Search Results

Search found 45920 results on 1837 pages for 'java design patterns'.

Page 33/1837 | < Previous Page | 29 30 31 32 33 34 35 36 37 38 39 40  | Next Page >

• java.rmi.UnmarshalException: unable to pull client classes by server

  - by andrews

  Hi, I have an RMI client/server set-up on two machines that works fine in a simple situation when the server doesn't require a client-side defned class. However, when I need to use a class defined on the client side I am unable to have the server unmarshall those classes. I suspect this is an issue with my java.rmi.server.codebase property that I pass in as argument to the client app. I followed Sun's RMI Tutorial trail and I think I have followed the steps exactly except that I don't specify a classpath argument when executing client and server because they execute in the directory right above the root package directory (however I tried that too with no effect). The exceptions I get when attempting to execute the different client-side combinations described in detail below are all the same: RmiServer exception: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: java.lang.ClassNotFoundException: test.MyTask at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:353) at sun.rmi.transport.Transport$1.run(Transport.java:177) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:173) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:553) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:178) at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:132) at $Proxy0.execute(Unknown Source) at test.myClient.main(myClient.java:32) The details are: My client/server rmi is set up over a home network behind a router. The router is assigned to a static ip address I will call myhostname. Appropriate port-mapping is set-up in the router that points to the right machines. role, machine, os, ip-address: server, venice, linux ubuntu 9.10, 10.0.1.2 client, naples, mac os x leopard, 10.0.1.4 I startup the server side as follows inside /home/andrews/workspace/epsilon/bin: 1 starting registry on the default port 1099: venice% rmiregistry & 2 starting web-server on port 2001 pointing to code base for common interfaces: venice% java webserver/ClassFileServer 2001 /home/andrew/workspace/epsilon/bin 3 starting server app (main class in test/myServer) which registers the server object: venice% java -Djava.rmi.server.codebase="http://myhostname:2001/" -Djava.security.policy=server.policy -Djava.rmi.server.hostname=myhostname test/myServer & Now the client side inside /Users/andrews/Development/Java/workspace/epsilon/bin: 1 start a local web server that can server client-side classes to the server (not sure if this is needed, but I added I tried it, and still no success; I have added port-mapping to the router for 2001 to venice, for 2002 to naples) naples$ java webserver/ClassFileServer 2002 /Users/andrews/Development/Java/workspace/epsilon/bin/ Trying to run the client (note: I don't specify the -cp argument because client executes right above the root package directory): 1 try #1 using an http hostname naples$ java -Djava.rmi.server.codebase=http://10.0.1.4:2002/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the myhostname argument at the end is passed-in to the client so that it resolves to server's rmi hostname. Note 2: I tried using localhost:2002 instead of 10.0.1.4:2002 too. Note 3: I tried using myhostname:2002 since myhostname is assigned to the router and I have proper port-mapping set-up, this address should resolve to naples and not venice 2 try #2: naples$ java -Djava.rmi.server.codebase=file:/Users/andrews/Development/Java/workspace/epsilon/bin/ -Djava.security.policy=client.policy test.myClient myhostname Note 1: the code base url format is correct, I created a small program to convert current file directory path into a url and used that. using file:///Users... has same effect. Other notes: 1 my server and client policy files correctly specify the path, as I've tested this setup with good and bad paths, and getting a security exception for bad path 2 this setup works if I don't use client-side defined objects, the client connects correctly to the server and the server executes. 3 when I place the client-side class on the server in the server's classpath, all executes fine. All help is appreciated.

  Read the article

• Design considerations for temporarily transforming a player into an animal in a role playing game

  - by mikedev

  I am working on a role playing game for fun and to practice design patterns. I would like players to be able to transform themselves into different animals. For example, a Druid might be able to shape shift into a cheetah. Right now I'm planning on using the decorator pattern to do this but my question is - how do I make it so that when a druid is in the cheetah form, they can only access skills for the cheetah? In other words, they should not be able to access their normal Druid skills. Using the decorator pattern it appears that even in the cheetah form my druid will be able to access their normal druid skills. class Druid : Character { // many cool druid skills and spells void LightHeal(Character target) { } } abstract class CharacterDecorator : Character { Character DecoratedCharacter; } class CheetahForm : CharacterDecorator { Character DecoratedCharacter; public CheetahForm(Character decoratedCharacter) { DecoratedCharacter= decoratedCharacter; } // many cool cheetah related skills void CheetahRun() { // let player move very fast } } now using the classes Druid myDruid = new Druid(); myDruid.LightHeal(myDruid); // casting light heal here is fine myDruid = new CheetahForm(myDruid); myDruid.LightHeal(myDruid); // casting here should not be allowed Hmmmm...now that I think about it, will myDruid be unable to us the Druid class spells/skills unless the class is down-casted? But even if that's the case, is there a better way to ensure that myDruid at this point is locked out from all Druid related spells/skills until it is cast back to a Druid (since currently it's in CheetahForm)

