帮帮忙—ssm框架中，简单自定义标签SimpleTagSupport如何注入spirng中的bean

ゝ一纸荒年。 2023-10-04 14:47 5阅读 0赞

权限太多，想用简单自定义标签来控制，但遇到一个头疼的问题，不能用@autowird自动注入spring管理的bean，让人恼火；

经过周折，终于解决问题，与大家一起分享，可能不是最好的方法，希望有更好方法的人能推荐给我，谢谢；

下面这样出现空指针异常

package com.bookstore.utils;
    
    import com.bookstore.client.user.handler.UserHandler;
    import com.bookstore.commons.beans.User;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.jsp.JspException;
    import javax.servlet.jsp.PageContext;
    import javax.servlet.jsp.tagext.SimpleTagSupport;
    import java.io.IOException;
    
    @Component
    public class LoginTag extends SimpleTagSupport {
        
        @Autowired
        private UserHandler userHandler;
        
    
        public void doTag() throws JspException, IOException {
        
            PageContext context = (PageContext) this.getJspContext();
            HttpServletResponse response = (HttpServletResponse) context.getResponse();
            HttpServletRequest request= (HttpServletRequest) context.getRequest();
            User user = (User) context.getSession().getAttribute("login_user");
            
            System.out.println(userHandler);
            
            if(user==null){
        
                System.out.println("aaaaaaaaaaaaaaaaaaaa");
                User user1 = userHandler.autologin(request);
                System.out.println(user1);
                if(user1==null){
        
                    System.out.println("BBBBBBBBBBbbbbb");
                    response.sendRedirect(request.getContextPath()+"/client/error/privilege.jsp");
                }
    
            }
        }
    }

![在这里插入图片描述][20210529103303673.png]  
而且显示注入成功，点击还能跳转  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzODQyMDkz_size_16_color_FFFFFF_t_70]  
换一种解决方法，使用下面这样可以解决

PageContext pageContext = (PageContext) this.getJspContext();
            ServletContext servletContext = pageContext.getServletContext();
            WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);
    
            UserHandler userHandler= (UserHandler) wac.getBean("userHandler");

不明白前边的方法为什么不行？希望有答案的推荐给我，万分感谢；

[20210529103303673.png]: https://img-blog.csdnimg.cn/20210529103303673.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzODQyMDkz_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20210529103350245.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzODQyMDkz,size_16,color_FFFFFF,t_70