1. 使用标签控制页面逻辑案例：
模拟sun公司开发的标签
– 开发<c:if>标签
– 开发<c:if><c:else>标签
– 开发迭代标签
开发<c:if>标签案例：
标签控制类：
package com.csdn.web.example;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class Demo1 extends SimpleTagSupport {
private boolean test;
public void setTest(boolean test) {
this.test = test;
}
@Override
public void doTag() throws JspException, IOException {
if(test){
JspFragment jf = this.getJspBody();
jf.invoke(null);
}
}
}
Tld描述文档：
<?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">
<tlib-version>1.0</tlib-version>
<short-name>example</short-name>
<uri>example</uri>
<tag>
<name>if</name>
<tag-class>com.csdn.web.example.Demo1</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>test</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>choose</name>
<tag-class>com.csdn.web.example.ChooseTag</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>when</name>
<tag-class>com.csdn.web.example.WhenTag</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>test</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
<tag>
<name>otherwise</name>
<tag-class>com.csdn.web.example.OtherwiseTag</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>forEach</name>
<tag-class>com.csdn.web.example.ForEach</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>var</name>
<required>true</required>
</attribute>
<attribute>
<name>items</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
JSP文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="example" prefix="example"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP '1.jsp' starting page</title>
</head>
<body>
<example:if test="${ user==null}">
<h5>aaaaaaaaaaa</h5>
</example:if>
</body>
</html>
开发迭代（forEach）标签
标签控制类：
package com.csdn.web.example;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class ForEach extends SimpleTagSupport {
private String var;
private List items;
public void setVar(String var) {
this.var = var;
}
public void setItems(List items) {
this.items = items;
}
@Override
public void doTag() throws JspException, IOException {
Iterator it = items.iterator();
while(it.hasNext()){
Object obj = it.next();
this.getJspContext().setAttribute(var,obj);
this.getJspBody().invoke(null);
}
}
}
JSP文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="example" prefix="example"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP '4.jsp' starting page</title>
</head>
<body>
<%
List list = new ArrayList();
list.add(1);
list.add("aa");
list.add("bb");
list.add(2);
request.setAttribute("list",list);
%>
<example:forEach var="str" items="${list}">
${ str }<br>
</example:forEach>
</body>
</html>
开发choose标签
标签控制类：
ChooseTag.java
package com.csdn.web.example;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class ChooseTag extends SimpleTagSupport {
private boolean isOk;
public boolean isOk() {
return isOk;
}
public void setOk(boolean isOk) {
this.isOk = isOk;
}
@Override
public void doTag() throws JspException, IOException {
this.getJspBody().invoke(null);
}
}
WhenTag.java
package com.csdn.web.example;
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 {
ChooseTag parent = (ChooseTag) this.getParent();
if(test && !parent.isOk()){
this.getJspBody().invoke(null);
parent.setOk(true);
}
}
}
OtherwiseTag.java
package com.csdn.web.example;
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 parent = (ChooseTag)this.getParent();
if(!parent.isOk()){
this.getJspBody().invoke(null);
parent.setOk(true);
}
}
}
JSP文件：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="example" prefix="example"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP '3.jsp' starting page</title>
</head>
<body>
<example:choose>
<example:when test="<%=false %>">asd</example:when><!-- 这里，标签体中如果没有内容会报错（空指针异常） -->
<example:otherwise>fghhjj</example:otherwise>
</example:choose>
</body>
</html>
2. 其他案例
设置带属性的标签：
标签控制类
package com.csdn.web.simple;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class Demo5 extends SimpleTagSupport{
private int count;
public void setCount(int count) {
this.count = count;
}
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
for(int i=0;i<=count;i++){
jf.invoke(null);
}
}
}
Tld描述文档
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>simple</short-name>
<uri>http://www.csdn.com</uri>
<tag>
<name>demo1</name>
<tag-class>com.csdn.web.simple.Demo1</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>demo2</name>
<tag-class>com.csdn.web.simple.Demo2</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>demo3</name>
<tag-class>com.csdn.web.simple.Demo3</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>demo4</name>
<tag-class>com.csdn.web.simple.Demo4</tag-class>
<body-content>scriptless</body-content>
</tag>
<tag>
<name>demo5</name>
<tag-class>com.csdn.web.simple.Demo5</tag-class>
<body-content>scriptless</body-content>
<attribute>
<name>count</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
JSP文件
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://www.csdn.com" prefix="simple"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>设置带属性的标签</title>
</head>
<body>
<simple:demo5 count="10">
<h3>dddddddddd</h3>
</simple:demo5>
</body>
</html>
修改标签体内容：
标签控制类
package com.csdn.web.simple;
import java.io.IOException;
import java.io.StringWriter;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;
public class Demo4 extends SimpleTagSupport {
@Override
public void doTag() throws JspException, IOException {
JspFragment jf = this.getJspBody();
StringWriter sw = new StringWriter();
jf.invoke(sw);
String body = sw.toString().toUpperCase();
this.getJspContext().getOut().write(body);
}
}
JSP文件
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://www.csdn.com" prefix="simple"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>修改标签体内容</title>
</head>
<body>
<simple:demo4>
<h3>nnnnnnnnnnnn</h3>
</simple:demo4>
</body>
</html>
