The first is the download tool: I suggest that beginners use EditPlus JDK, I think if I use, for example, JB, Eclipse, JCREATOR, although it is convenient to start, but even how to configure environment variables, it is difficult to achieve it. It is known to download: editplus (the latest version is V2.11): http://count.skycn.com/softdown.php?id = 3641 & url = http: //sc-http.skycn. Net / down / EPP211A_CN.EXE (I will find it yourself by the registration code, there are many online) JDK (the latest version is java2sdk1_4_2): http://count.skycn.com/softdown.php? id = 3116 & url = http: / /sc-http.skycn.net/down/j2sdk-1_4_2-windows-i586.exe (this is for Windows)
Then you install JDK, I put it below the C: / JDK directory: Then the ClassPath problem: Java running environment will also traverse classpath, even if the operating system uses PATH to search the executable. It is a simple program such as HelloWorld, and JVM will also traverse each path defined by classpath until the corresponding file is found. I believe that the system used is not 2K is XP, then set the path: My Computer -> Properties -> Advanced -> Environment Variables and add: C: / JDK / Bin ;; / JDK / lib can also be configured such: C: / JDK / BIN;; C: /JDK/LIB/dt.jar; c: /jdk/lib/tools.jar ★ Remember: Environment variables. Remember cannot Less, it represents the current path, if there is less error, etc.! Dt.jar is a class library about running the environment. Tools.jar is about the class library for some tools. If there is no configuration: C: / JDK / BIN, "Javac 'is not internal or external command, nor is it runable Or batch files. "This error. Then you will write the program below: First is (HelloWorld.java), open EditPlus, create a new Java file, please enter the following input, you want a word unlike, and select the case: public class helloworld {public static void main String [] args) {system.out.println ("Hello, World!");}} Then save this file (Ctrl S) to HelloWorld.java, remember the case must be divided, is helloworld.java is not HelloWorld.java or other below, start -> Run -> CMD Switch to the current directory in the console: Javac HelloWorld.javajava HelloWorld You will see the output of Hello, World! (no Come out? I take the computer :)) Javac is the compile command, which compiles helloWorld.java to HelloWorld.classjava is the explanation command, and JVM explains the HelloWorld.class. At this time: 1. If Exception in Thread "Main" java.lang.noclassdefounderror: HelloWorld is that you didn't add that in the environment variable. (Dot) 2. If an Exception in Thread "Main" java.lang.nosuchmethoder: main or helloWorld.java: main or helloworld.java: PUBLIC CLAS HELLOWORLD MUST BE Defined in a file caled "HelloWorld.java". That is, you didn't have a case write to this HelloWorld , Or keep it is not saved as helloworld.java, this name must be the same as the name of the public class.
When you have a problem with environmental variables, let's talk about how to compile and run in Editplus, in Tools-> Parameter Settings -> Configuring User Tools 1. Add Tools (Add Apps) Menu Text: Compile Java Program Programs : C: /jdk/bin/javac.exe Parameters: File Name Initial: File Directory 2. Add Tool (Add Application) Menu Text: Run Java Program Program: C: /jdk/bin/java.exe Parameters: File Name (excluding extension) Initial: File Directory Tools Group Name You can add, such as Debug Java Program, then in the Tools drop-down menu, you will see the two options of Compile Java Program and Run Java Program, you will You can use Ctrl 1 to compile and run the program.
Let's discuss the operation of servlet: First, you need to run the servlet, you need JSP / Servlet Container, I suggest that beginners use Tomcattomcat (latest version 5.0): http://cvs.apache.org/builds/jakarta-tomcat-5/nightly /jakarta-tomcat-5-bin-20030725.zip then extract this compressed package to: c: / tomcat and then configure environment variables: Add three system variables: java_home: c: / jdktomcat_home: c: / tomcatclasspath:% java_home % / lib;% Tomcat_Home% / libtomcat's environment variable is configured, check whether Tomcat can run: Go to C: / Tomcat / bin in the console, run startup, then return a window, join one Big string, finally said that Server has run in the browser to enter http: // localhost: 8080, the welcome interface, indicating that Tomcat has no problem, and writes your first servletimport java.io. *; import javax.servlet *;. import javax.servlet.http *;. public class HelloWorld extends HttpServlet {public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Response.setContentType ("text / html"); PrintWriter out = response.getwriter (); out.println ("
); Out.Println (" this is my first servlet); Out.println ("</ Title> </ head> <body>); out.println (" <h1> hello, world! </ h1> "); Out.println (" </ body> </ html > ");}} Then use Javac HelloWorld.java to compile this file, if there is no import javax.servlet. * So you should copy the servlet.jar file inside C: / Tomcat / Common / Lib to C: / JDK / JRE / LIB / EXT, compiled again, there is no problem! Then in the C: / Tomcat / WebApps / root in the Tomcat directory: root / index.html root / welcom.jsp root / web-inf / lib / myservlet.jar (if your servlet .class Prated .jar file, put it under lib) Root / Web-INF / CLASS / HELLOWORLD.CLASS (put the helloWorld.class file generated above) and enter http: // localhost in the browser: 8080 / servlet / helloWorld, that is wrong with the service of Server: Error 404 - NOT FOUND What is going on? Servlet must use the web.xml file below this directory below, open this web.xml file with EP, add <servlet> <servlet-name> HelloWorld </ servlet -Name> <servlet-class> HelloWorld </ servlet-class> </ servlet> <servlet-maping> <servlet-name> HelloWorld </ servlet-name> <url-pattern> / servlet / helloworld </ url-pattern > </ Servlet-maping></p></div><div class="text-center mt-3 text-grey">
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