自定义标签实现switch属性

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我是靠谱客的博主鲜艳手套，最近开发中收集的这篇文章主要介绍自定义标签实现switch属性，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

switch的实现考虑因素有很多，比else if还复杂原理其实很简单就是反复调用case 判断是否终止循环

switch类

package class3g.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class MySwitchTag extends SimpleTagSupport {
   private int exp;

   private boolean lastCase_break = false; //上一个标签的break状态
   private boolean lastCase_done = false; //上一个标签的执行状态

   private boolean terminate = false;


   public boolean isLastCase_break() {
       return lastCase_break;
   }

   public void setLastCase_break(boolean lastCase_break) {
       this.lastCase_break = lastCase_break;
   }

   public boolean isLastCase_done() {
       return lastCase_done;
   }

   public void setLastCase_done(boolean lastCase_done) {
       this.lastCase_done = lastCase_done;
   }

   public boolean isTerminate() {
       return terminate;
   }

   public void setTerminate(boolean terminate) {
       this.terminate = terminate;
   }

   public int getExp() {
       return exp;
   }

   public void setExp(int exp) {
       this.exp = exp;
   }

   @Override
   public void doTag() throws JspException, IOException {
       this.getJspBody().invoke(null);
   }

}

case类

package class3g.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class MyCaseTag extends SimpleTagSupport {
   private int value;
   private boolean breakSwitch;

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

   public void setBreakSwitch(boolean breakSwitch) {
       this.breakSwitch = breakSwitch;
   }

   @Override
   public void doTag() throws JspException, IOException {
       MySwitchTag parent = (MySwitchTag) this.getParent();

       if (parent.isTerminate() == false) {
           if (parent.isLastCase_done() == false) {
               if (parent.getExp() == value) {
                   this.getJspBody().invoke(null);
                   parent.setLastCase_done(true);

                   parent.setTerminate(breakSwitch);
               }
           } else {
               if (parent.isLastCase_break() == false) {
                   this.getJspBody().invoke(null);
                   parent.setLastCase_done(true);
                   parent.setLastCase_break(breakSwitch);

                   parent.setTerminate(breakSwitch);

               }
           }
       }
   }

}

default类

package class3g.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class MyDefaultTag extends SimpleTagSupport {

   @Override
   public void doTag() throws JspException, IOException {
       MySwitchTag parent = (MySwitchTag) this.getParent();
       if(parent.isTerminate() == false){
           this.getJspBody().invoke(null);
           parent.setTerminate(true);
       }
   }

}

JSP页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="http://www.class3g.com" prefix="g" %>
<%
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">
   
</head>

<body>

    <g:switch exp="2">
       <g:case value="1" breakSwitch="true" >
           11111111111<br/>
       </g:case>
       <g:case value="2" breakSwitch="false" >
           22222222222222<br/>
       </g:case>
       <g:case value="3" breakSwitch="true" >
           333333333333333<br/>
       </g:case>
       <g:default>
           dddddddddddddddddd<br/>
       </g:default>
    </g:switch>
    
</body>
</html>

g,tld:描述文件

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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 http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">

    <description>There are my custom tags.</description>
    <tlib-version>1.0</tlib-version>
    <short-name>g</short-name>
    <uri>http://www.class3g.com</uri>


    <tag>
       <description>switch tag</description>
        <name>switch</name>
       <tag-class>class3g.web.tag.MySwitchTag</tag-class>
       <body-content>scriptless</body-content>
       <attribute>
           <name>exp</name>
           <required>true</required>
           <rtexprvalue>true</rtexprvalue>
       </attribute>
    </tag>


    <tag>
       <description>case tag </description>
        <name>case</name>
       <tag-class>class3g.web.tag.MyCaseTag</tag-class>
       <body-content>scriptless</body-content>
       <attribute>
           <name>value</name>
           <required>true</required>
           <rtexprvalue>true</rtexprvalue>
       </attribute>
       <attribute>
           <name>breakSwitch</name>
           <required>true</required>
           <rtexprvalue>true</rtexprvalue>
       </attribute>
    </tag>

    <tag>
       <description>default </description>
        <name>default</name>
       <tag-class>class3g.web.tag.MyDefaultTag</tag-class>
       <body-content>scriptless</body-content>
    </tag>

</taglib>