  Read the article

• Implementation/interface inheritance design question.

  - by Neil G

  I would like to get the stackoverflow community's opinion on the following three design patterns. The first is implementation inheritance; the second is interface inheritance; the third is a middle ground. My specific question is: Which is best? implementation inheritance: class Base { X x() const = 0; void UpdateX(A a) { y_ = g(a); } Y y_; } class Derived: Base { X x() const { return f(y_); } } interface inheritance: class Base { X x() const = 0; void UpdateX(A a) = 0; } class Derived: Base { X x() const { return x_; } void UpdateX(A a) { x_ = f(g(a)); } X x_; } middle ground: class Base { X x() const { return x_; } void UpdateX(A a) = 0; X x_; } class Derived: Base { void UpdateX(A a) { x_ = f(g(a)); } } I know that many people prefer interface inheritance to implementation inheritance. However, the advantage of the latter is that with a pointer to Base, x() can be inlined and the address of x_ can be statically calculated.

  Read the article

• Design patterns for Agent / Actor based concurrent design.

  - by nso1

  Recently i have been getting into alternative languages that support an actor/agent/shared nothing architecture - ie. scala, clojure etc (clojure also supports shared state). So far most of the documentation that I have read focus around the intro level. What I am looking for is more advanced documentation along the gang of four but instead shared nothing based. Why ? It helps to grok the change in design thinking. Simple examples are easy, but in a real world java application (single threaded) you can have object graphs with 1000's of members with complex relationships. But with agent based concurrency development it introduces a whole new set of ideas to comprehend when designing large systems. ie. Agent granularity - how much state should one agent manage - implications on performance etc or are their good patterns for mapping shared state object graphs to agent based system. tips on mapping domain models to design. Discussions not on the technology but more on how to BEST use the technology in design (real world "complex" examples would be great).

  Read the article

• Issue with class design to model user preferences for different classes

  - by Mulone

  Hi all, I'm not sure how to design a couple of classes in my app. Basically that's a situation: each user can have many preferences each preference can be referred to an object of different classes (e.g. album, film, book etc) the preference is expressed as a set of values (e.g. score, etc). The problem is that many users can have preferences on the same objects, e.g.: John: score=5 for filmid=apocalypsenow Paul: score=3 for filmid=apocalypsenow And naturally I don't want to duplicate the object film in each user. So I could create a class called "preference" holding a score and then a target object, something like: User{ hasMany preferences } Preference{ belongsTo User double score Film target Album target //etc } and then define just one target. Then I would create an interface for the target Classes (album, film etc): Interface canBePreferred{ hasMany preferences } And implement all of those classes. This could work, but it looks pretty ugly and it would requires a lot of joins to work. Do you have some patterns I could use to model this nicely? Cheers, Mulone

  Read the article

• Abstract Design Pattern implementation

  - by Pathachiever11

  I started learning design patterns a while ago (only covered facade and abstract so far, but am enjoying it). I'm looking to apply the Abstract pattern to a problem I have. The problem is: Supporting various Database systems using one abstract class and a set of methods and properties, which then the underlying concrete classes (inheriting from abstract class) would be implementing. I have created a DatabaseWrapper abstract class and have create SqlClientData and MSAccessData concrete class that inherit from the DatabaseWrapper. However, I'm still a bit confused about how the pattern goes as far as implementing these classes on the Client. Would I do the following?: DatabaseWrapper sqlClient = new SqlClientData(connectionString); This is what I saw in an example, but that is not what I'm looking for because I want to encapsulate the concrete classes; I only want the Client to use the abstract class. This is so I can support for more database systems in the future with minimal changes to the Client, and creating a new concrete class for the implementations. I'm still learning, so there might be a lot of things wrong here. Please tell me how I can encapsulate all the concrete classes, and if there is anything wrong with my approach. Many Thanks! PS: I'm very excited to get into software architecture, but still am a beginner, so take it easy on me. :)

