springboot自定义过滤器的两种方式

1、过滤器是什么

过滤器是基于servlet技术实现的，在web项目开发中可以帮助我们过滤一些指定的url，对其进行一些特殊处理

作用：

1. 过滤掉一些不需要的东西，如错误请求
2. 可以修改请求和响应的内容
3. 过滤未登录的用户

2、过滤器实现的两种方法

方法一：创建一个过滤器，加上@WebFilter注解

项目结构:

MyFilter代码：

import org.springframework.core.annotation.Order;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

/**
	urlPatterns属性设置是过滤哪些url,filterName是该过滤器的名称
	@Order注解设置优先级，里面的数字越小越优先
*/
@WebFilter(urlPatterns = "/api/*", filterName = "myFilter")
@Order(1)
public class MyFilter implements Filter {	//实现Filter接口，重写该接口的抽象方法
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        String uri = request.getRequestURI();
        String method = request.getMethod();
        System.out.println("请求接口=" + uri + ", 请求方式=" + method);
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
    }
}

在启动类中加上 @ServletComponentScan 注解

/*
	@ServletComponentScan注解后，Servlet、Filter、Listener可以直接
    通过@WebServlet、@WebFilter、@WebListener注解自动注册，无需其他代码。
*/
@SpringBootApplication
@ServletComponentScan   
public class SpringbootFilterApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootFilterApplication.class, args);
    }

}

测试的controller代码

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api")
public class TestController {

    @GetMapping("/user/filter")
    public String hello(){
        return "经过过滤器";
    }
}

结果：

控制台输出：

方法二：利用配置类配置过滤器

配置类

import com.scitech.filter.MyFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FilterConfig {

    @Bean
    public MyFilter getMyFilter(){
        return new MyFilter();
    }

    @Bean
    public FilterRegistrationBean getFilterRegistrationBean(MyFilter myFilter){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        filterRegistrationBean.setFilter(myFilter); //设置过滤器
        filterRegistrationBean.setOrder(1); //设置优先级
        filterRegistrationBean.addUrlPatterns("/api/*");    //添加过滤的url
        filterRegistrationBean.setName("myFilter"); //设置过滤器的名称
        return filterRegistrationBean;
    }
}

启动类不需要改变

myfilter类的注解去掉

public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("init filter");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        String uri = request.getRequestURI();
        String method = request.getMethod();
        System.out.println("请求接口=" + uri + ", 请求方式=" + method);
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        System.out.println("destroy filter");
    }
}

最后结果同上