基于Spring Boot 实现简单的反向代理功能

Love The Way You Lie 2023-10-12 14:57 24阅读 0赞

最近收到一个新的需求，需要根据自定义的负载均衡策略从动态主机池选主之后，再通过反向代理到选中的主机上，这里面就涉及到服务注册、负载均衡策略、反向代理。本篇文章只涉及到如何实现反向代理功能。

# 功能实现 #

如果只是需要反向代理功能，那么有很多中间件可以选择，比如：Nginx、Kong、Spring Cloud Gateway,Zuul等都可以实现，但是还有一些客制化的需求，所以只能自己撸代码实现了,[附上源码][Link 1]。

# 请求拦截 #

实现请求拦截有两种方式，过滤器和拦截器，我们采用过滤器的方式去实现请求拦截。

在Spring 体系中最常用到的过滤器应该就是OncePerRequestFilter，这是一个抽象类。我们创建一个类叫ForwardRoutingFilter去继承这个类,同时实现Ordered，用于设置过滤器的优先级

java复制代码@Slf4j
    @Component
    public class ForwardRoutingFilter extends OncePerRequestFilter implements Ordered {
      @Override
      public int getOrder() {
        return 0; // 值越小，优先级别越高
      }
    
      @Override
      protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
    
        log.info("ForwardRoutingFilter doFilterInternal,request uri: {}", request.getRequestURI());
        filterChain.doFilter(request, response);
      }
    }

启动服务之后,浏览器中输入http://127.0.0.1:8080/aa,查看console 中的日志,可以看到过滤器以及开始工作了。

log复制代码2023-06-12T14:25:09.059+08:00  INFO 17472 --- [nio-8080-exec-2] c.r.b.filter.ForwardRoutingFilter        : ForwardRoutingFilter doFilterInternal,request uri: /aa
    2023-06-12T14:25:09.735+08:00  INFO 17472 --- [nio-8080-exec-1] c.r.b.filter.ForwardRoutingFilter        : ForwardRoutingFilter doFilterInternal,request uri: /favicon.ico

接下来，我们的实现就围绕着这个过滤器去做了。

# 配置规则定义 #

通常情况下，我们会在application.yml去配置哪些path需要被转发到具体的服务上去,例如

yml复制代码my:
      routes:
        - uri: lb://ai-server
          path: /ai/**
          rewrite: false
        - uri: https://api.oioweb.cn
          path: /oioweb/**
          rewrite: true

参数说明：

txt复制代码uri: 最终请求的服务地址，如果是lb:// 开头的，说明需要进行负责均衡
    path: 用于匹配代理的路径，命中的会被进行代理转发
    rewrite: 是否重写path,如果true, 访问 http://127.0.0.1:8080/uomg/api/rand.img1 请求path中/uomg会被删除，最终访问的是 https://api.uomg.com/api/rand.img1

在pom.xml dependencies 中添加新的依赖，用于自动装填配置

xml复制代码
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-configuration-processor</artifactId>
    </dependency>

创建实体类RouteInstance和配置类MyRoutes,这样服务启动之后就会自动读取装填my.routes下所有配置的实例到配置类了

java复制代码@Data
    public class RouteInstance {
      private String uri;
      private String path;
      private boolean rewrite;
    }

java复制代码@Configuration
    @ConfigurationProperties(prefix = "my", ignoreInvalidFields = true)
    @Data
    public class MyRoutes {
      private List<RouteInstance> routes;
    }

# 代理实现 #

在pom.xml dependencies 中添加需要用到的依赖

xml复制代码<dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
    </dependency>
    
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.11.0</version>
    </dependency>
    
    <dependency>
      <groupId>commons-beanutils</groupId>
      <artifactId>commons-beanutils</artifactId>
      <version>1.9.4</version>
    </dependency>
    
    <dependency>
      <groupId>org.apache.httpcomponents.client5</groupId>
      <artifactId>httpclient5</artifactId>
      <version>5.2.1</version>
    </dependency>
    
    <dependency>
      <groupId>com.alibaba.fastjson2</groupId>
      <artifactId>fastjson2</artifactId>
      <version>2.0.32</version>
    </dependency>

接下来就是改造我们之前的ForwardRoutingFilter 过滤器类了

java复制代码@Slf4j
    @Component
    public class ForwardRoutingFilter extends OncePerRequestFilter implements Ordered {
    
      @Resource
      private MyRoutes routes;
    
      @Resource
      private RoutingDelegateService routingDelegate;
    
