自定义标签,我的第一个自定义标签!
总共分两步
- 编写一个实现tag接口的java类,把jsp页面中的java代码移到这个类中,(标签处理器类)
- 编写标签库描述符(tld)文件,在tld文件中把标签处理器类描述成一个标签
一.案例,
输出客户端IP
ViewIP.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="/WEB-INF/firstTag.tld" prefix="itcast"%>
<!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>
</head>
<body>
<h4>您的iP:</h4>
<itcast:viewIP/>
</body>
</html>
ViewIP.jsp
在WEB-INF目录下建立一个tld文件,:
firstTag.tld
<?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">
<description>A tag library exercising SimpleTag handlers.</description>
<tlib-version>1.0</tlib-version>
<short-name>view</short-name>
<uri>/WEB-INF/firstTag.tld</uri>
<tag>
<name>viewIP</name>
<tag-class>Tag.viewIPTag</tag-class>
<body-content>empty</body-content>
</tag>
</taglib>
firstTag.tld
编写标签处理器类:
viewIPTag.java
package 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;
public class viewIPTag extends TagSupport{
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) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return super.doStartTag();
}
}
viewIPTag.java
效果截图: