[Java] JSP笔记 - 自定义标签

自定义标签的创建步骤：

自定义标签的四大功能：

[Java] JSP笔记 - 自定义标签

自定义标签的类结构：

[Java] JSP笔记 - 自定义标签

在 1.0 中呢，可以将 <body-content> 的值设置为 JSP， 2.0中则不允许在自定义标签体中出现jsp代码。

接下来呢，我直接贴一些Demo代码：

tagdatetag.tld (标签声明 XML，将之方于 WEB-INF 目录中)

<?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>A tag library exercising SimpleTag handlers.</description>

    <tlib-version>1.0</tlib-version>

    <short-name>SimpleTagLibrary</short-name>

    <!-- 标签URI，用于在jsp中指定uri -->

    <uri>/date-tag</uri>

    <tag>

        <description>Outputs Date String</description>

        <name>simple</name>

        <tag-class>com.demo.TagDate</tag-class>

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

        <attribute>

            <name>format</name>

            <required>false</required> <!-- 属性是否是必须的 -->

            <rtexprvalue>true</rtexprvalue> <!-- 让属性在运行时可以写入 -->

        </attribute>

    </tag>

    <tag>

        <description>Outputs Date String</description>

        <name>simple2</name>

        <tag-class>com.demo.TagDate2</tag-class>

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

        <attribute>

            <name>format</name>

            <required>false</required> <!-- 属性是否是必须的 -->

            <rtexprvalue>true</rtexprvalue> <!-- 让属性在运行时可以写入 -->

        </attribute>

    </tag>

    <tag>

        <name>displayOrSkipBody</name>

        <tag-class>com.demo.DisplayOrSkipBody</tag-class>

        <body-content>scriptless</body-content>

    </tag> 

    <tag>

        <name>skipPageOrEvalPage</name>

        <tag-class>com.demo.SkipPageOrEvalPage</tag-class>

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

    </tag>

    <tag>

        <name>interationTagDemo</name>

        <tag-class>com.demo.InterationTagDemo</tag-class>

        <body-content>scriptless</body-content>

        <attribute>

            <name>name</name>

            <required>true</required>

            <rtexprvalue>true</rtexprvalue>

        </attribute>

        <attribute>

            <name>items</name>

            <required>true</required>

            <rtexprvalue>true</rtexprvalue>

        </attribute>

    </tag>

    <tag>

        <name>modifyBodyContent</name>

        <tag-class>com.demo.ModifyBodyContent</tag-class>

        <body-content>scriptless</body-content>

    </tag>

    <tag>

        <name>if</name>

        <tag-class>com.demo.IfTag</tag-class>

        <body-content>scriptless</body-content>

        <attribute>

            <name>test</name>

            <required>true</required>

            <rtexprvalue>true</rtexprvalue>

        </attribute>

    </tag>

    <!-- 标签组 -->

    <tag>

        <name>choose</name>

        <tag-class>com.demo.ChooseTag</tag-class>

        <body-content>scriptless</body-content>

    </tag>

    <tag>

        <name>when</name>

        <tag-class>com.demo.WhenTag</tag-class>

        <body-content>scriptless</body-content>

        <attribute>

            <name>test</name>

            <required>true</required>

            <rtexprvalue>true</rtexprvalue>

        </attribute>

    </tag>

    <tag>

        <name>other</name>

        <tag-class>com.demo.OtherWiseTag</tag-class>

        <body-content>scriptless</body-content>

    </tag>

</taglib>

index.jsp (使用方法）

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

<%@ taglib prefix="date" uri="/date-tag" %>

<!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>

<%pageContext.setAttribute("name", request.getParameter("name")); %>

<%pageContext.setAttribute("score", request.getParameter("score")); %>

Hello. 今天是

<date:simple format="yyyy年MM月dd日 HH:mm:ss" /><br>

<date:simple/><br>

<date:simple2/><br>

<date:simple2 format="yyyy/MM/dd HH:mm:ss" /><br>

<date:displayOrSkipBody>

    <h2>中国最大的免费在线培训平台</h2>

</date:displayOrSkipBody>

<!-- 条件判断标签 -->

<date:if test="${name=='imooc'}">

慕课网是中国最大的IT技能免费学习平台<br>

</date:if>

<date:if test="${name!='imooc'}">

小伙伴们快点加入慕课网一起学习吧。www.imooc.com<br>

</date:if>

<%

    pageContext.setAttribute("nbastar", new String[]{"jordan", "kobe", "t-mac"});

