java runtime exec 运行挂起的问题

我写了一个简单的oracle的备份系统，需要调用expdp和impdp命令。结果发现

int exitCode = Runtime.getRuntime().exec(cmd).waitFor();
if(0 == exitCode){
    // success
}else{
    //failure
}

 这样书写代码之后，晚上执行几千个表的备份的时候，有个数不定的expdp或impdp进程被挂死，不退出。

后来我发现很多人都遇到了类似的问题。解决方法如下：

 

http://blog.csdn.net/rogerjava/article/details/7006987

http://dhruba.name/2012/10/16/java-pitfall-how-to-prevent-runtime-getruntime-exec-from-hanging/

 

public class TESTRuntime {

    public String cmdexeStr = "exp test/test file=d:/daochu.dmp tables=(t_test)";

    public String startRunTime(){
        try {
            Process proc = Runtime.getRuntime().exec(cmdexeStr);
            InputStream errorProcStream = proc.getErrorStream();
            InputStream outputProcStream = proc.getInputStream();
            InputStreamReader errorRead = new InputStreamReader(errorProcStream);
            InputStreamReader outputRead = new InputStreamReader(outputProcStream);
            BufferedReader errorbr = new BufferedReader(errorRead);
            String errorline = null;
               while ((errorline = errorbr.readLine()) != null) {
                   System.out.println("------error:/n"+errorline);
               }
            BufferedReader outputbr = new BufferedReader(outputRead);
            String outputline = null;
               while ((outputline = outputbr.readLine()) != null) {
                   System.out.println("------debug:/n"+outputline);
               }
            int num = proc.waitFor();
            System.out.println("------num:"+num);
                        proc.destroy();
                     } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    public static void main(String[] args) {
        System.out.println("------------start run--------------");
        TESTRuntime test = new TESTRuntime();
        test.startRunTime();
        System.out.println("------------end run--------------");
    }

}