Java _ custom tag, my first custom tag !, Java labels

Java _ custom tag, my first custom tag !, Java labels

Custom tag, my first custom tag!

 

Two steps in total. Case study,

Output Client IP Address

 

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"> ViewIP. jsp
 
 
Create a tld file in the WEB-INF directory ,:
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
 
 
Compile the tag processor class:
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
 
Effect: