Runtime.getRuntime().exec()执行阻塞和不能执行管道命令的问题
1.不能执行管道命令的处理方式：
windows平台使用 Runtime.getRuntime().exec(String[]{"cmd", "/k", "cmd str"});
linux平台使用 Runtime.getRuntime().exec(String[]{"sh", "-c", "cmd str"});
下面是Process类的完整例子：
String[] cmds = new String[]{"sh", "-c", "cmd str"};
if (System.getProperty("os.name").toLowerCase().contains("windows")) {
cmds = new String[]{"cmd", "/k", "cmd str"};
}
Process ps = null;
try {
ps = Runtime.getRuntime().exec(cmds);
doInputProcess(ps.getIntputStream());
doErrorProcess(ps.getErrorStream());
doOutProcess(ps.getOutputStream());
// System.out.println("start.");
ps.waitFor();
// System.out.println("done.");
} catch (Exception e) {
//
} finally{
try {
if(ps != null)
ps.destroy();
} catch (Exception ec) {
//
}
}
2.执行阻塞问题
必须要同时处理完输入流process.getInputStream()和输出流process.getOutputStream()，错误流process.getErrorStream()可以不用考虑，并且每个流都需要工作在不同的线程，否则上例中的ps.waitFor();后面的语句永远不会被执行！
我们可以把上例写个JSP web项目验证一下
新建index.jsp文件放在share项目下，代码如下：
<%@page import="java.io.*" contentType="text/html; charset=UTF-8" %>
<%@page import="java.lang.StringBuilder" contentType="text/html; charset=UTF-8" %>
<!DOCTYPE html>
<html>
<head>
<title>Runtime.getRuntime().exec()</title>
</head>
<body>
<%!
void inputProcess(final InputStream in, final JspWriter out, String name){
//必须是新线程
new Thread(new Runnable() {
@Override
public void run() {
if(in == null) return;
try {
int a = -1;
byte[] b = new byte[2048];
while ((a = in.read(b)) != -1) {
out.println(new String(b));
}
} catch (Exception e) {
} finally{
try {
if(in != null ) in.close();
} catch (Exception ec) {
}
}
}
}, name).start();
}
void doInputProcess(InputStream in, JspWriter out){
inputProcess(in, out, "inputProcess");
}
void doErrorProcess(InputStream in, JspWriter out){
inputProcess(in, out, "errProcess");
}
void doOutputProcess(OutputStream out){
try {
out.close();//直接关闭流
} catch (Exception ec) {
}
}
%>
<%
String cmd = request.getParameter("cmd");
if(cmd != null && !"".equals(cmd)){
String[] cmds = new String[]{"sh", "-c", cmd};
if (System.getProperty("os.name").toLowerCase().contains("windows")) {
cmds = new String[]{"cmd", "/k", cmd};
}
Process ps = null;
try {
ps = Runtime.getRuntime().exec(cmds);
out.println("start.");
out.println("<pre>");
doInputProcess(ps.getInputStream(), out);
doErrorProcess(ps.getErrorStream(), out);
doOutputProcess(ps.getOutputStream());
ps.waitFor();
out.println("</pre>");
out.println("done.");
} catch (Exception e) {
out.println("err.");
} finally{
try {
if(ps != null) ps.destroy();
} catch (Exception ec) {
}
}
return;
}
if("true".equals(request.getParameter("c"))){
return;
}
out.println("<div style='margin: 20px'>虚拟终端：<input id='command' type='text' value='netstat -an' style='width: 250px;border: none;color: red;background-color: black;'/>"
+ "<a style='color: blue' onclick=\"var m= top.document.getElementById('command').value;if(!m) return false; top.document.getElementById('view-file').setAttribute('src', './index.jsp?cmd=' + encodeURIComponent(m));\" href=\"#\">执行</a>"
+ "</div>");
out.println("<div style='margin-top: 20px; padding: 5px; height: 500px'>"
+ "<iframe id='view-file' src='./index.jsp?c=true' height='100%' style='width: 100%; height: 100%' frameborder='0'></iframe>"
+ "</div>");
%>
</body>
</html>
浏览器访问当前JSP文件，输入网址：http://localhost:8080/share/index.jsp
正常执行上面的index.jsp脚本，输入一个命令ipa，服务器相应了200，说明后台没被阻塞
当我们将index.jsp中标红的“doOutputProcess(ps.getOutputStream());”这行代码注释掉之后，在执行同一个命令，会发现请求一直处于阻塞状态，done.也没有被打印下来
总结此问题，要想Runtime.getRuntime().exec()这个进程正常退出，不被阻塞需要配合多个线程，并至少关闭ps.getInputStream()和ps.getOutputStream()两个输入输出流