Whatever the Java application server is, it has a built-in JDK version.
Therefore, mastering JDK is the first step to learn Java well.
The most mainstream JDK is the JDK released by Sun Company. Besides Sun, many companies and organizations have developed their own JDK, such as Jrocket developed by IBM, JRocket developed by BEA, GNU and so on.
Among them, the JVM included in IBM's JDK is much more efficient than the JVM included in SunJDK.
Jrocket, which runs exclusively on x86 platform, is much more efficient on the server side than SunJDK.
But in any case, you still have to master SunJDK first.
1, download and install JDK JDK, also called J2SE (Java 2 sdkstandardization), which can be downloaded from Sun's Java website, #/j2se/downloads.html; The latest version of JDK is J2SDK 1.4.2. It is recommended to download this version of JDK. The download page is here:/wsdd/; , download connection of Websphere: http://#/wsdd/downloads/wassupport.html; .
4.JbossJboss is a free and open source AppServer, which can be downloaded from Jboss website for free: #/index.html, but Jboss documents are not free and need to be purchased, so it sets certain obstacles for us to learn Jboss.
There are several good Jboss configuration documents on Jdon, which can be referred to as: http://#/idea.html; Fourth, the running environment of Java applications Java applications can be simply divided into the following aspects: 1, and Java desktop applications generally only need JRE support.
2.JavaWeb applications Java Web applications need to install at least JDK, a Web container (such as Tomcat) and a multi-user database. Web application is divided into at least three layers: browser layer: browser displays user pages, web layer: running Servlet/JSPDB layer: back-end database, providing data access services for Java programs. Java enterprise application Enterprise application is very complex and can be extended to N layers. The simplest case will be divided into four layers: browser layer: browser displays user pages; client layer: Java client graphics programs (or programs of embedded devices) directly interact with Web layer or EJB layer; Web layer: run Servlet/JSPEJB layer: run EJB to complete business logic operations; DB layer: back-end database to provide data access services for Java programs. Embedded application in 4.Java Java embedded application is a new field, and it is necessary to download J2ME development package from Sun to engage in embedded development. J2ME includes a special virtual machine KVM for embedded devices, which is different from the JVM included in ordinary JDK.
In addition, you need to download the emulator from a specific embedded vendor.