jsp通过自定义标签库实现数据列表显示的方法

网络编程 2024/11/1 佚名

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本文实例讲述了jsp通过自定义标签库实现数据列表显示的方法。分享给大家供大家参考，具体如下：

1. 定义标签库类 UserListTag.java

package com.yanek.cms.tag;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTagSupport;
import com.yanek.cms.vo.UserInfo;
public class UserListTag extends BodyTagSupport {
 private String name;// 一个属性名
 private Iterator it;// 要迭代的对象
 private int cateid; // 用户类别id
 @Override
 public int doEndTag() throws JspException {
 try {
  if (bodyContent != null) {
  bodyContent.writeOut(bodyContent.getEnclosingWriter());
  }
 } catch (IOException e) {
  e.printStackTrace();
 }
 return EVAL_PAGE;
 }
 @Override
 public int doStartTag() throws JspException {
 //这里根据用户类型,构造不同的列表数据,实现可以根据数据库获取
 List<UserInfo> users = new ArrayList<UserInfo>();
 if (cateid == 1) {
  users.add(new UserInfo("张三", 20, "Zhangsan@163.com"));
  users.add(new UserInfo("李四", 30, "Lisi@sina.com"));
 } else {
  users.add(new UserInfo("王五", 33, "Wangwu@qq.com"));
  users.add(new UserInfo("赵六", 33, "zhaoliu@qq.com"));
 }
 it = users.iterator();
 if (it == null) {
  return SKIP_BODY;
 } else {
  return continueNext();
 }
 }
 private int continueNext() {
 if (it.hasNext()) {
  pageContext.setAttribute(name, it.next(), pageContext.PAGE_SCOPE);
  return EVAL_BODY_TAG;
 } else {
  return SKIP_BODY;
 }
 }
 @Override
 public int doAfterBody() {
 return continueNext();
 }
 public String getName() {
 return name;
 }
 public void setName(String name) {
 this.name = name;
 }
 public int getCateid() {
 return cateid;
 }
 public void setCateid(int cateid) {
 this.cateid = cateid;
 }
}

2. 在WEB-INF目录下新建标签库描述文件my_cms_tag.tld：

my_cms_tag.tld

<"1.0" encoding="UTF-8""-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.0</jspversion>
<shortname>cms</shortname>
<uri>http://www.58tech.cn/mystruts/tags-cms</uri>
<!-- userListTag start -->
  <tag>
    <name>userListTag</name>
    <tag-class>com.yanek.cms.tag.UserListTag</tag-class>
    <body-content>jsp</body-content>
   <variable>
    <!--<name-given>user_info</name-given>-->
    <name-from-attribute>name</name-from-attribute>
    <variable-class>com.yanek.cms.vo.UserInfo</variable-class>
    <declare>true</declare>
    <scope>NESTED</scope>
   </variable>
    <attribute>
    <name>name</name>
    <required>true</required>
    </attribute>
    <attribute>
    <name>cateid</name>
    <required>true</required>
    </attribute>
</tag>
<!-- userListTag end -->
</taglib>

3. web.xml配置

<"1.0" encoding="UTF-8""2.5" 
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 <welcome-file-list>
  <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>
 <taglib>
   <taglib-uri>/tags/my-cms</taglib-uri>
   <taglib-location>/WEB-INF/my_cms_tag.tld</taglib-location>
 </taglib>
</web-app>

4. jsp调用

<%@ page language="java" import="java.util.*,com.yanek.cms.vo.*" pageEncoding="UTF-8"%>
<%@ taglib uri="/tags/my-cms" prefix="myTag" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
  <base href="<%=basePath%>">
  <title>My JSP 'test.jsp' starting page</title>
 <meta http-equiv="pragma" content="no-cache">
 <meta http-equiv="cache-control" content="no-cache">
 <meta http-equiv="expires" content="0">  
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
 <meta http-equiv="description" content="This is my page">
 <!--
 <link rel="stylesheet" type="text/css" href="styles.css">
 -->
 </head>
 <body>
<table width='500px' border='1' align='center'>
  <tr>
    <td width='20%'>UserName</td>
    <td width='20%'>Age</td>
    <td>Email</td>
  </tr>
<myTag:userListTag name="user_info1" cateid="1"> 
    <tr>
      <td><%=user_info1.getUserName() %></td>
      <td><%=user_info1.getAge() %></td>
      <td><%=user_info1.getEmail() %>
      </td>
    </tr> 
</myTag:userListTag>
</table>
<hr>
<table width='500px' border='1' align='center'>
  <tr>
    <td width='20%'>UserName</td>
    <td width='20%'>Age</td>
    <td>Email</td>
  </tr>
<myTag:userListTag name="user_info2" cateid="2">
    <tr>
      <td><%=user_info2.getUserName() %></td>
      <td><%=user_info2.getAge() %></td>
      <td><%=user_info2.getEmail() %>
      </td>
    </tr> 
</myTag:userListTag>
</table>
 </body>
</html>

实体类定义

package com.yanek.cms.vo;
public class UserInfo {
 private int age;
 private String userName;
 private String email;
 public int getAge() {
 return age;
 }
 public void setAge(int age) {
 this.age = age;
 }
 public String getUserName() {
 return userName;
 }
 public void setUserName(String userName) {
 this.userName = userName;
 }
 public String getEmail() {
 return email;
 }
 public void setEmail(String email) {
 this.email = email;
 }
 public UserInfo(String userName,int age, String email) {
 super();
 this.age = age;
 this.userName = userName;
 this.email = email;
 }
 public UserInfo() {
 }
}

运行效果如下图（URL输入：http://127.0.0.1:8080/TestCMS/page/userlist.jsp）