%>

<!-- 循环遍列数组 -->

<date:interationTagDemo items="${nbastar}" name="name">${name}<br></date:interationTagDemo>

<!-- 修改标签体中的内容 -->

<date:modifyBodyContent>虽然我出现在这里，但是我不会显示</date:modifyBodyContent>

<!-- 标签组 -->

<date:choose>

    <date:when test="${score>90}">非常优秀<br></date:when>

    <date:other>加油吧少年<br></date:other>

</date:choose>

<br>

<a href="index2.jsp">链接到index2.jsp</a><br>

<a href="index.jsp?score=98">非常优秀</a><br>

<a href="index.jsp?name=imooc">Name为imooc</a><br>

</body>

</html>

部分实现代码：

package com.demo;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class ChooseTag extends SimpleTagSupport {

    private boolean flag;

    public boolean isFlag() {

        return flag;

    }

    public void setFlag(boolean flag) {

        this.flag = flag;

    }

    @Override

    public void doTag() throws JspException, IOException {

        getJspBody().invoke(null); // 输出标签体的内容

    }

}

package com.demo;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class WhenTag extends SimpleTagSupport {

    private boolean test;

    public void setTest(boolean test) {

        this.test = test;

    }

    @Override

    public void doTag() throws JspException, IOException {

        if (test) {

            getJspBody().invoke(null);

            ChooseTag choose = (ChooseTag) getParent();

            choose.setFlag(true); // 设置父标签的标识为true

        }

    }

}

package com.demo;

import java.io.IOException;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

public class OtherWiseTag extends SimpleTagSupport {

    @Override

    public void doTag() throws JspException, IOException {

        ChooseTag choose = (ChooseTag) getParent();

        if (!choose.isFlag()) // 如果父标签的标识为true，表示WhenTag已被执行。那么这里就再执行了

            getJspBody().invoke(null);

    }

}

package com.demo;

import java.io.IOException;

import java.text.SimpleDateFormat;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.TagSupport;

/** 自定义 Jsp 标签  */

public class TagDate extends TagSupport {

    private static final long serialVersionUID = 1L;

    private String format;

    public TagDate() {}

    public String getFormat() {

        return format;

    }

    public void setFormat(String format) {

        this.format = format;

    }

    @Override

    public int doStartTag() throws JspException {

        if (format == null || format.length() == 0)

            format = "yyyy-MM-dd HH:mm:ss";

        SimpleDateFormat sdf = new SimpleDateFormat(format);

        try {

            pageContext.getOut().print(sdf.format(System.currentTimeMillis()));

        } catch (IOException e) {

            e.printStackTrace();

        }

        return super.doStartTag();

    }

}

package com.demo;

import java.io.IOException;

import java.text.SimpleDateFormat;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

/** 自定义 Jsp 标签  */

public class TagDate2 extends SimpleTagSupport {

    private String format;

    public String getFormat() {

        return format;

    }

    public void setFormat(String format) {

        this.format = format;

    }

    @Override

    public void doTag() throws JspException, IOException {

        if (format == null || format.length() == 0)

            format = "yyyy-MM-dd HH:mm:ss";

        SimpleDateFormat sdf = new SimpleDateFormat(format);

        try {

            getJspContext().getOut().print(sdf.format(System.currentTimeMillis()));

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

}

package com.demo;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.PageContext;

import javax.servlet.jsp.SkipPageException;

import javax.servlet.jsp.tagext.SimpleTagSupport;

/**

 * @author Administrator

 *

 */

public class SkipPageOrEvalPage extends SimpleTagSupport {

    @Override

    public void doTag() throws JspException, IOException {

        PageContext context = (PageContext) getJspContext();

        HttpServletRequest req = (HttpServletRequest) context.getRequest();

        String referer = req.getHeader("Referer");

        // 如果来源(referer)为空，则代表是在浏览器中直接输入地址访问的。不继续执行

        if (referer == null || referer.length() == 0)

            throw new SkipPageException();

    }

}

完整源码下载：

链接: http://pan.baidu.com/s/1nu851u5 密码: 456e

【感谢】

慕课网， Eleven_Lee JAVA开发工程师

http://www.imooc.com/learn/480

秒客网

[Java] JSP笔记 - 自定义标签

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