JSP自定义标签获取用户IP地址的方法

1、编写一个实现tag接口的标签处理器类

package cn.itcast.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.PageContext;
import javax.servlet.jsp.tagext.Tag;
public class ViewIPTag implements Tag {
    private PageContext pageContext;

    public int doStartTag() throws JspException {

        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();//获取页面Servlet中 request 和out 对象
        JspWriter out = pageContext.getOut();

        String ip = request.getRemoteAddr(); //获取用户IP地址
        try {
            out.write(ip);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        return 0;
    }

    public int doEndTag() throws JspException {
        return 0;
    }
    public Tag getParent() {
        return null;
    }
    public void release() {
    }
    public void setPageContext(PageContext arg0) {
        this.pageContext = arg0;//PageContext获取用户request out 等对象
    }
    public void setParent(Tag arg0) {
    }
}

2、在web-inf/目录下新建tld文件，在tld文件中对标签处理器进行描述

    A tag library exercising SimpleTag handlers.
    1.0
    SimpleTagLibrary
    /itcast

    
    
        viewIP  
        cn.itcast.web.tag.ViewIPTag
        empty
    

3、在jsp页面中导入并使用自定义标签

  
    
  

  
     您的IP是：