OGNL表达式

OGNL:对象视图导航语言. ${user.addr.name} 这种写法就叫对象视图导航.

OGNL不仅仅可以视图导航.支持比EL表达式更加丰富的功能.

 

代码流程：

1.OGNL不需要导入额外的jar包，因为struts2中包含了

代码基本框架：

@Test
    //准备工作
    public void fun1() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("汤姆猫",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("阿猫",18));
            context.put("user2", new User("阿狗",22));
        OgnlContext oc = new OgnlContext();
        //将rootUser作为root部分
        oc.setRoot(rootUser);
        //将context这个Map作为Context部分
        oc.setValues(context);
        //书写OGNL
        Ognl.getValue("", oc, oc.getRoot());
    }

语法：

1.基本取值

@Test
    //取出root中的属性值
    public void fun2() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        //取出root中user对象的name属性
        String name = (String) Ognl.getValue("name", oc, oc.getRoot());
        Integer age = (Integer) Ognl.getValue("age", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(age);
    }

    @Test
    //取出context中的属性值
    public void fun3() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        //取出context中键为user1对象的name属性
        String name = (String) Ognl.getValue("#user1.name", oc, oc.getRoot());
        String name2 = (String) Ognl.getValue("#user2.name", oc, oc.getRoot());
        Integer age = (Integer) Ognl.getValue("#user2.age", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(name2);
        System.out.println(age);
    }

2.赋值

@Test
    //为属性赋值
    public void fun4() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        //将root中的user对象的name属性赋值
        Ognl.getValue("name='jerry'", oc, oc.getRoot());
        String name = (String) Ognl.getValue("name", oc, oc.getRoot());
        
        String name2 = (String) Ognl.getValue("#user1.name='小明',#user1.name", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(name2);
    }

3.调用方法

@Test
    //调用方法
    public void fun5() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        //调用root中user对象的setName方法
        Ognl.getValue("setName('lilei')", oc, oc.getRoot());
        String name = (String) Ognl.getValue("getName()", oc, oc.getRoot());
        
        String name2 = (String) Ognl.getValue("#user1.setName('lucy'),#user1.getName()", oc, oc.getRoot());
        
        
        System.out.println(name);
        System.out.println(name2);
    }

4.调用静态方法

public class HahaUtils {
    
        //回音方法
        public static Object echo(Object o){
            return o;
        }
}

@Test
    //调用静态方法
    public void fun6() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        String name = (String) Ognl.getValue("@cn.itheima.a_ognl.HahaUtils@echo('hello 强勇!')", oc, oc.getRoot());
        //Double pi = (Double) Ognl.getValue("@java.lang.Math@PI", oc, oc.getRoot());
        Double pi = (Double) Ognl.getValue("@@PI", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(pi);
    }

5.创建对象(List,Map)

@Test
    //ognl创建对象-list|map
    public void fun7() throws Exception{
        //准备ONGLContext
            //准备Root
            User rootUser = new User("tom",18);
            //准备Context
            Map<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();
        oc.setRoot(rootUser);
        oc.setValues(context);
        //书写OGNL
        
        //创建list对象
        Integer size = (Integer) Ognl.getValue("{'tom','jerry','jack','rose'}.size()", oc, oc.getRoot());
        String name = (String) Ognl.getValue("{'tom','jerry','jack','rose'}[0]", oc, oc.getRoot());
        String name2 = (String) Ognl.getValue("{'tom','jerry','jack','rose'}.get(1)", oc, oc.getRoot());
    
        /*System.out.println(size);
        System.out.println(name);
        System.out.println(name2);*/
        //创建Map对象
        Integer size2 = (Integer) Ognl.getValue("#{'name':'tom','age':18}.size()", oc, oc.getRoot());
        String name3  = (String) Ognl.getValue("#{'name':'tom','age':18}['name']", oc, oc.getRoot());
        Integer age  = (Integer) Ognl.getValue("#{'name':'tom','age':18}.get('age')", oc, oc.getRoot());
        System.out.println(size2);
        System.out.println(name3);
        System.out.println(age);
    }