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  • JSP: How can I still get the code on my error page to run, even if I can't display it?

    - by Josh Hinman
    I've defined an error-page in my web.xml: <error-page> <exception-type>java.lang.Exception</exception-type> <location>/error.jsp</location> </error-page> In that error page, I have a custom tag that I created. The tag handler for this tag e-mails me the stacktrace of whatever error occurred. For the most part this works great. Where it doesn't work great is if the output has already begun being sent to the client at the time the error occurs. In that case, we get this: SEVERE: Exception Processing ErrorPage[exceptionType=java.lang.Exception, location=/error.jsp] java.lang.IllegalStateException I believe this error happens because we can't redirect a request to the error page after output has already started. The work-around I've used is to increase the buffer size on particularly large JSP pages. But I'm trying to write a generic error handler that I can apply to existing applications, and I'm not sure it's feasible to go through hundreds of JSP pages making sure their buffers are big enough. Is there a way to still allow my stack trace e-mail code to execute in this case, even if I can't actually display the error page to the client?

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  • Multi-platform development from one computer

    - by iama
    I am planning to build a new development computer for both Windows & Linux platforms. On Windows, my development would be primarily in .NET/C#/IIS/MSSQL Server. On Linux—preferably Ubuntu—my development would be in Ruby and Python. I am thinking of buying a laptop with Windows 7 pre-installed with 4GB RAM, Intel Core 2 Duo, and 320 GB HD; running 2 VMs for both Windows and Linux development with the host OS as my work station. Of course, I would be running DBs and web servers on the respective platforms. Is this a typical setup? My only concern is running two VMs side by side. Not sure if this configuration would be optimal. Alternative would be to do my Windows development on the host Windows 7 OS. What are your thoughts?

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  • finding ALL cycles in a huge sparse matrix

    - by Andy
    Hi there, First of all I'm quite a Java beginner, so I'm not sure if this is even possible! Basically I have a huge (3+million) data source of relational data (i.e. A is friends with B+C+D, B is friends with D+G+Z (but not A - i.e. unmutual) etc.) and I want to find every cycle within this (not necessarily connected) directed graph. I've found this thread (http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) which has pointed me to Donald Johnson's (elementary) cycle-finding algorithm which, superficially at least, looks like it'll do what I'm after (I'm going to try when I'm back at work on Tuesday - thought it wouldn't hurt to ask in the meanwhile!). I had a quick scan through the code of the Java implementation of Johnson's algorithm (in that thread) and it looks like a matrix of relations is the first step, so I guess my questions are: a) Is Java capable of handling a 3+million*3+million matrix? (was planning on representing A-friends-with-B by a binary sparse matrix) b) Do I need to find every connected subgraph as my first problem, or will cycle-finding algorithms handle disjoint data? c) Is this actually an appropriate solution for the problem? My understanding of "elementary" cycles is that in the graph below, rather than picking out A-B-C-D-E-F it'll pick out A-B-F, B-C-D etc. but that's not the end of the world given the task. E / \ D---F / \ / \ C---B---A d) If necessary, I can simplify the problem by enforcing mutuality in relations - i.e. A-friends-with-B <== B-friends-with-A, and if really necessary I can maybe cut down the data size, but realistically it is always going to be around the 1mil mark. z) Is this a P or NP task?! Am I biting off more than I can chew? Thanks all, any help appreciated! Andy

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  • Webfaction apache + mod_wsgi + django configuration issue

