JSP第四篇【EL表达式介绍、获取各类数据、11个内置对象、执行运算、回显数据、自定义函数、fn方法库】（二）

  <jsp:useBean id="person" class="domain.Person" scope="session"/>
    <jsp:setProperty name="person" property="age" value="22"/>

<%
    Person person = (Person) session.getAttribute("person");
    System.out.println(person.getAge());
%>

 //等同于person.getAge()
    ${person.age}

  <%
        List<Person> list = new ArrayList();
        Person person1 = new Person();
        person1.setUsername("zhongfucheng");
        Person person2 = new Person();
        person2.setUsername("ouzicheng");
        list.add(person1);
        list.add(person2);
        session.setAttribute("list",list);
    %>

 <%
        List<Person> list = (List) session.getAttribute("list");
        out.write(list.get(0).getUsername()+"<br>");
        out.write(list.get(1).getUsername());
    %>

<%--取出list集合的第1个元素（下标从0开始），获取username属性--%>
${list[0].username}
<br>
<%--取出list集合的第2个元素，获取username属性--%>
${list[1].username}

<%
    Map<String, Person> map = new HashMap<>();
    Person person1 = new Person();
    person1.setUsername("zhongfucheng1");
    Person person2 = new Person();
    person2.setUsername("ouzicheng1");
    map.put("aa",person1);
    map.put("bb",person2);
    session.setAttribute("map",map);
%>