MVEL2.0的使用实例(一)

本文是对java整合mvel2.0的一点示例:

如果表达式中有变量,解析表达式时必须传一个map

MVEL.eval(expression, vars);

/**
 * 基本解析表达式
 */
@Test
public void test(){
    String expression ="foobar > 99";
    Map vars = new HashMap();
    vars.put("foobar",new Integer(100));
    // We know this expressionshould return a boolean.
    Boolean result = (Boolean) MVEL.eval(expression, vars);
    if (result.booleanValue()) {
        System.out.println("Itworks!");
    }
}

/**
 * 变量判空
 */
@Test
public void test4(){
    String expression = "a == empty && b == empty";

    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("a", "");
    paramMap.put("b", null);
    Object object = MVEL.eval(expression, paramMap);
    System.out.println(object); // true
}

 　　/**
     * 
     */
    @Test
    public void test(){
        HashMap<Object, Object> srcMap = new HashMap<>();
        srcMap.put("name","zs");
        srcMap.put("age",10);
        srcMap.put("sex","女");
//字段映射关系
        HashMap<String, String> mapping = new HashMap<>();
        mapping.put("name","name");
        mapping.put("age","age");
//这里先把当前年份写死为2019
        mapping.put("birthYear","2019-age");
//目标对象
        HashMap<Object, Object> targetMap = new HashMap<>();
//k为目标表字段，v为转换规则
        mapping.forEach((k,v)->{
            Object reValue = MVEL.eval(v,srcMap);
            System.out.println(v+":"+reValue);
            targetMap.put(k,reValue);
        });
        System.out.println("源对象"+srcMap); //源对象{sex=女, name=zs, age=10}
        System.out.println("目标对象"+targetMap); //目标对象{birthYear=2009, name=zs, age=10}
    }

/**
 * 获取对象属性
 */
@Test
public void test2(){
    UserInfo user = new UserInfo();
    user.setUserName("1234");
    String expression = "user.userName = '123'";
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("user",user);
    Object object = MVEL.eval(expression, paramMap);
    System.out.println(object); // true
}

 /**
     * 多语句分号隔开   返回值无需 return
     */
    @Test
    public void test3(){
    String expression = " a = 10; b = (a = a * 2) + 10;b;";

　　Map<String, Object> paramMap = new HashMap<>();
//即便map没有任何内容 ,也需要传map 不然会报错

        Object object = MVEL.eval(expression,paramMap );

        System.out.println(object); // true
    }[

/**
 * null 和nil 都表示空
 */
@Test
public void test4(){
    String expression = "a == null && b == nil";
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("a", null);
    paramMap.put("b", null);
    Object object = MVEL.eval(expression, paramMap);
    System.out.println(object); // true
}

/**
 * 两种解析表达式方式
 */
@Test
public void test5(){
    UserInfo foo = new UserInfo();
    foo.setUserName("test");
    Map context = new HashMap();
    String expression = "foo.userName == 'test'";
    VariableResolverFactory functionFactory = new MapVariableResolverFactory(context);
    context.put("foo",foo);
    Boolean result = (Boolean) MVEL.eval(expression,functionFactory);
    System.out.println(result);

    Serializable compileExpression = MVEL.compileExpression(expression);
    result = (Boolean) MVEL.executeExpression(compileExpression, context, functionFactory);
    System.out.print(result);
}

/**
 *基本表达式计算,map工厂
 */
@Test
public void test3(){
    UserInfo userInfo = new UserInfo();
    String exp = "a + b > c";
    Map varsMap = new HashMap();
    varsMap.put("a", 1); varsMap.put("b", 2);varsMap.put("c", 2);
    VariableResolverFactory factory = new MapVariableResolverFactory(varsMap);
    Object eval = MVEL.eval(exp, factory);
    System.out.println(eval);
}

/**
     *空安全运算符user.?parent.name
     */
    @Test
    public void test4(){
        UserInfo user = new UserInfo();
        user.setUserName("xm");
        user.setPassword("123");
        user.setParent(new Parent("xmfather"));
        //user 有一个parent对象属性 parent属性中有一个name属性
        String exp = "user.?parent.name";
        Map<String,Object> factory = new HashMap<>();
        factory.put("user",user);
//        VariableResolverFactory factory = new MapVariableResolverFactory();
        Object eval = MVEL.eval(exp, factory);
        System.out.println(eval);
    }