    - by Dmitry Guyvoronsky
    A problem that I stumbled upon recently, and, even though I solved it, I would like to hear your opinion of what correct/simple/adopted solution would be. I'm developing website using Django + python. When I run it on local machine with "python manage.py runserver", local address is http://127.0.0.1:8000/ by default. However, on production server my app has other url, with path - like "http://server.name/myproj/" I need to generate and use permanent urls. If I'm using {% url view params %}, I'm getting paths that are relative to / , since my urls.py contains this urlpatterns = patterns('', (r'^(\d+)?$', 'myproj.myapp.views.index'), (r'^img/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/img' }), (r'^css/(.*)$', 'django.views.static.serve', {'document_root': settings.MEDIA_ROOT + '/css' }), ) So far, I see 2 solutions: modify urls.py, include '/myproj/' in case of production run use request.build_absolute_uri() for creating link in views.py or pass some variable with 'hostname:port/path' in templates Are there prettier ways to deal with this problem? Thank you. Update: Well, the problem seems to be not in django, but in webfaction way to configure wsgi. Apache configuration for application with URL "hostname.com/myapp" contains the following line WSGIScriptAlias / /home/dreamiurg/webapps/pinfont/myproject.wsgi So, SCRIPT_NAME is empty, and the only solution I see is to get to mod_python or serve my application from root. Any ideas?

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  • How to create a test environnement on the production FTP

    - by Clement Herreman
    Hello, I'm currently working on a symfony webapp, which is already on production. To develop and add/delete/modify functionnality of the model, I work on my laptop, using symfony 'dev' environnemment. I test if everything work fine, then I pray a little and deploy it on the prod server (with all the risk of data error, like when I add new not null attributes on the model, prod server configuration special stuff, version of php/apache etc.). The problem is that I would like to setup a "staging" server, which would be a copy of the production server (same database, same configuration apache/php), so that, if the deployment goes bad, the production user stay untouched and working, only the staging server is down. But my client has only 1 FTP available. So, the question is : can I run 2 symfony project, with different models, on the same FTP ? Or is there another way to do what I want to do ? Thank you !

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  • How do I set the Eclipse build path and class path from an Ant build file?

    - by Nels Beckman
    Hey folks, There's a lot of discussion about Ant and Eclipse, but no previously answered seems to help me. Here's the deal: I am trying to build a Java program that compiles successfully with Ant from the command-line. (To confuse matters further, the program I am attempting to compile is Ant itself.) What I really want to do is to bring this project into Eclipse and have it compile in Eclipse such that the type bindings and variable bindings (nomenclature from Eclipse JDT) are correctly resolved. I need this because I need to run a static analysis on the code that is built on top of Eclipse JDT. The normal way I bring a Java project into Eclipse so that Eclipse will build it and resolve all the bindings is to just import the source directories into a Java project, and then tell it to use the src/main/ directory as a "source directory." Unfortunately, doing that with Ant causes the build to fail with numerous compile errors. It seems to me that the Ant build file is setting up the class path and build path correctly (possibly by excluding certain source files) and Eclipse does not have this information. Is there any way to take the class path & build path information embedded in an Ant build file, and given that information to Eclipse to put in its .project and .classpath files? I've tried, creating a new project from an existing build file (an option in the File menu) but this does not help. The project still has the same compile errors. Thanks, Nels

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  • Is there a limit for the number of files in a directory on an SD card?

    - by jamesh
    I have a project written for Android devices. It generates a large number of files, each day. These are all text files and images. The app uses a database to reference these files. The app is supposed to clear up these files after a little use (perhaps after a few days), but this process may or may not be working. This is not the subject of this question. Due to a historic accident, the organization of the files are somewhat naive: everything is in the same directory; a .hidden directory which contains a zero byte .nomedia file to prevent the MediaScanner indexing it. Today, I am seeing an error reported: java.io.IOException: Cannot create: /sdcard/.hidden/file-4200.html at java.io.File.createNewFile(File.java:1263) Regarding the sdcard, I see it has plenty of storage left, but counting $ cd /Volumes/NO_NAME/.hidden $ ls | wc -w 9058 Deleting a number of files seems to have allowed the file creation for today to proceed. Regrettably, I did not try touching a new file to try and reproduce the error on a commandline; I also deleted several hundred files rather than a handful. However, my question is: are there hard limits on filesize or number of files in a directory? am I even on the right track here? Nota Bene: The SD card is as-is - i.e. I haven't formatted it, so I would guess it would be a FAT-* format. The FAT-32 format has hard limits of filesize of 2GB (well above the filesizes I am dealing with) and a limit of number of files in the root directory. I am definitely not writing files in the root directory.

