Java的RMI(远程方法调用)的实现范例

这个范例是基于JDK1.5的RMI程序搭建。

主要将服务器端和客户端分布在两个独立的项目工程中，以实现客户端传递参数到服务器端，服务器端返回查询结果的过程。

1.在Eclipse里面创建一个server 端的project。然后创建一个接口(IRemote)，这个接口是你要向client端开放的方法定义。 里面开放一个通过参数返回结果的方法。并且这个接口继承java.rmi.Remote接口。

package rmi.server.remote;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface IRemote extends Remote {

public String querySQL(String userId) throws RemoteException;

}

2.创建上述接口(IRemote)的实现类(RemoteImpl)。

package rmi.server.remote;

import java.rmi.RemoteException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class RemoteImpl implements IRemote {

private final static String URL = "jdbc:oracle:thin:@(description=(address_list=(address=(host=192.168.0.80)(protocol=tcp)(port=1521))(load_balance=yes)(failover=on))(connect_data=(service_name=mgdb01)))";
private final static String USERNAME = "DBUSER";
private final static String PASSWORD = "DBPASSWORD	";

public RemoteImpl() throws RemoteException {
}

public String querySQL(String userId) throws RemoteException {
StringBuffer sb = new StringBuffer();

Connection connection = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);

String query = "select * from u_user where user_id = '" + userId + "'";
Statement statement = connection.createStatement();
ResultSet rs = statement.executeQuery(query);

while (rs.next()) {
sb.append(" | user id:");
sb.append(rs.getString("USER_ID"));
sb.append(" | nick name:");
sb.append(rs.getString("USER_NICK_NAME"));
sb.append(" | password:");
sb.append(rs.getString("USER_PASSWORD"));
sb.append("\r\n");
}
rs.close();
statement.close();
connection.close();
} catch (Exception e) {
try {
if (connection != null) {
connection.close();
}
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
}

return sb.toString();
}
}

3. 定义一个服务器端主程序入口，注册你已经实现的RMI接口，包括开放端口等。

package rmi.server;

import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

import rmi.server.remote.IRemote;
import rmi.server.remote.RemoteImpl;

public class Server {

public static void main(String[] args) throws AlreadyBoundException,
RemoteException {

RemoteImpl remoteObj = new RemoteImpl();

IRemote userManager = (IRemote) UnicastRemoteObject.exportObject(remoteObj, 0);

// Bind the remote object in the registry
Registry registry = LocateRegistry.createRegistry(2001);
registry.rebind("userManager", userManager);

System.out.println("server is ready");
}
}

4.到目前为止，Server端的代码已经全部写完。现在将接口（IRemote）打包成jar，导入到客户端工程中。



5.开始创建client端的程序。新建一个project。创建完成后，把刚才jar包导入进client的项目中。

6.导入接口jar以后，可以开始编写一个client端的主程序，并调用server端的方法。

package rmi.client;

import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

import rmi.server.remote.IRemote;

public class Client {

public static void main(String[] args) {
try {
Registry registry = LocateRegistry.getRegistry("localhost", 2001);

IRemote userManager = (IRemote) registry.lookup("userManager");

String strResult = userManager.querySQL("EU0000000095");
System.out.println(strResult);

strResult = userManager.querySQL("EU0000000168");
System.out.println(strResult);

strResult = userManager.querySQL("EU0000000169");
System.out.println(strResult);

} catch (RemoteException e) {
e.printStackTrace();
} catch (NotBoundException e) {
e.printStackTrace();
}

}
}

7.执行步骤，先执行服务器端程序，然后再执行客户端程序。