/**
 * 集合遍历
 */
@Test
public void test5(){
    List<Integer> list = new ArrayList<>();
    Map<String,Object> map = new HashMap<>();
    Map<String,Object> map2 = new HashMap<>();
    list.add(0);
    list.add(1);
    list.add(2);
    String exp = "list[0]";
    String exp2 = "map2.list";
    map2.put("list",list);
    map.put("list",list);
    map.put("map2",map2);
    Object eval = MVEL.eval(exp2,map);
    System.out.println(eval);
}
/**
 * Strings as Arrays
 */
@Test
public void test6(){
    String foo = "My String";
    String exp = "foo[0]";
    Map<String,Object> map = new HashMap<>();
    map.put("foo",foo);
    Object eval = MVEL.eval(exp,map);
    System.out.println(eval);
}

/**
 *  If-Then-Else
 */
@Test
public void test7(){
    String exp = "\n" +
            "if (a > 0) {\n" +
            "   System.out.println(\"Greater than zero!\");\n" +
            "}\n" +
            "else if (a == -1) { \n" +
            "   System.out.println(\"Minus one!\");\n" +
            "}\n" +
            "else { \n" +
            "   System.out.println(\"Something else!\");\n" +
            "}\n";
    Map<String,Object> map = new HashMap<>();
    map.put("a",1);
    Object eval = MVEL.eval(exp,map);
}　　

/**
 *  三元声明
 */
@Test
public void test9(){
    String expression = "num > 0 ? \"Yes\" : \"No\";";
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("num", 2);
    Object object = MVEL.eval(expression, paramMap);
    System.out.println(object);
}

/**
 * Foreach  它接受由冒号分隔的两个参数，第一个是当前元素的局部变量，
 * 第二个是要迭代的集合或数组。
 */
@Test
public void test10(){

    List<String> people = new ArrayList<>();
    people.add("name");
    people.add("xm");
    people.add("xl");
    String expression = "count = 0;\n" +
            "foreach (name : people) {\n" +
            "   count++;\n" +
            "   System.out.println(\"Person #\" + count + \":\" + name);\n" +
            "}";
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("people", people);
    Object object = MVEL.eval(expression, paramMap);
    System.out.println(object);

    String exp2 = "str = \"ABCDEFGHIJKLMNOPQRSTUVWXYZ\";\n" +
            " \n" +
            "foreach (el : str) {\n" +
            "   System.out.print(\"[\"+ el + \"]\"); \n" +
            "}";
    MVEL.eval(exp2,paramMap);

}

/**
 * MVEL 2.0，使用for关键字简单地简化foreach
 */
@Test
public void test10_2(){
   String expression ="['Jim','Bob','Tom']";
   List<String> l =(List<String>) MVEL.eval(expression);
   for(String str:l){
       System.out.println(str);
   }

    String exp = "count = 0;\n" +
            "for (name : l) {\n" +
            "   count++;\n" +
            "   System.out.println(\"l #\" + count + \":\" + name);\n" +
            "}";
    Map<String, Object> paramMap = new HashMap<>();
    paramMap.put("l",l);
     MVEL.eval(exp,paramMap);
}

  /**
     *MVEL对列表、数组、map的操作
     */
    @Test
    public void test11(){
        //list
        String expression ="['Jim','Bob','Tom']";
        List<String> l =(List<String>) MVEL.eval(expression);
        for(String str:l){
            System.out.println("list"+str);
        }

        //数组
        String exp2 = "{'Jim','Bob','Tom'}";
          Object str = MVEL.eval(exp2);
            if(str.getClass().isArray()){
           System.out.println("array"+String.valueOf(Array.get(str, 0)));
            }

            //map
        String exp3 ="['Bob' : new com.demo.po.UserInfo('Bob'), 'Michael' : new com.demo.po.UserInfo('Michael')]";
        Map o = (Map ) MVEL.eval(exp3);
        UserInfo u = (UserInfo) o.get("Bob");
        System.out.println("map"+u.getUserName());

