JSP中EL表达式用法_动力节点Java学院整理

<%
     String name = "Ding";
     request.setAttribute("personName", name);
   %>
   
   ${personName }

<%
    Person p = new Person("Ding",25);
    request.setAttribute("person", p);
   %>
   
   ${person }      <br>
   ${person.name }  <br>

public class Person {
  
  private String name;
  private int age;
  private Address address;
  
  。。。省略各个属性的get和set方法
  }

public class Address {
  private String city;
  
  。。。省略city属性的get和set方法
}

<%
      Person p = new Person();
      Address a = new Address();
      a.setCity("Amoy");
      p.setAddress(a);
      request.setAttribute("person", p);
   %>
   
   ${person.address.city }

<%
    List<Person> personList = new ArrayList<Person>();
    personList.add(new Person("Ding",25));
    personList.add(new Person("LRR",24));
    request.setAttribute("persons",personList);
   %>
   
   ${persons[0].name } love ${persons[1].name}

<%
    Map<String,Person> personMap = new HashMap<String,Person>();
    personMap.put("p1",new Person("Ding",25));
    personMap.put("p2",new Person("LRR",24));
    
    request.setAttribute("pMap", personMap);
   %>
   
   ${pMap.p1.name }  <br>
   love <br>
   ${pMap['p2'].name }

<%
  request.setAttribute("username", "root");
  request.setAttribute("password", "123");
  %>
  ${username == "root" && password == "123" }

<%
      request.setAttribute("person", null);
      request.setAttribute("address", "");
      request.setAttribute("user", new User());
   %>
   ${empty(person)}   <br>
   ${empty(address)}  <br>
   ${empty(user)}     <br>

<%
    User user = new User();
    user.setUsername("fjdingsd");
    pageContext.setAttribute("user", user);
   %>
    
  欢迎您：${user!=null "text-align: center">

　　上面这个例子使用EL表达式的二元表达式，如果user对象不为null，则输出该对象中的username属性，否则输出空字符。
　　二元表达式的另一种用途还可以用来做数据回显，假设有一个用户要修改其注册信息，那么服务器(或从数据库)在返回其数据到显示页面时，应该在他编辑过的信息重新显示出来。
例9：


<% 

  request.setAttribute("gender", "female");

%>

<input type="radio" name="gender" value="male" ${gender=='male'"radio" name="gender" value="female" ${gender=='female'"text-align: center">

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。