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• Website to assist OO design

  - by JavaRocky

  Do any web 2.0 like websites exist for prototyping object oriented class diagrams?

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• Need advice to design 'crack-proof' software

  - by alee

  I am currently working on a project where i need to create some architecture, framework or any standards by which i can "at least" increase the cracking method for a software, i.e, to add to software security. There are already different ways to activate a software which includes online activation, keys etc. I am currently studying few research papers as well. But there are still lot of things that i want to discuss. Could someone guide me to some decent forum, mailing list or something like that? or any other help would be appreciated.

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• relational database: how to design this table

  - by donpal

  I'm a database newbie designing a database. I'll use SO to ask my question because it's easier to ask it on something that you can see already, but it's not the same, it will just help me understand the right approach. As you can see, there are many questions here and each can have many answers. How should I store the answers in a table? Should I store all the answers in the SAME table with a unique id (make it the key) and just a new field for the question id? What if there are 100,000 answers like there is here? Do I still store them in 1 table? What keys should I use to minimize search time when I want to search for the answers of a specific question? The database is both read and write if that makes any difference in this case.

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• Interpolation of scattered data: What could I do?

  - by Simon

  Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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• database design to speed up hibernate querying of large dataset

  - by paddydub

  I currently have the below tables representing a bus network mapped in hibernate, accessed from a Spring MVC based bus route planner I'm trying to make my route planner application perform faster, I load all the above tables into Lists to perform the route planner logic. I would appreciate if anyone has any ideas of how to speed my performace Or any suggestions of another method to approach this problem of handling a large set of data Coordinate Connections Table (INT,INT,INT)( Containing 50,000 Coordinate Connections) ID, FROMCOORDID, TOCOORDID 1 1 2 2 1 17 3 1 63 4 1 64 5 1 65 6 1 95 Coordinate Table (INT,DECIMAL, DECIMAL) (Containing 4700 Coordinates) ID , LAT, LNG 0 59.352669 -7.264341 1 59.352669 -7.264341 2 59.350012 -7.260653 3 59.337585 -7.189798 4 59.339221 -7.193582 5 59.341408 -7.205888 Bus Stop Table (INT, INT, INT)(Containing 15000 Stops) StopID RouteID COORDINATEID 1000100001 100 17 1000100002 100 18 1000100003 100 19 1000100004 100 20 1000100005 100 21 1000100006 100 22 1000100007 100 23 This is how long it takes to load all the data from each table: stop.findAll = 148ms, stops.size: 15670 Hibernate: select coordinate0_.COORDINATEID as COORDINA1_2_, coordinate0_.LAT as LAT2_, coordinate0_.LNG as LNG2_ from COORDINATES coordinate0_ coord.findAll = 51ms , coordinates.size: 4704 Hibernate: select coordconne0_.COORDCONNECTIONID as COORDCON1_3_, coordconne0_.DISTANCE as DISTANCE3_, coordconne0_.FROMCOORDID as FROMCOOR3_3_, coordconne0_.TOCOORDID as TOCOORDID3_ from COORDCONNECTIONS coordconne0_ coordinateConnectionDao.findAll = 238ms ; coordConnectioninates.size:48132 Hibernate Annotations @Entity @Table(name = "STOPS") public class Stop implements Serializable { @Id @GeneratedValue @Column(name = "COORDINATEID") private Integer CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Table(name = "COORDINATES") public class Coordinate { @Id @GeneratedValue @Column(name = "COORDINATEID") private Integer CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Entity @Table(name = "COORDCONNECTIONS") public class CoordConnection { @Id @GeneratedValue @Column(name = "COORDCONNECTIONID") private Integer CoordinateID; /** * From Coordinate_id value */ @Column(name = "FROMCOORDID", nullable = false) private int fromCoordID; /** * To Coordinate_id value */ @Column(name = "TOCOORDID", nullable = false) private int toCoordID; //private Coordinate toCoordID; }

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• Good Domain Driven Design samples

  - by jlembke

  I'm learning about DDD and enjoying every minute of it. However, there are some practical issues that are confusing to me that I think seeing some good samples might clear up. So being at peace with those issues, does anyone know of some good working code samples that do a good job of modeling basic DDD concepts? Particularly interested in An illustrative Domain Model Repositories Use of Domain/Application Services Value Objects Aggregate Roots I know I'm probably asking for too much, but anything close will help.

