第十节、自定义标签

其他 2021-11-19 14:29:09 阅读次数: 0

文章目录

编写自定义标签

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版权标签

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package com.eshore;

import jakarta.servlet.jsp.tagext.TagSupport;
import java.io.IOException;
public class CopyRightTag extends TagSupport{
    
    
    @Override
    public int doStartTag(){
    
    
    	String copyRight = "版权所有  &copy2018";
    	try {
    
    
			pageContext.getOut().print(copyRight);
		} catch (IOException e) {
    
    
			e.printStackTrace();
		}
    	return EVAL_PAGE; 
    }
    public int doEndTag(){
    
    
    	
    	return EVAL_PAGE;
    }

}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
        version="2.1">
    <tlib-version>1.0</tlib-version>
    <short-name>linl</short-name>
    <uri>/copyr-tags</uri>

    <!--上述文件中只有一个taglib标签，而taglib标签下可以有多个tag标签，每个tag标签代表一个自定义标签-->
    <tag>
        <!-- 自定义标签的功能描述 -->
        <description>自定义版权</description>
        <name>copyright</name>
        <!-- 自定义标签的实现类路径 -->
        <tag-class>com.eshore.CopyRightTag</tag-class>
        <!-- 正文内容类型  没有正文内容用empty表示 -->
        <body-content>empty</body-content>
    </tag>
</taglib>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/copyr-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <body>
      <p>这里是正文的内容</p>
      <linl:copyright/>
  </body>
</html>

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tld标签库描述文件

tld文件中常用的元素有taglib，tag，attribute，variable。
< t a g l i b > <taglib> <taglib>元素用来设置整个标签库信息的； < t a g > <tag> <tag>元素用来定义标签里面的具体内容； < a t t r i b u t e > <attribute> <attribute>元素用来定义 < t a g > <tag> <tag>中的属性； < v a r i a b l e > <variable> <variable>元素用来定义 < t a g > <tag> <tag>中的变量属性。

TagSupport类

自定义标签库的实现类大多继承自TagSupport类来实现自身的方法，其有四个重要接口：
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带参数的自定义标签

package com.eshore;

import jakarta.servlet.jsp.tagext.BodyTagSupport;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CopyRightTagV extends BodyTagSupport{
    
    
	private String user;
	private String startY;
    @Override
    public int doStartTag(){
    
    
    	SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
    	String endY = sdf.format(new Date());
    	String copyRight = user+"&nbsp;版权所有&nbsp;&nbsp;"+startY+"-"+endY;
    	try {
    
    
			pageContext.getOut().print(copyRight);
		} catch (IOException e) {
    
    
			e.printStackTrace();
		}
    	return EVAL_PAGE; 
    }
    public int doEndTag(){
    
    
    	return EVAL_PAGE;
    }
	public void setUser(String user) {
    
    
		this.user = user;
	}
	public void setStartY(String startY) {
    
    
		this.startY = startY;
	}
    
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
		version="2.1">
	<tlib-version>1.0</tlib-version>
	<short-name>linl</short-name>
    <uri>/copyrightv-tags</uri>
	
	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>自定义版权</description>
		<name>copyrightV</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.CopyRightTagV</tag-class>
		<!-- 正文内容类型  没有正文内容用empty表示 -->
		<body-content>empty</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>版权拥有者</description>
		   <name>user</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
		 <attribute>
			 <description>开始时间</description>
		   <name>startY</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
	</tag>
</taglib>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/copyrightv-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <body>
      <p>这里是正文的内容</p>
      <linl:copyrightV startY="2013" user="林龙"/>
  </body>
</html>

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带标签体的自定义标签

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package com.eshore;

import jakarta.servlet.jsp.JspWriter;
import jakarta.servlet.jsp.tagext.BodyContent;
import jakarta.servlet.jsp.tagext.BodyTagSupport;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class CopyRightBodyContentTag extends BodyTagSupport {
    
    
    private String user;
    private String startY;
    @Override
    public int doStartTag(){
    
    
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
        String endY = sdf.format(new Date());
        String copyRight = user+"&nbsp;版权所有&nbsp;&nbsp;"+startY+"-"+endY;
        try {
    
    
            pageContext.getOut().print(copyRight);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
        return EVAL_PAGE;
    }
    public int doAfterBody(){
    
    
        //取得标签体
        BodyContent bc = getBodyContent();
        JspWriter out = getPreviousOut();
        try{
    
    
            //将标签中的内容写入到JSP页面中
            out.write(bc.getString());
        }catch(IOException e){
    
    
            e.printStackTrace();
        }
        return SKIP_BODY;
    }
    public int doEndTag(){
    
    
        return EVAL_PAGE;
    }
    public void setUser(String user) {
    
    
        this.user = user;
    }
    public void setStartY(String startY) {
    
    
        this.startY = startY;
    }
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
		version="2.1">
	<tlib-version>1.0</tlib-version>
	<short-name>linl</short-name>
    <uri>/copyrightBodycontent-tags</uri>
	