      @Override
      public int getOrder() {
        return 0;
      }
    
      @Override
      protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
    
        log.info("ForwardRoutingFilter doFilterInternal,request uri: {}", request.getRequestURI());
        String currentURL = StringUtils.isEmpty(request.getContextPath()) ? request.getRequestURI() :
            StringUtils.substringAfter(request.getRequestURI(), request.getContextPath());
        AntPathMatcher matcher = new AntPathMatcher();
        RouteInstance instance = routes.getRoutes().stream().filter(i -> matcher.match(i.getPath(), currentURL)).findFirst().orElse(new RouteInstance());
    
        if (instance.getUri() == null) {
          //转发的uri为空，不进行代理转发，交由过滤器链后续过滤器处理
          filterChain.doFilter(request, response);
        } else {
          // 创建一个service 去处理代理转发逻辑
          routingDelegate.doForward(instance, request, response);
          return;
        }
      }
    }

代理转发会使用到RestTemplate，默认使用的是java.net.URLConnection去进行http请求，我们这边替换成httpclient，具体配置就不贴出来了。

编写两个工具栏，分别用于转换 HttpServletRequest 为 RequestEntity 和 HttpServletResponse 为 ResponseEntity，并把结果写回客户端

java复制代码@Slf4j
    public class HttpRequestMapper {
    
      public RequestEntity<byte[]> map(HttpServletRequest request, RouteInstance instance) throws IOException {
        byte[] body = extractBody(request);
        HttpHeaders headers = extractHeaders(request);
        HttpMethod method = extractMethod(request);
        URI uri = extractUri(request, instance);
        return new RequestEntity<>(body, headers, method, uri);
      }
    
      private URI extractUri(HttpServletRequest request, RouteInstance instance) throws UnsupportedEncodingException {
        //如果content path 不为空，移除content path
        String requestURI = StringUtils.isEmpty(request.getContextPath()) ? request.getRequestURI() :
            StringUtils.substringAfter(request.getRequestURI(), request.getContextPath());
    
        //处理中文被自动编码问题
        String query = request.getQueryString() == null ? EMPTY : URLDecoder.decode(request.getQueryString(), "utf-8");
    
        // 需要重写path
        if (instance.isRewrite()) {
          String prefix = StringUtils.substringBefore(instance.getPath(), "/**");
          requestURI = StringUtils.substringAfter(requestURI, prefix);
        }
        URI redirectURL = UriComponentsBuilder.fromUriString(instance.getUri() + requestURI).query(query).build().encode().toUri();
        log.info("real request url: {}", redirectURL.toString());
        return redirectURL;
      }
    
      private HttpMethod extractMethod(HttpServletRequest request) {
        return valueOf(request.getMethod());
      }
    
      private HttpHeaders extractHeaders(HttpServletRequest request) {
        HttpHeaders headers = new HttpHeaders();
        Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
          String name = headerNames.nextElement();
          List<String> value = list(request.getHeaders(name));
          headers.put(name, value);
        }
        return headers;
      }
    
      private byte[] extractBody(HttpServletRequest request) throws IOException {
        return toByteArray(request.getInputStream());
      }
    }

java复制代码public class HttpResponseMapper {
      public void map(ResponseEntity<byte[]> responseEntity, HttpServletResponse response) throws IOException {
        setStatus(responseEntity, response);
        setHeaders(responseEntity, response);
        setBody(responseEntity, response);
      }
    
      private void setStatus(ResponseEntity<byte[]> responseEntity, HttpServletResponse response) {
        response.setStatus(responseEntity.getStatusCode().value());
      }
    
      private void setHeaders(ResponseEntity<byte[]> responseEntity, HttpServletResponse response) {
        responseEntity.getHeaders().forEach((name, values) -> values.forEach(value -> response.addHeader(name, value)));
      }
    
      /**
       * 把结果写回客户端
       *
       * @param responseEntity
       * @param response
       * @throws IOException
       */
      private void setBody(ResponseEntity<byte[]> responseEntity, HttpServletResponse response) throws IOException {
        if (responseEntity.getBody() != null) {
          response.getOutputStream().write(responseEntity.getBody());
        }
      }
    }

以下为实际处理逻辑RoutingDelegateService的代码

java复制代码@Slf4j
    @Service
    public class RoutingDelegateService {
    
      private HttpResponseMapper responseMapper;
    
      private HttpRequestMapper requestMapper;
    
      @Resource
      private RestTemplate restTemplate;
    