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• Database Design Primay Key, ID vs String

  - by LnDCobra

  Hi, I am currently planning to develop a music streaming application. And i am wondering what would be better as a primary key in my tables on the server. An ID int or a Unique String. Methods 1: Songs Table: SongID(int), Title(string), Artist*(string), Length(int), Album*(string) Genre Table Genre(string), Name(string) SongGenre: SongID*(int), Genre*(string) Method 2 Songs Table: SongID(int), Title(string), ArtistID*(int), Length(int), AlbumID*(int) Genre Table GenreID(int), Name(string) SongGenre: SongID*(int), GenreID*(int) Key: Bold = Primary Key, Field* = Foreign Key I'm currently designing using method 2 as I believe it will speed up lookup performance and use less space as an int takes a lot less space then a string. Is there any reason this isn't a good idea? Is there anything I should be aware of?

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• Strategy Design Pattern -- *dynamic* !!!

  - by alexeypro

  My application will have different strategies for my objects. What's the best way of implementing that? I would really love the case when we can make strategy classes implementation dynamically loaded from, say, some relational database. Not sure how do that better, though. What's the best approach? Idea is that say we want to apply to object MyObj strategy Strategy123 then we just load from database by ID 123 the object, deserialize it, get the Strategy class, and use it with MyObj. The maintenance while sounds easier from the first look can be a pain in the long run if Strategy interfaces changes, etc. What can I do also? I want to find solution when I should be keeping Strategy classes in codebase -- just for the sake that I don't need code change and re-deployment of the application if my Strategy changes, or I add new strategy. Please advise!

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• I/O between AIR client using Native process and executable java .jar

  - by aseem behl

  I am using Adobe AIR 2.0 native process API to launch a java executable jar. I/O is handled by writing to the input stream of the java process and reading from the output stream. The application is event based where several events are fired from the server. We catch these events in java code, handle them and write the output to the outputstream using the synchronized static method below. public class ReaderWriter { static Logger logger = Logger.getLogger(ReaderWriter.class); public synchronized static void writeToAir(String output){ try{ byte[] byteArray = output.getBytes(); DataOutputStream dataOutputStream = new DataOutputStream(System.out); dataOutputStream.write(byteArray); dataOutputStream.flush(); } catch (IOException e) { logger.info("Exception while writing the output. " + e); } } } The issue is that some messages are lost between the transfer and not all messages reach the AIR client. If I run the java application from the console I am receiving all the messages. It would be great if somebody could point out what I am missing. Following are some of the listeners used to send the event data to the AIR client. // class used to process Shutdown events from the Session private class SessionShutdownListener implements SessionListener{ public void onEvent(Event e) { Session.Shutdown sd = (Session.Shutdown) e; Session.ShutdownReason sr = sd.getReason(); String eventOutput = "eo;" + "Session Shutdown event ocurred reason=" + sr.strValue() + "\n"; ReaderWriter.writeToAir(eventOutput); } } // class used to process OperationSucceeded events from the Session private class SessionOperationSucceededListener implements SessionListener{ public void onEvent(Event e) { Session.OperationSucceeded os = (Session.OperationSucceeded) e; String eventOutput = "eo;" + "Session OperationSucceeded event ocurred" + "\n"; ReaderWriter.writeToAir(eventOutput); } }

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• How to propagate .java file change to .class under eclipse, tomcat & stripes

  - by BigBourin

  Hi, i'm new to java and i got some problems. i'm developping a web application using the framework stripes on tomcat 6.0. I'm working with eclipse EE on windows. i successfully managed to get the stripes example application (called Bugzooky) up and running on my tomcat server. I imported the .war file and stripes libs in Eclipse. Here is the stripes archive containing the examples and libs But now i'm trying to change the example source files to learn how does it work. but whatever the modification made to the source files "WebContent/WEB-INF/src/*.java", nothing change! even after restarting the server. i noticed that the classes are compiled into .class files in the "ImportedClasses" folder, and tomcat always use these files, they are never updated, and if i removed one of them, the application just don't start. it look like my source files don't exists! I also tried to build my webapp from scratch, but when i tried to use the features used in the example files (like SecurityFilter.java): import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import ... It ends up with plenty of: the import javax.servlet.Filter cannot be resolved I checked the Librairies and it look like i'm using exactly the same as the example. It's probably something i didn't understood about java but i googled 100 times yesterday, and i can't find the solution (i probably didn't search the right place because i don't really understand my problem). I hope you'll be able to help me.

