Application of jsp custom tag in project

 There are more and more codes in JSP, and there are naturally more redundant content. Often, you need to change N pages for a small change, which is not only a lot of work, but also prone to errors. Take you to solve this problem completely today!

 

tips:

 

1. Image click to enlarge

 

This article introduces the general usage of jsp:tag, and the other one is called: jsp:tld. The use of the two at the same time does not conflict. We are used to calling them page controls, and usually both are used in a project.

 

1. jsp:tag is mainly used to display the page after logical processing. The final effect is that you can give T some parameters, and T will process the result and display it on the page. For example: < c:if >, < c:for >, < c:set > are all implemented in this way, if you don’t believe me, you can click ctrl to see it.
2. jsp:tld will be mapped to a specific class method, the final effect is that you can write a label on the page to display the data of the database on the page. For example: < sec:authorize >,< shiro:hasRole >, if you don't believe me, try again. . . . Ha ha ha ha
   
3. Display is just one of the usages. You can think of how many usages of T can be based on your business scenarios and brain holes, because this label belongs to you.
4. tld does not introduce the use of T in this article, you can add it later: [JSP] The application of tld in the project

 

 

1. Create a Tag file

 

My habit is to first create a tag folder under WEB-INF, and then divide it into a folder according to different functions or different divisions of modules. For example: WEB-INF/tags/layout

 Create my Tag again. For example: ＊＊＊.tag

 

 

<%--
  To change this template use File | Settings | File Templates.
--%>
<%@ tag language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!--Object-->
<%@ attribute name="nowSitet" type="com.wttech.tciss.jsxy.core.vo.statistics.ShutdownSite" required="false" description="当前时间节点temp"%>
<%@ attribute name="shutdownSitest" type="java.util.List" required="false" description="年度列表数据temp"%>
<!--Attribute name-->
<%@ attribute name="selectName" type="java.lang.String" required="false" description="选择框Name"%>
<%@ attribute name="selectId" type="java.lang.String" required="false" description="选择框Id"%>
<%@ attribute name="selectDes" type="java.lang.String" required="false" description="select box text description"%>
<!--Business logic:
    Practice: Copy one object and collection to another to another pair of properties
    Purpose: To prevent the problem that the parameter name of the control setting is inconsistent with the parameter name used by the tag
-->
<c:if test="${null!=nowSitet&&null!=shutdownSitest}">
    <c:set var="nowSite" scope="request" target="nowSite" value="${nowSitet}"/>
    <c:set var="shutdownSites" scope="request" target="shutdownSites" value="${shutdownSitest}"/>
</c:if>
<th class="r" width="116">${not empty selectDes?selectDes:"年度信息"}：</th>
<td width="220">
    <select id="${not empty selectId?selectId:'shutdownSiteId'}" name="${not empty selectName?selectName:'shutdownSiteName'}"
    class="form-control w210px">
        <c:forEach var="site" items="${shutdownSites}">
            <c:choose>
                <c:when test="${v.id==nowSite.id}">
                    <option value="${site.id}" selected>${site.year}</option>
                </c:when>
                <c:otherwise>
                    <option value="${site.id}">${site.year}</option>
                </c:otherwise>
            </c:choose>
        </c:forEach>
    </select>
</td>

 

 

 

2. Use Tag files

My requirements here are as follows: many pages need to add the annual option to query data, and these data come from my background database (tld is more suitable for this requirement, I just want to give a chestnut and don't spray me), the front desk display The way is to use select to display.

I first add my jsp:tag to common.jsp

 

<!--Display control tag-->
<%@ taglib prefix="layout" tagdir="/WEB-INF/tags/layout" %>

 use my jsp:tag in the page

 

 

 

 

<layout:shudownsitelist selectId="shutdownSIteID" selectName="shutdownSIteID"/>

 

The final effect: a drop-down option box with loaded data.

1. If I need this content elsewhere, I just need to copy one more line of the above code to other pages,
2. If the display effect of the page needs to be modified due to changes in demand one day, I found that after my tag is modified, all the places where this control is used have been modified.