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Filter不能注入bean

hehuijava 人气:0

Filter中不能注入bean的问题

WebApplicationContext webApplicationContext = WebApplicationContextUtils.getWebApplicationContext(request.getSession().getServletContext());
ApiController apiController = (ApiController) webApplicationContext.getBean("apiController");

Filter中注入bean 无效为null

问题原因

Web应用的启动顺序是:

Lisenter->Fliter->Servlet, 应用程序上下文, 初始化 Fliter的时候,还没有初始化Servlert,所有没有进入DispacterServlet的初始化,故在Fliter中使用注解注入bean为空;

解决办法

添加初始化bean配置,手动创建对象new

代码如下:

package com.test.config; 
import com.alibaba.druid.support.http.StatViewServlet;
import com.test.service.RequestFilter;
import javax.servlet.Filter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.DelegatingFilterProxy;
 
/**
 * @author lucasliang
 * @date 08/11/2018 5:56 afternoon filter load before dispathServlet ,so load RequestFilter as a
 * bean,new a RequestFilter
 */
@Configuration
public class FilterConfig {
 
  /*
    *@param: []
    *@return javax.servlet.Filter
    *@author lucasliang
    *@date 20/12/2018
    *@Description filter
   */
  @Bean
  public Filter uploadFilter() {
    return new RequestFilter();
  } 
 
  /*
    *@param: []
    *@return org.springframework.boot.web.servlet.FilterRegistrationBean
    *@author lucasliang
    *@date 20/12/2018
    *@Description filter
   */
  @Bean
  @SuppressWarnings("unchecked")
  public FilterRegistrationBean testFilterRegistration() {
    FilterRegistrationBean registration = new FilterRegistrationBean();
    registration.setFilter(new DelegatingFilterProxy("uploadFilter"));
    registration.addUrlPatterns("/*");
    registration.addInitParameter("paramName", "paramValue");
    registration.setName("testFilter");
    registration.setOrder(1);
    registration.setEnabled(false);
    return registration;
  } 
}

其中RequestFilter是手动创建的bean,实现了Filter接口

package com.test.service; 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig; 
 
public class RequestFilter implements Filter { 
  private Logger logger = LoggerFactory.getLogger(Filter.class);  
  @Value(value = "${encodeRules}")
  private String encodeRules;  
}

此时,在RequestFilter中使用@Value注解,就可以取到值了,注入bean也相同,会取到对应的bean。

至此问题解决!

总结:不管做什么事,首先要搞清楚他的原理,要不,解决了问题下次遇到了还是不会!

以上为个人经验,希望能给大家一个参考,也希望大家多多支持。

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