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• Database design grouping contacts by lists and companies

  - by Serge

  Hi, I'm wondering what would be the best way to group contacts by their company. Right now a user can group their contacts by custom created lists but I'd like to be able to group contacts by their company as well as store the contact's position (i.e. Project Manager of XYZ company). Database wise this is what I have for grouping contacts into lists contact [id_contact] [int] PK NOT NULL, [lastName] [varchar] (128) NULL, [firstName] [varchar] (128) NULL, ...... contact_list [id_contact] [int] FK, [id_list] [int] FK, list [id_list] [int] PK [id_user] [int] FK [list_name] [varchar] (128) NOT NULL, [description] [TEXT] NULL Should I implement something similar for grouping contacts by company? If so how would I store the contact's position in that company and how can I prevent data corruption if a user modifies a contact's company name. For instance John Doe changed companies but the other co-workers are still in the old company. I doubt that will happen often (might not even happen at all) but better be safe than sorry. I'm also keeping an audit trail so in a way the contact would still need to be linked to the old company as well as the new one but without confusing what company he's actually working at the moment. I hope that made sense... Has anyone encountered such a problem? UPDATE Would something like this make sense contact_company [id_contact_company] [int] PK [id_contact] [int] FK [id_company] [int] FK [contact_title] [varchar] (128) company [id_company] [int] PK NOT NULL, [company_name] [varchar] (128) NULL, [company_description] [varchar] (300) NULL, [created_date] [datetime] NOT NULL This way a contact can work for more than one company and contacts can be grouped by companies

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• Flexible design - customizable entity model, UI and workflow

  - by Ngm

  Hi All, I want to achieve the following aspects in the software I am building: 1. Customizable entity model 2. Customizable UI 3. Customizable workflow I have thought about an approach to achieve this, I want you to review this and make suggestions: Entity objects should be plain objects and will hold just data Separate Entity model and DB Schema by using an framework (like NHibernate?). This will allow easy modification of entity objects. Business logic to fetch/modify entities has to be granular enough so that they can be invoked as part of the workflow. Business objects should not hold any state, and hence will contain only static methods The workflow will decide depending upon the "state" of an entity/entities which methods on business object/objects to invoke. The workflow should obtain the results of the processing and then pass on the business objects to the appropriate UI screen. The UI screen has to contain instructions about how to display a given entity/entites. Possibly the UI has to be generated dynamically based on a set of UI instructions. (like XUL) What do you think about this approach? Suggest which existing frameworks (like NHiberante, Window Workflow) fit into this model, so that I will not spend time on coding these frameworks Also suggest is there any asp.net framework that can generate dynamic asp.net ajax pages based on a set of UI instructions (like Mozilla XUL)? I have recently been exploring Apache Ofbiz and was impressed by its ability to customize most areas of the application: UI, workflow, entities. Is there any similar (not necessarily an ERP system) application developed in C#/.Net which offers a similar level of customization? I am looking for examples of applications developed in C# that are highly customizable in terms of UI, Workflow and Entity Model

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• MVC design question for forms

  - by kenny99

  Hi, I'm developing an app which has a large amount of related form data to be handled. I'm using a MVC structure and all of the related data is represented in my models, along with the handling of data validation from form submissions. I'm looking for some advice on a good way to approach laying out my controllers - basically I will have a huge form which will be broken down into manageable categories (similar to a credit card app) where the user progresses through each stage/category filling out the answers. All of these form categories are related to the main relation/object, but not to each other. Does it make more sense to have each subform/category as a method in the main controller class (which will make that one controller fairly massive), or would it be better to break each category into a subclass of the main controller? It may be just for neatness that the second approach is better, but I'm struggling to see much of a difference between either creating a new method for each category (which communicates with the model and outputs errors/success) or creating a new controller to handle the same functionality. Thanks in advance for any guidance!

