框架中的自定义网关----手撸一个网关

框架中的自定义网关

背景：

​ 有些公司项目中使用了自建的项目框架，网关进行了一些自定义的实现。如何实现一个自定义网关，又有哪些作用呢？本文将进行一些浅显的说明。

搭建一个项目 hand-gateway，并注册到nacos注册中心

项目依赖

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
  <groupId>com.alibaba.cloud</groupId>
  <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

配置路由转发拦截器 RouteInterceptor

​ 路由映射可以从配置文件、配置中心或者数据库中进行加载，然后做映射转换，然后通过RestTemplate进行转发，restTemplate通过loadblance可以实现负载均衡。下面代码实现了Post、get的方法请求，json请求暂未实现，感兴趣的可以试下。

@Slf4j
@Component
public class RouteInterceptor implements HandlerInterceptor {

  @Autowired
  private RestTemplate restTemplate;
  @Autowired
  private DiscoveryClient discoveryClient;

  @Override
  public boolean preHandle (HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    HttpHeaders httpHeaders = new HttpHeaders();
    String requestUrl = request.getRequestURI();
    if(StrUtil.isNotEmpty(request.getQueryString())){
      String query = URLDecoder.decode(request.getQueryString(),"UTF-8");
      requestUrl =requestUrl+"?"+query;
    }
    log.info("requestUrl {}",requestUrl);
    // 注册中心获取注册的服务
//    List<ServiceInstance> instances = discoveryClient.getInstances("paw-dogs-sky-service");
//    String ipAddr = instances.get(0).getUri().toString();
    // 加载路由映射 如配置文件、配置中心、redis、数据库
    Map<String,String> routerMap = new HashMap<>(16);
    routerMap.put("/sky-api","paw-dogs-sky-service");
    String routerKey = requestUrl;
    if(requestUrl.indexOf("/",1)>0){
      routerKey = requestUrl.substring(0,requestUrl.indexOf("/",1));
    }
    if(routerMap.containsKey(routerKey)){
      String serverName = routerMap.get(routerKey);
      // 做地址映射
      String targetUrl  = "http://"+requestUrl.replaceFirst(routerKey,serverName);

      log.info("requestUrl {} ==> targetUrl {}",requestUrl, targetUrl);

      ResponseEntity<String> responseEntity;
      if("POST".equalsIgnoreCase(request.getMethod())){
        MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
        Map<String, String[]> paramMap = request.getParameterMap();
        for (String paramName: paramMap.keySet()) {
          params.addAll(paramName, Arrays.asList(paramMap.get(paramName)));
        }
        httpHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        HttpEntity<Object> requestEntity = new HttpEntity<>(params, httpHeaders);
        responseEntity = restTemplate.postForEntity(targetUrl, requestEntity, String.class);
      }else{
        responseEntity = restTemplate.getForEntity(targetUrl, String.class);
      }

      try {
        response.setStatus(responseEntity.getStatusCodeValue());
        String responseBody = responseEntity.getBody();
        response.setContentType("application/json;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.print(responseBody);
        out.flush();
        out.close();
      } catch (IOException e) {
        e.printStackTrace();
      }

      return false;
    }
    return true;
  }

  @Override
  public void postHandle (HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
  }

  @Override
  public void afterCompletion (HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
  }
}

​ 增加权限校验拦截器 TokenInterceptor，获取token后根据验证方式 jwt 或者redis的方式进行权限校验，并将用户的一些信息放入到header中，往下传播。

@Slf4j
@Component
public class TokenInterceptor implements HandlerInterceptor {

  public static final String TOKEN_NAME = "token";

  @Override
  public boolean preHandle (HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    log.info("TokenInterceptor requestUrl "+request.getRequestURI());
    String token = request.getHeader(TOKEN_NAME);
    if(StrUtil.isEmpty(token)){
      token = request.getParameter(TOKEN_NAME);
    }
    // 校验token jwt 或者 redis 此处省略
    if(StrUtil.isNotEmpty(token)){
      return true;
    }

    try {
      response.setStatus(HttpStatus.UNAUTHORIZED.value());
      response.setContentType("application/json;charset=UTF-8");
      PrintWriter out = response.getWriter();
      out.print(HttpStatus.UNAUTHORIZED.getReasonPhrase());
      out.flush();
      out.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return false;
  }
}

配置服务，RestTemplate添加@LoadBalanced注解进行负载均衡，添加拦截器，注意添加的顺序。

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

  @Autowired
  private TokenInterceptor tokenInterceptor;

  @Autowired
  private RouteInterceptor routeInterceptor;

  @Bean
  @LoadBalanced
  @ConditionalOnClass(RestTemplate.class)
  public RestTemplate restTemplate(){
    return new RestTemplate();
  }

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(tokenInterceptor).addPathPatterns("/**").excludePathPatterns("/anonymous/**");
    registry.addInterceptor(routeInterceptor).addPathPatterns("/**");

  }

至此简单的网关项目完成。

搭建应用服务 sky-service，并注册到nacos注册中心

服务名称

spring:
  application:
    name: paw-dogs-sky-service

服务接口，增加port查看负载均衡，示例实现了get post方法

@RestController
public class SkyController {

  @Value("${spring.application.name:sky-service}")
  private String applicationName;

  @Value("${server.port:8080}")
  private Integer serverPort;

  @GetMapping("/sky")
  public String sky (@RequestParam(required = false) String name) {
    String msg = "this is " + applicationName + " port " + serverPort + " Time: " + DateUtil.now();
    if (StrUtil.isNotEmpty(name)) {
      msg = msg + " name: " + name;
    }
    return msg;
  }

  @PostMapping("/deliver")
  public String deliver (String packageBox) {
    String msg = "this is " + applicationName + " port " + serverPort + " Time: " + DateUtil.now();
    return msg + " delivered packageBox: " + packageBox;
  }

}

通过idea的方式设置不同的端口启动两个服务，VM options 设置 -Dserver.port=8081

通过postman访问网关项目，header 携带token

http://127.0.0.1:8080/sky-api/sky?name=fly

返回结果

this is paw-dogs-sky-service port 8082 Time: 2021-06-17 16: 45: 05 name: fly

访问Post请求，header携带token，form-urlencoded参数 packageBox=cake

http://127.0.0.1:8080/sky-api/deliver

返回结果

this is paw-dogs-sky-service port 8082 Time: 2021-06-17 16: 11: 23 delivered packageBox: cake

多访问几次会发现 port端口在8081 8082切换，负载均衡实现。

至此一个自定义网关项目雏形完成，可以根据项目实际需要自定义其他内容，增加拦截器来实现不同的业务，如增加签名校验，对路由映射也可以做更复杂的业务，如接口是否需要签名校验，再如增加业务统一的内容放到header中，增加接口限流等。

总结：

自定义网关是一个spring-boot-web项目，基于RestTemplate进行路由转发，通过LoadBlance实现负载均衡，通过拦截器实现路由映射、token权限校验及其他业务内容。