问题描述
我正在尝试编写一个带有接口的Java程序，该接口允许用户创建.java文件并进行编译和运行(本质上是一个非常简单的IDE).我正在使用Java swing作为gui，到目前为止，已经能够将接口中的.java文件编译为.class文件.我一直在研究如何从Java代码中运行.class文件，但发现了很多无法解决的答案.以下是相关的编译代码:
I'm trying to write a java program with an interface that allows the user to create .java file and compile and run it (essentially a very simplistic IDE). I'm using java swing for the gui and have so far been able to compile a .java file from within the interface into a .class file. I've been researching how to run a .class file from within java code but have found a wide range of answers which I haven't been able to get working. Here is the relevant code for compilation:
File javaFile = new File( "test1.java" );
String code = entry.getText(); // get text entered by user in GUI
try{
PrintWriter writer = new PrintWriter( javaFile ); // write text to .java file
writer.print( code );
writer.close();
}
catch( FileNotFoundException e ){
System.err.println( e );
}
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
List<File> sourceFileList = new ArrayList<File>();
sourceFileList.add( javaFile );
StandardJavaFileManager fileManager = compiler.getStandardFileManager( null, null, null );
Iterable<? extends JavaFileObject> javaSource = fileManager.getJavaFileObjectsFromFiles( sourceFileList );
CompilationTask task = compiler.getTask(null, fileManager, null, null, null, javaSource);
task.call(); // compile .java file into .class file
如何运行已编译的.class文件并在代码中捕获其输出?
How can I run a compiled .class file and capture its output within my code?
推荐答案
编译后，您将需要加载 Class 对象，然后调用 main(String [])方法.要捕获标准输出，您将需要使用 System.setOut .
Once it's compiled, you will need to load the Class object and then invoke the main(String[]) method. To capture the stdout, you will need to use System.setOut.
private String invokeClass(String className) throws URISyntaxException, IOException, ReflectiveOperationException {
Class<?> clazz = Class.forName(className);
// Alternatively, you can load the new class with a new Classloader, if you don't want to pollute the current Classloader
// Class<?> clazz = new URLClassLoader(new URL[]{getClass().getClassLoader().getResource("").toURI().toURL()}, getClass().getClassLoader()).loadClass(className);
Method main = clazz.getDeclaredMethod("main", String[].class);
try ( ByteArrayOutputStream out = new ByteArrayOutputStream();
PrintStream ps = new PrintStream(out)) {
System.setOut(ps);
main.invoke(main, new Object[]{new String[0]});
return out.toString();
}
finally {
// Reset to the console
System.setOut(new PrintStream(new FileOutputStream(FileDescriptor.out)));
}
}
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