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  • how to Solve the "Digg" problem in MongoDB

    - by user193116
    A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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  • Making Eclipse behave like Visual Studio

    - by FlySwat
    I'm doing some Android dev, and I much prefer Visual Studio, but I'll have to use Eclipse for this. Has anyone made a tool that switches Eclipse to look and behave more like visual studio? I mainly can't stand its clippyesqe suggestions on how I should program (Yes, I know I have not yet used that private field! Thanks Eclipse!), or its incredibly lousy intellisense. For example, in eclipse, if I don't type "this" first, its intellisense won't realize I want to look for locally scoped members. Also, the TAB to complete VS convention is drilled into my head, and Eclipse is ENTER to complete, I could switch everything by hand but that would take hours, and I was hoping someone had some sort of theme or something that has already done it :)

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  • Jetty: Stopping programatically causes "1 threads could not be stopped"

    - by Ondra Žižka
    Hi, I have an embedded Jetty 6.1.26 instance. I want to shut it down by HTTP GET sent to /shutdown. So I created a JettyShutdownServlet: @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setStatus(202, "Shutting down."); resp.setContentType("text/plain"); ServletOutputStream os = resp.getOutputStream(); os.println("Shutting down."); os.close(); resp.flushBuffer(); // Stop the server. try { log.info("Shutting down the server..."); server.stop(); } catch (Exception ex) { log.error("Error when stopping Jetty server: "+ex.getMessage(), ex); } However, when I send the request, Jetty does not stop - a thread keeps hanging in org.mortbay.thread.QueuedThreadPool on the line with this.wait(): // We are idle // wait for a dispatched job synchronized (this) { if (_job==null) this.wait(getMaxIdleTimeMs()); job=_job; _job=null; } ... 2011-01-10 20:14:20,375 INFO org.mortbay.log jetty-6.1.26 2011-01-10 20:14:34,756 INFO org.mortbay.log Started [email protected]:17283 2011-01-10 20:25:40,006 INFO org.jboss.qa.mavenhoe.MavenHoeApp Shutting down the server... 2011-01-10 20:25:40,006 INFO org.mortbay.log Graceful shutdown [email protected]:17283 2011-01-10 20:25:40,006 INFO org.mortbay.log Graceful shutdown org.mortbay.jetty.servlet.Context@1672bbb{/,null} 2011-01-10 20:25:40,006 INFO org.mortbay.log Graceful shutdown org.mortbay.jetty.webapp.WebAppContext@18d30fb{/jsp,file:/home/ondra/work/Mavenhoe/trunk/target/classes/org/jboss/qa/mavenhoe/web/jsp} 2011-01-10 20:25:43,007 INFO org.mortbay.log Stopped [email protected]:17283 2011-01-10 20:25:43,009 WARN org.mortbay.log 1 threads could not be stopped 2011-01-10 20:26:43,010 INFO org.mortbay.log Shutdown hook executing 2011-01-10 20:26:43,011 INFO org.mortbay.log Shutdown hook complete It blocks for exactly one minute, then shuts down. I've added the Graceful shutdown, which should allow me to shut the server down from a servlet; However, it does not work as you can see from the log. I've solved it this way: Server server = new Server( PORT ); server.setGracefulShutdown( 3000 ); server.setStopAtShutdown(true); ... server.start(); if( server.getThreadPool() instanceof QueuedThreadPool ){ ((QueuedThreadPool) server.getThreadPool()).setMaxIdleTimeMs( 2000 ); } setMaxIdleTimeMs() needs to be called after the start(), becase the threadPool is created in start(). However, the threads are already created and waiting, so it only applies after all threads are used at least once. I don't know what else to do except some awfulness like interrupting all threads or System.exit(). Any ideas? Is there a good way? Thanks, Ondra

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  • hibernate versioning parent entity

    - by Priit
    Consider two entities Parent and Child. Child is part of Parent's transient collection Child has a ManyToOne mapping to parent with FetchType.LAZY Both are displayed on the same form to a user. When user saves the data we first update Parent instance and then Child collection (both using merge). Now comes the tricky part. When user modifies only Child property on the form then hibernate dirty checking does not update Parent instance and thus does not increase optimistic locking version number for that entity. I would like to see situation where only Parent is versioned and every time I call merge for Parent then version is always updated even if actual update is not executed in db.

