Java动态编译

package com.chensr.util.function;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

import javax.tools.JavaCompiler;
import javax.tools.JavaCompiler.CompilationTask;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;


public class Reflection {
    public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {
        String str ="package com.chensr.util.function; \r\t"+                    
                    "public class Function { \r\t"+
                    "    public Function(String a) { \r\t"+
                    "         System.out.println(\"我是构造函数!\"+a);\r\t"+
                    "    }\r\t"+
                    "    public static void say(){ \r\t"+
                    "        System.out.println(\"我由string生成class\");\r\t"+
                    "    }\r\t"+
                    "}";
        
        //根据str生成.java文件
        String fileName=System.getProperty("user.dir")+
                        "\\src\\main\\java\\com\\chensr\\util\\function\\Function.java";
        System.out.println(fileName);
        File file = new File(fileName);
        FileWriter fw = new FileWriter(file);
        fw.write(str);
        fw.flush();
        fw.close();
        
        //调用JavaCompiler获取编译器，该类允许开发人员编译java文件为class文件
        JavaCompiler compiler =ToolProvider.getSystemJavaCompiler();
        //Java 标准文件管理器,第一个参数为监听器，第二个参数语音环境，第三个参数为字符集
        StandardJavaFileManager fileManger = compiler.getStandardFileManager(null, null, null);
        //获取表示给定文件的文件对象
        Iterable unils = fileManger.getJavaFileObjects(fileName);
        //CompilationTask表示编译任务的未来的接口。调用call()启动任务。getTask方法编译源代码,并将对应的class文件生成到指定目录
        CompilationTask t = compiler.getTask(null, fileManger, null, null, null, unils);
        t.call();
        fileManger.close();
        
        //load内存，并且创建一个实例
        URL[] urls = new URL[]{new URL("file:/"+System.getProperty("user.dir")+"/scr")};        
        URLClassLoader cl = new URLClassLoader(urls);
        Class c = cl.loadClass("com.chensr.util.function.Function");    
        //获取构造函数和执行对应的方法
        Constructor constructor = c.getConstructor(String.class);
        Object b =constructor.newInstance("哈哈");
        
        Method method=c.getDeclaredMethod("say"); 
        method.invoke(b);  
    }
}