JAVA嵌入运行Groovy脚本

Posted 2021-01-19 贫民窟里的程序高手

最近设计一个数据统计系统,系统中上百种数据统计维度,而且这些数据统计的指标可能随时会调整.如果基于java编码的方式逐个实现数据统计的API设计,工作量大而且维护起来成本较高;最终确定为将"数据统计"的计算部分单独分离成脚本文件(javascript,或者Groovy),非常便捷了实现了"数据统计Task" 与 "数据统计规则(计算)"解耦,且可以动态的加载和运行的能力.顺便对JAVA嵌入运行Groovy脚本做个备忘.

    Java中运行Groovy,有三种比较常用的类支持:GroovyShell,GroovyClassLoader以及Java-Script引擎(JSR-223).

    1) GroovyShell: 通常用来运行"script片段"或者一些零散的表达式(Expression)

    2) GroovyClassLoader: 如果脚本是一个完整的文件,特别是有API类型的时候,比如有类似于JAVA的接口,面向对象设计时,通常使用GroovyClassLoader.

    3) ScriptEngine: JSR-223应该是推荐的一种使用策略.规范化,而且简便.

 

一.GroovyShell代码样例

    1) 简单的表达式执行,方法调用

 /** 
 * 简答脚本执行 
 * @throws Exception 
 */  
public static void evalScriptText() throws Exception{  
    //groovy.lang.Binding  
    Binding binding = new Binding();  
    GroovyShell shell = new GroovyShell(binding);  
      
    binding.setVariable("name", "zhangsan");  
    shell.evaluate("println ‘Hello World! I am ‘ + name;");  
    //在script中,声明变量,不能使用def,否则scrope不一致.  
    shell.evaluate("date = new Date();");  
    Date date = (Date)binding.getVariable("date");  
    System.out.println("Date:" + date.getTime());  
    //以返回值的方式,获取script内部变量值,或者执行结果  
    //一个shell实例中,所有变量值,将会在此"session"中传递下去."date"可以在此后的script中获取  
    Long time = (Long)shell.evaluate("def time = date.getTime(); return time;");  
    System.out.println("Time:" + time);  
    binding.setVariable("list", new String[]{"A","B","C"});  
    //invoke method  
    String joinString = (String)shell.evaluate("def call(){return list.join(‘ - ‘)};call();");  
    System.out.println("Array join:" + joinString);  
    shell = null;  
    binding = null;  
}

2)  伪main方法执行.

 /** 
 * 当groovy脚本,为完整类结构时,可以通过执行main方法并传递参数的方式,启动脚本. 
 */  
public static void evalScriptAsMainMethod(){  
    String[] args = new String[]{"Zhangsan","10"};//main(String[] args)  
    Binding binding = new Binding(args);  
    GroovyShell shell = new GroovyShell(binding);  
    shell.evaluate("static void main(String[] args){ if(args.length != 2) return;println(‘Hello,I am ‘ + args[0] + ‘,age ‘ + args[1])}");  
    shell = null;  
    binding = null;  
} 

3)  通过Shell运行具有类结构的Groovy脚本

 /** 
 * 运行完整脚本 
 * @throws Exception 
 */  
public static void evalScriptTextFull() throws Exception{  
    StringBuffer buffer = new StringBuffer();  
    //define API  
    buffer.append("class User{")  
            .append("String name;Integer age;")  
            //.append("User(String name,Integer age){this.name = name;this.age = age};")  
            .append("String sayHello(){return ‘Hello,I am ‘ + name + ‘,age ‘ + age;}}
");  
    //Usage  
    buffer.append("def user = new User(name:‘zhangsan‘,age:1);")  
            .append("user.sayHello();");  
    //groovy.lang.Binding  
    Binding binding = new Binding();  
    GroovyShell shell = new GroovyShell(binding);  
    String message = (String)shell.evaluate(buffer.toString());  
    System.out.println(message);  
    //重写main方法,默认执行  
    String mainMethod = "static void main(String[] args){def user = new User(name:‘lisi‘,age:12);print(user.sayHello());}";  
    shell.evaluate(mainMethod);  
    shell = null;  
}

