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：
1 package org.zln.thread;
2
3 import java.io.File;
4 import java.io.IOException;
5
6 /**
7 * Created by coolkid on 2015/6/21 0021.
8 */
9 public class TestFile {
10 public static void main(String[] args) {
11 try {
12 File file = new File("D:\\my.txt");
13 file.createNewFile();
14 System.out.println("被调用成功!");
15
16 } catch (IOException e) {
17 e.printStackTrace();
18 }
19 }
20 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestFile.java
主进程：
1 package org.zln.thread;
2
3 import java.io.IOException;
4
5 /**
6 * Created by coolkid on 2015/6/21 0021.
7 */
8 public class TestRuntime {
9 public static void main(String[] args) {
10 String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
11 String mainPath = "org.zln.thread.TestFile";
12 String command = "java -classpath "+rootPath+" "+mainPath;
13 Runtime runtime = Runtime.getRuntime();
14 try {
15 System.out.println(command);
16 runtime.exec(command);
17
18 } catch (IOException e) {
19 e.printStackTrace();
20 }
21 }
22 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java
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
1 package org.zln.thread;
2
3 import java.io.*;
4
5 /**
6 * Created by coolkid on 2015/6/21 0021.
7 */
8 public class TestRuntime {
9 public static void main(String[] args) {
10 String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
11 String mainPath = "org.zln.thread.TestFile";
12 String command = "java -classpath "+rootPath+" "+mainPath;
13 Runtime runtime = Runtime.getRuntime();
14 try {
15 System.out.println(command);
16 Process process = runtime.exec(command);
17 BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
18 String line;
19 while ((line = bufferedReader.readLine())!=null){
20 System.out.println("子进程输出："+line);
21 }
22 bufferedReader.close();
23 } catch (IOException e) {
24 e.printStackTrace();
25 }
26 }
27 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java
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：
1 package org.zln.thread;
2
3 import java.io.BufferedReader;
4 import java.io.File;
5 import java.io.IOException;
6 import java.io.InputStreamReader;
7
8 /**
9 * Created by coolkid on 2015/6/21 0021.
10 */
11 public class TestFile {
12 public static void main(String[] args) {
13 try {
14 File file = new File("D:\\my.txt");
15 file.createNewFile();
16 System.out.println("被调用成功!");
17
18 BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
19 System.out.println("父进程输入信息："+bufferedReader.readLine());
20
21 } catch (IOException e) {
22 e.printStackTrace();
23 }
24 }
25 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestFile.java
父进程修改：
1 package org.zln.thread;
2
3 import java.io.*;
4
5 /**
6 * Created by coolkid on 2015/6/21 0021.
7 */
8 public class TestRuntime {
9 public static void main(String[] args) {
10 String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
11 String mainPath = "org.zln.thread.TestFile";
12 String command = "java -classpath "+rootPath+" "+mainPath;
13 Runtime runtime = Runtime.getRuntime();
14 try {
15 System.out.println(command);
16 Process process = runtime.exec(command);
17 /*向子进程输入*/
18 BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
19 bufferedWriter.write("Hello 子进程!");
20 bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
21 /*获取子进程输出*/
22 BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
23 String line;
24 while ((line = bufferedReader.readLine())!=null){
25 System.out.println("子进程输出："+line);
26 }
27 bufferedReader.close();
28 } catch (IOException e) {
29 e.printStackTrace();
30 }
31 }
32 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java
2、使用ProcessBuilder建立子进程
1 package org.zln.thread;
2
3 import java.io.*;
4
5 /**
6 * Created by coolkid on 2015/6/21 0021.
7 */
8 public class TestProcessBuilder {
9 public static void main(String[] args) throws IOException {
10 ProcessBuilder processBuilder = new ProcessBuilder("java","org.zln.thread.TestFile");
11 /*设置工作目录*/
12 processBuilder.directory(new File("E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1"));
13 Process process = processBuilder.start();
14
15 /*向子进程输入*/
16 BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
17 bufferedWriter.write("Hello 子进程!");
18 bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
19 /*获取子进程输出*/
20 BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
21 String line;
22 while ((line = bufferedReader.readLine())!=null){
23 System.out.println("子进程输出："+line);
24 }
25 bufferedReader.close();
26
27
28 }
29 }
E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestProcessBuilder.java
时间： 2024-10-26 23:06:59