Java-Scripting代码备忘

    Java scripting工具包提供了java可以访问其他语言脚本的能力，脚本片段将会在运行时编译成中间代码(字节码)，并能够被java scripting引擎调用。在某些场景下，很有用。

1. 简单调用

/**
 * simple,默认java.*包中的API已经倒入到engine中。你可以使用那些API
 * @throws Exception
 */
private static void invoke1() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	ScriptEngine engine = engineManager.getEngineByName("javascript");
	//根据“脚本语言名称”获取执行引擎，java本身默认只支持javascript，对于其他脚本，可以
	//使用第三方包(apache bsf,不过不是很好用)
	//getEngineByName方法每次都会创建一个心的Engine对象
	//java.lang包默认已经导入
	String script = "var message = 'This is javascript.';println(message);var total = 2;";
	engine.eval(script);
	Double total = (Double)engine.get("total");
	System.out.println(total);
}

2. 向JS脚本传递参数

/**
 * 向当前engine调用中put参数，并交给script
 * @throws Exception
 */
private static void invoke2() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	ScriptEngine engine = engineManager.getEngineByName("javascript");
	String script = "for(var i=0;i< times;i++) {println(i);}";
	engine.put("times", 10);
	engine.eval(script);
}

3. 在JS中使用java对象的方法或属性

private static void invoke3() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	ScriptEngine engine = engineManager.getEngineByName("javascript");
	String script = "println(string + ',length:' + string.length);";
	engine.put("string", "javascript");
	engine.eval(script);
}

4.  显式的调用JS的function

private static void invoke4() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "function hello(message){println(message);}";
	engine.eval(script);
	engine.invokeFunction("hello", "javascript");
}

5.  调用JS方法并传递参数

/**
 * script方法调用
 * @throws Exception
 */
private static void invoke5() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "function hello(message){println(message);}";
	engine.eval(script);
	engine.invokeFunction("hello", "javascript");
}

6.  通过JS创建Object，并在JAVA中使用(JS面向对象)

/**
 * 在script中使用对象，创建对象,并调用script对象的方法
 * @throws Exception
 */
private static void invoke6() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	//user是一个全局对象，和js一致
	String script = "var user = new Object();" +
					"user.name='';" + 
					"user.age=1;" + 
					"user.toString = function(){println('Name:' + user.name + ',age' + user.age)};" + 
					"user.init = function(name,age){user.name = name;user.age = age};";
	engine.eval(script);
	Object user = engine.get("user");
	engine.invokeMethod(user, "init", "zhangsan",32);
	engine.invokeMethod(user, "toString", null);
}

7. JS与面向对象

/**
 * 调用script中的function，使用function返回的值
 * @throws Exception
 */
private static void invoke7() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	//API
	String script = "function create(name,age){var user = new Object();user.name= name;user.age = age; return user};" + 
					"function toString(user){println('Name:' + user.name + ',age:' + user.age);};";
	engine.eval(script);
	Object user = engine.invokeFunction("create", "zhangsan",32);
	engine.invokeFunction("toString", user);
}

8. 在JS脚本中，引入JAVA API

/**
 * 外部API的倒入和使用
 * @throws Exception
 */
private static void invoke8() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "importClass(org.apache.commons.lang.time.DateFormatUtils);" +
					"println(java.lang.System.currentTimeMillis());";
	engine.eval(script);
}

9. 在JS中使用java object：API混合使用

/**
 * 将java对象与JS结合使用
 * @throws Exception
 */
private static void invoke9() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "importClass(com.test.script.ScriptingTestMain.User);function info(user){return user.info();}";
	User user = new User("zhangsan",32);
	engine.eval(script);
	String info = (String)engine.invokeFunction("info", user);
	System.out.println(info);
}

10. JS-function作为JAVA 接口的实现

/**
 * 让js作为java API的实现类
 * @throws Exception
 */
private static void invoke10() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "function run(){var i = 0;while(i<100){println(i);i++;}}";
	engine.eval(script);
	Runnable runnable = engine.getInterface(Runnable.class);
	Thread thread = new Thread(runnable);
	thread.start();
}

11.  Engine与binding使用：参数传递和context管理

/**
 * 使用binding传递参数，类似于engine.put
 * @throws Exception
 */
private static void invoke11() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "i;println(message);println(i)";
	//default：ENGINE_SCOPE
	Bindings bindings = engine.createBindings();//Map
	bindings.put("message", "javascript");
	bindings.put("i", "10");
	engine.eval(script,bindings);//binding被当前eval使用
}

12. 尝试使用Context来保存engine执行的结果或者保持变量传递

/**
 * 使用context保存对象，以便在外部被使用
 * @throws Exception
 */
private static void invoke12() throws Exception{
	ScriptEngineManager engineManager = new ScriptEngineManager();
	RhinoScriptEngine engine = (RhinoScriptEngine)engineManager.getEngineByName("javascript");
	String script = "println(message)";
	//
	ScriptContext engineContext = new SimpleScriptContext();
	engineContext.setAttribute("globalMessage", "globalMessage", ScriptContext.ENGINE_SCOPE);
	engine.setContext(engineContext);
	engine.put("message", "javascript");
	engine.eval(script);
	
	//GLOBAL_SCOPE似乎对JS引擎有些问题。
	String globalMessage = (String)engine.getContext().getAttribute("globalMessage",ScriptContext.ENGINE_SCOPE);
	engine.put("message", globalMessage);
	engine.eval(script);
	
}