  Read the article

• robocode engine: how to design (write) the runtime engine -- the robot world

  - by Bob

  IBM has (had) a free learn-Java program called RoboCode, in which custom robots could be written that would then do battle in a 2D space. I would like to write the environment that supports such robots, but don't know what pattern or design to use. Each robot is a thread. Each thread is given a certain (indeterminate) amount of run-time by the JRE. A robot world engine would start by building a list of the players/robots, then enter a loop that allows each player in turn to do whatever it likes: move forward, turn left, fire toward the northwest corner, whatever. Each robot is also informed of events of interest: an enemy or several enemies are within range, it has been hit by a bullet, etc. The combination of handling threads that are also event listeners (are they also producers?) confuses me; it seems that there's more to the game engine. Even some general ideas would help. TIA.

  Read the article

• How to learn high-level Java web development concepts

  - by titaniumdecoy

  I have some experience writing web applications in Java for class projects. My first project used Servlets and my second, the Stripes framework. However, I feel that I am missing the greater picture of Java web development. I don't really understand the web.xml and context.xml files. I'm not sure what constitutes a Java EE application as opposed to a generic Java web application. I can't figure out how a bean is different from an ordinary Java class (POJO?) and how that differs from an Enterprise Java Bean (EJB). These are just the first few questions I could think of, but there are many more. What is a good way to learn how Java web applications function from the top down rather than simply how to develop an application with a specific framework? (Is there a book for this sort of thing?) Ultimately, I would like to understand Java web applications well enough to write my own framework.

  Read the article

• ASIHTTPRequest code design

  - by nico

  I'm using ASIHTTPRequest to communicate with the server asynchronously. It works great, but I'm doing requests in different controllers and now duplicated methods are in all those controllers. What is the best way to abstract that code (requests) in a single class, so I can easily re-use the code, so I can keep the controllers more simple. I can put it in a singleton (or in the app delegate), but I don't think that's a good approach. Or maybe make my own protocol for it with delegate callback. Any advice on a good design approach would be helpful. Thanks.

  Read the article

• Error in java code.

  - by user243680

  I am getting the following error when i try to use a blue tooth dongle to transfer a video file from pc to mobile phone. does anyone know run: BlueCove log redirected to log4j log4j:WARN No appenders could be found for logger (com.intel.bluetooth). log4j:WARN Please initialize the log4j system properly. BlueCove version 2.1.0 on bluesoleil java.io.IOException: Device not discovered BlueCove stack shutdown completed at com.intel.bluetooth.BluetoothStackBlueSoleil.connectionRfOpenClientConnection(BluetoothStackBlueSoleil.java:361) at com.intel.bluetooth.BluetoothRFCommClientConnection.<init>(BluetoothRFCommClientConnection.java:37) at com.intel.bluetooth.MicroeditionConnector.openImpl(MicroeditionConnector.java:379) at com.intel.bluetooth.MicroeditionConnector.open(MicroeditionConnector.java:162) at javax.microedition.io.Connector.open(Connector.java:83) at de.avetana.obexsolo.OBEXConnector.open(OBEXConnector.java:103) at OBEXTest.main(OBEXTest.java:23)

  Read the article

• N-Tiered application design tool

  - by Ben V

  I'm beginning the design of a medium-sized web application. I usually like to design from the top down, i.e., start at the highest level and design my way down. I am planning to have the following layers: Presentation (PHP/Ajax) Business Logic Data Access Database Now I'd like to start sketching out the major objects in each layer and the interaction between layers. Is there a tool more specific to this purpose than just using a graphics/diagramming tool like Visio?

  Read the article

• Best approach to design a service oriented system

  - by Gustavo Paulillo

  Thinking about service orientation, our team are involved on new application designs. We consist in a group of 4 developers and a manager (that knows something about programming and distributed systems). Each one, having own opinion on service design. It consists in a distributed system: a user interface (web app) accessing the services in a dedicated server (inside the firewall), to obtain the business logic operations. So we got 2 main approachs that I list above : Modular services Having many modules, each one consisting of a service (WCF). Example: namespaces SystemX.DebtService, SystemX.CreditService, SystemX.SimulatorService Unique service All the business logic is centralized in a unique service. Example: SystemX.OperationService. The web app calls the same service for all operations. In your opinion, whats the best? Or having another approach is better for this scenario?

