在 Java 中捕获标准输出的内容
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/5389632/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Capturing contents of standard output in Java
提问by Shailesh Tainwala
I am invoking a function that is printing some string in my console/standard output. I need to capture this string. I cannot modify the function that is doing the printing, nor change runtime behavior through inheritance. I am unable to find any pre-defined methods that will allow me to do this.
我正在调用一个在控制台/标准输出中打印一些字符串的函数。我需要捕获这个字符串。我无法修改正在执行打印的函数，也无法通过继承更改运行时行为。我无法找到任何允许我执行此操作的预定义方法。
Does the JVM store a buffer of printed contents?
JVM 是否存储打印内容的缓冲区？
Does anyone know of a Java method that will aid me?
有谁知道可以帮助我的 Java 方法？
采纳答案by Ingo
You could temporarily replace System.err or System.out with a stream that writes to string buffer.
您可以使用写入字符串缓冲区的流临时替换 System.err 或 System.out。
回答by Andreas Dolk
You can redirect the standard output by calling
您可以通过调用重定向标准输出
System.setOut(myPrintStream);
Or - if you need to log it at runtime, pipe the output to a file:
或者 - 如果您需要在运行时记录它，请将输出通过管道传输到一个文件：
java MyApplication > log.txt
Another trick - if you want to redirect and can't change the code: Implement a quick wrapper that calls your application and start that one:
另一个技巧 - 如果您想重定向并且无法更改代码：实现一个调用您的应用程序并启动该应用程序的快速包装器：
public class RedirectingStarter {
public static void main(String[] args) {
System.setOut(new PrintStream(new File("log.txt")));
com.example.MyApplication.main(args);
}
}
回答by Kartik Domadiya
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;
public class RedirectIO
{
public static void main(String[] args)
{
PrintStream orgStream = null;
PrintStream fileStream = null;
try
{
// Saving the orginal stream
orgStream = System.out;
fileStream = new PrintStream(new FileOutputStream("out.txt",true));
// Redirecting console output to file
System.setOut(fileStream);
// Redirecting runtime exceptions to file
System.setErr(fileStream);
throw new Exception("Test Exception");
}
catch (FileNotFoundException fnfEx)
{
System.out.println("Error in IO Redirection");
fnfEx.printStackTrace();
}
catch (Exception ex)
{
//Gets printed in the file
System.out.println("Redirecting output & exceptions to file");
ex.printStackTrace();
}
finally
{
//Restoring back to console
System.setOut(orgStream);
//Gets printed in the console
System.out.println("Redirecting file output back to console");
}
}
}
