多线程 调用多线程的方法 Runtime与ProcessBuilder

一般我们使用Java运行其他类中的方法的时候，无论是静态调用还是动态调用，都是在当前的进程中执行的。也就是只有一个Java虚拟机实例在运行。有时候需要通过Java代码启动多个Java子进程，这样做会消耗些资源，但是程序变得更稳定。因为新启动的进程是在不同的虚拟机中运行的。

在Windows中，一个虚拟机就是一个

---

有两种方式调用一个进程

1、System.exec

子进程：

package org.zln.thread;

import java.io.File;
import java.io.IOException;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestFile {
    public static void main(String[] args)  {
        try {
            File file = new File("D:\my.txt");
            file.createNewFile();
            System.out.println("被调用成功!");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

主进程：

package org.zln.thread;

import java.io.IOException;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestRuntime {
    public static void main(String[] args) {
        String rootPath = "E:\GitHub\tools\JavaEEDevelop\out\production\Lesson1_JavaSe_Demo1";
        String mainPath = "org.zln.thread.TestFile";
        String command = "java -classpath "+rootPath+" "+mainPath;
        Runtime runtime = Runtime.getRuntime();
        try {
            System.out.println(command);
            runtime.exec(command);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

调用发现在指定目录下创建了文件，但是并没有在控制台输出信息。因为TestFile子进程并没有自己的控制台，改进代码

package org.zln.thread;

import java.io.*;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestRuntime {
    public static void main(String[] args) {
        String rootPath = "E:\GitHub\tools\JavaEEDevelop\out\production\Lesson1_JavaSe_Demo1";
        String mainPath = "org.zln.thread.TestFile";
        String command = "java -classpath "+rootPath+" "+mainPath;
        Runtime runtime = Runtime.getRuntime();
        try {
            System.out.println(command);
            Process process = runtime.exec(command);
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
            String line;
            while ((line = bufferedReader.readLine())!=null){
                System.out.println("子进程输出："+line);
            }
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这里不知为何，在IDE中运行，输出的是乱码，在控制台运行则不是乱码

既然父进程可以获取到子进程的输出，那么父进程如何发送消息给子进程呢？

子进程修改：

package org.zln.thread;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestFile {
    public static void main(String[] args)  {
        try {
            File file = new File("D:\my.txt");
            file.createNewFile();
            System.out.println("被调用成功!");

            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("父进程输入信息："+bufferedReader.readLine());

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

父进程修改：

package org.zln.thread;

import java.io.*;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestRuntime {
    public static void main(String[] args) {
        String rootPath = "E:\GitHub\tools\JavaEEDevelop\out\production\Lesson1_JavaSe_Demo1";
        String mainPath = "org.zln.thread.TestFile";
        String command = "java -classpath "+rootPath+" "+mainPath;
        Runtime runtime = Runtime.getRuntime();
        try {
            System.out.println(command);
            Process process = runtime.exec(command);
            /*向子进程输入*/
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
            bufferedWriter.write("Hello 子进程!");
            bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
            /*获取子进程输出*/
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
            String line;
            while ((line = bufferedReader.readLine())!=null){
                System.out.println("子进程输出："+line);
            }
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

---

2、使用ProcessBuilder建立子进程

package org.zln.thread;

import java.io.*;

/**
 * Created by coolkid on 2015/6/21 0021.
 */
public class TestProcessBuilder {
    public static void main(String[] args) throws IOException {
        ProcessBuilder processBuilder = new ProcessBuilder("java","org.zln.thread.TestFile");
        /*设置工作目录*/
        processBuilder.directory(new File("E:\GitHub\tools\JavaEEDevelop\out\production\Lesson1_JavaSe_Demo1"));
        Process process = processBuilder.start();

         /*向子进程输入*/
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
        bufferedWriter.write("Hello 子进程!");
        bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
            /*获取子进程输出*/
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
        String line;
        while ((line = bufferedReader.readLine())!=null){
            System.out.println("子进程输出："+line);
        }
        bufferedReader.close();


    }
}