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自定义标签

2015-03-23 11:15 141 查看

java--自定义标签(tag、tld两种)

博客分类： java基础

java自定义标签

1.一篇不错的 java自定义标签的文章地址：http://gaoshu2006.blog.sohu.com/113222643.html

2.sun公司java自定义标签原文地址：http://java.sun.com/developer/technicalArticles/xml/WebAppDev3/

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jsp自定义标签 Tag文件版

实现一个与上篇文章类似的Select标签功能

1.在WEB-INF/tags/select.tag

<%@ tag body-content="empty" %>

<%@ tag dynamic-attributes="tagAttrs" %>

<%@ attribute name="optionsList" type="java.util.List" required="true" rtexprvalue="true"%>

<%@ attribute name="name" required="true"%>

<%@ attribute name="size" required="true" %>

<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core_rt" %>

<select name="${name }" size="${size }"

   <c:forEach var="attrEntry" items="${tagAttrs }">

     ${attrEntry.key}="${attrEntry.value }"

   </c:forEach>

>

   <c:forEach var="option" items="${optionsList}">

     <option value="${option }">${option}</option>

    </c:forEach>

</select>

这里要注意tag文件只能放在如下位置:

1.WEB-INF/tags

2.WEB-INF/tags的子目录

3.WEB-INF/lib中jar包的META-INF/tags

4.WEB-INF/lib中jar包的META-INF/tags下的子目录

5.jar包中的tag文件需要tld

添加jstl.jar与standard.jar到WEB-INF/lib目录,还有一点就是上面标红的部分:不要使用http://java.sun.com/jstl/core这个url,否则会报foreach中的item属性有问题

2.在jsp中的使用

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ page import="java.util.*" %>

<%@ taglib prefix="formTag" tagdir="/WEB-INF/tags" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<%

List<String> colorList = new ArrayList<String>();

    colorList.add("red");

    colorList.add("blue");

    colorList.add("white");

    request.setAttribute("colorList",colorList);

%>

<form action="" method="post">

<formTag:select name="color" size="1" optionsList="${requestScope.colorList}" style="width:140px"/>

</form>

</body>

</html>

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jsp 自定义标签

jsp标签有两组api

JspTag ->SimpleTag ->SimpleTagSupport

JspTag ->Tag ->IterationTag->BodyTag

第二组是classic的,比较早的使用方式,doStartTag(),doEndTag()有N多返回值的那种,使用起来也确实不方便,今天学到了另一个使用第一组api方式的,让人大快人心,贴码

例子是一个Select的标签,支持动态属性设置

1.编写标签类

public class SelectTagHandler extends SimpleTagSupport implements DynamicAttributes {

private static final String ATTR_TEMPLATE = "%s='%s'";

private static final String OPTION_TEMPLATE = "<option value='%1$s'>%1$s</option>";

private List optionsList;

private String name;

private String size;

private Map<String, Object> tagAttrs = new HashMap<String, Object>();

public void setName(String name) {

this.name = name;

}

public void setSize(String size) {

this.size = size;

}

public void setOptionsList(List optionsList) {

this.optionsList = optionsList;

}

@Override

public void doTag() throws JspException, IOException {

PageContext pageContext = (PageContext) getJspContext();

JspWriter out = pageContext.getOut();

out.print("<select ");

out.print(String.format(ATTR_TEMPLATE, "name", this.name));

out.print(String.format(ATTR_TEMPLATE, "size", this.size));

for (String attrName : tagAttrs.keySet()) {

   String attrDefinition = String.format(ATTR_TEMPLATE, attrName, tagAttrs.get(attrName));

   out.print(attrDefinition);

}

out.print(">");

for (Object option : this.optionsList) {

   String optionTag = String.format(OPTION_TEMPLATE, option.toString());

   out.println(optionTag);

}

out.println("</select>");

}

@Override

public void setDynamicAttribute(String uri, String name, Object value) throws JspException {

tagAttrs.put(name, value);

}

}

看到没,代码如此的简洁,动态属性配置也十分的方便,不用写N多个setter与getter方法.

2.编写tld文件WebRoot/tld/select.tld

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

<taglib xmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3g.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"

version="2.0">

<tlib-version>1.2</tlib-version>

<jsp-version>1.2</jsp-version>

<short-name>Forms Taglib</short-name>

<uri>http://hi.baidu.com/tags/forms</uri>

<description>

An example tab library of replacements for the html form tags.

</description>

<tag>

<name>select</name>

<tag-class>com.baidu.hi.tag.SelectTagHandler</tag-class>

<body-content>empty</body-content>

<attribute>

   <name>optionsList</name>

   <required>true</required>

   <rtexprvalue>true</rtexprvalue>

   <type>java.util.List</type>

</attribute>

<attribute>

   <name>name</name>

   <required>true</required>

</attribute>

<attribute>

   <name>size</name>

   <required>true</required>

</attribute>

<dynamic-attributes>true</dynamic-attributes>

</tag>

</taglib>

3.在jsp中的使用

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

    <%@ page import="java.util.*" %>

<%@ taglib prefix="formTags" uri="/tld/select.tld"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<%@page import="java.util.ArrayList"%><html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

</head>

<body>

<%

List<String> colorList = new ArrayList<String>();

    colorList.add("red");

    colorList.add("blue");

    colorList.add("white");

    request.setAttribute("colorList",colorList);

%>

<form action="" method="post">

<formTags:select name="color" size="1" optionsList="${requestScope.colorList}" style="width:140px"/>

</form>

</body>

</html>

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