springboot添加过滤器filter 并解决@Autowired注入为null问题

1、 写一个filter 类

import javax.servlet.*;
import java.io.IOException;
import org.springframework.beans.factory.annotation.Autowired;

@Component // 将Filter交给spring管理，目录是使@autowired生效
public class DemoFilter implements Filter {

    @Autowired
    private ProductMapper productMapper;
    
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println(" 进入了filter " );
        chain.doFilter(request,response);
    }
}

2、注册filter（即让filter生效）

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.beans.factory.annotation.Autowired;

@Configuration
public class FilterConfiger {

    @Autowired   // 一定要注入，才会让 DemoFilter中的 @Autowrie生效
    private DemoFilter demoFilter;
    
    @Bean
    // @Order(1)    //spring boot会按照order值的大小，越小越先执行。(选用)  
    // 如果有多个filter , 写多一个这方法，用不同的方法名 ,setName也要不同
    public FilterRegistrationBean configFilter(){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(demoFilter);
        filterRegistrationBean.addUrlPatterns("/*");  // 配置需要过滤的路径
        filterRegistrationBean.setName("filterDemo");
        return filterRegistrationBean;
    }
}

 

 

也可以换种方式写，将bean对象传过去。如下：

filter要用到 studentMapper对象

第一步：先建filter类

import javax.servlet.*;
import java.io.IOException;

public class DemoFilter implements Filter {

    private StudentMapper studentMapper;
    // 构造函数
    public DemoFilter(StudentMapper studentMapper) {
        this.studentMapper = studentMapper;
    }
    
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println(" 进入了filter " );
        chain.doFilter(request,response);
    }
}

第二步，注册filter

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;

import javax.annotation.Resource;

@Configuration
public class FilterConfiger {
    @Resource
    private StudentMapper studentMapper;

    @Bean
    // @Order(1)    //spring boot会按照order值的大小，越小越先执行
    public FilterRegistrationBean configFilter(){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(new DemoFilter(studentMapper)); // new DemoFilter时传bean过去
        filterRegistrationBean.addUrlPatterns("/*");
        filterRegistrationBean.setName("filterDemo");
        return filterRegistrationBean;
    }
}