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  • Question about WeakHashMap

    - by michael
    Hi, In the Javadoc of "http://java.sun.com/j2se/1.4.2/docs/api/java/util/WeakHashMap.html", it said "Each key object in a WeakHashMap is stored indirectly as the referent of a weak reference. Therefore a key will automatically be removed only after the weak references to it, both inside and outside of the map, have been cleared by the garbage collector." And then Note that a value object may refer indirectly to its key via the WeakHashMap itself; that is, a value object may strongly refer to some other key object whose associated value object, in turn, strongly refers to the key of the first value object. But should not both Key and Value should be used weak reference in WeakHashMap? i.e. if there is low on memory, GC will free the memory held by the value object (since the value object most likely take up more memory than key object in most cases)? And if GC free the Value object, the Key Object can be free as well? Basically, I am looking for a HashMap which will reduce memory usage when there is low memory (GC collects the value and key objects if necessary). Is it possible in Java? Thank you.

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  • which Server I have to buy?

    - by sri
    Hello, Recently i have registered startup (home office). My intension is to have virtual(company) server for LAMP website development(virtual). Initially thinking, 2-5 people will be logging virtually to the server. a. but not sure where to shop or what to shop. b. Should I go for my own Server or i have to share some server. c. If i have to go My Server, should I go with rack or tower model. d. which brand and model i have to buy. d. If I have to go with shared(cloud), not sure which is the best place It will be great help, if some one provide in site. Thanks in advance. Sri

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  • problem with running Servlet on Tomcat: InvocationTargetException

    - by Fahim
    Hi, I am new to Tomcat, and trying to run a simple HelloWorld servlet. I have installed Tomcat 6, and Jdk1.6 on Mandriva Linux, set CLASSPATH and JAVA_HOME. I have the following files and directories: $CATALINA_HOME/webapps/MyApp/WEB_INF/classes/TestServlet.class $CATALINA_HOME/webapps/MyApp/WEB_INF/web.xml My web.xml file contains the following: http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5" <description>ZibJana Localization</description> <display-name>ZibJana Localization</display-name> <!-- Define the servlets for this application--> <servlet> <servlet-name>ZibJana</servlet-name> <servlet-class>TestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ZibJana</servlet-name> <url-pattern>*</url-pattern> </servlet-mapping> But when I try to invoke my servlet with url http://localhost:8080/MyApp, tomcat fails to launch launch the servlet. I checked in the $CATALINA_HOME/logs/catalina.out log-file and found the following error, which occurs every time I start tomcat service. INFO: Deploying web application directory MyApp 16-Mar-2010 12:05:38 AM org.apache.tomcat.util.digester.Digester endElement SEVERE: End event threw exception java.lang.reflect.InvocationTargetException at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) Please let me know where my mistake is. Thanks in advance.

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  • Node & Redis: Crucial Design Issues in Production Mode

    - by Ali
    This question is a hybrid one, being both technical and system design related. I'm developing the backend of an application that will handle approx. 4K request per second. We are using Node.js being super fast and in terms of our database struction we are using MongoDB, with Redis being a layer between Node and MongoDB handling volatile operations. I'm quite stressed because we are expecting concurrent requests that we need to handle carefully and we are quite close to launch. However I do not believe I've applied the correct approach on redis. I have a class Student, and they constantly change stages(such as 'active', 'doing homework','in lesson' etc. Thus I created a Redis DB for each state. (1 for being 'active', 2 for being 'doing homework'). Above I have the structure of the 'active' students table; xa5p - JSON stringified object #1 pQrW - JSON stringified object #2 active_student_table - {{studentId:'xa5p'}, {studentId:'pQrW'}} Since there is no 'select all keys method' in Redis, I've been suggested to use a set such that when I run command 'smembers' I receive the keys and later on do 'get' for each id in order to find a specific user (lets say that age older than 15). I've been also suggested that in fact I used never use keys in production mode. My question is, no matter how 'conceptual' it is, what specific things I should avoid doing in Node & Redis in production stage?. Are they any issues related to my design? Students must be objects and I sure can list them in a list but I haven't done yet. Is it that crucial in production stage?

