在JAVA中调用JavaScript代码

有些时候&＃xff0c;我们在执行JAVA代码的时候&＃xff0c;希望能够通过执行其他脚本语言(如js, 修改脚本新逻辑立即生效&＃xff0c;不需要重新加载)根据其结果来进行逻辑判断,自java SE 8开始已经集成了Nashorn Javascript引擎作为JDK的一部分。

1.使用nashorn引擎

1.1直接执行脚本

1.1.1查询引擎使用nashorn

public static void main(String[] args) throws Exception {ScriptEngineManager scriptEngineManager &＃61; new ScriptEngineManager();ScriptEngine scriptEngine &＃61;scriptEngineManager.getEngineByName("nashorn");//执行脚本scriptEngine.eval("print(&＃39;Hello,World&＃39;)");
}


1.1.2查询引擎使用Javascript

public static void main(String[] args) throws Exception {
ScriptEngineManager scriptEngineManager &＃61; new ScriptEngineManager();
ScriptEngine scriptEngine &＃61; scriptEngineManager.getEngineByName("Javascript");
//执行脚本
scriptEngine.eval("print(&＃39;Hello,World&＃39;)");
}


1.2 执行脚本指定函数

1.2.1查询引擎使用nashorn

public static void main(String[] args) throws Exception {ScriptEngineManager scriptEngineManager &＃61; new ScriptEngineManager();ScriptEngine scriptEngine &＃61;scriptEngineManager.getEngineByName("nashorn");//传入脚本scriptEngine.eval("function hello(name){print(&＃39;Hello,&＃39;&＃43; name )}");//ScriptEngine强转为InvocableInvocable inv &＃61; (Invocable) scriptEngine;//调用函数&＃xff0c;传入参数inv.invokeFunction("hello", "Javascript");}


1.2.2查询引擎使用Javascript

public static void main(String[] args) throws Exception {ScriptEngineManager scriptEngineManager &＃61; new ScriptEngineManager();ScriptEngine scriptEngine &＃61; scriptEngineManager.getEngineByName("nashorn");//传入脚本scriptEngine.eval("function hello(param) {\n" &＃43;" if(param &＃61;&＃61; &＃39;123&＃39;) {\n" &＃43;" return true;\n" &＃43;" }\n" &＃43;" return false;\n" &＃43;"}");//ScriptEngine强转为InvocableInvocable inv &＃61; (Invocable) scriptEngine;//调用函数&＃xff0c;传入参数boolean result &＃61; (Boolean) inv.invokeFunction("hello", "12");System.out.println(result);


1.3 获取的都是nashorn引擎

//获取的都是nashorn引擎scriptEngineManager.getEngineByName("nashorn");scriptEngineManager.getEngineByName("Javascript");


2. 使用脚本语言的优点

1. 脚本语言可以直接运行&＃xff0c;不需要编译为字节码&＃xff0c;如果修改了逻辑不需要重新启动应用&＃xff0c;立刻生效
2. 动态类型&＃xff0c;创建变量不需要创建及声明类型&＃xff0c;可以重复使用变量

参考
https://docs.oracle.com/javase/8/docs/technotes/guides/scripting/prog_guide/about.html#sthref8
https://docs.oracle.com/javase/8/docs/technotes/guides/scripting/prog_guide/api.html#CDEGJDJF