName="alwaysHere") String user, @WebParam(name="fooId") Long fooId); // ... } There could be twenty methods in a service, each with the first parameter as user. And there could be twenty web services. We don't actually use the 'user' argument in the implementations - in fact, I don't know why it's there - but I wasn't involved in the design, and the person that put it there had a reason (I hope). Anyway, I'm trying to straighten out this Big Ball of Mud. I have already come a long way by wrapping the web services by a Spring proxy, which allows me to do some before-and-after processing in an interceptor (before there were at least 20 lines of copy-pasted boiler plate per method). I'm wondering if there's some kind of "message header" I can apply to the method or package and that can be accessed by some type of handler or something outside of each web service method. Thanks in advance for the advice, LES

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  • Find messages[from-to]

    - by Alfred
    I would like to return all messages from certain key to a certain key. The class should be thread-safe and old keys should be able to be deleted say for example after 30 seconds. I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the items from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement this or maybe use a library?

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  • Axis2 issue with comment in WSDL

    - by Sirs
    I'm using an Axis2 client to access an external Webservice, whose WSDL starts with the following content: <?xml version="1.0" encoding="UTF-8"?><!--Created by TIBCO WSDL--><wsdl:definitions xmlns:wsdl=... My call to sendReceive crashes with the following error: com.ctc.wstx.exc.WstxUnexpectedCharException: Unexpected character 'C' (code 67) in prolog; expected '<' The 'C' is the first character on the comment in the WSDL. Without that comment everything works fine, but as far as my knowledge of basic XML dictates that comment is correct. My question would be: Is this a bug in Axis2 or is the accessed WSDL malformed? Is there any way to prevent Axis2 from crashing under these circumstances?

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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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  • How can one extra rdf:about or rdf:ID properties from triples using SPARKQL?

    - by lennyks
    It seemed a trivial matter at the beginning but so far I had not managed to get unique identifier for a given resource using SPARKQL. What I mean is given and then some properties identifiying this resource in perfect world I want to first know how to retrieve an individual triple given some uri. I have tried naive approaches by writing statements in a WHERE clause such as ?x rdf:about ?y and ?x rdfs:about ?y. I hope I am being precise.

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  • Can it be done in a more elegant way with the Swing Timer?

    - by Roman
    Bellow is the code for the simplest GUI countdown. Can the same be done in a shorter and more elegant way with the usage of the Swing timer? import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; public class CountdownNew { static JLabel label; // Method which defines the appearance of the window. public static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. public static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText("You have " + i + " seconds."); } } ); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); counter.start(); } }); } }

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  • Updatable false behvior incosistent

    - by jpanewbie
    I need LastUpdatedDttm to be updated by SYSDATE whenever record is updated. But below annoataions do nt work as desired. SYSDATE is inserted only once and not updated for subsequent updations. Also, lastUpdDTTM is not part of sql generated by hibernate. @Generated(GenerationTime.ALWAYS) @Column(name="LAST_UPDATED_DTTM",insertable=false,updatable=true, columnDefinition ="timestamp default SYSDATE") private Date lastUpdDTTM; @Generated(GenerationTime.ALWAYS) @Column(name="CREATED_DTTM", insertable=false, updatable=false) private Date createdDTTM;

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  • How to set response header in JAX-RS so that user sees download popup for Excel?

    - by masato-san
    I wrote code that generate Excel file using REST JAX-RS and I confirmed that the generated Excel file is in GlassFish server directory. But my goal is when user click on the button (which generate Excel .xls), I want download popup to show up asking user whether to save or open the .xls file just like any other web services doing for downloading any type of files. According to my search, the step is: generate Excel .xls (DONE) write the excel to stream in JAX-RS file, set response header to something like, String fileName = "Blah_Report.xls"; response.setHeader("Content-Disposition", "attachment; filename=" + fileName); My question is I'm doing all of this in JAX-RS file and I don't have HttpServletResponse object available. According to the answer from Add Response Header to JAX-RS Webservice He says: You can inject a reference to the actual HttpServletResponse via the @Context annotation in your webservice and use addHeader() etc. to add your header. I can't really figure what exactly that means without sample code..

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