JSP 自定义标签

JSP 自定义标签

首先新建一个项目，项目目录如下：

 

声明一个TLD文件，代码及说明如下：

<?xml version="1.0" encoding="UTF-8"?> 
<!-- 标记库描述 --> 
<taglib version="2.0" 
xmlns="http://java.sun.com/xml/ns/j2ee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd">
    <tlib-version>1.0.0</tlib-version><!-- 自定义标签版本 -->
    <jsp-version>2.2</jsp-version><!-- jsp-api 版本 -->
    <short-name>self</short-name><!-- 指定Tag Library默认的前缀名(prefix) -->
    <uri>/WEB-INF/self.tld</uri><!-- 设定Tag Library的惟一访问表示符 -->
    <display-name>"Self Tags"</display-name><!-- -->
    <tag><!-- 具体标签说明 -->
        <name>date</name><!-- 标签名 -->
        <tag-class>com.self.framework.ui.tag.DateTag</tag-class><!-- 标签处理类 -->
        <!--
             1)empty：表示标签中没有body；
             2)JSP：表示标签的body中可以加入JSP程序代码；
             3)tagdependent：表示标签中的内容由标签自己去处理。 
        -->
        <body-content>empty</body-content>
        <!-- 定义属性 -->
        <attribute>
            <name>pattern</name> <!-- 属性名字 -->
            <type>String</type>  <!-- 属性类型 -->
            <requried>false</requried> <!-- 属性是否必需的，默认为false -->
            <rtexprvale>false</rtexprvale><!-- 属性值是否可以为request-time表达式，也就是类似于< %=…% >的表达式 -->
        </attribute>
    </tag>
    <tag> 
        <name>iterator</name> 
        <tag-class>com.self.framework.ui.tag.BodyTag</tag-class> 
        <body-content>jsp</body-content> 
        <attribute> 
           <name>count</name>
           <type>int</type> 
           <requried>false</requried>
           <rtexprvale>false</rtexprvale> 
          </attribute> 
    </tag> 
    
    <tag> 
        <name>list</name> 
        <tag-class>com.self.framework.ui.tag.ListTag</tag-class> 
        <body-content>jsp</body-content>         
        <attribute> 
           <name>name</name>
          </attribute> 
          <attribute> 
           <name>value</name>         
          </attribute> 
    </tag> 
     
</taglib> 

web.xml 文件中：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="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">
    <display-name>SelfTag</display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <!-- 配置标签库及JSP页面编码 -->
    <jsp-config>
        <taglib>
            <taglib-uri>self</taglib-uri>
            <taglib-location>/WEB-INF/self.tld</taglib-location>
        </taglib>
        <jsp-property-group>
            <url-pattern>*.jsp</url-pattern>
            <el-ignored>true</el-ignored>
            <page-encoding>UTF-8</page-encoding>
            <scripting-invalid>false</scripting-invalid>
        </jsp-property-group>
        <jsp-property-group>
            <url-pattern>*.html</url-pattern>
            <el-ignored>true</el-ignored>
            <page-encoding>UTF-8</page-encoding>
            <scripting-invalid>false</scripting-invalid>
        </jsp-property-group>
    </jsp-config>
</web-app>

ListTag处理类代码如下：

package com.self.framework.ui.tag;

import java.util.Iterator;
import java.util.List;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;

public class ListTag extends BodyTagSupport {

    private static final long serialVersionUID = -8112121551855679060L;
    
    private Iterator it;
    
    private String name;
    private String value;
    
    @Override
    public int doStartTag() throws JspException {
        System.out.println("doStartTag...");
        List list = (List)pageContext.findAttribute(value);
        if(list==null && list.size() > 0)
            return SKIP_BODY;
        it = list.iterator();        
        if (it.hasNext()) {
            pageContext.setAttribute(name, it.next());
        }
        return EVAL_BODY_INCLUDE;
    }
    
    @Override
    public int doAfterBody() throws JspException {
        System.out.println("doAfterBody...");
        if (it.hasNext()) {
            pageContext.setAttribute(name, it.next());
            return EVAL_BODY_AGAIN;
        }
        return SKIP_BODY;
    }

    @Override
    public int doEndTag() throws JspException {
        System.out.println("doEndTag...");
        return EVAL_PAGE;
    }

    @Override
    public void doInitBody() throws JspException {
        System.out.println("doInitBody...");
        super.doInitBody();
    }

    @Override
    public BodyContent getBodyContent() {
        System.out.println("getBodyContent...");
        return super.getBodyContent();
    }


    @Override
    public void release() {
        System.out.println("list release...");
        super.release();
    }

    @Override
    public void setBodyContent(BodyContent b) {
        System.out.println("setBodyContent...");
        super.setBodyContent(b);
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setValue(String value) {
        this.value = value;
    }

    
}

index.jsp 使用代码如下：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@ taglib uri="self" prefix="s" %> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>Self Tag</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>
<%
    List<String> list = new ArrayList<String>();   
    list.add("jsp tag...");
    list.add("android...");
    list.add("j2ee...");   
    request.setAttribute("list", list);
%>
<!-- 
    1:<s:date pattern="yyyy-MM-dd"/><br>
    2:<s:date pattern="yyyy.MM.dd HH.mm.ss" /><br>
    3:<s:iterator count="10">HelloWorld!</s:iterator><br>
-->
      list:<s:list name="it" value="list">
      <%
              try {
                pageContext.getOut().write(pageContext.getAttribute("it").toString());
            } catch (Exception e) {
                e.printStackTrace();
            }
    %>
    </s:list>
      
  </body>
</html>

最终效果：

 

备注说明：

 

EVAL_BODY_INCLUDE：把Body读入存在的输出流中，doStartTag()函数可用
EVAL_PAGE：继续处理页面，doEndTag()函数可用
SKIP_BODY：忽略对Body的处理，doStartTag()和doAfterBody()函数可用
SKIP_PAGE：忽略对余下页面的处理，doEndTag()函数可用
EVAL_BODY_TAG：已经废止，由EVAL_BODY_BUFFERED取代
EVAL_BODY_BUFFERED：申请缓冲区，由setBodyContent()函数得到的BodyContent对象来处理tag的body，如果类实现了BodyTag，那么doStartTag()可用，否则非法
EVAL_BODY_BUFFERED 要将BodyContent的内容输出