动态生成java文件的方法

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package com.hongsoft.test;

import java.io.*;

//定制的类装入器

public class TestCompile extends ClassLoader

{

String _compiler;

String _classpath;

public static void main(String[] args)

{

new TestCompile();

}

public TestCompile()

{

super(ClassLoader.getSystemClassLoader());

//默认编译器

if (_compiler == null)

_compiler = "D://j2sdk1.4.2//bin//javac";

_classpath = ".";

String extraclasspath =

"c://Program Files//Java//j2re1.4.2//lib//rt.jar";

// = System.getProperty("calc.classpath");

if (extraclasspath != null)

{

_classpath =

_classpath

+ System.getProperty("path.separator")

+ extraclasspath;

}

compile();

}

public void compile()

{

String filename = "";

String classname = "";

try

{

//创建临时文件

File javafile =

File.createTempFile("compiled_", ".java", new File("."));

filename = javafile.getName();

classname = filename.substring(0, filename.lastIndexOf("."));

generateJavaFile(javafile, classname);

//编译文件

invokeCompiler(javafile);

//创建java类

byte[] buf = readBytes(classname + ".class");

Class c = defineClass(buf, 0, buf.length);

try

{

c.newInstance();

}

catch (IllegalAccessException e)

{

throw new RuntimeException(e.getMessage());

}

catch (InstantiationException e)

{

throw new RuntimeException(e.getMessage());

}

}

catch (IOException e)

{

throw new RuntimeException(e.getMessage());

}

}

//生成java文件

void generateJavaFile(File javafile, String classname) throws IOException

{

FileOutputStream out = new FileOutputStream(javafile);

String text =

"public class "

+ classname

+ " {"

+ " public int getCreater() {return 1;}"

+ "}";

out.write(text.getBytes());

out.close();

}

//编译java文件

void invokeCompiler(File javafile) throws IOException

{

String[] cmd =

{ _compiler, "-classpath", _classpath, javafile.getName()};

//执行编译命令

//A1：

Process process = Runtime.getRuntime().exec(cmd);

try

{ //等待编译器结束

process.waitFor();

}

catch (InterruptedException e)

{

}

int val = process.exitValue();

if (val != 0)

{

throw new RuntimeException("编译错误:" + "错误代码" + val);

}

}

//以byte数组形式读入类文件

byte[] readBytes(String filename) throws IOException

{

File classfile = new File(filename);

byte[] buf = new byte[(int) classfile.length()];

FileInputStream in = new FileInputStream(classfile);

in.read(buf);

in.close();

return buf;

}

}