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• yet another question about migrating to Java

  - by aloneguid

  Hi, There are plenty similar questions, but maybe responses to this one will save a developer's life :) I want to migrate to Java. The reasons are very clear: all the .NET vacancies are client and windows oriented (Silverlight developer, ASP.NET developer, WPF developer etc.) and none of them are any interest to me. I worked with .NET since it's beginning as our company decided to invest in .NET having C++ stack and all the natual problems, so I was just blindly following and actually enjoyed it as the products were mostly server oriented with mixed C++/C# code. Today I have beforementioned problem - can't find an inspiring job. I'd rather kill myself than start working on a Silverlight or WPF project. Searching Java vacancies shows promising results, however they all require a huge java-related technology stack and experience. The question is is there any chance to find a job quickly and without dramatic salary drop (I know that Java guys are usually better paid, so there must be a kind of a credit) and if not, how must time and effort does it take to migrate (my .NET knowledge mostly includes server-oriented technologies like NHibernate, WCF, threading, sockets, ASP.NET web services, Enterprise Library, NInject etc etc etc, and (still) some C++ leftovers). Thanks!

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• How to use URLClassLoader to load a *.class file?

  - by DeletedAccount

  I'm playing around with Reflection and I thought I'd make something which loads a class and prints the names of all fields in the class. I've made a small hello world type of class to have something to inspect: kent@rat:~/eclipsews/SmallExample/bin$ ls IndependentClass.class kent@rat:~/eclipsews/SmallExample/bin$ java IndependentClass Hello! Goodbye! kent@rat:~/eclipsews/SmallExample/bin$ pwd /home/kent/eclipsews/SmallExample/bin kent@rat:~/eclipsews/SmallExample/bin$ Based on the above I draw two conclusions: It exists at /home/kent/eclipsews/SmallExample/bin/IndependentClass.class It works! (So it must be a proper .class-file which can be loaded by a class loader) Then the code which is to use Reflection: (Line which causes an exception is marked) import java.lang.reflect.Field; import java.net.MalformedURLException; import java.net.URL; import java.net.URLClassLoader; public class InspectClass { @SuppressWarnings("unchecked") public static void main(String[] args) throws ClassNotFoundException, MalformedURLException { URL classUrl; classUrl = new URL("file:///home/kent/eclipsews/SmallExample/bin/IndependentClass.class"); URL[] classUrls = { classUrl }; URLClassLoader ucl = new URLClassLoader(classUrls); Class c = ucl.loadClass("IndependentClass"); // LINE 14 for(Field f: c.getDeclaredFields()) { System.out.println("Field name" + f.getName()); } } } But when I run it I get: Exception in thread "main" java.lang.ClassNotFoundException: IndependentClass at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at InspectClass.main(InspectClass.java:14) My questions: What am I doing wrong above? How do I fix it? Is there a way to load several class files and iterate over them?

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• Database Design Composite Keys

  - by guazz

  I am going to use a contrived example: one headquarter has one-or-many contacts. A contact can only belong to one headquarter. TableName = Headquarter Column 0 = Id : Guid [PK] Column 1 = Name : nvarchar(100) Column 2 = IsAnotherAttribute: bool TableName = ContactInformation Column 0 = Id : Guid [PK] Column 1 = HeadquarterId: Guid [FK] Column 2 = AddressLine1 COlumn 3 = AddressLine2 Column 4 = AddressLine3 I would like some help setting the table primary keys and foreign keys here? How does the above look? Should I use a composite key for ContactInformation on [Column 0 and Column1]? Is it ok to use surrogate key all of the time?

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• java RMI connection to server

  - by user85116

  I have a very simple rmi client / server application. I don't use the "rmiregistry" application though, I use this to create the server: server = new RemoteServer(); registry = LocateRegistry.createRegistry(PORT); registry.bind("RemoteServer", server); The client part is: registry = LocateRegistry.getRegistry(IPADDRESS, PORT); remote = (IRemoteServer) registry.lookup("RemoteServer"); Here is the fascinating problem: The application works perfectly when both server and client are running in my (private) local network. As soon as I put the server on a public server, the application hangs for a minute, then gives me the following error: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.ConnectException: Connection refused to host: 192.168.x.y; nested exception is: java.net.ConnectException: Connection timed out: connect at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source) at sun.rmi.transport.Transport$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source ... (the rest is truncated) The key I think is that the client (running on my private network) cannot connect to myself (my address is 192.168.x.y where x.y is some other numbers, but the real error message shows my ip address listed there) If I kill the rmi server on the public internet, then I instantly get a "connection refused to host: a.b.c.d") message, so I know that something at the server end is at least working. Any suggestions? EDIT: just to make this a little more clear: 192.168.x.y is the client address, a.b.c.d is the server address. The stacktrace shows the client cannot connect to the client.

