服务端JavaScript之Rhino

最近在看js的书，书上有介绍两个服务端js,以前只听说过node.js，第一次听说Rhino.js,并且已经集成到了jdk1.6;看来还是见的少啊！

Rhino是一种用Java编写的javaScript解释器，能自动完成JavaScript原生类型到Java原生类型之间的相互转换，有了它，可以通过JavaScript脚本设置。查询Java属性，并调用java方法；

先上学习的代码：

package com.my.rhino;

import java.io.FileReader;
import java.util.List;

import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.Invocable;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class RhinoDemo {

    public static void main(String[] args) {
        // create ScriptEngineManager
        ScriptEngineManager manager = new ScriptEngineManager();

        ScriptEngine engine = manager.getEngineByName("js");
        String script = "print ('hello nm')";
        try {
            engine.eval(script);
            System.out.println();
        } catch (ScriptException e) {
            e.printStackTrace();
        }

        try {
            Double hour = (Double) engine.eval("var date = new Date(); date.getHours();");
            String msg;
            if (hour < 10) {
                msg = "Good morning";
            } else if (hour < 16) {
                msg = "Good afternoon";
            } else if (hour < 20) {
                msg = "Good evening";
            } else {
                msg = "Good night";
            }
            System.out.println(hour);
            System.out.println(msg);
        } catch (ScriptException e) {
            System.err.println(e);
        }

        try {
            FileReader reader = new FileReader("src/com/my/rhino/file.js");
            Double num = (Double) engine.eval(reader);
            System.out.println(num);
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            engine.put("a", 1);
            engine.put("b", 5);

            Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
            Object a = bindings.get("a");
            Object b = bindings.get("b");
            System.out.println("a = " + a);
            System.out.println("b = " + b);

            FileReader reader = new FileReader("src/com/my/rhino/vars.js");
            Double num = (Double) engine.eval(reader);
            System.out.println(num);
            reader.close();

            reader = new FileReader("src/com/my/rhino/fun.js");
            // engine.eval("function add (a, b) {c = a + b; return c; }");
            engine.eval(reader);
            Invocable jsInvoke = (Invocable) engine;

            Object result1 = jsInvoke.invokeFunction("add", new Object[] { 10, 5 });
            System.out.println(result1);

            Adder adder = jsInvoke.getInterface(Adder.class);
            int result2 = adder.add(10, 5);
            System.out.println(result2);

            Compilable jsCompile = (Compilable) engine;
            CompiledScript vscript = jsCompile.compile("function hi () {print ('ddddd !'); }; hi ();");

            for (int i = 0; i < 5; i++) {
                vscript.eval();
            }

        } catch (Exception e) {
            // TODO: handle exception
        }

        try {
            FileReader reader = new FileReader("src/com/my/rhino/java.js");
            @SuppressWarnings("unchecked")
            List<String> num = (List<String>) engine.eval(reader);
            System.out.println();
            for (String word : num) {
                System.out.print(word);
            }
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        List<ScriptEngineFactory> factoryList = manager.getEngineFactories();
        for (ScriptEngineFactory factory : factoryList) {
            System.out.println("=====");
            System.out.println(factory.getEngineName());
            System.out.println(factory.getEngineVersion());
            System.out.println(factory.getLanguageName());
            System.out.println(factory.getLanguageVersion());
            System.out.println(factory.getExtensions());
            System.out.println(factory.getMimeTypes());
            System.out.println(factory.getNames());
        }
    }
}

下面解析下：

1、创建一个script 引擎管理器并根据名称获取需要的js引擎；以下所有操作基于这两行代码；

// create ScriptEngineManager
ScriptEngineManager manager = new ScriptEngineManager();
// create a JavaScript engine
ScriptEngine engine = manager.getEngineByName("js");

