java 动态编译与用Rhino引擎执行javascript代码

动态编译

/**
 * 动态编译
 * @author L J
 */
@SuppressWarnings("all")
public class TestCompile {
public static void main(String[] args) {
        String str = "public class Compile {public static void main(String[] args) {System.out.println(\"hello world!\");}}";
try {
//将字符串输出到文件中
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("F:/DB/Compile.java")));
            writer.write(str);
            writer.flush();
            writer.close();

//动态编译
            JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
int result = compiler.run(null, null, null, "F:/DB/Compile.java");
            System.out.println(result == 0 ? "编译成功" : "编译失败");

/*1、通过RunTime动态运行
 Runtime run = Runtime.getRuntime();
 Process process = run.exec("java -cp F:/DB Compile");

 //获取输出结果
 InputStream in = process.getInputStream();
 BufferedReader reader = new BufferedReader(new InputStreamReader(in));
 String info = "";
 while((info = reader.readLine()) != null) {
 System.out.println(info); //hello world!
 }*/

//2、通过URLClassLoader加载编译好的文件，利用反射运行main方法
            URL[] urls = new URL[]{new URL("file:/" + "F:/DB/")};
            URLClassLoader loader = new URLClassLoader(urls);
            Class c = loader.loadClass("Compile");
//调用加载类的main方法
            Method m = c.getMethod("main", String[].class);
//由于可变参数是JDK5.0之后才有的，所以会被编译成：m.invoke(null, "aa", "bb")，会发生参数不匹配的问题
//所以强制转换成Object类型
            m.invoke(null, (Object)new String[]{"aa", "bb"});
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

用脚本引擎执行javascript代码

/**
 * 测试脚本引擎执行javascript代码
 * @author L J
 */
@SuppressWarnings("all")
public class JavaScriptEngine {
public static void main(String[] args) throws Exception {
//获得脚本引擎对象
        ScriptEngineManager sem = new ScriptEngineManager();
        ScriptEngine engine = sem.getEngineByName("javascript");

//定义变量(即可以被js操作，又可以被java操作)，存储到引擎上下文中
        engine.put("msg", "that's why you go away!");
        String str = "var user = {name:'小明', age:18, schools:['清华大学', '北京大学']};";
        str += "println(user.name)"; //println只能打印在java控制台

//执行脚本
        engine.eval(str);  //小明
        engine.eval("msg = 'baby!'");
        System.out.println(engine.get("msg")); //baby!

//定义函数
        engine.eval("function add(a, b) {var sum = a + b; return sum}");
//取得调用接口
        Invocable jsInvoke = (Invocable) engine;
        Object result = jsInvoke.invokeFunction("add", new Object[]{12, 23});
        System.out.println(result); //35.0

//导入其他java包、使用其他包中的java类
        String jsCode = "importPackage(java.util);" +
"var list = Arrays.asList([\"清华大学\", \"北京大学\", \"浙江大学\"]);";
        engine.eval(jsCode);

        List<String> list = (List<String>) engine.get("list");
for(String temp : list) {
            System.out.println(temp);
        }

//执行一个js文件(以下需要将js文件置于项目的src目录下)
        URL url = JavaScriptEngine.class.getClassLoader().getResource("test.js");
        FileReader fr = new FileReader(url.getPath());
        engine.eval(fr);
        fr.close();
    }
}