TagSupport使用入门

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Java代码

定义最简单的标签
自定义标签采用Default Adapter模式（缺省适配模式）
Java代码
//最简单的标签
public class LangHuaTag extends TagSupport {
private long startTime;
private long endTime;
public int doStartTag() throws JspException {
startTime = System.currentTimeMillis();
//表示定制标记里面有所包括的JSP页面
return TagSupport.EVAL_BODY_INCLUDE;
}
public int doEndTag() throws JspException {
endTime = System.currentTimeMillis();
long elapsed = endTime - startTime;
try {
JspWriter out = pageContext.getOut();
out.println("runtime is "+ elapsed);
} catch (IOException e) {
e.printStackTrace();
}
//表示JSP页面继续运行
return TagSupport.EVAL_PAGE;
}
}
//代属性的标签
public class DateTag extends TagSupport {
private String pattern = "yyyy-MM-dd hh:mm:ss";
private Date date;
//必须要有Set方法，因为是属性可以设值
public void setPattern(String pattern) {
this.pattern = pattern;
}
public void setDate(Date date) {
this.date = date;
}
public int doEndTag() throws JspException {
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
//如果没有就是当前时间
if(date==null){
date = new Date();
}
JspWriter out = pageContext.getOut();
try {
out.print(sdf.format(date));
} catch (IOException e) {
e.printStackTrace();
}
return TagSupport.EVAL_PAGE;
}
}
/**
* 循环输出
* @author Administrator
*
*/
public class LoopTag extends TagSupport {
private int times =0;
//Set方法设值
public void setTimes(int times) {
this.times = times;
}
public int doStartTag() throws JspException {
//表示定制标记里面有所包括的JSP页面
return TagSupport.EVAL_BODY_INCLUDE;
}
public int doAfterBody() throws JspException {
if(times>0){
times--;
//表示双从标签开始输入
return TagSupport.EVAL_BODY_AGAIN;
}
//表示结束，忽略标签内部的内容
return TagSupport.SKIP_BODY;
}
}
//最简单的标签
public class LangHuaTag extends TagSupport {
private long startTime;
private long endTime;
public int doStartTag() throws JspException {
startTime = System.currentTimeMillis();
//表示定制标记里面有所包括的JSP页面
return TagSupport.EVAL_BODY_INCLUDE;
}
public int doEndTag() throws JspException {
endTime = System.currentTimeMillis();
long elapsed = endTime - startTime;
try {
JspWriter out = pageContext.getOut();
out.println("runtime is "+ elapsed);
} catch (IOException e) {
e.printStackTrace();
}
//表示JSP页面继续运行
return TagSupport.EVAL_PAGE;
}
}
//代属性的标签
public class DateTag extends TagSupport {
private String pattern = "yyyy-MM-dd hh:mm:ss";
private Date date;
//必须要有Set方法，因为是属性可以设值
public void setPattern(String pattern) {
this.pattern = pattern;
}
public void setDate(Date date) {
this.date = date;
}
public int doEndTag() throws JspException {
SimpleDateFormat sdf = new SimpleDateFormat(pattern);
//如果没有就是当前时间
if(date==null){
date = new Date();
}
JspWriter out = pageContext.getOut();
try {
out.print(sdf.format(date));
} catch (IOException e) {
e.printStackTrace();
}
return TagSupport.EVAL_PAGE;
}
}
/**
* 循环输出
* @author Administrator
*
*/
public class LoopTag extends TagSupport {
private int times =0;
//Set方法设值
public void setTimes(int times) {
this.times = times;
}
public int doStartTag() throws JspException {
//表示定制标记里面有所包括的JSP页面
return TagSupport.EVAL_BODY_INCLUDE;
}
public int doAfterBody() throws JspException {
if(times>0){
times--;
//表示双从标签开始输入
return TagSupport.EVAL_BODY_AGAIN;
}
//表示结束，忽略标签内部的内容
return TagSupport.SKIP_BODY;
}
}
配置文件
Xml代码
<?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>util</short-name>
<uri>http://langhua.com/taglib/util</uri>
<tag>
<name>timer</name>
<tag-class>com.langhua.tagsupport.LangHuaTag</tag-class>
<body-content>JSP</body-content>
</tag>
<tag>
<name>date</name>
<tag-class>com.langhua.tagsupport.DateTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>time</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>pattern</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>
<tag>
<name>loop</name>
<tag-class>com.langhua.tagsupport.LoopTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>times</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
<?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>util</short-name>
<uri>http://langhua.com/taglib/util</uri>
<tag>
<name>timer</name>
<tag-class>com.langhua.tagsupport.LangHuaTag</tag-class>
<body-content>JSP</body-content>
</tag>
<tag>
<name>date</name>
<tag-class>com.langhua.tagsupport.DateTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>time</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>pattern</name>
<required>true</required>
<rtexprvalue>false</rtexprvalue>
</attribute>
</tag>
<tag>
<name>loop</name>
<tag-class>com.langhua.tagsupport.LoopTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>times</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
JSP页面
Html代码
<%@ taglib prefix="util" uri="http://langhua.com/taglib/util"%>
<util:timer></util:timer>
<util:loop times="3">
<util:date pattern="yyyy-MM-dd" /><br/>
</util:loop>
<%@ taglib prefix="util" uri="http://langhua.com/taglib/util"%>
<util:timer></util:timer>
<util:loop times="3">
<util:date pattern="yyyy-MM-dd" /><br/>
</util:loop>
TagSupport的流程图
EVAL_BODY_INCLUDE 处理标记内容,并把这些内容写到输出流中doStartTag()
SKIP_BODY 不处理标记内容doStartTag()，doAfterBody()
EVAL_BODY_AGAIN 又重头处理doAfterBody()
EVAL_PAGE 继续执行JSP里面的代码 doEndTag()
SKIP_PAGE 不继续执行JSP里面的代码 doEndTag()
[img]http://langhua9527.iteye.com/upload/attachment/77593/2ce5c561-a5ea-36d1-9082-25e62273dcb2.jpg[/img]

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