动态生成、编译、运行java文件

动态生成，编译，运行java文件，jdk动态代理底层实现就是利用此方法，demo已上传。

package com.code.test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;

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

public class CodeGenerate {

	/**
	 * 编译java类
	 * @param writerPath
	 */
	public void javac(String writerPath){
		//java编译器
		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
		//文件管理器，参数1：diagnosticListener  监听器,监听编译过程中出现的错误
		StandardJavaFileManager manager = compiler.getStandardFileManager(null, null, null);
		//java文件转换到java对象，可以是多个文件
		Iterable<? extends JavaFileObject> it = manager.getJavaFileObjects(writerPath);
		//编译任务,可以编译多个文件
		CompilationTask t = compiler.getTask(null, manager, null, null, null, it);
		//执行任务
		t.call();
		try {
			manager.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 利用反射，实例化对象，此方法可指定class路径，放在classpath下可能会和jdk编译的文件冲突
	 * @param packPath
	 */
	public void java(String packPath){
		URL[] urls = null;
		try {
			//类路径,url的本地文件格式需要加file:/
			urls = new URL[] {new URL("file:/"+System.getProperty("user.dir")+"/src/")};
		} catch (MalformedURLException e) {
			e.printStackTrace();
		}
		//类加载器
		URLClassLoader url = new URLClassLoader(urls);
		Class clazz = null;
		try {
			//加载到内存
			clazz = url.loadClass(packPath);
			//实例化对象
			clazz.newInstance();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 读文件
	 * @param readerPath
	 * @return
	 */
	public BufferedReader fileReader(String readerPath){
		BufferedReader br = null;
		try {
			br = new BufferedReader(new FileReader(readerPath));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
		return br;
	}
	
	/**
	 * 写文件
	 * @param br
	 * @param writerPath
	 */
	public void fileWriter(BufferedReader br,String writerPath){
		String line;
		BufferedWriter bw = null;
		try {
			line = br.readLine();
			bw = new BufferedWriter(new FileWriter(writerPath));
			while(line != null){
				bw.write(line+"\r\n");
				line = br.readLine();
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				br.close();
			} catch (IOException e) {
				e.printStackTrace();
			} finally {
				try {
					bw.flush();
					bw.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

package com.code.test;

import java.io.BufferedReader;

/**
 * 测试类，注：eclipse设置中  运行环境设置为jdk，如果设置为jre无法编译成功。
 * @author Administrator
 *
 */
public class CodeTest  { 
	
	//文件读取路径
	private static final String READER_PATH = System.getProperty("user.dir")+"/codeFile/codeText.txt";
	
	//文件输出路径
	private static final String WRITER_PATH = System.getProperty("user.dir")+"/src/com/code/java/CodeText.java";
	
	//包路径
	private static final String PACK_PATH = "com.code.java.CodeText";
	
	public static void main(String[] args) {
		CodeGenerate code = new CodeGenerate();
		//读文本文件
		BufferedReader br = code.fileReader(READER_PATH);	
		//生成java类
		code.fileWriter(br, WRITER_PATH);					
		//编译java类
		code.javac(WRITER_PATH);							
		//运行java类
		code.java(PACK_PATH);								
	}
};
 
package com.code.java;
/**
 * 
 * txt文件中的动态类
 *
 */
public class CodeText  { 
	
    public CodeText() { 
    	System.out.println("代码生成并且编译运行成功！");
    } 
    
};