实现一个基本防盗链标签

1. 标签处理类

public class MyReferer extends BodyTagSupport {
    private String site;
    private String back;
    public String getSite() {
        return site;
    }
    public void setSite(String site) {
        this.site = site;
    }
    public String getBack() {
        return back;
    }
    public void setBack(String back) {
        this.back = back;
    }
    public int doEndTag() throws JspException {
        // 获取JSP上下文环境对象
        PageContext pageContext = this.pageContext;
        // 获取到request对象
        HttpServletRequest request = (HttpServletRequest)pageContext.getRequest();
        // 判断
        String header = request.getHeader("referer");
        if(header != null && header.startsWith(getSite())){
            // 执行后续的页面
            return Tag.EVAL_PAGE;
        }else{
            // 页面的重定向
            HttpServletResponse response = (HttpServletResponse)pageContext.getResponse();
            try {
                response.sendRedirect(getBack());
            } catch (IOException e) {
                e.printStackTrace();
            }
            // 不执行
            return Tag.SKIP_PAGE;
        }
    }
}

2. 描述文件

<?xml version="1.0" encoding="UTF-8"?>
<taglib 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">
  <!-- 2. 编写标签库描述文件 -->  
  <tlib-version>1.0</tlib-version>
  <short-name>jnb</short-name>
   <tag>  
    <name>referer</name>
    <tag-class>cn.itcast.custom.MyReferer</tag-class>
    <body-content>empty</body-content>
     <attribute>
        <name>site</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
     <attribute>
        <name>back</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>    

3. 引入和使用

<%@taglib uri="/WEB-INF/referer.tld" prefix="my"%>
   <my:referer site=http://localhost:8080/day11/list.jsp
 back="/day11/list.jsp"/>