1.java类,使用简单标签,jsp2.0规范, 继承 SimpleTagSupport
public class ViewIpSimpleTag extends SimpleTagSupport { @Override public void doTag() throws JspException, IOException { PageContext pageContext = (PageContext) this.getJspContext(); String ip = ((HttpServletRequest) pageContext.getRequest()).getRemoteAddr(); pageContext.getOut().write(ip); } }
1.java类,使用传统标签 jsp1.0, 继承 TagSupport(弃用)
/**
* jsp 自定义标签的步骤：
* 1.写一个类实现Tag接口(继承TagSupport类)
* 2.在WEB-INF文件夹中新建一个tld文件
* 3.在jsp 页面中导入taglib标签库，然后调用
*
*/
public class ViewIp extends TagSupport {
@Override
public int doStartTag() throws JspException {
try {
HttpServletRequest request = (HttpServletRequest) this.pageContext
.getRequest();
JspWriter out = this.pageContext.getOut();
String ip = request.getRemoteAddr();
out.print(ip);
} catch (IOException e) {
e.printStackTrace();
}
return super.doStartTag();
}
}
2.tld文件(/webProjectName/WEB-INF/web.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"> <tlib-version>1.0</tlib-version> <short-name>web</short-name> <uri>www.bvb.de</uri> <tag> <name>viewIp</name> <tag-class>de.bvb.web.tag.ViewIpSimpleTag</tag-class> <body-content>empty</body-content> </tag> </taglib>
3.jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!-- 3.1导入标签库 prefix和文件名一致，uri和.tld文件夹中的uri一致,uri也可以写为 uri="/WEB-INF/web.tld" --> <%@ taglib prefix="web" uri="www.bvb.de"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> 你的ip是： <!--3.2 使用自定义标签 --> <web:viewIp /> 不使用自定义标签 <% String ip = request.getRemoteAddr(); out.print(ip); %> </head> <body></body>