[JavaWeb基础] 012.Struts2 自定义标签使用

　　在做开发中，我们会把一些比较经常使用到的代码封装起来，这样可以加快开发的速度和减少错误，并且在修改bug可以一次修改多次修复。那么在前端页面上，如果我们要经常用到公用的显示功能，并涉及到服务端逻辑操作的时候，我们就需要使用到自定义标签，自定义标签使我们可以很方便的去调用一段共同的代码。下面就来看看实现自定义标签的步骤。

一.我们需要创建一个标签类，继承自javax.servlet.jsp.tagext.TagSupport;

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package com.babybus.sdteam.tag;   import java.io.IOException; import java.sql.SQLException; import java.util.ArrayList;   import javax.servlet.jsp.JspException; import javax.servlet.jsp.JspWriter; import javax.servlet.jsp.tagext.TagSupport;   import com.babybus.sdteam.dao.StudentHibernateDao; import com.babybus.sdteam.vo.Student;   public class DisplayStudentAttributeTag extends TagSupport {       /**      * 序列号      */     private static final long serialVersionUID = 1L;     private int studentid;     private String classname;           public int getStudentid() {         return studentid;     }       public void setStudentid(int studentid) {         this.studentid = studentid;     }       public String getClassname() {         return classname;     }       public void setClassname(String classname) {         this.classname = classname;     }       public DisplayStudentAttributeTag() {               System.out.println("DisplayStudentAttributeTag 构造函数");           }               public int doStartTag() throws JspException {               System.out.println("doStartTag函数");                            return SKIP_BODY;  //不实现标签的体，即空体标签。           }              public int doEndTag() throws JspException {              System.out.println("doEndTag函数");              // 查询数据库              StudentHibernateDao studentDao=new StudentHibernateDao();             Student querystudent = new Student();            querystudent.setId(this.getStudentid());            querystudent.setClassname(this.getClassname());            ArrayList<Student> arrayList = new ArrayList<Student>();        try {                 arrayList = (ArrayList<Student>)studentDao.queryStudent(querystudent);        } catch (SQLException e1) {                e1.printStackTrace();        }                           // 通过父类TagSupport的属性值pageContext 取得相关的内置对象              JspWriter out=pageContext.getOut();              // 遍历循环打印。                       try {                       out.println("<table>");                       out.println("<tr>");                       out.println("<td>姓名</td>");                       out.println("<td>年龄</td>");                       out.println("<td>班级</td>");                        out.println("</tr>");                       for(int i=0;i<arrayList.size();i++){                           Student student=(Student)arrayList.get(i);                           out.println("<tr>");                           out.println("<td>" + student.getStudentname() + "</td>");                           out.println("<td>" + student.getAge() + "</td>");                           out.println("<td>" + student.getClassname() + "</td>");                            out.println("</tr>");                       }                       out.println("<table>");              } catch (IOException e) {                       e.printStackTrace();              }                return EVAL_PAGE;       }   }

 第二.我们需要在WebRoot/WEB-INF下面新建一个tld文件。

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<?xml version="1.0" encoding="UTF-8"?>  <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">  <taglib>     <!-- 自定义库标签的根 -->      <tlibversion>1.2</tlibversion>               <!-- 版本号 -->      <jspversion>1.1</jspversion>                 <!-- JSP版本号 -->      <shortname>CustomTags</shortname>            <!-- 标签名称-->      <uri>customtags</uri>                        <!-- 外界导入标签时，认识的名字，很重要。-->           <tag>          <name>displayStudent</name>                                     <!-- 标签名称 -->          <tagclass>com.babybus.sdteam.tag.DisplayStudentTag</tagclass>   <!-- 对应的类 -->      </tag>            <tag>          <name>displayStudentAttribute</name>                                     <!-- 标签名称 -->          <tagclass>com.babybus.sdteam.tag.DisplayStudentAttributeTag</tagclass>   <!-- 对应的类 -->          <attribute>            <name>studentid</name>            <required>true</required>          </attribute>         <attribute>            <name>classname</name>            <required>false</required>          </attribute>     </tag>  </taglib>

 第三.在页面上引入标签，并使用

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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib uri="customtags" prefix="stu"%> <% 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 'index.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 style="overflow:auto;margin:0">     <stu:displayStudent>     </stu:displayStudent>     <stu:displayStudentAttribute studentid= "3" classname = "初三">     </stu:displayStudentAttribute>   </body> </html>

 以上就是自定义标签的实现步骤

 

 

结语

• 受益，掌握了Struts2自定义标签

 

 

本站文章为 宝宝巴士 SD.Team 原创，转载务必在明显处注明：（作者官方网站： 宝宝巴士 ) 

转载自【宝宝巴士SuperDo团队】 原文链接: http://www.cnblogs.com/superdo/p/4755806.html