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  • JBoss envers and huge audit tables

    - by LeChe
    All, I am auditing my JEE application with JBoss Evers and the nature of my application causes the audit table to grow very fast. The historic data is queried infrequently and access time is not really an issue, apart from the data from the last week. This data IS queried frequently and access needs to be fast. Ideally, I would split the data and distribute it over two tables, with the older data in compressed format. Unfortunately, Envers does not allow spreading data over multiple tables as far as I can tell from the docs. Does somebody have any idea what would be the best way to achieve this (if possible while still using Envers)? Cheers, LeChe

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  • Avoid Spring ApllicationContext instanciation

    - by Ceddoc
    I use Spring 3 to make a simple configuration. I have an XML file called PropertyBeans.xml like that : <bean id="propertyBean" class="com.myapp.PropertyBean"> <property name="rootDirLogPath" value="C:\Users\dede" /> </bean> I have the bean which match this XML and then I want to use this bean with the value injected. Actually I have : ApplicationContext context = new ClassPathXmlApplicationContext("AppPropertyBeans.xml"); PropertyBean obj = (PropertyBean) context.getBean("propertyBean"); String rootDirLogPath = obj.getRootDirLogPath(); This works great but I want to know if there's a way to avoid the instantiation of ApplicationContext at each time I want to use a bean. I've heard about BeanFactory is that a good idea? Which are the others solutions? In other words: Am I supposed to called this Application context instanciation in every Controller in spring MVC?

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  • Delete an entity by key without fetching it first in app engine (using JDO)

    - by Peter Recore
    Is there a way to delete an entity without having to fetch it from the datastore first? I am assuming I already have the key or id for the entity. I'm thinking of something like deleteObjectById that would be an analogue to getObjectById on PersistenceManager. The closest I can think of is using Query.deletePersistentAll() (as seen here) and specifying a query that only relies on the key, but I can't tell if that is going to fetch the entity before deleting it. thanks EDIT: I know how to do this using the low level API, as well as in the python API. I was wondering if there was a way to do it within the JDO layer.

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  • Scanner cuts off my String after about 2400 characters

    - by Ventrue
    I've got some very basic code like while (scan.hasNextLine()) { String temp = scan.nextLine(); System.out.println(temp); } where scan is a Scanner over a file. However, on one particular line, which is about 6k chars long, temp cuts out after something like 2470 characters. There's nothing special about when it cuts out; it's in the middle of the word "Australia." If I delete characters from the line, the place where it cuts out changes; e.g. if I delete characters 0-100 in the file then Scanner will get what was previously 100-2570. I've used Scanner for larger strings before. Any idea what could be going wrong?

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  • tomcat session replication without multicast

    - by Andreas Petersson
    i am planning to use 2 dedicated root servers rented at a hosting provider. those machines will run tomcat 6 in a cluster. if i will add additional machines later on - it is unlikely that they will be accessible with multicast, because they will be located in different subnets. is it possible to run tomcat without multicast? all tutorials for tomcat 6 clustering include multicast heartbeat. are there any alternatives to SimpleTcpCluster? or are other alternatives more appropriate in this situation?

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  • JPA Database strcture for internationalisation

