JDK1.6版添加了新的ScriptEngine类,允许用户直接执行js代码。
在Java中直接调用js代码
在Java中绑定js变量
在调用engine.get(key);时,如果key没有定义,则返回null
输出:
result = 7.0
c = 7.0在Java中调用js文件中的function,传入调用参数,并获取返回值
在Java代码中读取js文件,并参数两个参数,然后回去返回值
输出结果:
c = 5.0
在Java中直接调用js代码
不能调用浏览器中定义的js函数,会抛出异常提示ReferenceError: “alert” is not defined。
- package com.sinaapp.manjushri;
- import javax.script.ScriptEngine;
- import javax.script.ScriptEngineManager;
- import javax.script.ScriptException; /** * 直接调用js代码 */
- public class ScriptEngineTest {
- public static void main(String[] args) {
- ScriptEngineManager manager = new ScriptEngineManager();
- ScriptEngine engine = manager.getEngineByName("javascript");
- try {
- engine.eval("var a=3; var b=4;print (a+b);");
- // 不能调用浏览器中定义的js函数
- // engine.eval("alert(\"js alert\");");
- // 错误,会抛出alert引用不存在的异常
- } catch (ScriptException e) {
- e.printStackTrace();
- }
- }
- }
输出结果:7
在Java中绑定js变量
- package com.sinaapp.manjushri;
- import javax.script.Bindings;
- import javax.script.ScriptContext;
- import javax.script.ScriptEngine;
- import javax.script.ScriptEngineManager;
- import javax.script.ScriptException;
- public class ScriptEngineTest2 {
- public static void main(String[] args) {
- ScriptEngineManager manager = new ScriptEngineManager();
- ScriptEngine engine = manager.getEngineByName("javascript");
- engine.put("a", 4); engine.put("b", 3);
- Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
- try {
- // 只能为Double,使用Float和Integer会抛出异常
- Double result = (Double) engine.eval("a+b");
- System.out.println("result = " + result);
- engine.eval("c=a+b");
- Double c = (Double)engine.get("c");
- System.out.println("c = " + c);
- } catch (ScriptException e) {
- e.printStackTrace();
- }
- }
- }
result = 7.0
c = 7.0
在Java中调用js文件中的function,传入调用参数,并获取返回值
js文件中的merge函数将两个参数a,b相加,并返回c。
- // expression.js
- function merge(a, b) {
- c = a * b;
- return c;
- }
- package com.sinaapp.manjushri;
- import java.io.FileReader;
- import javax.script.Invocable;
- import javax.script.ScriptEngine;
- import javax.script.ScriptEngineManager;
- /** * Java调用并执行js文件,传递参数,并活动返回值 * * @author manjushri */
- public class ScriptEngineTest {
- public static void main(String[] args) throws Exception {
- ScriptEngineManager manager = new ScriptEngineManager();
- ScriptEngine engine = manager.getEngineByName("javascript");
- String jsFileName = "expression.js";
- // 读取js文件
- FileReader reader = new FileReader(jsFileName);
- // 执行指定脚本
- engine.eval(reader);
- if(engine instanceof Invocable) {
- Invocable invoke = (Invocable)engine;
- // 调用merge方法,并传入两个参数
- // c = merge(2, 3);
- Double c = (Double)invoke.invokeFunction("merge", 2, 3);
- System.out.println("c = " + c);
- }
- reader.close();
- }
- }
c = 5.0