Java
Everthing related to the Java programming language
EJB an MDB best practices on WebLogic Cluster
2Recently I did an audit on a WebLogic 11g platform of one of our customers. There were many problems with the availability of their JAVA Applications. Some of the problems we’re platform related ( installation, configuration and infrastructure related) but a lot of them already existed in an earlier stage at application programming and configuration level.
So I decided to bundle some tips for JAVA programmers how they should configure their EJB, MDB and Servlet applications when they will be deployed on a WebLogic cluster.
This is an example of a typical EJB application architecture in WebLogic Server:
Some hints and tips:
Create simple Java application to post JSON message to CometD Bayeux Channel using Apache HttpClient and Maven style NetBeans project
0The objective discussed in this article is to post messages to a CometD Bayeux Channel with a standalone Java Class – without dependencies on CometD. For example to control from Java the Slideshow introduced in the synchronized Slideshow demo application created using CometD (see previous articles Push based synchronized Slideshow demo application implemented using CometD and jQuery running on Tomcat and Publishing to CometD Bayeux Channel from inside the Oracle Database – PL/SQL based push to CometD Web Client ).
This article describes the creation of a simple Java Class leveraging Apache HttpClient to post HTTP requests (JSON messages) to a CometD Bayeux Channel. The main point is to show working code with the lest dependencies, not an optimal program (it is far from optimal). The article demonstrates how NetBeans and Maven conspire here to make the task as simple as possible. The Maven support in NetBeans allows me to simply create a new Maven style project of (arche)type Java Application.
Using custom functions in EL expressions in JSF 1.x
1EL expressions are one of the main driving forces for JavaServer Faces. Most dynamic characteristics of pages and widgets are governed by EL expressions. In JSF 1.x, there are some limitations for EL expressions that can at times be a little frustrating. One of the limitations is the fact that no custom functions or operators can be used in EL expressions. Quite some time ago, I wrote this article – http://technology.amis.nl/blog/622/how-to-call-methods-from-el-expressions-pre-jsp-20-trick-for-jsps-with-jstl – to demonstrate a trick for using a Map interface implementation to access custom functionality from EL expression after all.
However, things can even be better. Rather than jumping through the somewhat elaborate hoops of implementing the Map and consructing complex EL expressions, there are two other approaches. One is to create a custom EL Resolver can configure it in the faces-config.xml. Another is discussed in this article. It involves registering custom Java methods as eligible for use in EL expressions. And that really makes life a lot easier. It allows us to create EL expressions such as:
#{cel:concat (cel:upper( bean.property), cel:max(bean2.property, More >
Retrieve song lyrics in Java using Screenscraping with JSoup
0Last year I wrote about JSoup, a Java library that helps with screenscraping: Screenscraping from Java using jsoup – effective data gathering from websites (http://technology.amis.nl/blog/13121/screenscraping-from-java-using-jsoup-effective-data-gathering-from-websites). Last month I had another opportunity for using JSoup, this time to gather song lyrics for the songs on a CD. The context in this case was the internal SOA for Java Professionals training program at AMIS. The students did an assignment to complete the second block in this three-piece program. Their assignment required them to implement a Web Service that produced the CD Booklet for a certain CD – returned as PDF document with illustration, song titles and song lyrics. One of the resources we made available to the students was a Java Class that returned song lyrics. It was their challenge to integrate this class in a proper way in their application (be it PL/SQL, SOA Suite 11g or OSB based).
The LyricsGatherer is easily constructed using JSoup and the website http://www.songlyrics.com/ (that suffers from periodic and unfortunate loss of service) :
Using Java to create a report with the JasperReport java API
2In this blog I will describe how to create a Report with JasperReport in Java. For this purpose I have used the Communitie edition of iReport. This edition contains besides JasperReport also iReport. iReport is a report designer for JasperReport. You can download it from http://jasperforge.org/projects/ireport
After installation I started iReport to design a report. I have design a report to create CD booklets. It contains the name of the artist, an album title, an image, the tracklist and the lyrics of these tracks.
Stand-alone Java Client for jWebSocket Server – communicating from Java Client to Web Clients and vice versa over WebSockets
0In a previous article, I have discussed the open source jWebSocket Server and a simple installation and configuration (http://technology.amis.nl/blog/14940/first-steps-with-jwebsocket-open-source-java-framework-for-websockets-installation-and-running-samples). Subsequently, I have shown the implementation of a web client for a synchronized Slideshow application, where WebSocket communication is used to perform Client 2 Client push (http://technology.amis.nl/blog/14949/push-based-synchronized-slideshow-web-application-implemented-using-websockets-and-jwebsocket-server-the-open-source-java-websocket-server). In a third article I have explained how jWebSocket server can be integrated with a Java application that can start the server and interact with it (http://technology.amis.nl/blog/14973/implementing-a-java-server-side-component-for-jwebsocket-server-for-websocket-interaction-with-web-clients). Finally in this article I demonstrate how a stand alone Java Client can connect to a ‘remote’ jWebSocket server and open WebSocket interactions with it.
The functionality realized in this article is a simple Java application that listens to slide selection events as pushed from the clients More >
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