    - by IrishDubGuy
    I am trying to get a JPA implementation of a simple approach to internationalisation. I want to have a table of translated strings that I can reference in multiple fields in multiple tables. So all text occurrences in all tables will be replaced by a reference to the translated strings table. In combination with a language id, this would give a unique row in the translated strings table for that particular field. For example, consider a schema that has entities Course and Module as follows :- Course int course_id, int name, int description Module int module_id, int name The course.name, course.description and module.name are all referencing the id field of the translated strings table :- TranslatedString int id, String lang, String content That all seems simple enough. I get one table for all strings that could be internationalised and that table is used across all the other tables. How might I do this in JPA, using eclipselink 2.4? I've looked at embedded ElementCollection, ala this... JPA 2.0: Mapping a Map - it isn't exactly what i'm after cos it looks like it is relating the translated strings table to the pk of the owning table. This means I can only have one translatable string field per entity (unless I add new join columns into the translatable strings table, which defeats the point, its the opposite of what I am trying to do). I'm also not clear on how this would work across entites, presumably the id of each entity would have to use a database wide sequence to ensure uniqueness of the translatable strings table. BTW, I tried the example as laid out in that link and it didn't work for me - as soon as the entity had a localizedString map added, persisting it caused the client side to bomb but no obvious error on the server side and nothing persisted in the DB :S I been around the houses on this about 9 hours so far, I've looked at this Internationalization with Hibernate which appears to be trying to do the same thing as the link above (without the table definitions it hard to see what he achieved). Any help would be gratefully achieved at this point... Edit 1 - re AMS anwser below, I'm not sure that really addresses the issue. In his example it leaves the storing of the description text to some other process. The idea of this type of approach is that the entity object takes the text and locale and this (somehow!) ends up in the translatable strings table. In the first link I gave, the guy is attempting to do this by using an embedded map, which I feel is the right approach. His way though has two issues - one it doesn't seem to work! and two if it did work, it is storing the FK in the embedded table instead of the other way round (I think, I can't get it to run so I can't see exactly how it persists). I suspect the correct approach ends up with a map reference in place of each text that needs translating (the map being locale-content), but I can't see how to do this in a way that allows for multiple maps in one entity (without having corresponding multiple columns in the translatable strings table)...

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  • Catching an exception that is nested into another exception

    - by Bernhard V
    Hi, I want to catch an exception, that is nested into another exception. I'm doing it currently this way: } catch (RemoteAccessException e) { if (e != null && e.getCause() != null && e.getCause().getCause() != null) { MyException etrp = (MyException) e.getCause().getCause(); ... } else { throw new IllegalStateException("Error at calling service 'beitragskontonrVerwalten'"); } } Is there a way to do this more efficient and elegant?

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  • Comparing two Objects which implement the same interface for equality / equivalence - Design help

    - by gav
    Hi All, I have an interface and two objects implementing that interface, massively simplied; public interface MyInterface { public int getId(); public int getName(); ... } public class A implements MyInterface { ... } public class B implements MyInterface { ... } We are migrating from using one implementation to the other but I need to check that the objects of type B that are generated are equivalent to those of type A. Specifically I mean that for all of the interface methods an object of Type A and Type B will return the same value (I'm just checking my code for generating this objects is correct). How would you go about this? Map<String, MyInterface> oldGeneratedObjects = getOldGeneratedObjects(); Map<String, MyInterface> newGeneratedObjects = getNewGeneratedObjects(); // TODO: Establish that for each Key the Values in the two maps return equivalent values. I'm looking for good coding practices and style here. I appreciate that I could just iterate through one key set pulling out both objects which should be equivalent and then just call all the methods and compare, I'm just thinking there may be a cleaner, more extensible way and I'm interested to learn what options there might be. Would it be appropriate / possible / advised to override equals or implement Comparable? Thanks in advance, Gavin

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  • log4j relative file path

    - by Bob
    Hi, I'd like my web app to log into files with this path: webapp/logs/ I can set the absolute path in the log4j.properties file, but the production environment's directory structure will be different. Is there any way I could do it? Here is how I do: log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=log.out log4j.appender.f.MaxFileSize=100KB This is printing logs into a file named log.log in my eclipse directory (c://eclipse). I'm using Tomcat 6.

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  • How to sanitize log messages in Log4j to save them in database

    - by Rafael
    Hello, I'm trying to save log messages to a central database. In order to do this, I configured the following Appender in log4j's xml configuration: <appender name="DB" class="org.apache.log4j.jdbc.JDBCAppender"> <param name="URL" value="jdbc:postgresql://localhost/logging_test" /> <param name="user" value="test_user" /> <param name="password" value="test_password" /> <param name="sql" value="INSERT INTO log_messages ( log_level, message, log_date ) VALUES ( '%p', '%m', '%d{yyyy-MM-dd HH:mm:ss}' )" /> </appender> This works fine, except some of the messages contain ', and then the appender fails. Is there an easy way to do this?

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  • Refreshing a JPA result list which is bound with a jTable

    - by exhuma
    First off, I hage to write this on my mobile. But I'll try to format it properly. In Netbeans I created a jTable and bound it's values to a JPA result set. This works great. The qery contains a param which i set in the pre-create box of the "query result" component. So just before netbeans creates the query result i write this: myQuery.setParameter("year", "1997"); This works fine. Now, I have an event handler which is supposed to change the param and display the new values in the table. So I do this: myQuery.setParameter("year", "2005"); myResultList.clear(); myResultList.addAll(myQuery.getResultList()); jTable1.updateUI(); This works, but it feels wrong to me. Note: the result set is bound to the table. So I was hoping there was something like this: myQuery.setParameter("year", "2005"); myResultList.refresh(); Is there something like this?