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• Subroutine & GoTo design

  - by sub

  I have a strange question concerning subroutines: As I'm creating a minimal language and I don't want to add high-level loops like while or for I was planning on just adding gotos to keep it Turing-Complete. Now I thought, eww - gotos - I wouldn't want to program in that language if I had to use gotos so often. So I thought about adding subroutines instead. I see the difference as the following: gotos Go to (captain obvious) a previously defined point and continue executing the program from there. Leads to hardly understandable and buggy code, I think that's a fact. subroutines Similiar: You define their starting point somewhere, as you call them the program jumps there - but the subroutine can go back to the point it was called from with return. Okay. Why didn't I just add the more function-like, nice looking subroutines? Because: In order to make return work if I call subroutines from within subroutines from within other subroutines, I'd have to use a stack containing the point where the currently running subroutine came from at top. That would then mean that I would, if I create loops using the subroutines, end up with an extremely memory-eating, overflowing stack with return locations. Not good. Don't think of my subroutines as functions. They are just gotos that return to the point they were called from, they don't actually give back values like the return x; statement in nearly all today's languages. Now to my actual questions: How can I solve the above problem with the stack overflow on loops with subroutines? Do I have to add a separate goto language construct without the return option? Assembler doesn't have loops but as I have seen myJumpPoint:, jnz, jz, retn. That means to me that there must also be a stack containing all the return locations. Am I right with that? What about long running loops then? Don't they overflow the stack/eat memory then? Am I getting the retn symbol in assembler totally wrong? If yes, please explain it to me.

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• using PHP for "Fluid" design(using viewport resolution)

  - by Jreeter

  I need some opinions on using PHP to make completely "scalable" websites.. For instance, using viewport resolution and resizing images, applying dynamic css styles..... In my mind doing this just add's to the complexity and should not be done, it should be fixed or fluid using strictly css and no server-side languages to generate layouts based on the device size.. I need some input and maybe some philosophy on why using this approach is not used at all..

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• Design a GUI browser to view a tree

  - by iamrohitbanga

  I have a large tree. I want to be able to visualize it using a GUI tool. I want the ability to pan and zoom the tree image so that i can focus on part of the tree. Is there an existing tool to achieve this? If not i would like to write a small tool for myself to be able to do this. what is the simplest way of doing this? what computer language should i use? the image should look something like http://upload.wikimedia.org/wikipedia/commons/d/df/Binary_tree.png I should be able to zoom and pan the image.

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• Installing ant; clearly misunderstanding JAVA_HOME

  - by StormShadow

  Hey all, I am installing ant on a Windows XP machine, and am following the instructions at Apache's manual site. It said to set JAVA_HOME, so I checked, saw there was no environment variable named JAVA_HOME, made one, and set it to "C:\Program Files\Java\jdk1.6.0_19" When I try to run ant debug, however, it tells me that JAVA_HOME is currently set to "C:\Program Files\Java\jre6" I'm guessing JAVA_HOME isn't an environment variable. But if it isn't one, I'm at a loss as to where to start looking for it. Anybody know? Edit: Oh yeah - it's bugging me for tools.jar as well, but I'm guessing that when I fix the JAVA_HOME issue, that will help the terminal find tools.jar as well. Or maybe I'm wrong. Thanks

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• Buddy List: Relational Database Table Design

  - by huntaub

  So, the modern concept of the buddy list: Let's say we have a table called Person. Now, that Person needs to have many buddies (of which each buddy is also in the person class). The most obvious way to construct a relationship would be through a join table. i.e. buddyID person1_id person2_id 0 1 2 1 3 6 But, when a user wants to see their buddy list, the program would have to check the column 'person1_id' and 'person2_id' to find all of their buddies. Is this the appropriate way to implement this kind of table, or would it be better to add the record twice.. i.e. buddyID person1_id person2_id 0 1 2 1 2 1 So that only one column has to be searched. Thanks in advance.

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• How to fix this java.lang.LinkageError?

