ScriptEngineManager类(Java和JS互相调用)

Posted 2020-11-26 图图小淘气_real

Java和Js之间的调用时基于ScriptEngineManager类，这个类是jdk8新增的:

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import javax.script.Bindings;
import javax.script.Invocable;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.SimpleScriptContext;

import org.junit.Test;


public class javascriptFunction {

    @Test
    public void print() throws Exception{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        engine.eval("print(\'hello word!!\')");
    }
    
    @Test
    public void obj() throws Exception {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        StringBuffer script = new StringBuffer();
        script.append("var obj = new Object();");
        script.append("obj.hello = function(name){print(\'hello, \'+name);}");
        //执行这段script脚本
        engine.eval(script.toString());
        // javax.script.Invocable 是一个可选的接口
        // 检查你的script engine 接口是否已实现!
        // 注意：JavaScript engine实现了Invocable接口
        Invocable inv = (Invocable) engine;
        // 获取我们想调用那个方法所属的js对象
        Object obj = engine.get("obj");
        // 执行obj对象的名为hello的方法
        inv.invokeMethod(obj, "hello", "Script Method !!" );
    }
    
    @Test
    public void file() throws Exception{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        engine.eval(new java.io.FileReader(new File("F:/test/test.js")));
        Invocable inv = (Invocable) engine;
        Object obj = engine.get("obj");
        inv.invokeMethod(obj, "name", "知道了" );
    }
    
    
    /**
     * 脚本变量
     * @throws Exception 
     */
    @Test
    public void scriptVar() throws Exception{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        File file = new File("F:/test/test.txt");
        //将File对象f直接注入到js脚本中并可以作为全局变量使用
        engine.put("files", file);
        engine.eval("print(files.getPath());print(files.getName());");
    }
    
    /**
     *  使用Script实现java接口
     * @throws Exception 
     */
    public void runnableImpl() throws Exception{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        
        // String里定义一段JavaScript代码脚本
        String script = "function run() { print(\'run called\'); }";
        // 执行这个脚本
        engine.eval(script);
        
        // 从脚本引擎中获取Runnable接口对象（实例）. 该接口方法由具有相匹配名称的脚本函数实现。
        Invocable inv = (Invocable) engine;
        // 在上面的脚本中，我们已经实现了Runnable接口的run()方法
        Runnable runnable = inv.getInterface(Runnable.class);
        
        // 启动一个线程运行上面的实现了runnable接口的script脚本
        Thread thread = new Thread(runnable);
        thread.start();
    }
    
    /**
     * 脚本引擎的多个scope
     * @throws Exception 
     */
    @Test
    public void multiScopes() throws Exception{
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("nashorn");
        // 打印全局变量 "x"
        engine.put("x", "hello word!!");
        engine.eval("print(x);");
        // 上面的代码会打印"hello word！！"
        
        // 现在，传入另一个不同的script context
        ScriptContext context = new SimpleScriptContext();
        //新的Script context绑定ScriptContext的ENGINE_SCOPE
        Bindings bindings = context.getBindings(ScriptContext.ENGINE_SCOPE);
        
        // 增加一个新变脸到新的范围 engineScope 中
        bindings.put("x", "word hello!!");
        // 执行同一个脚本 - 但这次传入一个不同的script context
        engine.eval("print(x);", bindings);
        engine.eval("print(x);");
    }
    
    
    
    public static void main(String[] args) throws Exception {
        new JavaScriptFunction().runnableImpl();
        
        List list = new ArrayList();
        list.add("1");
        list.add("1");
        list.add("1");
        
        for (Object object : list) {
            System.out.println(object);
        }
        
    }
}

 

运用Java中的封装技术将运行js脚本程序进行封装:

import java.io.FileNotFoundException;
import java.io.FileReader;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

/**
 * 运行脚本
 * @author Ruby
 *
 */
public class RunScript {

    private ScriptEngineManager manager = new ScriptEngineManager();
    private ScriptEngine engine;
    private String fileName;
    
    public RunScript(String fileName){
        engine = manager.getEngineByName("JavaScript");
        this.fileName = fileName;
    }
    
    /**
     * 设置变量
     * @param varName
     * @param obj
     */
    public void setVar(String varName, Object obj){
        engine.put(varName, obj);
    }
    
    /**
     * 启动脚本
     * @throws FileNotFoundException
     * @throws ScriptException
     */
    public void start() throws FileNotFoundException, ScriptException{
        engine.eval(new FileReader(fileName));
    }
}

 

测试

将Logger对象注入到js对象中，那么在js文件中就可以使用java中的Logger对象了:

public static void main(String[] args) throws Exception {
    RunScript rs = new RunScript("D:\\test.js");
    rs.setVar("Logger", Logger.getLogger(ConsoleListener.class));
    rs.start();
}

 

扩展：

使用ScriptEngineManager类判断JSON字符串是否合法：

ScriptEngineManager sem = new ScriptEngineManager ();
        ScriptEngine se = sem.getEngineByName ("js");
        String jsonstr = "({name: 1, obj: 3,[dd]})";
        try
        {
            System.out.println (se.eval (jsonstr));
        }
        catch (ScriptException e)
        {
            System.out.println ("json格式有误");
        }

其他方式：

package util;

import com.alibaba.fastjson.JSONException;
import com.alibaba.fastjson.JSONObject;

public class Test {

    public static void main(String[] args) {
        try {
            JSONObject.parse("{\'a\':1 \'b\':1}");
        } catch (JSONException e) {
            System.out.println("JSON字符串错误");
        }
    }

}