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  • Android return to the original position of the view after MotionEvent

    - by Kurty
    My application currently changes to another random int (View) when I let go of it (ACTION_UP) but the view stays in the same spot where I dropped it. I want it to return to the original location (the middle of the screen) when I drop it so I can repeat the process. // OnTouch and MotionEvent OnTouchListener dragt = new OnTouchListener() { public boolean onTouch(View v, MotionEvent me) { FrameLayout.LayoutParams par = (FrameLayout.LayoutParams) v.getLayoutParams(); switch (v.getId()) { case R.id.randomView: } switch(me.getAction()) { case MotionEvent.ACTION_MOVE: par.gravity = 0; par.setMargins((int)me.getRawX() - (v.getWidth())/2, (int)me.getRawY() - (v.getHeight())/2, 0, 0); v.setLayoutParams(par); break; case MotionEvent.ACTION_UP: // tallies score. score++; textScore.setText(String.valueOf(score)); // this generates the new view but the location is still the same color.setImageResource(mImageIds[rgenerator.nextInt(mImageIds.length)]); break; } return true; } };

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  • Poor performance / speed of regex with lookahead

    - by Hugo Zaragoza
    I have been observing extremely slow execution times with expressions with several lookaheads. I suppose that this is due to underlying data structures, but it seems pretty extreme and I wonder if I do something wrong or if there are known work-arounds. The problem is determining if a set of words are present in a string, in any order. For example we want to find out if two terms "term1" AND "term2" are somewhere in a string. I do this with the expresion: (?=.*\bterm1\b)(?=.*\bterm2\b) But what I observe is that this is an order of magnitude slower than checking first just \bterm1\b and just then \bterm2\b This seems to indicate that I should use an array of patterns instead of a single pattern with lookaheads... is this right? it seems wrong... Here is an example test code and resulting times: public static void speedLookAhead() { Matcher m, m1, m2; boolean find; int its = 1000000; // create long non-matching string char[] str = new char[2000]; for (int i = 0; i < str.length; i++) { str[i] = 'x'; } String test = str.toString(); // First method: use one expression with lookaheads m = Pattern.compile("(?=.*\\bterm1\\b)(?=.*\\bterm2\\b)").matcher(test); long time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m.reset(test); find = m.find(); } time = System.currentTimeMillis() - time; System.out.println(time); // Second method: use two expressions and AND the results m1 = Pattern.compile("\\bterm1\\b").matcher(test); m2 = Pattern.compile("\\bterm2\\b").matcher(test); time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m1.reset(test); m2.reset(test); find = m1.find() && m2.find(); } time = System.currentTimeMillis() - time; System.out.println(time); } This outputs in my computer: 1754 150

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  • How to set default values to all wrong or null parameters of method?

    - by Roman
    At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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  • how to trigger notification from other framework in atmosphere (comet)?

    - by Sean Xiong
    basically i have read some samples, but all are self contained in one servlet. such as: use doGet to establish the long polling connection, and then use doPost to trigger the event to notify all suspended connections. Here is my question: I have other web actions programming in spring mvc, in the spring mvc controller a user post a message via /message/post, how can I make this action to trigger the atmosphere handler to notify the suspended connections?

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  • Spring security and Struts 2

    - by Thanksforfish
    I have a struts2 action with an @Secured({"ROLE_ADMIN"}) to secure the execute method. In the execute method i assign a message to a member variable of the action, then return SUCCESS and end up on the jsp page. On the page I retrieve the actions member variable with <sroperty. private String greeting; public String execute() throws Exception { this.greeting="Hello"; return SUCCESS; } // getters and setters for greeting ... <s:property value="greeting" /> The problem is when the secured annotation is present the jsp shows nothing for the member variable but when @Secured is removed the whole thing behaves properly and shows the message that was set into the member variable. It appears that the actual security is working ok but when enabled via the annotation the member variable (or maybe the instance of the action) is not making its way onto the value stack. I cant see any error messages.

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