尝试使用 Runtime.getRuntime().exec() 执行 Java jar
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Trying to execute a Java jar with Runtime.getRuntime().exec()
提问by Envin
In the project I am working on, I need to execute a script that I have in a resources folder -- in the class path. I am simply testing the final script functionality, since I am on Windows, I needed a way to output a file to STDIN so I created a simple cat.jar program to clone unixs cat command.
在我正在处理的项目中，我需要执行我在资源文件夹中的脚本——在类路径中。我只是在测试最终的脚本功能，因为我在 Windows 上，我需要一种将文件输出到 STDIN 的方法，所以我创建了一个简单的 cat.jar 程序来克隆 unixs cat 命令。
So when I do "java -jar cat.jar someFile.txt" it will output the file to stdout. I'm sure there are different ways of doing what I did.
因此，当我执行“java -jar cat.jar someFile.txt”时，它会将文件输出到标准输出。我确信有不同的方式来做我所做的事情。
Anyways, I want to run that JAR from my main java program. I am doing
无论如何，我想从我的主 Java 程序运行该 JAR。我在做
Runtime.getRuntime().exec("java -jar C:/cat.jar C:/test.txt");
I've tried switching the forward slash to a backward slash and escaping it -- didn't work. Nothing is getting sent to standard out.
我试过将正斜杠切换为反斜杠并转义它 - 没有用。没有任何东西被发送到标准输出。
Where as, if I run the cat jar on its own, I get the file directed to standard out.
如果我自己运行 cat jar，我会将文件定向到标准输出。
What am I doing wrong here? Is this enough information?
我在这里做错了什么？这是足够的信息吗？
采纳答案by Ravi Thapliyal
Use the Processinstance returned by exec()
使用Process返回的实例exec()
Process cat = Runtime.getRuntime().exec("java -jar C:/cat.jar C:/test.txt");
BufferedInputStream catOutput= new BufferedInputStream(cat.getInputStream());
int read = 0;
byte[] output = new byte[1024];
while ((read = catOutput.read(output)) != -1) {
System.out.println(output[read]);
}
References:
http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html
参考资料：http:
//docs.oracle.com/javase/7/docs/api/java/lang/Process.html
By default, the created subprocess does not have its own terminal or console. All its standard I/O (stdin, stdout, stderr) operations will be redirected to the parent process, where they can be accessed via the streams obtained using the methods getOutputStream(), getInputStream(), and getErrorStream().
默认情况下，创建的子进程没有自己的终端或控制台。它的所有标准 I/O（stdin、stdout、stderr）操作都将被重定向到父进程，在那里可以通过使用 getOutputStream()、getInputStream() 和 getErrorStream() 方法获得的流访问它们。
http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html#getInputStream()
http://docs.oracle.com/javase/7/docs/api/java/lang/Process.html#getInputStream()
getInputStream() returns the input stream connected to the normal output of the subprocess.
getInputStream() 返回连接到子进程正常输出的输入流。
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