EL与JSTL的简单使用

先引用两个实体bean

package com.EL.bean;


public class person {

	private String username;
	private String password;
	private Address address;
	public person()
	{
		
	}
	public person(String username) {
		this.username = username;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}

package com.EL.bean;

public class Address {

	private String city;

	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}
	
}

　　

//--EL表达式是为了取值的，取出servlet域中(request,session,application)中的数据<br>
  //${取值 }相当于pageContent.findAttribute("取值")<br>
  //取值通过.或者[] 
<%
   // (servlet中产生数据，于普通方式转发到jsp),把数据存到域中。那么jsp取出servlet中的数据?
   String data="jack";
   request.setAttribute("data",data);
 %>
 ${data} <br>


<%
 //(servlet产生数据，将数据封装为javabean),在带给jsp页面，那么jsp页面怎么取值呢？
person p=new person();
p.setUsername("lucy");
request.setAttribute("person",p);
 %>
 ${person.username} //相当于person类有个Getusername()方法
 



<%
  //(servlet 复杂bean,将数据封装为复杂javabean)，在调用另一个javabean，jsp怎么取值呢？
 person p1=new person();
 Address a=new Address();
 a.setCity("nanjing");
 p1.setAddress(a);
 request.setAttribute("person",p1);
 %>
 <br>${person.address.city}


<%
 //servlet中产生数据，如多个人的集合对象list,那么jsp怎么取值呢
 List list=new ArrayList();
 list.add(new person("aaa"));
 list.add(new person("bbb"));
 list.add(new person("ccc"));
 list.add(new person("ddd"));
 request.setAttribute("listdata",list);
 //list[0]表示第一个person对象
 %>
<br>
${listdata[0].username}
 
 
 <%
    //servlet产生map数据，存在域中，jsp怎么取值呢？
    
 Map map=new HashMap();
 map.put("aa", new person("aaaaaaa"));
 map.put("bb", new person("bbbbbbb"));
 map.put("cc", new person("ccccccc"));
 request.setAttribute("map", map);
 // ${map.bb }表示找到了new person("bbbbb")这个对象，在通过name找出
  %>
  <br>
  ${map.bb.username}

 
 <br>${pageContext.request.contextPath} //获得当前web应用名称
 
 
 
 //jstl+El迭达集合中的数据

<br><br> 
 <%
 List list1=new ArrayList();
 list1.add(new person("aaa"));
 list1.add(new person("bbb"));
 list1.add(new person("ccc"));
 list1.add(new person("ddd"));
 request.setAttribute("listdata",list1);
 //list[0]表示第一个person对象
 %>
 <c:forEach items="${listdata }" var="person">
   ${person.name }
 </c:forEach>