java热部署的简单例子

核心提示：本文纯粹就是将一篇英文文章的一个段落翻译一下，并将例子跑通，java热部署的简单例子，原文出处：http://java.sun.com/developer/TechTips/2000/tt1027.html我的目录结构是 d://hotdeploy//Client.javad://hotdeploy//ServerIt

本文纯粹就是将一篇英文文章的一个段落翻译一下，并将例子跑通。

原文出处：http://java.sun.com/developer/TechTips/2000/tt1027.html

我的目录结构是

d://hotdeploy//Client.java

d://hotdeploy//ServerItf.java

d://hotdeploy//server//ServerImpl.java

文件内容依次为：

//file Client.java
import java.net.URL;
import java.net.URLClassLoader;
import java.io.BufferedReader;
import java.io.InputStreamReader;


public class Client {
static ClassLoader cl;

static ServerItf server;

public static void loadNewVersionOfServer() throws Exception {
　URL[] serverURLs = new URL[] { new URL("file://d:/hotdeploy/server/") };
　cl = new URLClassLoader(serverURLs);
　server = (ServerItf) cl.loadClass("ServerImpl").newInstance();
}

public static void test() throws Exception {
　BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
　loadNewVersionOfServer();
　while (true) {
　 System.out.PRint("Enter QUOTE, RELOAD, GC, or QUIT: ");
　 String cmdRead = br.readLine();
　 String cmd = cmdRead.toUpperCase();
　 if (cmd.equals("QUIT")) {
　　return;
　 } else if (cmd.equals("QUOTE")) {
　　System.out.println(server.getQuote());
　 } else if (cmd.equals("RELOAD")) {
　　loadNewVersionOfServer();
　 } else if (cmd.equals("GC")) {
　　System.gc();
　　System.runFinalization();
　 }
　}
}

public static void main(String[] args) {
　try {
　 test();
　} catch (Exception e) {
　 e.printStackTrace();
　}
}
}

-------------------------------------------------------------------------

public interface ServerItf {
　public String getQuote();
}

-------------------------------------------------------------------------


public class ServerImpl implements ServerItf {

// catch the class being unloaded from the VM
static Object reporter = new Reporter(ServerImpl.class);

public String getQuote() {
　return "i love you";
}
}

// file ServerImpl.java. Place this file
// in a subdirectory named 'server'.
class Reporter {
Class cls;

Reporter(Class cls) {
　this.cls = cls;
　System.out.println("ServerImpl class " + cls.hashCode()
　　+ " loaded into VM");
}

protected void finalize() {
　System.out.println("ServerImpl class " + cls.hashCode()
　　+ " unloaded from VM");
}
}

-------------------------------------------------------------------------

运行的命令依次为：

D:\hotdeploy>javac Client.java

D:\hotdeploy>javac ServerItf.java

D:\hotdeploy>javac -cp d:\hotdeploy d:\hotdeploy\server\ServerImpl.java

D:\hotdeploy>java Client
ServerImpl class 1641745 loaded into VM
Enter QUOTE, RELOAD, GC, or QUIT: quote
i love you
Enter QUOTE, RELOAD, GC, or QUIT:

-------------------------------------------------------------------------

编辑ServerImpl.java为：

public class ServerImpl implements ServerItf {

// catch the class being unloaded from the VM
static Object reporter = new Reporter(ServerImpl.class);

public String getQuote() {
　return "you love me";
}
}

// file ServerImpl.java. Place this file
// in a subdirectory named 'server'.
class Reporter {
Class cls;

Reporter(Class cls) {
　this.cls = cls;
　System.out.println("ServerImpl class " + cls.hashCode()
　　+ " loaded into VM");
}

protected void finalize() {
　System.out.println("ServerImpl class " + cls.hashCode()
　　+ " unloaded from VM");
}
}

-------------------------------------------------------------------------

打开另外一个dos窗口，运行javac -cp d:\hotdeploy d:\hotdeploy\server\ServerImpl.java

-------------------------------------------------------------------------

回到原先的doc窗口，依次运行

Enter QUOTE, RELOAD, GC, or QUIT: reload
ServerImpl class 12677476 loaded into VM
Enter QUOTE, RELOAD, GC, or QUIT: quote
you love me
Enter QUOTE, RELOAD, GC, or QUIT:

可以看到效果。