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  • Django "Error: cannot import name escape" on windows

    - by Sam
    I cannot run the dev server because of this error ("Error: cannot import name escape"). I assume its because of modifications I've done to the project, but i have no idea how to find where the error is originating from to fix it. I don't import anything called escape anywhere. Update Using django-admin.py rather than the projects manage.py, don't know why... Update 2 Now manage.py is working. This may be because I had a file called email.py which was trying to import email.mime.text (ie trying to import itself) renaming to sendemail.py solved this problem.

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  • No production mode in Rails 3 Beta 3?

    - by ulf
    I wrote my first Rails 3 app and it ran absolutely fine in development mode. Now I deployed it on my server and wanted to start it in production mode. The app starts but none of my images or stylesheets are being loaded. The Rails console outputs a lot of RoutingErrors to those files. Isn't that mode available yet?

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  • Improving field get and set performance with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • Generating a field setter and getter with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • Copying a massive databse for local ruby on rails development?

    - by tesmar
    Hi guys, There is a massive database (GB) that I am working with now and all of the previous development has been done on a slicehost slice. I am trying to get ready for more developers to come in and work so I need each person to be able to setup his own machine for development, which means potentially copying this database. Selecting only the first X rows in each table to cut size could be problematic for data consistency. Is there any way around this, or is a 1 hour download for each developer going to be necessary? And beyond that, what if I need to copy the production DB down for dev purposes in the future? Sincerely, Tyler

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  • what to do when you are completely burnt out from working on a project ?

    - by dfafa
    so i started this SaaS project around July 2009, was expecting to finish it in 2 months. i ended up working on it for about 4 months straight, spending about 6~12 hours nearly everyday. then one day i just couldn't bare to look at the code. it seems like my efforts are being sucked in by some black hole. i would need to put lot of work to make incremental changes. i felt burnt out in December....and now it's May. i am working on the project maybe for about 10 hours every 2 weeks...i am not getting much done. it seems like it will never be perfect. the more i code, more problems and bugs to fix, its absolutely sickening. so what should i do now ? i have invested all of my available time and money, i've shut off all social connections and basically have been spending most of my time in my room working on my project alone. i feel consumed by this project i created ironically, to make my life easier.

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  • How do I make this nested for loop, testing sums of cubes, more efficient?

    - by Brian J. Fink
    I'm trying to iterate through all the combinations of pairs of positive long integers in Java and testing the sum of their cubes to discover if it's a Fibonacci number. I'm currently doing this by using the value of the outer loop variable as the inner loop's upper limit, with the effect being that the outer loop runs a little slower each time. Initially it appeared to run very quickly--I was up to 10 digits within minutes. But now after 2 full days of continuous execution, I'm only somewhere in the middle range of 15 digits. At this rate it may end up taking a whole year just to finish running this program. The code for the program is below: import java.lang.*; import java.math.*; public class FindFib { public static void main(String args[]) { long uLimit=9223372036854775807L; //long maximum value BigDecimal PHI=new BigDecimal(1D+Math.sqrt(5D)/2D); //Golden Ratio for(long a=1;a<=uLimit;a++) //Outer Loop, 1 to maximum for(long b=1;b<=a;b++) //Inner Loop, 1 to current outer { //Cube the numbers and add BigDecimal c=BigDecimal.valueOf(a).pow(3).add(BigDecimal.valueOf(b).pow(3)); System.out.print(c+" "); //Output result //Upper and lower limits of interval for Mobius test: [c*PHI-1/c,c*PHI+1/c] BigDecimal d=c.multiply(PHI).subtract(BigDecimal.ONE.divide(c,BigDecimal.ROUND_HALF_UP)), e=c.multiply(PHI).add(BigDecimal.ONE.divide(c,BigDecimal.ROUND_HALF_UP)); //Mobius test: if integer in interval (floor values unequal) Fibonacci number! if (d.toBigInteger().compareTo(e.toBigInteger())!=0) System.out.println(); //Line feed else System.out.print("\r"); //Carriage return instead } //Display final message System.out.println("\rDone. "); } } Now the use of BigDecimal and BigInteger was delibrate; I need them to get the necessary precision. Is there anything other than my variable types that I could change to gain better efficiency?

