java执行bat阻塞的解决方法

java在执行.bat文件时,经常会出现卡住不动的情况,我们称之为阻塞.
发生阻塞的原因是,在使用Runtime.getRuntime.exec("xx:/xxxx.bat")时,会有outputStream,ErrStream,InputStream三个IO流,如果这三个IO流都有数据的传输操作,那么必须对每一个IO流进行处理,如果有一个IO流漏处理了,那么程序将无限期的等待该IO流被处理,继而程序阻塞.
下面,已java打开安装apache2.2的.bat文件为例,说明一下如何处理阻塞.

package com.multiable.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.concurrent.CountDownLatch;

public class TestApache {

	public static void main(String[] args) {
		try {
			final CountDownLatch threadSignal = new CountDownLatch(2);//初始化countDown
			
			System.out.println("Start ......");
			final Process pro = Runtime.getRuntime().exec("cmd /c \"c:\\start.bat\"");
			pro.getOutputStream().close();
			Runnable errThread = new Runnable() {
				@Override
				public void run() {
					try {
						InputStream is = pro.getErrorStream();
						InputStreamReader isr = new InputStreamReader(is);
						BufferedReader br = new BufferedReader(isr);
						String line = "";
						StringBuilder sb = new StringBuilder();
						while((line = br.readLine()) != null) {
							sb.append(line);
						}
						System.out.println("error : " + sb.toString());
					} catch (IOException e) {
						e.printStackTrace();
					}
					
					threadSignal.countDown();//线程结束时计数器减1 
				}
			};
			
			new Thread(errThread).start();
			
			Runnable inputThread = new Runnable() {
				@Override
				public void run() {
					try {
						InputStream is = pro.getInputStream();
						InputStreamReader isr = new InputStreamReader(is);
						BufferedReader br = new BufferedReader(isr);
						String line = "";
						StringBuilder sb = new StringBuilder();
						while((line = br.readLine()) != null) {
							sb.append(line);
						}
						System.out.println("input : " + sb.toString());
						
						is.close();
						isr.close();
						br.close();
					} catch (IOException e) {
						e.printStackTrace();
					}
					
					threadSignal.countDown();//线程结束时计数器减1 
				}
			};
			
			new Thread(inputThread).start();
			try {
				threadSignal.await();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println("=========================");
			Runtime.getRuntime().exec("cmd /c net start apache2.2");
			System.out.println("cmd /c net start apache2.2");
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

关于OutputStream,程序用不到,直接在开始的时候就应该close掉.对于errStream & inputStream应该分别用一个线程来读取出IO流中的内容.
注意:必须使用线程,否则依然会阻塞.

final CountDownLatch threadSignal = new CountDownLatch(2);//初始化countDown
这一个栏位是用来让主线程等待两个子线程执行完毕用的.

评论

2 楼 lanfen100 2014-06-16  

try { 
                threadSignal.await(); 
            } catch (InterruptedException e) { 
                e.printStackTrace(); 
            } 


这里为什么要 await() 等待呢？？？？

1 楼 染色体zz 2013-01-09  

  学习了,找了好久,用线程处理也试过几种,都差不多类型,后来需要读取到运行Bat文件的内容,只有写入文件,才能.