First, JAVA Development Kit)
JDK is the core of the entire Java, including Java Runtime Envir, a bunch of Java Tools, and Java-based class libraries (RT.jar). Regardless of the Java application server, it is built into a version of JDK. So master JDK is the first step in learning Java. The mainstream JDK is the JDK released by Sun. In addition to Sun, many companies and organizations have developed their JDK, such as the JDKTed by IBM, BEA's JROCKET, as well as GNU organizations, etc. . The JVM (Java Virtual Machine) of the IBM's JDK is much higher than the JVM contained in Sun JDK. Jrockets running in the X86 platform are also much better than Sun JDK in the X86 platform. But no matter what, we still need to master Sun JDK first.
1, JDK download and installation
JDK is also known as J2SE (Java2 SDK Standard Edition), you can download from Sun's Java website, http: //java.sun.com/j2se/downloads.html, JDK current latest version is J2SDK1.4.2, it is recommended to download it Version JDK, download page here: http://java.sun.com/j2se/1.4.2/download.html.
Downloading JDK is an executable installer, the default installation will be installed in the C: / Program files / java / directory, install a set under C: /J2SDK1.4.2 JDK (also included a set of JRE). Then we need to increase Java path C: /J2SDK1.4.2/bin at the forefront of the environment variable Path. This way, JDK is installed.
2, JDK command tool
JDK's most important command line tool:
Java: Start JVM to perform CLASS
Javac: Java compiler
JAR: Java Packing Tool
Javadoc: Java Document Builder
These command lines must be very familiar, and they must be very proficient in each parameter. For these commands, there is a detailed documentation on the JDK Documentation.
Second, JDK Documentation
Documentation also has downloaded connections in the JDK download page, which is recommended to download the Documentation at the same time. Documentation is the most important programming manual covers the description of all Java all aspects. It can be said that learning Java programming, most of the time is watching this documentation. I am carrying it with you, when I write Java code, I will see it at any time.
Third, the application server (App Server)
App Server is a platform running Java Enterprise Components that forms the main operating environment of the application. The current mainstream App Server is a WebLogic Server and IBM's WebSphere and free JBOS, and one of them can be learned. Personally recommend WebLogic, because it is more convenient, developed and deployed, is Java Enterprise software developers preferred development platform. Believe in a brief introduction to several common App Server:
1, Tomcat
Tomcat is not a real app server, it is just a web container that supports running Servervet / JSP, but Tomcat has also extended some App Server features such as JNDI, database connection pool, user transaction, and more. Tomcat is very widely used in small and medium-sized Java web applications, so this article does a little download, install, and configure Tomcat: Tomcat is a sub-project under the Jakarta project under Apache, its main website is: http: / /jakarta.apache.org/tomcat/, Tomcat The latest version is Tomcat 5.0.16, the software download connection is: http://www.apache.org/dist/jakarta/tomcat-5/v5.0.16/.
Download Tomcat can download the ZIP package directly, you can also download the EXE installation package (personal suggestion zip cleaner), no matter which case, after downloading (ZIP direct decompression). Need to set two environment variables:
Java_Home = C: /J2SDK1.4.2
Catalina_home = d: / tomcat4 (your Tomcat installation directory)
This is installed, start Tomcat Run Catalina_Home / Bin / Startup.bat, close Tomcat running shutdown.bat scripts. After Tomcat starts, the 8080 port is used by default, so you can use your browser to access http: // localhost: 8080 to test whether Tomcat is started normally.
Tomcat provides two management tools for two web interfaces, and the URLs are:
Http: // localhost: 8080 / admin / index.jsp.jsp
Http: // localhost: 8080 / manager / html
Before enabling these two management tools, you need to manually configure the administrator user and password. Use a text tool to open Catalina_home / conf / tomcat-user.xml, add the following line:
This user "Robbin" has super administrator privileges. After restarting Tomcat, you can use the user to log in to the above two management tools, and perform Tomcat configuration and manage through the web mode.
2, Bea WebLogic
WebLogic can be downloaded to WebLogic8.1 Enterprise Edition after free from the BEA website. License can use for free for free, in fact, this is complete enough. WebLogic download: http://commerce.bea.com/index.jsp, webLogic's online document: http://edocs.bea.com/.
3, IBM WebShpere
WebSphere can also be downloaded to the free trial version, to the IBM's developerWorks website, you can see the download and related WebSphere's data for WebSphere trial products, the connection of WebSphere, the connection: http://www-900.ibm.com/developerWorks / CN / WSDD /, WebSphere download: http://www7b.software.ibm.com/wsdd/downloads/wassupport.html. 4, JBoss
JBoss is a free open source App Server, you can download free from JBoss website: http://www.jboss.org/index.html, however JBoss's document is not free, you need to spend money, so learn JBoss settings for us. A certain obstacle. There are a few good JBoss configuration documents on JDON, which can be used for reference: http://www.jdon.com/idea.html
Fourth, Java application operating environment
Java applications can be divided into the following aspects:
1, Java desktop application
Desktop applications generally only need JRE support is sufficient.
2, Java web application
Java's web application requires at least JDK and a web container (such as Tomcat), and a multi-user database, the web application is at least three layers:
Browser layer: browser displays user page
Web layer: Run servlet / jsp
DB layer: backend database provides data access services to Java programs
3, Java enterprise application
Enterprise applications are more complicated, can be extended to N layers, the simplest situation will be divided into 4 layers:
Browser layer: browser displays user page
Client layer: Java client graphics (or programs for embedded devices) interact with Web or EJB
Web layer: Run servlet / jsp
EJB layer: Run EJB, complete business logic
DB layer: backend database provides data access services to Java programs
4, Java embedded application
Java embedded applications are the field of unreasonable, engage in embedded development, need to download J2ME development kits from Sun, J2ME contains embedded device-specific virtual machine KVM, and the JVM contained in the normal JDK is different. It also needs to download the simulator to a specific embedded vendor.