  Read the article

• amazon design doubt

  - by praveen

  I was looking at the amazon website and was wondering how one of the feature would have been implemented. The feature : what customers buy after viewing a particular item. If i were to develop such a feature i would probably generate a session id for each user session and store the session id-page id combination in a log file. and if a book is bought set a separate flag for the session id-page id. A separate program can then be run on the log file periodically, to identify the groups that were bought together/viewed together and that information can be stored in a persistent file. This is ofcourse a simple solution without taking into consideration the distributed nature of the servers - but would this suffice or can you help me identify a better design.

  Read the article

• Need help understanding the MVC design pattern

  - by Doron Sinai

  Hi, I am trying to find a ood example of MVC design pattern in java. This is what i understood from reading about it, please correct me if I am wrong: I have the Model part which is the logic behind the program, let's say if we have a phonebook, so adding and removing contact from the Array will be the model. The Gui is the view and it contains buttons that upon clicking them, the model is changing. What I am trying to undersand what is the controller part, is it the ActionListeners? how to you seperate those modules in practice. thank you

  Read the article

• What software design pattern is best for the following scenario (C#)

  - by askjdh

  I have a gps device that records data e.g. datetime, latitude, longitude I have an sdk that reads the data from the device. The way the data is read: A command packet (basically a combination of int values in a struct) is sent to the device. The device responds with the data in fixed size chunks e.g. 64bytes Depending on the command issued I will get back differect data structs e.g. sending command 1 to the device returns a struct like struct x { id int, name char[20] } command 2 returns a collection of the following structs (basically it boils down to an array of the structs - y[12]) struct y { date datetime, lat decimal, lon decimal } I would then want to convert the struct to a class and save the data to a database. What would be the best way to encapsulate the entire process, preferably using some established design pattern? Many thanks M

  Read the article

• Design pattern for extending Android's activities?

  - by Carl

  While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

  Read the article

• 'is instanceof' Interface bad design

  - by peterRit

  Say I have a class A class A { Z source; } Now, the context tells me that 'Z' can be an instance of different classes (say, B and C) which doesn't share any common class in their inheritance tree. I guess the naive approach is to make 'Z' an Interface class, and make classes B and C implement it. But something still doesn't convince me because every time an instance of class A is used, I need to know the type of 'source'. So all finishes in multiple 'ifs' making 'is instanceof' which doesn't sound quite nice. Maybe in the future some other class implements Z, and having hardcoded 'ifs' of this type definitely could break something. The escence of the problem is that I cannot resolve the issue by adding functions to Z, because the work done in each instance type of Z is different. I hope someone can give me and advice, maybe about some useful design pattern. Thanks

  Read the article

• Design patter for extending Android's activities?

  - by Carl

  While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

  Read the article

• Could you please suggest any good books for Java EE

  - by attal

  Hi people, I am comfortable with Java SE 6 and I wanted to go deeper into Java by learning Java EE 6. However, I am confused and I don't know which book(s) should I read to master Java EE 6 (I have never learned Java EE previously). Could you please suggest any appropriate book(s) to help me master Java EE completely? Thank you for reading

  Read the article

• Web applet game design

  - by Vlad

  I making web games in java and having troubles each time when getting to the GUI design, usually I'm looking at others codes and copy most of the design, and I can't decide which design should I use. I used Applet, Canvas, JFrame. What i need is the main loop and draw function that changing between different games. So what class should I use and what design, which is better, why, maybe links to useful tutorials and examples... Please explain. Thanks.