      /**
       * 根据相应策略转发请求到对应后端服务
       *
       * @param instance RouteInstance
       * @param request  HttpServletRequest
       * @param response HttpServletResponse
       */
      public void doForward(RouteInstance instance, HttpServletRequest request, HttpServletResponse response) {
    
        boolean shouldLB = StringUtils.startsWith(instance.getUri(), MyConstants.LB_PREFIX);
        if (shouldLB) {
          // 需要负载均衡,获取appName
          String appName = StringUtils.substringAfter(instance.getUri(), MyConstants.LB_PREFIX);
          //从请求头中获取是否必须按user去路由到同一节点
          // 可用节点
          ServerInstance chooseInstance = chooseLBInstance(appName);
          if (chooseInstance == null) {
            // 无可用节点，返回异常,
            JSONObject result = new JSONObject();
            result.put("status", MyConstants.NO_AVAILABLE_NODE_STATUS);
            result.put("msg", MyConstants.NO_AVAILABLE_NODE_MSG);
            renderString(response, result.toJSONString());
            return;
          } else {
            //设置route instance uri 为负载均衡之后的URI地址
            String uri = MyConstants.HTTP_PREFIX + chooseInstance.getHost() + ":" + chooseInstance.getPort();
            instance.setUri(uri);
          }
        }
        // 转发请求
        try {
          goForward(request, response, instance);
        } catch (Exception e) {
          // 连接超时、返回异常
          e.printStackTrace();
          log.error("request error {}", e.getMessage());
          JSONObject result = new JSONObject();
          result.put("status", MyConstants.UNKNOWN_EXCEPTION_STATUS);
          result.put("msg", e.getMessage());
          renderString(response, result.toJSONString());
        }
    
      }
    
      /**
       * 发送请求到对应后端服务
       *
       * @param request  HttpServletRequest
       * @param response HttpServletResponse
       * @param instance RouteInstance
       * @throws IOException
       */
      private void goForward(HttpServletRequest request, HttpServletResponse response, RouteInstance instance) throws IOException {
        requestMapper = new HttpRequestMapper();
        RequestEntity<byte[]> requestEntity = requestMapper.map(request, instance);
        //用byte数组处理返回结果，因为返回结果可能是字符串也可能是数据流
        ResponseEntity<byte[]> responseEntity = restTemplate.exchange(requestEntity, byte[].class);
        responseMapper = new HttpResponseMapper();
        responseMapper.map(responseEntity, response);
      }
    
      private ServerInstance chooseLBInstance(String appName) {
        //TODO 根据appName 选择对应的host
        ServerInstance instance = new ServerInstance();
        instance.setHost("127.0.0.1");
        instance.setPort(10000);
        return instance;
      }
    
      /**
       * 写回字符串结果到客户端
       *
       * @param response
       * @param string
       */
      public void renderString(HttpServletResponse response, String string) {
        try {
          response.setStatus(200);
          response.setContentType("application/json");
          response.setCharacterEncoding("utf-8");
          response.getWriter().print(string);
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

启动server，浏览器中输入http://127.0.0.1:8080/oioweb/api/common/rubbish?name=香蕉，就可以把请求代理到https://api.oioweb.cn/api/common/rubbish?name=香蕉了

json复制代码{
        "code": 200,
        "result": [
            {
                "name": "香蕉",
                "type": 2,
                "aipre": 0,
                "explain": "厨余垃圾是指居民日常生活及食品加工、饮食服务、单位供餐等活动中产生的垃圾。",
                "contain": "常见包括菜叶、剩菜、剩饭、果皮、蛋壳、茶渣、骨头等",
                "tip": "纯流质的食物垃圾、如牛奶等，应直接倒进下水口。有包装物的湿垃圾应将包装物去除后分类投放、包装物请投放到对应的可回收物或干垃圾容器"
            },
            {
                "name": "香蕉干",
                "type": 2,
                "aipre": 0,
                "explain": "厨余垃圾是指居民日常生活及食品加工、饮食服务、单位供餐等活动中产生的垃圾。",
                "contain": "常见包括菜叶、剩菜、剩饭、果皮、蛋壳、茶渣、骨头等",
                "tip": "纯流质的食物垃圾、如牛奶等，应直接倒进下水口。有包装物的湿垃圾应将包装物去除后分类投放、包装物请投放到对应的可回收物或干垃圾容器"
            },
            {
                "name": "香蕉皮",
                "type": 2,
                "aipre": 0,
                "explain": "厨余垃圾是指居民日常生活及食品加工、饮食服务、单位供餐等活动中产生的垃圾。",
                "contain": "常见包括菜叶、剩菜、剩饭、果皮、蛋壳、茶渣、骨头等",
                "tip": "纯流质的食物垃圾、如牛奶等，应直接倒进下水口。有包装物的湿垃圾应将包装物去除后分类投放、包装物请投放到对应的可回收物或干垃圾容器"
            }
        ],
        "msg": "success"
    }

[Link 1]: https://link.juejin.cn/?target=https%3A%2F%2Fgitee.com%2Frikylee%2Fboot-reverse-proxy.git