一、bean封装
public class Person {
private String name="张三";
private int age;
private Date birthday;
private Address addr;
public Person() {
super();
}
public Person(String name) {
super();
this.name = name;
}
public Address getAddr() {
return addr;
}
public void setAddr(Address addr) {
this.addr = addr;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
public class Address {
private String city;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
}
二、el表达式显示（模拟数据库）
<body>
<!-- 普通方式传递数据 -->
<%
String data="abcd";
request.setAttribute("data",data);
%>
${data} <%-- pageContext.findAttribute("data") --%>
</br>
<!-- 数据从bean带过来 -->
<%
Person p=new Person();
p.setName("张三");
request.setAttribute("person",p);
%>
${person.name}
</br>
<!-- 数据从复杂bean带过来 -->
<%
Person p1=new Person();
Address a=new Address();
a.setCity("上海");
p1.setAddr(a);
request.setAttribute("p1",p1);
%>
${p1.addr.city}
</br>
<!-- 产生多个数据 -->
<%
List list=new ArrayList();
list.add(new Person("aa"));
list.add(new Person("bb"));
list.add(new Person("cc"));
request.setAttribute("list",list);
%>
${list[1].name}
</br>
<%
Map map=new HashMap();
map.put("aaa",new Person("a"));
map.put("bbb",new Person("b"));
map.put("ccc",new Person("c"));
map.put("ddd",new Person("d"));
request.setAttribute("map",map);
%>
${map.aaa.name}
</br>
<!-- 获取当前web应用的名字 -->
${pageContext.request.contextPath }
<a href="${pageContext.request.contextPath }/2.jsp">点击我</a>
</body>
三、使用jstl+el完成集合迭代
在页面中使用JSTL标签需要完成的两个步骤：
1）导入jstl.jar和standard.jar这两个jar包
2）在JSP页面中使用<%@tablib url="" prefix="" %>元素导入标签库 （uri standard.jar -> meta-inf -> c.tlduri standard.jar -> meta-inf -> c.tld）
JSTL标签库中常用标签：
<c:foreach var="" items="">
<c:if test="">
<body>
<%
List list=new ArrayList();
list.add(new Person("aa"));
list.add(new Person("bb"));
list.add(new Person("cc"));
request.setAttribute("list",list);
%>
<c:forEach var="person" items="${list}">
${person.name }</br>
</c:forEach>
</br>
<%
Map map=new HashMap();
map.put("aaa",new Person("aaa"));
map.put("bbb",new Person("bbb"));
map.put("ccc",new Person("ccc"));
map.put("ddd",new Person("ddd"));
request.setAttribute("map",map);
%>
<c:forEach items="${map}" var="entry">
${entry.key}:${entry.value.name} </br>
</c:forEach>
</br>
<!-- 代表用户登陆了 -->
<c:if test="${user!=null}">
欢迎您：${user.username}
</c:if>
<c:if test="${user=null}">
用户名：<input type="text"/>
密 码:<input type="password"/>
</c:if>
</body>
时间： 2024-11-05 10:20:08