  Read the article

• CIC 2010 - Ghost Stories and Model Based Design

  - by warren.baird

  I was lucky enough to attend the collaboration and interoperability congress recently. The location was very beautiful and interesting, it was held in the mountains about two hours outside Denver, at the Stanley hotel, famous both for inspiring Steven King's novel "The Shining" and for attracting a lot of attention from the "Ghost Hunters" TV show. My visit was prosaic - I didn't get to experience the ghosts the locals promised - but interesting, with some very informative sessions. I noticed one main theme - a lot of people were talking about Model Based Design (MBD), which is moving design and manufacturing away from 2d drawings and towards 3d models. 2d has some pretty deep roots in industrial manufacturing and there have been a lot of challenges encountered in making the leap to 3d. One of the challenges discussed in several sessions was how to get model information out to the non-engineers in the company, which is a topic near and dear to my heart. In the 2D space, people without access to CAD software (for example, people assembling a product on the shop floor) can be given printouts of the design - it's not particularly efficient, and it definitely isn't very green, but it tends to work. There's no direct equivalent in the 3D space. One of the ways that AutoVue is used in industrial manufacturing is to provide non-CAD users with an easy to use, interactive 3D view of their products - in some cases it's directly used by people on the shop floor, but in cases where paper is really ingrained in the process, AutoVue can be used by a technical publications person to create illustrative 2D views that can be printed that show all of the details necessary to complete the work. Are you making the move to model based design? Is AutoVue helping you with your challenges? Let us know in the comments below.

  Read the article

• Boston: Free Java Developer Event March 3rd!

  - by Jacob Lehrbaum

  Attention Boston area developers!  Oracle has been running a series of free one-day Java Developer events in the US, Europe, and Asia since last November, and on March 3rd, this highly popular series is coming to the Westin Copley Place in Boston.  The Java Developer Day will include four tracks of sessions and hands-on-labs designed for developers interested in Server, Desktop, Embedded, and core Java SE platform topics.  Technologies covered include Java EE, Java ME and Java SE (including the JDK).  From the event page: Come to this free event if you are interested in:Evaluating the Java platformUsing other languages on the JVMBuilding server side JavaConstructing Rich Web or Desktop ApplicationsUnderstanding the JVM and its built in diagnosticsMaking Smart Devices even smarterCheck out the event page to read more and/or register.  The event is free, but space is limited so register today!

  Read the article

• scalablity of Scala over Java

  - by Marcus

  I read an article that says Scala handles concurrency better than Java. http://www.theserverside.com/feature/Solving-the-Scalability-Paradox-with-Scala-Clojure-and-Groovy ...the scalability limitation is confined specifically to the Java programming language itself, but it is not a limitation of the Java platform as a whole... The scalability issues with Java aren't a new revelation. In fact, plenty of work has been done to address these very issues, with two of the most successful projects being the programming languages named Scala and Clojure... ...Scala is finding ways around the problematic thread and locking paradigm of the Java language... How is this possible? Doesn't Scala use Java's core libraries which brings all the threading and locking issues from Java to Scala?

  Read the article

• Java - learning / migrating fast

  - by Yippie-Kai-Yay

  This is not one of those questions like "How do I learn Java extremely fast, I know nothing about programming, but I heard Java is cool, yo". I have an interview for a Java Software Developer in a couple of weeks and the thing is that I think that I know C++ really good and I am somewhat good at C# (like, here I can probably answer on a lot of questions related to these languages), but I have almost zero experience with Java. I have a lot of projects written in both languages, I participiated in several open-source projects (mostly C++, though). Now, what should I do (in your opinion) to prepare myself for this Java interview. I guess migrating from C# to Java should be kind of fast, especially when you know a lot about programming in global, patterns, modern techniques and have a lot of practical experience behind you. But still two weeks is obviously not enough to get Java in-depth - so what should I focus on to have the best chances to pass the interview? Thank you.

  Read the article

• Design for XML mapping scenarios between two different systems [on hold]

  - by deepak_prn

  Mapping XML fields between two systems is a mundane routine in integration scenarios. I am trying to make the design documents look better and provide clear understanding to the developers especially when we do not use XSLT or any other IDE such as jDeveloper or eclipse plugins. I want it to be a high level design but at the same time talk in developer's language. So that there is no requirements that slip under the crack. For example, one of the scenarios goes: the store cashier sells an item, the transaction data is sent to Data management system. Now, I am writing a functional design for the scenario which deals with mapping XML fields between our system and the data management system. Question : I was wondering if some one had to deal with mapping XML fields between two systems? (without XSLT being involved) and if you used a table to represent the fields mapping (example is below) or any other visualization tool which does not break the bank ? I am trying to find out if there is a better way to represent XML mapping in your design documents. The widely accepted and used method seems to be using a simple table such as in the picture to illustrate the mapping. I am wondering if there are alternate ways/ tools to represent such as in Altova:

  Read the article

< Previous Page | 29 30 31 32 33 34 35 36 37 38 39 40  | Next Page >