Java知识点总结（动态执行JS代码 ）

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import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.net.URL;
import java.util.List;
 
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
 
public class Test09 {
 
  // 定义变量,存储到引擎上下文中
  private static void test1(ScriptEngine engine) {
 
    engine.put("msg", "张三是个好学生");
    System.out.println(engine.get("msg")); // 获取变量的值
 
    try {
     engine.eval("msg='java是门好用的语言';"); // 修改变量的值
    } catch (ScriptException e1) {
     e1.printStackTrace();
    }
    System.out.println(engine.get("msg"));
  }
 
  // 定义一个对象
  private static void test2(ScriptEngine engine) {
    String str = "var user = {name:'张三',age:18,subjects:['计算机','英语']};";
    str += "println(user.name);";
    try {
     engine.eval(str);
    } catch (ScriptException e) {
     e.printStackTrace();
    }
  }
 
  // 定义一个函数
  private static void test3(ScriptEngine engine) {
 
    try {
     engine.eval("function add(a,b){var sum = a+b;return sum;}");
    } catch (ScriptException e) {
     e.printStackTrace();
    }
 
    try {
     // 取得调用接口
     Invocable jsInvoke = (Invocable) engine;
     // 执行脚本中定义的方法
     Object result = jsInvoke.invokeFunction("add", new Object[] { 13, 20 });
     System.out.println(result);
    } catch (NoSuchMethodException | ScriptException e) {
     e.printStackTrace();
    }
  }
 
  // 导入其他java包,使用其他包中的java类
  private static void test4(ScriptEngine engine) {
 
    String jsCode = "importPackage(java.util); var list = Arrays.asList(["浙江大学","清华大学","北京大学"]); ";
    try {
     engine.eval(jsCode);
    } catch (ScriptException e) {
     e.printStackTrace();
    }
    List<String> list2 = (List<String>) engine.get("list");
    for (String temp : list2) {
     System.out.println(temp);
    }
 
  }
 
  //执行一个js文件(我们将a.js至于项目的src下即可)
  private static void test5(ScriptEngine engine) {
        URL is = Test09.class.getClassLoader().getResource("a.js");
        Reader r= null;
    try {
     r = new FileReader(is.getPath());
     engine.eval(r);
    } catch (FileNotFoundException | ScriptException e) {
     e.printStackTrace();
    }finally {
     try {
       r.close();
     } catch (IOException e) {
       e.printStackTrace();
     }  
    }
  }
 
  public static void main(String[] args) {
 
    // 获得脚本引擎
    ScriptEngineManager sem = new ScriptEngineManager();
    ScriptEngine engine = sem.getEngineByName("javascript");
 
    test1(engine);
    test2(engine);  // java 8 出现异常：Caused by: <eval>:1 ReferenceError: "println" is not defined
    test3(engine);
    test4(engine);  // java 8出现异常：Caused by: <eval>:1 ReferenceError: "importPackage" is not defined
    test5(engine);
  }
 
}