因为在JSP中不要使用一行
java代码，所以说必须使用标签来移除显示的
java代码，下面罗列一下标签的开发过程。
1.首先编写一个实现tag接口的
java类
package com.bird.
web.tag;
import
java.io.IOException;
import
javax.servlet.http.HttpServletRequest;
import
javax.servlet.jsp.JspException;
import
javax.servlet.jsp.JspWriter;
import
javax.servlet.jsp.tagext.TagSupport;
/**
* 显示来访者IP的自定义标签
* @author Bird
*
*/
public class ViewIPTag extends TagSupport{
private static final long serialVersionUID = 1L;
@Override
public int
DOStartTag() throws JspException {
HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
JspWriter out = this.pageContext.getOut();
String ip = request.getRemoteAddr();
try {
out.print(ip);
} catch (IOException e) {
throw new RuntimeException(e);
}
return super.
DOStartTag();
}
}
package com.bird.web.tag;
import
java.io.IOException;
import
javax.servlet.http.HttpServletRequest;
import
javax.servlet.jsp.JspException;
import
javax.servlet.jsp.JspWriter;
import
javax.servlet.jsp.tagext.TagSupport;
/**
* 显示来访者IP的自定义标签
* @author Bird
*
*/
public class ViewIPTag extends TagSupport{
private static final long serialVersionUID = 1L;
@Override
public int
DOStartTag() throws JspException {
HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
JspWriter out = this.pageContext.getOut();
String ip = request.getRemoteAddr();
try {
out.print(ip);
} catch (IOException e) {
throw new RuntimeException(e);
}
return super.
DOStartTag();
}
}
2.在tld文件里面对标签处理器类进行描述，tld文件的位置在web-inf下面可以在tomcat的webapps下面抄一下
<?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"
xsichemaLocation="http://
java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>Bird</short-name>
<uri>
http://www.bird.net</uri>
<tag>
<name>viewIP</name>
<tag-class>com.bird.web.tag.ViewIPTag</tag-class>
<body-content>empty</body-content>
</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"
xsichemaLocation="http://
java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<description>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>Bird</short-name>
<uri>
http://www.bird.net</uri>
<tag>
<name>viewIP</name>
<tag-class>com.bird.web.tag.ViewIPTag</tag-class>
<body-content>empty</body-content>
</tag>
</taglib>
4.在界面里面使用tablib命令到导入和使用标签就可以了，
<%@ page language="
java" import="
java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri="http://www.bird.net" prefix="bird" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>一个简单的自定义标签</title>
</head>
<body>
您访问的IP为: <bird:viewIP/>
</body>
</html>
<%@ page language="
java" import="
java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri=
http://www.atcpu.com prefix="bird" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>一个简单的自定义标签</title>
</head>
<body>
您访问的IP为: <bird:viewIP/>
</body>
</html>
