Java动态编译执行代码示例

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

//获取java文件管理类
StandardJavaFileManager manager = compiler.getStandardFileManager(null, null, null);
//获取java文件对象迭代器
Iterable<? extends JavaFileObject> it = manager.getJavaFileObjects(files);
//设置编译参数
ArrayList<String> ops = new ArrayList<String>();
ops.add("-Xlint:unchecked");
//设置classpath
ops.add("-classpath");
ops.add(CLASS_PATH);
//获取编译任务
JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, ops, null, it);
//执行编译任务
task.call();

//要加载的类名
String className = "xxx.xxx.xxx";
//获取类加载器
ClassLoader classLoader = XXX.class.getClassLoader();
//加载类
Class<?> cls = classLoader.loadClass(className);

//调用方法名称
String methodName = "execute";
//方法参数类型数组
Class<?>[] paramCls = {...};
//获取方法
Method method = cls.getDeclaredMethod(methodName , paramCls);
//创建类实例
Object obj = cls.newInstance();
//方法参数
Object[] params = {...};
//调用方法
Object result = method.invoke(obj, params);

//ClassUtil.java
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class ClassUtil {
	private static final Log logger = LogFactory.getLog(ClassUtil.class);
	private static JavaCompiler compiler;
	static{
		compiler = ToolProvider.getSystemJavaCompiler();
	}
	/**
   * 获取java文件路径
   * @param file
   * @return
   */
	private static String getFilePath(String file){
		int last1 = file.lastIndexOf('/');
		int last2 = file.lastIndexOf('\\');
		return file.substring(0, last1>last2?last1:last2)+File.separatorchar;
	}
	/**
   * 编译java文件
   * @param ops 编译参数
   * @param files 编译文件
   */
	private static void javac(List<String> ops,String... files){
		StandardJavaFileManager manager = null;
		try{
			manager = compiler.getStandardFileManager(null, null, null);
			Iterable<? extends JavaFileObject> it = manager.getJavaFileObjects(files);
			JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, ops, null, it);
			task.call();
			if(logger.isDebugEnabled()){
				for (String file:files)
				          logger.debug("Compile Java File:" + file);
			}
		}
		catch(Exception e){
			logger.error(e);
		}
		finally{
			if(manager!=null){
				try {
					manager.close();
				}
				catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
	/**
   * 生成java文件
   * @param file 文件名
   * @param source java代码
   * @throws Exception
   */
	private static void writeJavaFile(String file,String source)throws Exception{
		if(logger.isDebugEnabled()){
			logger.debug("Write Java Source Code to:"+file);
		}
		BufferedWriter bw = null;
		try{
			File dir = new File(getFilePath(file));
			if(!dir.exists())
			        dir.mkdirs();
			bw = new BufferedWriter(new FileWriter(file));
			bw.write(source);
			bw.flush();
		}
		catch(Exception e){
			throw e;
		}
		finally{
			if(bw!=null){
				bw.close();
			}
		}
	}
	/**
   * 加载类
   * @param name 类名
   * @return
   */
	private static Class<?> load(String name){
		Class<?> cls = null;
		ClassLoader classLoader = null;
		try{
			classLoader = ClassUtil.class.getClassLoader();
			cls = classLoader.loadClass(name);
			if(logger.isDebugEnabled()){
				logger.debug("Load Class["+name+"] by "+classLoader);
			}
		}
		catch(Exception e){
			logger.error(e);
		}
		return cls;
	}
	/**
   * 编译代码并加载类
   * @param filePath java代码路径
   * @param source java代码
   * @param clsName 类名
   * @param ops 编译参数
   * @return
   */
	public static Class<?> loadClass(String filePath,String source,String clsName,List<String> ops){
		try {
			writeJavaFile(CLASS_PATH+filePath,source);
			javac(ops,CLASS_PATH+filePath);
			return load(clsName);
		}
		catch (Exception e) {
			logger.error(e);
		}
		return null;
	}
	/**
   * 调用类方法
   * @param cls 类
   * @param methodName 方法名
   * @param paramsCls 方法参数类型
   * @param params 方法参数
   * @return
   */
	public static Object invoke(Class<?> cls,String methodName,Class<?>[] paramsCls,Object[] params){
		Object result = null;
		try {
			Method method = cls.getDeclaredMethod(methodName, paramsCls);
			Object obj = cls.newInstance();
			result = method.invoke(obj, params);
		}
		catch (Exception e) {
			logger.error(e);
		}
		return result;
	}
}

public class ClassUtilTest {
	private static final Log logger = LogFactory.getLog(ClassUtilTest.class);
	public static void main(String args[]){
		StringBuilder sb = new StringBuilder();
		sb.append("package com.even.test;");
		sb.append("import java.util.Map;\nimport java.text.DecimalFormat;\n");
		sb.append("public class Sum{\n");
		sb.append("private final DecimalFormat df = new DecimalFormat(\"#.#####\");\n");
		sb.append("public Double calculate(Map<String,Double> data){\n");
		sb.append("double d = (30*data.get(\"f1\") + 20*data.get(\"f2\") + 50*data.get(\"f3\"))/100;\n");
		sb.append("return Double.valueOf(df.format(d));}}\n");
		//设置编译参数
		ArrayList<String> ops = new ArrayList<String>();
		ops.add("-Xlint:unchecked");
		//编译代码，返回class
		Class<?> cls = ClassUtil.loadClass("/com/even/test/Sum.java",sb.toString(),"com.even.test.Sum",ops);
		//准备测试数据
		Map<String,double> data = new HashMap<String,double>();
		data.put("f1", 10.0);
		data.put("f2", 20.0);
		data.put("f3", 30.0);
		//执行测试方法
		Object result = ClassUtil.invoke(cls, "calculate", new Class[]{Map.class}, new Object[]{data});
		//输出结果
		logger.debug(data);
		logger.debug("(30*f1+20*f2+50*f3)/100 = "+result);
	}

16:12:02.860 DEBUG com.even.tools.ClassUtil - Write Java Source Code to: .../classes//com/even/test/Sum.java
16:12:03.544 DEBUG com.even.tools.ClassUtil - Compile Java File:.../classes//com/even/test/Sum.java
16:12:03.545 DEBUG com.even.tools.ClassUtil - Load Class[com.even.test.Sum] by sun.misc.Launcher$AppClassLoader@73d16e93
16:12:03.547 DEBUG com.even.test.ClassUtilTest - {f1=10.0, f2=20.0, f3=30.0}
16:12:03.547 DEBUG com.even.test.ClassUtilTest - (30*f1+20*f2+50*f3)/100 = 22.0