	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>自定义版权</description>
		<name>copyright</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.CopyRightBodyContentTag</tag-class>
		<!-- 正文内容类型  允许有JSP代码-->
		<body-content>JSP</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>版权拥有者</description>
		   <name>user</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
		 <attribute>
			 <description>开始时间</description>
		   <name>startY</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
	</tag>
	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>自定义版权</description>
		<name>loop</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.CopyRightBodyContentTag</tag-class>
		<!-- 正文内容类型  允许有JSP代码-->
		<body-content>JSP</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>循环次数</description>
			<name>time</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<type>java.lang.Integer</type>
		</attribute>
	</tag>
</taglib>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/copyrightBodycontent-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <body>
         <p>这里是正文的内容</p>
         <linl:copyright startY="2013" user="林龙">
            <a href="http://www.sina.com">新浪网</a>
        </linl:copyright>
  </body>
</html>

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多次执行的循环标签

package com.eshore;

import jakarta.servlet.jsp.JspWriter;
import jakarta.servlet.jsp.tagext.BodyTagSupport;
import java.io.IOException;

public class CopyRightTagLoop extends BodyTagSupport{
    
    
	private static final long serialVersionUID = 1L;
	private int time;
    @Override
    public int doStartTag(){
    
    
    	return EVAL_BODY_INCLUDE; 
    }
    public int doAfterBody(){
    
    
    	if(time>1){
    
    
    		time--;
    		return EVAL_BODY_AGAIN;
    	}else{
    
    
    		return SKIP_BODY;
    	}
    }
    public int doEndTag(){
    
    
    	JspWriter out = pageContext.getOut();
    	try {
    
    
			out.print("");
		} catch (IOException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    	return EVAL_PAGE;
    }
	public void setTime(int time) {
    
    
		this.time = time;
	}
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
		version="2.1">
	<tlib-version>1.0</tlib-version>
	<short-name>linl</short-name>
    <uri>/copyrightBodycontent-tags</uri>
	
	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>自定义版权</description>
		<name>copyright</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.CopyRightBodyContentTag</tag-class>
		<!-- 正文内容类型  允许有JSP代码-->
		<body-content>JSP</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>版权拥有者</description>
		   <name>user</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
		 <attribute>
			 <description>开始时间</description>
		   <name>startY</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
	</tag>
	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>自定义版权</description>
		<name>loop</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.CopyRightTagLoop</tag-class>
		<!-- 正文内容类型  允许有JSP代码-->
		<body-content>JSP</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>循环次数</description>
			<name>time</name>
			<required>true</required>
			<rtexprvalue>true</rtexprvalue>
			<type>java.lang.Integer</type>
		</attribute>
	</tag>
</taglib>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/copyrightBodycontent-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <body>
         <p>这里是正文的内容</p>
         <linl:loop time="5">
            <a href="http://www.sina.com">新浪网</a><br/>
        </linl:loop>
  </body>
</html>

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带动态属性的自定义标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/copyrightBodycontent-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <%
        int num = (int)(Math.random()*6)+1;
     %>
  <body>
         <p>这里是正文的内容</p>
         <linl:loop time="<%=num%>">
            <a href="http://www.sina.com">新浪网</a><br/>
        </linl:loop>
  </body>
</html>

嵌套的自定义标签

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package com.eshore;

public class UserInfo {
    
    
	private String userName;//用户名
	private int age;//年龄
	private String email;//用户邮箱

	public UserInfo(String userName, int age, String email) {
    
    
		super();
		this.userName = userName;
		this.age = age;
		this.email = email;
	}
	public UserInfo() {
    
    
		super();
		// TODO Auto-generated constructor stub
	}
	
	public String getUserName() {
    
    
		return userName;
	}
	public void setUserName(String userName) {
    
    
		this.userName = userName;
	}
	public int getAge() {
    
    
		return age;
	}
	public void setAge(int age) {
    
    
		this.age = age;
	}
	public String getEmail() {
    
    
		return email;
	}
	public void setEmail(String email) {
    
    
		this.email = email;
	}
}

package com.eshore;

import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.JspWriter;
import jakarta.servlet.jsp.tagext.TagSupport;

public class UserInfoTag extends TagSupport{
    
    
	private static final long serialVersionUID = 1L;
	private UserInfo user;
    @Override
    public int doStartTag() throws JspException {
    
    

        try {
    
    
            JspWriter out = this.pageContext.getOut();
            if(user == null) {
    
    
                out.println("No UserInfo Found...");
                return SKIP_BODY;
            }
            String content = "<td>"+user.getUserName()+"</td>";
            content+="<td>"+user.getAge()+"</td>";
            content+="<td>"+user.getEmail()+"</td>";
            out.println("<tr>"+content+"</tr>");

        } catch(Exception e) {
    
    
            throw new JspException(e.getMessage());
        }
        return SKIP_BODY;
    }
    @Override
    public int doEndTag() throws JspException {
    
    
        return EVAL_PAGE;
    }
    @Override
    public void release() {
    
    
        //释放资源
        super.release();
        this.user = null;

