1. 程式人生 > >Netty URL路由方案探討

Netty URL路由方案探討

最近在用Netty做開發,需要提供一個http web server,供呼叫方呼叫。採用Netty本身提供的HttpServerCodec handler進行Http協議的解析,但是需要自己提供路由。

最開始是通過對Http method及uri 採用多層if else 巢狀判斷的方法路由到真正的controller類:

String uri = request.uri();
HttpMethod method = request.method();
if (method == HttpMethod.POST) {
    if (uri.startsWith("/login")) {
        //url引數解析,呼叫controller的方法
    } else if (uri.startsWith("/logout")) {
        //同上
    }
} else if (method == HttpMethod.GET) {
    if (uri.startsWith("/")) {

    } else if (uri.startsWith("/status")) {

    }
}

在只需提供loginlogoutAPI時,程式碼可以完成功能,可是隨著API的數量越來越多,需要支援的方法及uri越來越多,else if 越來越多,程式碼越來越複雜。

time-for-change

在阿里開發手冊中也提到過:

因此首先考慮採用狀態設計模式及策略設計模式重構。

狀態模式

狀態模式的角色:

  • state狀態 表示狀態,定義了根據不同狀態進行不同處理的介面,該介面是那些處理內容依賴於狀態的方法集合,對應例項的state類
  • 具體的狀態 實現了state介面,對應daystate和nightstate
  • context context持有當前狀態的具體狀態的例項,此外,他還定義了供外部呼叫者使用的狀態模式的介面。

首先我們知道每個http請求都是由method及uri來唯一標識的,所謂路由就是通過這個唯一標識定位到controller類的中的某個方法。

因此把HttpLabel作為狀態

@Data
@AllArgsConstructor
public class HttpLabel {
    private String uri;
    private HttpMethod method;
}

狀態介面:

public interface Route {
    /**
     * 路由
     *
     * @param request
     * @return
     */
    GeneralResponse call(FullHttpRequest request);
}

為每個狀態新增狀態實現:

public void route() {
    //單例controller類
    final DemoController demoController = DemoController.getInstance();
    Map<HttpLabel, Route> map = new HashMap<>();
    map.put(new HttpLabel("/login", HttpMethod.POST), demoController::login);
    map.put(new HttpLabel("/logout", HttpMethod.POST), demoController::login);
}

接到請求,判斷狀態,呼叫不同介面:

public class ServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    @Override
    public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) {
        String uri = request.uri();
        GeneralResponse generalResponse;
        if (uri.contains("?")) {
            uri = uri.substring(0, uri.indexOf("?"));
        }
        Route route = map.get(new HttpLabel(uri, request.method()));
        if (route != null) {
            ResponseUtil.response(ctx, request, route.call(request));
        } else {
            generalResponse = new GeneralResponse(HttpResponseStatus.BAD_REQUEST, "請檢查你的請求方法及url", null);
            ResponseUtil.response(ctx, request, generalResponse);
        }
    }
}

使用狀態設計模式重構程式碼,在增加url時只需要網map裡面put一個值就行了。

類似SpringMVC路由功能

下面介紹Netty使用反射實現URL路由。

路由註解:

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RequestMapping {
    /**
     * 路由的uri
     *
     * @return
     */
    String uri();

    /**
     * 路由的方法
     *
     * @return
     */
    String method();
}

掃描classpath下帶有@RequestMapping註解的方法,將這個方法放進一個路由Map:Map<HttpLabel, Action<GeneralResponse>> httpRouterAction,key為上面提到過的Http唯一標識 HttpLabel,value為通過反射呼叫的方法:

@Slf4j
public class HttpRouter extends ClassLoader {

    private Map<HttpLabel, Action<GeneralResponse>> httpRouterAction = new HashMap<>();

    private String classpath = this.getClass().getResource("").getPath();

    private Map<String, Object> controllerBeans = new HashMap<>();

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        String path = classpath + name.replaceAll("\\.", "/");
        byte[] bytes;
        try (InputStream ins = new FileInputStream(path)) {
            try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
                byte[] buffer = new byte[1024 * 5];
                int b = 0;
                while ((b = ins.read(buffer)) != -1) {
                    out.write(buffer, 0, b);
                }
                bytes = out.toByteArray();
            }
        } catch (Exception e) {
            throw new ClassNotFoundException();
        }
        return defineClass(name, bytes, 0, bytes.length);
    }

    public void addRouter(String controllerClass) {
        try {
            Class<?> cls = loadClass(controllerClass);
            Method[] methods = cls.getDeclaredMethods();
            for (Method invokeMethod : methods) {
                Annotation[] annotations = invokeMethod.getAnnotations();
                for (Annotation annotation : annotations) {
                    if (annotation.annotationType() == RequestMapping.class) {
                        RequestMapping requestMapping = (RequestMapping) annotation;
                        String uri = requestMapping.uri();
                        String httpMethod = requestMapping.method().toUpperCase();
                        // 儲存Bean單例
                        if (!controllerBeans.containsKey(cls.getName())) {
                            controllerBeans.put(cls.getName(), cls.newInstance());
                        }
                        Action action = new Action(controllerBeans.get(cls.getName()), invokeMethod);
                        //如果需要FullHttpRequest,就注入FullHttpRequest物件
                        Class[] params = invokeMethod.getParameterTypes();
                        if (params.length == 1 && params[0] == FullHttpRequest.class) {
                            action.setInjectionFullhttprequest(true);
                        }
                        // 儲存對映關係
                        httpRouterAction.put(new HttpLabel(uri, new HttpMethod(httpMethod)), action);
                    }
                }
            }
        } catch (Exception e) {
            log.warn("{}", e);
        }
    }

    public Action getRoute(HttpLabel httpLabel) {
        return httpRouterAction.get(httpLabel);
    }
}

通過反射呼叫controller 類中的方法:

@Data
@RequiredArgsConstructor
@Slf4j
public class Action<T> {
    @NonNull
    private Object object;
    @NonNull
    private Method method;

    private boolean injectionFullhttprequest;

    public T call(Object... args) {
        try {
            return (T) method.invoke(object, args);
        } catch (IllegalAccessException | InvocationTargetException e) {
            log.warn("{}", e);
        }
        return null;
    }

ServerHandler.java處理如下:

 //根據不同的請求API做不同的處理(路由分發)
Action<GeneralResponse> action = httpRouter.getRoute(new HttpLabel(uri, request.method()));
if (action != null) {
    if (action.isInjectionFullhttprequest()) {
        ResponseUtil.response(ctx, request, action.call(request));
    } else {
        ResponseUtil.response(ctx, request, action.call());
    }
} else {
    //錯誤處理
    generalResponse = new GeneralResponse(HttpResponseStatus.BAD_REQUEST, "請檢查你的請求方法及url", null);
    ResponseUtil.response(ctx, request, generalResponse);
}

測試結果如下:

完整程式碼在 https://github.com/morethink/Netty-Route