4)  方法执行和分部调用

     /** 
     * 以面向"过程"的方式运行脚本 
     * @throws Exception 
     */  
    public static void evalScript() throws Exception{  
        Binding binding = new Binding();  
        GroovyShell shell = new GroovyShell(binding);  
        //直接方法调用  
        //shell.parse(new File(//))  
        Script script = shell.parse("def join(String[] list) {return list.join(‘--‘);}");  
        String joinString = (String)script.invokeMethod("join", new String[]{"A1","B2","C3"});  
        System.out.println(joinString);  
        ////脚本可以为任何格式,可以为main方法,也可以为普通方法  
        //1) def call(){...};call();  
        //2) call(){...};  
        script = shell.parse("static void main(String[] args){i = i * 2;}");  
        script.setProperty("i", new Integer(10));  
        script.run();//运行,  
        System.out.println(script.getProperty("i"));  
        //the same as  
        System.out.println(script.getBinding().getVariable("i"));  
        script = null;  
        shell = null;  
    }  

二. GroovyClassLoader代码示例

    1) 解析groovy文件

     /** 
     * from source file of *.groovy 
     */  
    public static void parse() throws Exception{  
        GroovyClassLoader classLoader = new GroovyClassLoader(Thread.currentThread().getContextClassLoader());  
        File sourceFile = new File("D:\TestGroovy.groovy");  
        Class testGroovyClass = classLoader.parseClass(new GroovyCodeSource(sourceFile));  
        GroovyObject instance = (GroovyObject)testGroovyClass.newInstance();//proxy  
        Long time = (Long)instance.invokeMethod("getTime", new Date());  
        System.out.println(time);  
        Date date = (Date)instance.invokeMethod("getDate", time);  
        System.out.println(date.getTime());  
        //here  
        instance = null;  
        testGroovyClass = null;  
    }  

  2) 如何加载已经编译的groovy文件(.class)

     public static void load() throws Exception {  
        GroovyClassLoader classLoader = new GroovyClassLoader(Thread.currentThread().getContextClassLoader());  
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\TestGroovy.class"));  
        ByteArrayOutputStream bos = new ByteArrayOutputStream();  
        for(;;){  
            int i = bis.read();  
            if( i == -1){  
                break;  
            }  
            bos.write(i);  
        }  
        Class testGroovyClass = classLoader.defineClass(null, bos.toByteArray());  
        //instance of proxy-class  
        //if interface API is in the classpath,you can do such as:  
        //MyObject instance = (MyObject)testGroovyClass.newInstance()  
        GroovyObject instance = (GroovyObject)testGroovyClass.newInstance();  
        Long time = (Long)instance.invokeMethod("getTime", new Date());  
        System.out.println(time);  
        Date date = (Date)instance.invokeMethod("getDate", time);  
        System.out.println(date.getTime());  
          
        //here  
    bis.close();  
        bos.close();  
        instance = null;  
        testGroovyClass = null;  
    }  

三. ScriptEngine

    1) pom.xml依赖

 <dependency>  
    <groupId>org.codehaus.groovy</groupId>  
    <artifactId>groovy</artifactId>  
    <version>2.1.6</version>  
</dependency>  
<dependency>  
    <groupId>org.codehaus.groovy</groupId>  
    <artifactId>groovy-jsr223</artifactId>  
    <version>2.1.6</version>  
</dependency> 

2) 代码样例

 public static void evalScript() throws Exception{  
    ScriptEngineManager factory = new ScriptEngineManager();  
    //每次生成一个engine实例  
    ScriptEngine engine = factory.getEngineByName("groovy");  
    System.out.println(engine.toString());  
    assert engine != null;  
    //javax.script.Bindings  
    Bindings binding = engine.createBindings();  
    binding.put("date", new Date());  
    //如果script文本来自文件,请首先获取文件内容  
    engine.eval("def getTime(){return date.getTime();}",binding);  
    engine.eval("def sayHello(name,age){return ‘Hello,I am ‘ + name + ‘,age‘ + age;}");  
    Long time = (Long)((Invocable)engine).invokeFunction("getTime", null);  
    System.out.println(time);  
    String message = (String)((Invocable)engine).invokeFunction("sayHello", "zhangsan",new Integer(12));  
    System.out.println(message);  
}

需要提醒的是,在groovy中,${expression} 将会被认为一个变量,如果需要输出"$"符号,需要转义为"$".   

关于ScriptEngine更多介绍,请参考.