  - by Péter Török

  I am trying to configure a custom layout class to Log4J as described in my previous post. The class uses java.util.regex.Matcher to identify potential credit card numbers in log messages. It works perfectly in unit tests (I can also programmatically configure a logger to use it and produce the expected output). However when I try to deploy it with our app in JBoss, I get the following error: --- MBEANS THAT ARE THE ROOT CAUSE OF THE PROBLEM --- ObjectName: jboss.web.deployment:war=MyWebApp-2010_02-SNAPSHOT.war,id=476602902 State: FAILED Reason: java.lang.LinkageError: java/util/regex/Matcher I couldn't even find any info on this form of the error - typically LinkageError seems to show up with a "loader constrain violation" message, like in here. Technical details: we use JBoss 4.2, Java 5, Log4J 1.2.12. We deploy our app in an .ear, which contains (among others) the above mentioned .war file, and the custom layout class in a separate jar file. We override the default settings in jboss-log4J.xml with our own log4j.properties located in a different folder, which is added to the classpath at startup, and is provided via Carbon. I can only guess: are two different Matcher class versions loaded from somewhere, or is Matcher loaded by two different classloaders when it is used from the jar and the war? What does this error message mean, and how can I fix it?

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• Simple typemap example in swig java

  - by celil

  I am trying to wrap a native C++ library using swig, and I am stuck at trying to convert time_t in C, to long in Java. I have successfully used swig with python, but so far I am unable to get the above typemap to work in Java. In python it looks like this %typemap(in) time_t { if (PyLong_Check($input)) $1 = (time_t) PyLong_AsLong($input); else if (PyInt_Check($input)) $1 = (time_t) PyInt_AsLong($input); else if (PyFloat_Check($input)) $1 = (time_t) PyFloat_AsDouble($input); else { PyErr_SetString(PyExc_TypeError,"Expected a large number"); return NULL; } } %typemap(out) time_t { $result = PyLong_FromLong((long)$1); } I guess the in map from Java to C would be: %typemap(in) time_t { $1 = (time_t) $input; } How would I complete the out map from C to Java? %typemap(out) time_t ??? Would I need typemaps like the ones below? %typemap(jni) %typemap(jtype) %typemap(jstype) I need this in order to wrap C functions like this: time_t manipulate_time (time_t dt);

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• Does this inheritance design belong in the database?

  - by Berryl

  === CLARIFICATION ==== The 'answers' older than March are not answers to the question in this post! Hello In my domain I need to track allocations of time spent on Activities by resources. There are two general types of Activities of interest - ones base on a Project and ones based on an Account. The notion of Project and Account have other features totally unrelated to both each other and capturing allocations of time, and each is modeled as a table in the database. For a given Allocation of time however, it makes sense to not care whether the allocation was made to either a Project or an Account, so an ActivityBase class abstracts away the difference. An ActivityBase is either a ProjectActivity or an AccountingActivity (object model is below). Back to the database though, there is no direct value in having tables for ProjectActivity and AccountingActivity. BUT the Allocation table needs to store something in the column for it's ActivityBase. Should that something be the Id of the Project / Account or a reference to tables for ProjectActivity / Accounting? How would the mapping look? === Current Db Mapping (Fluent) ==== Below is how the mapping currently looks: public class ActivityBaseMap : IAutoMappingOverride<ActivityBase> { public void Override(AutoMapping<ActivityBase> mapping) { //mapping.IgnoreProperty(x => x.BusinessId); //mapping.IgnoreProperty(x => x.Description); //mapping.IgnoreProperty(x => x.TotalTime); mapping.IgnoreProperty(x => x.UniqueId); } } public class AccountingActivityMap : SubclassMap<AccountingActivity> { public void Override(AutoMapping<AccountingActivity> mapping) { mapping.References(x => x.Account); } } public class ProjectActivityMap : SubclassMap<ProjectActivity> { public void Override(AutoMapping<ProjectActivity> mapping) { mapping.References(x => x.Project); } } There are two odd smells here. Firstly, the inheritance chain adds nothing in the way of properties - it simply adapts Projects and Accounts into a common interface so that either can be used in an Allocation. Secondly, the properties in the ActivityBase interface are redundant to keep in the db, since that information is available in Projects and Accounts. Cheers, Berryl ==== Domain ===== public class Allocation : Entity { ... public virtual ActivityBase Activity { get; private set; } ... } public abstract class ActivityBase : Entity { public virtual string BusinessId { get; protected set; } public virtual string Description { get; protected set; } public virtual ICollection<Allocation> Allocations { get { return _allocations.Values; } } public virtual TimeQuantity TotalTime { get { return TimeQuantity.Hours(Allocations.Sum(x => x.TimeSpent.Amount)); } } } public class ProjectActivity : ActivityBase { public virtual Project Project { get; private set; } public ProjectActivity(Project project) { BusinessId = project.Code.ToString(); Description = project.Description; Project = project; } }

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