jsp自定义标签

1. jsp自定义标签

1) jsp自定义没有属性标签

HelloWorldTag.java

package com.andrew.tag;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
public class HelloWorldTag extends TagSupport {
    @Override
    public int doStartTag() throws JspException {
        JspWriter out = this.pageContext.getOut();
        try {
            out.println("自定义标签你好！");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return TagSupport.SKIP_BODY; // 直接结束标签
    }
}

andrew.tld

<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>andrewTag</short-name>
    <tag>
        <name>helloWorld</name>
        <tag-class>
            com.andrew.tag.HelloWorldTag
        </tag-class>
        <body-content>empty</body-content>
    </tag>
</taglib>

helloWorldTag.jsp

<%@ taglib prefix="andrew" uri="/WEB-INF/andrew.tld" %>
<andrew:helloWorld/>

http://localhost:8080/HeadFirstJspServletChap07/helloWorldTag.jsp
运行结果：
自定义标签你好！ 

2) jsp自定义有属性标签

HelloWorldTag2.java

package com.andrew.tag;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
public class HelloWorldTag2 extends TagSupport {
    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 + "自定义标签你好！");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return TagSupport.SKIP_BODY; // 直接结束标签
    }
}

andrew.tld

<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>andrewTag</short-name>
    <tag>
        <name>helloWorld2</name>
        <tag-class>
            com.andrew.tag.HelloWorldTag2
        </tag-class>
        <body-content>empty</body-content>
        <attribute>
            <name>name</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
</tag>
</taglib>

helloWorldTag2.jsp

<%@ taglib prefix="andrew" uri="/WEB-INF/andrew.tld" %>
<andrew:helloWorld2 name="JspServlet屌炸天"/>

http://localhost:8080/HeadFirstJspServletChap07/helloWorldTag2.jsp
运行结果：
JspServlet屌炸天自定义标签你好！ 

3) jsp自定义有标签体的标签

IterateTag.java

package com.andrew.tag;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class IterateTag extends TagSupport {
    private String var;
    private String items;
    private Iterator iter;
    // getter and setter
    @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
        }
    }
}

andrew.tld

<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>andrewTag</short-name>
    <tag>
        <name>iterate</name>
        <tag-class>
            com.andrew.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>
</taglib>

iterateTag.jsp

<%@ page import="java.util.*" %>
<%@ taglib prefix="andrew" uri="/WEB-INF/andrew.tld" %>
<% List people=new ArrayList();
    people.add("王小一");
    people.add("王小二");
    people.add("王小三");
    pageContext.setAttribute("people", people);%>
</head>
<body>
<andrew:iterate items="people" var="p">
    <h2>${p }</h2>
</andrew:iterate>
</body>

http://localhost:8080/HeadFirstJspServletChap07/iterateTag.jsp
运行结果：
王小一
王小二
王小三

4) 简单标签

IterateSimpleTag.java

package com.andrew.tag;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
import javax.servlet.jsp.tagext.TagSupport;
public class IterateSimpleTag extends SimpleTagSupport {
    private String var;
    private String items;
    // getter and setter
    @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
            }
        }
    }
}

andrew.tld

<?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>andrewTag</short-name>
    <tag>
        <name>iterate2</name>
        <tag-class>
            com.andrew.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>

iterateSimpleTag.jsp

<%@ page import="java.util.*" %>
<%@ taglib prefix="andrew" uri="/WEB-INF/andrew.tld" %>
<%
    List people=new ArrayList();
    people.add("王小一");
    people.add("王小二");
    people.add("王小三");
    pageContext.setAttribute("people", people);
%>
</head>
<body>
<andrew:iterate2 items="people" var="p">
    <h2>${p }</h2>
</andrew:iterate2>
</body>

http://localhost:8080/HeadFirstJspServletChap07/iterateSimpleTag.jsp
运行结果：
王小一
王小二
王小三