Java Learning Path (i), tools
First, JDK (Java development Kit)
The JDK is the core of the entire Java, including the Java Runtime (Java Runtime Envirnment), a stack of Java tools, and a Java-based class library (Rt.jar). Any Java application server is essentially a built-in version of the JDK. So mastering the JDK is the first step to learning Java. The most mainstream JDK is the JDK released by Sun, and in addition to sun, many companies and organizations have developed their own JDK, such as Jrocket, a JDK,BEA company developed by IBM, and a JDK developed by the GNU organization. Where IBM's JDK contains a JVM (Java Virtual machine) that runs much more efficiently than the JVM contained in the Sun JDK. The jrocket running on the x86 platform is also much more efficient than the sun JDK on the service side. But in any case, we need to get the sun JDK in the first place.
1. Download and install the JDK
The JDK, also known as J2SE (Java2 SDK standard Edition), can be downloaded from the Sun's Java Web site, http://java.sun.com/j2se/ DOWNLOADS.HTML,JDK currently the latest version is j2sdk1.4.2, it is recommended to download the version of the JDK, download page here: http://java.sun.com/j2se/1.4.2/download.html.
The downloaded JDK is an executable installer that installs a set of JRE (for browser use) in the C:\Program files\java\ directory and installs a JDK (including a set of JRE) under C:\j2sdk1.4.2 under the default installation. Then we need to add the Java path C:\j2sdk1.4.2\bin to the front of the environment variable path. The JDK is ready to install.
2. Command Tools for JDK
The most important command-line tool for the JDK:
java: Start JVM execution Class
Javac:java Compiler
Jar:java Packaging Tools
Javadoc:java Document Generator
These command lines must be very familiar and proficient for each parameter. For the learning of these commands, there are detailed documentation on the JDK documentation.
Second, JDK documentation
documentation also has a download connection on the download page of the JDK, and it is recommended to download documentation. Documentation is one of the most important programming manuals, covering all aspects of Java's content description. It can be said that learning Java programming, most of the time is spent looking at this documentation above. I am carrying, write Java code, at any time to view, a moment not to leave the hand.
Application servers (app server)
App Server is the platform for running Java Enterprise Components, which forms the main operating environment of the application software. The current mainstream app server is Bea's WebLogic server and IBM's WebSphere and free JBoss, choose one to study on it, personally recommend WebLogic, because its architecture is cleaner, Development and deployment are more convenient and are the preferred development platform for Java enterprise software developers. Here's a brief introduction to several common app servers:
1. Tomcat
Tomcat is strictly not a real app server, it's just a web container that can support running serlvet/jsp, but Tomcat also extends some of the features of app server, such as Jndi, database connection pooling, user transaction processing, and so on. Tomcat is very widely used in small to medium-sized Java Web applications, so this article does a little about downloading, installing, and configuring Tomcat:
Tomcat is a subproject under the Jakarta Project under the Apache organization, and its main site is: http://jakarta.apache.org/tomcat/.
The latest version of Tomcat is Tomcat4.1.27, the connection for software downloads is: http://www.apache.org/dist/jak...ta/tomcat-4/binaries/.
download Tomcat can either download the zip package directly, or download the EXE installation package (personal advice zip cleaner), in either case, the download is complete after the installation (Zip Direct decompression is OK). Two environment variables need to be set:
java_home=c:\j2sdk1.4.2
CATALINA_HOME=D:\TOMCAT4 (your Tomcat installation directory)
This installs, launches the Tomcat run Catalina_home\bin\startup.bat, closes the Tomcat run Shutdown.bat script. After Tomcat is started, 8080 ports are used by default, so you can use your browser to access http://localhost:8080 to test whether Tomcat starts properly.
Tomcat provides two web interface management tools, the URLs are:
http://localhost:8080/admin/index.jsp
http://localhost:8080/manager/html
Before you enable these two administrative tools, you need to manually configure the administrator user and password. Open the Catalina_home\conf\tomcat-users.xml file with a text tool and add the following lines:
<role rolename= "manager"/>
<role rolename= "admin"/>
<user username= "Robbin" password= "12345678" roles= "Admin,manager,tomcat"/>
This allows the user "Robbin" to have Super Administrator privileges. After you restart Tomcat, you can use that user to log in to the two administrative tools on the Web for Tomcat configuration and management.
2. BEA Weblogic
WebLogic can go to Bea's website for free to download to the latest Weblogic8.1 Enterprise Edition, license free to use 1 years, in fact, this is completely enough. Download connection for WebLogic: Http://commerce.bea.com/index.jsp,Weblogic's online document: http://edocs.bea.com/.
3. IBM Webshpere
WebSphere can also be downloaded to a free trial version of IBM's Developerworks website to see the download of WebSphere trial products and related WebSphere data, DeveloperWorks Chinese website is connected to: http://www-900.ibm.com/developerWorks/cn/wsdd/, WebSphere Download connection:/http Www7b.software.ibm.com/...loads/wassupport.html.
4. Jboss
JBoss is a free, open source app Server that can be downloaded free of charge from the JBoss website: http://www.jboss.org/index.html, but JBoss documentation is not free and needs to be paid for, so there are some hurdles to learning about JBoss.
There are several good JBoss configuration documents on Jdon, which can be used for reference: http://www.jdon.com/idea.html
IV. Operating environment for Java applications
Java applications can be easily divided into the following areas:
1. Desktop applications for Java
desktop applications generally require only the JRE support to be sufficient.
2. Java Web Application
Java Web Apps require at least a JDK and a web container (such as Tomcat), and a multiuser database, with at least three layers of web apps:
Browser layer: Browser display user page
Web tier: Running servlet/jsp
DB layer: Back-end database, providing data access services to Java programs
3, Java Enterprise-class applications
enterprise applications are more complex and can be scaled to n-tier, with the simplest case being divided into 4 tiers:
Browser layer: Browser display user page
Client layer: the Java Client graphics program (or the embedded device's program) interacts directly with the Web layer or the EJB layer
Web tier: Running servlet/jsp
EJB layer: Run EJB to complete business logic operation
DB layer: Back-end database, providing data access services to Java programs
4. Java Embedded Application
Java Embedded application is a burgeoning field, engaged in embedded development, need to download the J2ME development package from Sun, J2ME contains the embedded device dedicated virtual machine KVM, and the common JDK contains a different JVM. There is also a need to download the simulator to a specific embedded vendor.
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