解决springboot中配置过滤器以及可能出现的问题

在springboot添加过滤器有两种方式：

1、通过创建FilterRegistrationBean的方式（建议使用此种方式，统一管理，且通过注解的方式若不是本地调试，如果在filter中需要增加cookie可能会存在写不进前端情况）

2、通过注解@WebFilter的方式

通过创建FilterRegistrationBean的方式创建多个filter以及设置执行顺序：

1、创建两个实现Filter接口的类TestFilter1 、TestFilter2

package com.aoxun.core.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class TestFilter1 implements Filter {

 @Override
 public void init(FilterConfig filterConfig) throws ServletException {}

 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
  throws IOException, ServletException {
 chain.doFilter(request, response);
 }

 @Override
 public void destroy() {}

}

package com.aoxun.core.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class TestFilter2 implements Filter {

 @Override
 public void init(FilterConfig filterConfig) throws ServletException {}

 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
  throws IOException, ServletException {
 chain.doFilter(request, response);
 }

 @Override
 public void destroy() {}

}

2、创建配置类

有多个filter就创建多个FilterRegistrationBean ，若需注明filter的执行顺序，可通过registration.setOrder(FilterRegistrationBean.LOWEST_PRECEDENCE - 1)配置，值越大，执行顺序越靠后

package com.aoxun.config.web;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.aoxun.core.filter.TestFilter1;
import com.aoxun.core.filter.TestFilter2;


@Configuration
public class FilterConfig2 {

 @Bean
 public FilterRegistrationBean companyUrlFilterRegister() {
 FilterRegistrationBean registration = new FilterRegistrationBean();
 //注入过滤器
 registration.setFilter(new TestFilter1());
 //拦截规则
 registration.addUrlPatterns("
@RestController
public class DemoController {
 
 // 带参GET请求: http://localhost:8080/demo/get/param?param=111222333444
 @RequestMapping(value = "/demo/get/param", method = RequestMethod.GET)
 public String getParam(@RequestParam(value = "param") String param) {
  System.out.println("=====>进入DemoController /demo/get/param");
  return "/demo/get/param," + param;
 }
}

第二步：使用@WebFilter注解方式，实现Filter过滤器

当使用@WebFilter、@WebServlet、@WebListener等注解时, 需要在springboot启动类中启用@ServletComponentScan注解指定扫描包。

package com.oysept.filter; 
import java.io.IOException;
import java.util.Enumeration; 
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 
import org.springframework.core.env.Environment;
import org.springframework.web.filter.OncePerRequestFilter;
 

@WebFilter(value = "
@Component
public class PathFilter implements Filter {
 
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
   throws IOException, ServletException {
  // 转换
  HttpServletRequest request = (HttpServletRequest) servletRequest;
  HttpServletResponse response = (HttpServletResponse) servletResponse;
  System.out.println("====>进入PathFilter doFilter过滤器====");
 
  System.out.println("====>结束PathFilter doFilter过滤器====");
  filterChain.doFilter(request, response);
 }
}

第四步：通过@Bean注解方式，实现Filter过滤器

@Configuration注解：相当于spring中的标签

@Bean注解：相当于spring中标签

package com.oysept.config; 
import java.io.IOException; 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 

@Configuration
public class MyFilterConfig {
 
 @Bean
 public FilterRegistrationBean testFilterRegistration() {
  FilterRegistrationBean registration = new FilterRegistrationBean<>();
  registration.setFilter(new MyFilter());
  registration.addUrlPatterns("
@SpringBootApplication
@ServletComponentScan(basePackages = "com.oysept.filter")
public class FilterApplication {
 
 public static void main(String[] args) {
  new SpringApplicationBuilder(FilterApplication.class).run(args);
 }
}

启动main方法，在浏览器输入地址：http://localhost:8080/demo/get/param?param=111222333444

在控制台查看打印日志：

项目结构图：

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