    }
    public UserInfo getUser() {
    
    
        return user;
    }
    public void setUser(UserInfo user) {
    
    
        this.user = user;
    }

}

package com.eshore;
import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.tagext.TagSupport;
import java.util.Collection;
import java.util.Iterator;
public class TableTag extends TagSupport {
    
    
	private static final long serialVersionUID = 1L;
	private Collection items;
    private Iterator it;
    private String var;
    @Override
    public int doStartTag() throws JspException {
    
    
        if(items == null || items.size() == 0) return SKIP_BODY;
        it = items.iterator();  
        if(it.hasNext()) {
    
    
            pageContext.setAttribute(var, it.next());
        }
        return EVAL_BODY_INCLUDE;
    }
    @Override
    public int doAfterBody() throws JspException {
    
    
        if(it.hasNext()) {
    
    
            pageContext.setAttribute(var, it.next());
            return EVAL_BODY_AGAIN;
        }
        return SKIP_BODY;
    }
    @Override
    public int doEndTag() throws JspException {
    
    
        return EVAL_PAGE;
    }
    public void setItems(Collection items) {
    
    
        this.items = items;
    }
    public void setVar(String var) {
    
    
        this.var = var;
    }
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
		version="2.1">
	<tlib-version>1.0</tlib-version>
	<short-name>linl</short-name>
    <uri>/table-tags</uri>
	<!-- 显示表格标签内容 -->
	<tag>
		<name>showUserInfo</name>
		<tag-class>com.eshore.UserInfoTag</tag-class>
		<body-content>empty</body-content>
		<attribute>
			<name>user</name>
			<required>false</required>
			<rtexprvalue>true</rtexprvalue>
		</attribute>
	</tag>
	<!-- 表格标签遍历 -->
	<tag>
	    <name>table</name>
	    <tag-class>com.eshore.TableTag</tag-class>
	    <body-content>JSP</body-content>
	    <!-- 属性 -->
	    <attribute>
	        <name>items</name>
	        <required>false</required>
	        <rtexprvalue>true</rtexprvalue>
	    </attribute>
	    <attribute>
	        <name>var</name>
	        <required>true</required>
	        <rtexprvalue>true</rtexprvalue>
	    </attribute>
    </tag>
</taglib>

<%@ page language="java" import="java.util.*,com.eshore.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/table-tags" %> 
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义表格标签示例</title>
  </head>
  <%
    //模拟从数据库中取出数据
    List<UserInfo> users = new ArrayList<UserInfo>();   
    users.add(new UserInfo("张三", 20, "[email protected]"));
    users.add(new UserInfo("李四", 26, "[email protected]"));
    users.add(new UserInfo("王五", 33, "[email protected]"));
    pageContext.setAttribute("users", users);
   %>
  <body>
  <div style="text-align: center;">
      用户信息<br/>
   </div>
	<table width='400px' border='1' align='center'>
	    <tr>
	        <td width='20%'>用户名</td>
	        <td width='20%'>年龄</td>
	        <td>邮箱</td>
	    </tr>
	    <!-- 使用标签输出用户信息 -->
	    <linl:table var="item" items="${users}">
	       <linl:showUserInfo user="${item}" />
	    </linl:table>
	</table>
       
  </body>
</html>

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JSP2.X标签

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package com.eshore;

import jakarta.servlet.jsp.JspException;
import jakarta.servlet.jsp.tagext.SimpleTagSupport;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class SimpleTagCopyRight extends SimpleTagSupport{
    
    

	private String user;
	private String startY;
	@Override
    public void doTag() throws JspException, IOException {
    
    
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
    	String endY = sdf.format(new Date());
    	String copyRight = user+"&nbsp;��Ȩ����&nbsp;&nbsp;"+startY+"-"+endY;
		getJspContext().getOut().write(copyRight);
    }
	public void setUser(String user) {
    
    
		this.user = user;
	}
	public void setStartY(String startY) {
    
    
		this.startY = startY;
	}
}

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 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-jsptaglibrary_2_1.xsd"
		version="2.1">
	<tlib-version>1.0</tlib-version>
	<short-name>linl</short-name>
    <uri>/simpleTagCopyright-tags</uri>

	<tag>
		<!-- 自定义标签的功能描述 -->
		<description>SimpleTag版权</description>
		<name>simpleTagcopyright</name>
		<!-- 自定义标签的实现类路径 -->
		<tag-class>com.eshore.SimpleTagCopyRight</tag-class>
		<!-- 正文内容类型  没有正文内容用empty表示 -->
		<body-content>empty</body-content>
		<!-- 添加attribute属性 -->
		<attribute>
			<description>版权拥有者</description>
		   <name>user</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
		 <attribute>
			 <description>开始时间</description>
		   <name>startY</name>
		   <required>true</required>
		   <rtexprvalue>true</rtexprvalue>
		   <type>java.lang.String</type>
		</attribute>
	</tag>
</taglib>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="linl" uri="/simpleTagCopyright-tags" %>
<!DOCTYPE HTML >
<html>
  <head>
    <title>自定义版本标签示例</title>
  </head>
  <body>
      <p>这里是正文的内容</p>
      <linl:simpleTagcopyright startY="2013" user="林龙"/>
  </body>
</html>

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