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  • How to set up precision attribute used by @Collumn annotation ???

    - by Arthur Ronald F D Garcia
    I often use java.lang.Integer as primary key. Here you can see some piece of code @Entity private class Person { private Integer id; @Id @Column(precision=8, nullable=false) public Integer getId() { } } I need to set up its precision attribute value equal to 8. But, when exporting The schema (Oracle), it does not work as expected. AnnotationConfiguration configuration = new AnnotationConfiguration(); configuration .addAnnotatedClass(Person.class) .setProperty(Environment.DIALECT, "org.hibernate.dialect.OracleDialect") .setProperty(Environment.DRIVER, "oracle.jdbc.driver.OracleDriver"); SchemaExport schema = new SchemaExport(configuration); schema.setOutputFile("schema.sql"); schema.create(true, false); schema.sql outputs create table Person (id number(10,0) not null) Always i get 10. Is There some workaround to get 8 instead of 10 ?

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  • Request size limitation when using MultipartHttpServletRequest of Spring 3.0

    - by Spiderman
    I'd like to know what is the size limitation if I upload list of files in one client's form submition using HTTP multipart content type. On the server side I am using Spring's MultipartHttpServletRequest to handle the request. mM questions: Is there should be different file size limitation and total request size limitation or file size is the only limitation and the request is capable of uploading 100s of files as lonng as they are not too large. Doest the Spring request wrapper read the complete request and store it in the JAVA heap memory or it store temporaray files of it to be able to use big quota. Is the use of reading the httpservlet request in streaming would change the size limitation than using complete http request read at-once by the application server. What is the bottleneck of this process - Java heap size, the quota of the filesystem on which my web-server runs, the maximum allowed BLOB size that the DataBase in which I am gonna save the file alows? or Spring internal limitations? Related threads that still don't have exact answer to this: does-spring-framework-support-streaming-mode-in-mutlipart-requests is-there-a-way-to-get-raw-http-request-stream-from-java-servlet-handler how-to- drop-body-of-a-request-after-checking-headers-in-servlet apache-commons-fileupload-throws-malformedstreamexception

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  • How to store child objects on GAE using JDO from Scala

    - by Gero
    Hi, I'm have a parent-child relation between 2 classes, but the child objects are never stored. I do get an warning: "org.datanucleus.store.appengine.MetaDataValidator checkForIllegalChildField: Unable to validate relation net.vermaas.kivanotify.model.UserCriteria.internalCriteria" but it is unclear to me why this occurs. Already tried several alternatives without luck. The parent class is "UserCriteria" which has a List of "Criteria" as children. The classes are defined as follows (Scala): class UserCriteria(tu: String, crit: Map[String, String]) extends LogHelper { @PrimaryKey @Persistent{val valueStrategy = IdGeneratorStrategy.IDENTITY} var id = KeyFactory.createKey("UserCriteria", System.nanoTime) @Persistent var twitterUser = tu @Persistent var internalCriteria: java.util.List[Criteria] = flatten(crit) def flatten(crits: Map[String, String]) : java.util.List[Criteria] = { val list = new java.util.ArrayList[Criteria] for (key <- crits.keySet) { list.add(new Criteria(this, key, crits(key))) } list } def criteria: Map[String, String] = { val crits = mutable.Map.empty[String, String] for (i <- 0 to internalCriteria.size-1) { crits(internalCriteria.get(i).name) = internalCriteria.get(i).value } Map.empty ++ crits } // Stripped the equals, canEquals, hashCode, toString code to keep the code snippet short... } @PersistenceCapable @EmbeddedOnly class Criteria(uc: UserCriteria, nm: String, vl: String) { @Persistent var userCriteria = uc @Persistent var name = nm @Persistent var value = vl override def toString = { "Criteria name: " + name + " value: " + value } } Any ideas why the childs are not stored? Or why I get the error message? Thanks, Gero

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