Jsp自定义标签

标签的运行原理：

容器依据JSP标签的命名空间uri找到标签的描述文件tld文件，然后依据标签名字（helloWorld）找到标签类（com.java1234.tag.HelloWorldTag）。接下来实例化该标签，同时属性值赋给参数，调用doTag方法。

最简单的自定义标签<java1234:helloWorld/> ，输出一句话。

public class HelloWorldTag extends TagSupport{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Override
    public int doStartTag() throws JspException {
        JspWriter out=this.pageContext.getOut();
        try {
            out.println("自定义标签大爷你好！");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return TagSupport.SKIP_BODY; // 直接结束标签
    }
    

}

---------------------java1234.tld------------------------------------------
  <tag>
        <name>helloWorld</name>
        <tag-class>
            com.java1234.tag.HelloWorldTag
        </tag-class>
        <body-content>empty</body-content>
    </tag>
-------------------------HelloWorldTag.jsp--------------------------------
<%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %>
<body>
<java1234:helloWorld/>
</body>

HelloWorldTag

自定义有属性的标签

<java1234:helloWorld2 name="JspServlet屌炸天"/> name值会作为参数传入tag类。

public class HelloWorldTag2 extends TagSupport{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    private String name;
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public int doStartTag() throws JspException {
        JspWriter out=this.pageContext.getOut();
        try {
            out.println(name+"自定义标签大爷你好！");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return TagSupport.SKIP_BODY; // 直接结束标签
    }

}
------------------------------------------------------------------------
  <tag>
        <name>helloWorld2</name>
        <tag-class>
            com.java1234.tag.HelloWorldTag2
        </tag-class>
        <body-content>empty</body-content>
        <attribute>
            <name>name</name>
            <required>true</required>       <!-- 属性必须要填 -->
            <rtexprvalue>true</rtexprvalue>  <!-- 是否支持EL表达式 -->
        </attribute>
    </tag>
------------------------------------------------------------------------
<%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %>
<body>
<java1234:helloWorld2 name="JspServlet屌炸天"/>
</body>

HelloWorldTag2

自定义有标签体的标签（注意：tag类里面是老版本的写法，继承TagSupport）

<java1234:iterate items="people" var="p">
<h2>${p }</h2>
</java1234:iterate>

public class IterateTag extends TagSupport{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    private String var;
    private String items;
    private Iterator iter;
    
    public String getVar() {
        return var;
    }

    public void setVar(String var) {
        this.var = var;
    }

    public String getItems() {
        return items;
    }

    public void setItems(String items) {
        this.items = items;
    }

    public Iterator getIter() {
        return iter;
    }

    public void setIter(Iterator iter) {
        this.iter = iter;
    }

    @Override
    public int doStartTag() throws JspException {
        Object value=this.pageContext.getAttribute(items);
        if(value!=null && value instanceof List){
            this.iter=((List)value).iterator();
            if(iter.hasNext()){
                this.pageContext.setAttribute(var, iter.next());
                return TagSupport.EVAL_BODY_INCLUDE; // 执行标签体
            }else{
                return TagSupport.SKIP_BODY; // 退出标签执行
            }
        }else{
            return TagSupport.SKIP_BODY; // 退出标签执行
        }
    }

    @Override
    public int doAfterBody() throws JspException {
        if(iter.hasNext()){
            this.pageContext.setAttribute(var, iter.next());
            return TagSupport.EVAL_BODY_AGAIN; // 再执行一次标签体
        }else{
            return TagSupport.SKIP_BODY; // 退出标签执行
        }
    }
    
}

------------------------------------------------------------------------
 <tag>
        <name>iterate</name>
        <tag-class>
            com.java1234.tag.IterateTag
        </tag-class>
        <body-content>JSP</body-content> <!-- 代表有标签体，老版本的写法 -->
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

---------------------------------------------------------------------

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>
<%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %>
<!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>
<%
    List people=new ArrayList();
    people.add("王二小");
    people.add("丝丝光");
    people.add("草泥马");
    pageContext.setAttribute("people", people);
%>
</head>
<body>
<java1234:iterate items="people" var="p">
    <h2>${p }</h2>
</java1234:iterate>
</body>
</html>

IterateTag

简单标签（注意：JSP2.0 新定义的SimpleTagSupport，比老版本TagSupport使用简单）

<java1234:iterate2 items="people" var="p">
<h2>${p }</h2> 
</java1234:iterate2>

//JSP2.0 新定义的SimpleTagSupport，比老版本TagSupport使用简单
public class IterateSimpleTag extends SimpleTagSupport{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    private String var;
    private String items;
    
    public String getVar() {
        return var;
    }

    public void setVar(String var) {
        this.var = var;
    }

    public String getItems() {
        return items;
    }

    public void setItems(String items) {
        this.items = items;
    }


    @Override
    public void doTag() throws JspException, IOException {
        Object value=this.getJspContext().getAttribute(items);
        if(value!=null && value instanceof List){
            Iterator iter=((List)value).iterator();
            while(iter.hasNext()){
                this.getJspContext().setAttribute(var, iter.next());
                this.getJspBody().invoke(null); // 响应页面
            }
        }
    }
    
}

-------------------------------------------------------------------

 <tag>
        <name>iterate2</name>
        <tag-class>
            com.java1234.tag.IterateSimpleTag
        </tag-class>
        <body-content>scriptless</body-content><!-- JSP2.0 继承SimpleTagSupport，代表有标签体，指运行脚本 -->
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

---------------------------------------------------------

<%
    List people=new ArrayList();
    people.add("王二小2");
    people.add("丝丝光2");
    people.add("草泥马2");
    pageContext.setAttribute("people", people);
%>
</head>
<body>
<java1234:iterate2 items="people" var="p">
    <h2>${p }</h2>
</java1234:iterate2>
</body>

IterateSimpleTag

标签文件总览：

<?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>java1234Tag</short-name>
    
    <tag>
        <name>helloWorld</name>
        <tag-class>
            com.java1234.tag.HelloWorldTag
        </tag-class>
        <body-content>empty</body-content>
    </tag>
    
    <tag>
        <name>helloWorld2</name>
        <tag-class>
            com.java1234.tag.HelloWorldTag2
        </tag-class>
        <body-content>empty</body-content>
        <attribute>
            <name>name</name>
            <required>true</required>       <!-- 属性必须要填 -->
            <rtexprvalue>true</rtexprvalue>  <!-- 是否支持EL表达式 -->
        </attribute>
    </tag>
    
    <tag>
        <name>iterate</name>
        <tag-class>
            com.java1234.tag.IterateTag
        </tag-class>
        <body-content>JSP</body-content>
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    <tag>
        <name>iterate2</name>
        <tag-class>
            com.java1234.tag.IterateSimpleTag
        </tag-class>
        <body-content>scriptless</body-content>
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

java1234.tld

posted @ 2017-03-03 19:41 SKYisLimit 阅读(95) 评论(0) 收藏举报

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