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

Filter中注入bean 無效為null

問題原因

Web應(yīng)用的啟動順序是：

Lisenter->Fliter->Servlet, 應(yīng)用程序上下文，初始化 Fliter的時(shí)候，還沒有初始化Servlert，所有沒有進(jìn)入DispacterServlet的初始化，故在Fliter中使用注解注入bean為空；

解決辦法

添加初始化bean配置，手動創(chuàng)建對象new

代碼如下：

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是手動創(chuàng)建的bean，實(shí)現(xiàn)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;  
}

此時(shí)，在RequestFilter中使用@Value注解，就可以取到值了，注入bean也相同，會取到對應(yīng)的bean。

至此問題解決！

總結(jié)：不管做什么事，首先要搞清楚他的原理，要不，解決了問題下次遇到了還是不會！

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

您可能感興趣的文章: