JSP技术中的开发自定义标签

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();