    }

    /**
     * Do While
     */
    @Test
    public void test12(){
        String exp3 = "do { \n" +
                "  System.out.println(\"当符合while中条件就执行:\"+x);\n" +
                " --x } \n" +
                "while (x >= 5 );";
        Map<String,Object> map = new HashMap<>();
        map.put("x",10);
        MVEL.eval(exp3,map);

    }
    /**
     * Do Until
     */
    @Test
    public void test13(){
        String exp3 = "do { \n" +
            "  System.out.println(\"当不符合while中条件就执行:\"+x);\n" +
            " --x } \n" +
            "until  (x < 5 );";
        Map<String,Object> map = new HashMap<>();
        map.put("x",10);
        MVEL.eval(exp3,map);}

}

/**
 * while
 */
@Test
public void test(){
    String exp3 = "while(x >= 5){" +
            "System.out.println(\"当符合while中条件就执行:\"+x);" +
            "--x}";
    Map<String,Object> map = new HashMap<>();
    map.put("x",10);
    MVEL.eval(exp3,map);
}

/**
 * until
 */
@Test
public void test2(){
    String exp3 = "until(x < 5){" +
            "System.out.println(\"当不符合while中条件就执行:\"+x);" +
            "--x}";
    Map<String,Object> map = new HashMap<>();
    map.put("x",10);
    MVEL.eval(exp3,map);
}

/**
 * 投影1.0
 */
@Test
public void test3(){
    List<UserInfo> users = new ArrayList<>();
    users.add(new UserInfo("xm"));
    users.add(new UserInfo("xh"));
    users.add(new UserInfo("xl"));
    String exp3 = "parentNames = (userName in users); parentNames;" ;
    Map<String,Object> map = new HashMap<>();
    map.put("users",users);
    List<UserInfo> eval = (List<UserInfo>) MVEL.eval(exp3, map);
    System.out.println(eval);
}
/**
 *投影2.0
 */
@Test
public void test3_2(){
    List<UserInfo> users = new ArrayList<>();
    users.add(new UserInfo(new Parent("xm")));
    users.add(new UserInfo(new Parent("xh")));
    users.add(new UserInfo(new Parent("xl")));
//    String exp3 = "foo=(name in (parent in users));foo" ;
   String exp3 = "foo=(parent.name in users);foo" ;
    Map<String,Object> map = new HashMap<>();
    map.put("users",users);
    List<UserInfo> eval = (List<UserInfo>) MVEL.eval(exp3, map);
    System.out.println(eval);
}

/**
 *投影3.0过滤投影
 */
@Test
public void test3_3(){
    List<UserInfo> users = new ArrayList<>();
    List<UserInfo> fams = new ArrayList<>();
    users.add(new UserInfo("xm",fams));
    users.add(new UserInfo("xh",fams));
    users.add(new UserInfo("xl",fams));
    String exp3 = "($ in users if $.userName contains 'h');" ;
    Map<String,Object> map = new HashMap<>();
    map.put("users",users);
    Object eval =  MVEL.eval(exp3, map);
    System.out.println(eval);
}
/**
 * 过滤投影2.0
 */
@Test
public void test4(){
    String exp3 = "(($ < 10) in [2,4,8,16,32]);  " ;
    String exp4 =  "($ in [2,4,8,16,32] if $ < 10); ";    // returns [2,4,8]
    Object eval =  MVEL.eval(exp3);
    System.out.println(eval);
    Object eval2 =  MVEL.eval(exp4);
    System.out.println(eval2);
}

/**
 * 导入调用简单hello函数
 */
@Test
public void test()throws IOException {
    File scriptFile = new File("src/main/resources/mvel/hello.el");
    Map map = new HashMap();
    map.put("name", "小明");
    MVEL. evalFile(scriptFile, ParserContext.create(), map);
    Object obj = MVEL. eval("hello(name);", map);
}

//hello.el的内容
def hello(String name){
     System.out.println("hello" + name);
}

/**
 * Lambda(匿名函数)
 */
@Test
public void test2(){
    String exp = "threshold = def (x) { x >= 10 ? x : 0 };\n" +
            "result = threshold(num);\n" +
            "System.out.println(result);";
    Map map = new HashMap();
    map.put("num",15);
     MVEL. eval(exp,map);
}

目前拦截器,闭包,交集,类型转换以及使用格式还有些问题没研究透