引擎也许不止一个，可以通过以下代码输出查看；

List<ScriptEngineFactory> factoryList = manager.getEngineFactories();
        for (ScriptEngineFactory factory : factoryList) {
            System.out.println("=====");
            System.out.println(factory.getEngineName());
            System.out.println(factory.getEngineVersion());
            System.out.println(factory.getLanguageName());
            System.out.println(factory.getLanguageVersion());
            System.out.println(factory.getExtensions());
            System.out.println(factory.getMimeTypes());
            System.out.println(factory.getNames());
        }

获取支持的所有引擎的详细信息；我的机器输出如下：

Mozilla Rhino
1.7 release 3 PRERELEASE
ECMAScript
1.8
[js]
[application/javascript, application/ecmascript, text/javascript, text/ecmascript]
[js, rhino, JavaScript, javascript, ECMAScript, ecmascript]

2、简单输出字符串：

String script = "print ('hello nm')";
        try {
            engine.eval(script);
            System.out.println();
        } catch (ScriptException e) {
            e.printStackTrace();
        }

console:  hello nm

3、执行简单的js代码获取返回值：

try {
            Double hour = (Double) engine.eval("var date = new Date(); date.getHours();");
            System.out.println(hour);
        } catch (ScriptException e) {
            System.err.println(e);
        }
console输出当前时间的小时数：  
//13.0

4、执行js文件里面的语句，并获取返回值：

//java代码：  
  try {
            FileReader reader = new FileReader("src/com/my/rhino/file.js");
            Double num = (Double) engine.eval(reader);
            System.out.println(num);
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
console ---> 18.0

//file.js
function add(a,b){
    return a+b;
}

//add(10,8);  
result = add(10,8);
//以上两行语句皆可实现

5、传递变量给js文件并执行js文件代码：

//java代码
　　　　　　　engine.put("a", 1);
            engine.put("b", 5);

            Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
            Object a = bindings.get("a");
            Object b = bindings.get("b");
            System.out.println("a = " + a);
            System.out.println("b = " + b);

            FileReader reader = new FileReader("src/com/my/rhino/vars.js");
            Double num = (Double) engine.eval(reader);
            System.out.println(num);
            reader.close();

//vars.js
m = a+5;
n = b+6;
d = a+b;

console---> 6.0  //只会返回最后一行的结果值

6、java调用js中的方法：

                   
            reader = new FileReader("src/com/my/rhino/file.js");
            // engine.eval("function add (a, b) {c = a + b; return c; }");
            engine.eval(reader);
            Invocable jsInvoke = (Invocable) engine;

            Object result1 = jsInvoke.invokeFunction("add", new Object[] { 10, 5 });
            System.out.println(result1);
　　　　　　  //动态实现接口，从脚本引擎中得到Java Interface 的实例；也就是说，可以定义个一个Java接口，其实现是由脚本完成,函数名称必须相同；
            Adder adder = jsInvoke.getInterface(Adder.class);
            int result2 = adder.add(10, 5);
            System.out.println(result2);            

package com.my.rhino;
interface Adder {
  int add(int a, int b);
}

console----->  

15.0  15

7、编译执行

　　脚本引擎默认是解释执行的，如果需要反复执行脚本，可以使用它的可选接口Compilable来编译执行脚本，以获得更好的性能，示例代码如下：

Compilable jsCompile = (Compilable) engine;
            CompiledScript vscript = jsCompile.compile("function hi () {print ('ddddd !'); }; hi ();");

            for (int i = 0; i < 5; i++) {
                vscript.eval();
            }
//其中js代码可以从js文件中加载

8、使用java中的对象：

    try {
            FileReader reader = new FileReader("src/com/my/rhino/java.js");
            @SuppressWarnings("unchecked")
            List<String> num = (List<String>) engine.eval(reader);
            System.out.println();
            for (String word : num) {
                System.out.print(word);
            }
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

//java.js
importPackage(java.util);
//var list = java.util.ArrayList();
var list = ArrayList();
list.add('ni');
list.add(' zai');
list.add(' zuo');
list.add(' sha');
list;

//var list = java.util.ArrayList();等价于importPackage(java.util); var list = ArrayList();

9、总结：

    这都是很基本的，高级应用还需研究！