在开发过程中我们可能需要通过Java来调用执行JavaScript脚本，比如我们在用Java做网络爬虫时，有时需要执行JS代码来对一些请求的参数进行加密。下面简单介绍一下如何用Java执行JS脚本代码。

简单的使用:

package com.my.js;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class First {
    /**
     * 
     * @param jsStr js脚本内容
     * @param function  要调用的js方法名
     * @param args  调用js方法时传入的参数
     * @return
     */
    public static Object jsObjFunc(String jsStr,String function,Object... args) {
        ScriptEngineManager sem = new ScriptEngineManager();
        ScriptEngine scriptEngine = sem.getEngineByName("js");
        try {
            scriptEngine.eval(jsStr);
            Invocable inv2 = (Invocable) scriptEngine;
            return  inv2.invokeFunction(function,args);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    public static void main(String[] args)throws Exception {
        String jsStr ="function myFuc(param){return \"the param is:\"+param;}";//js脚本内容
        System.out.println(jsObjFunc(jsStr,"myFuc","test"));
    }
}

针对多次调用的优化，并进行简单的封装后：

package com.my.js;

import javax.script.*;
import java.util.Map;

public class ScriptCompile {
    CompiledScript script;
    ScriptEngine engine ;
    ScriptCompile(String scriptText){
        this.script =initScript(scriptText,null);
    }
    /**
     *
     * @param scriptText    js脚本内容
     * @param initParams    在编译时, 初始化时传入脚本的参数
     */
    ScriptCompile(String scriptText,Map<String,Object> initParams){   //构造函数, 先编译
        this.script =initScript(scriptText,initParams);
    }
    public CompiledScript initScript(String scriptText,Map<String,Object> initParams){
        CompiledScript script =null;
        ScriptEngine engine = new ScriptEngineManager().getEngineByExtension("js");
        if(initParams!=null&&!initParams.isEmpty()) {
            for (Map.Entry<String, Object> entry : initParams.entrySet()) {
                engine.put(entry.getKey(), entry.getValue());
            }
        }
        this.engine= engine;
        if (engine instanceof Compilable) {
            try {
                script = ((Compilable) engine).compile(scriptText);
            } catch (ScriptException e) {
                e.printStackTrace();
            }
        }
        return script;
    }

    /**
     * 执行脚本
     * @param bindingsMap   本次执行时传入的参数
     * @return
     * @throws ScriptException
     */
    public Object execute(Map<String,Object> bindingsMap) throws ScriptException {
        if(bindingsMap!=null&&!bindingsMap.isEmpty()){
            Bindings bindings = new SimpleBindings();
            for(Map.Entry<String,Object> entry: bindingsMap.entrySet()){
                bindings.put(entry.getKey(),entry.getValue());
            }
            return script.eval(bindings);
        }else{
            return script.eval();
        }
    }
    public Object execute() throws ScriptException {
        return execute(null);
    }

    /**
     * 调用脚本中的某个函数
     * @param bindingsMap   本次执行传入的参数
     * @param fucName  函数名
     * @param args  函数参数,可以有多个参数
     * @return
     * @throws Exception
     */
    public Object executeFuc(Map<String,Object> bindingsMap,String fucName,Object...args) throws Exception {
        execute(bindingsMap);
        Invocable inv2 = (Invocable) engine;
        return  inv2.invokeFunction(fucName,args);
    }
    public Object executeFuc(String fucName,Object...args) throws Exception {
        return executeFuc(null,fucName,args);
    }
}

调用:

    public static void main(String[] args) {
        Map<String,Object> map=new HashMap<>();
        map.put("counter",9);
        ScriptCompile sc = new ScriptCompile(
                "function count(num) {counter = counter +num; " +
                " return counter; }; " +
//                "count();" +
                "",map);

        for(int i=0;i<5;i++) {
            try {
//                map.put("counter",9);   //本次执行 要传递的参数
//                System.out.println(sc.run());
                System.out.println(sc.executeFuc("count",2));
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    }

执行结果:
11.0
13.0
15.0
17.0
19.0