Javalin

Javalin是一个轻量级http框架，我们可以很容易的了解请求的处理过程及其设计，具有较高的学习意义。

从demo说起

public static void main(String[] args) {
        Javalin app = Javalin.create(config -> {
            System.out.println("用户配置");
        });
        app.get("/", ctx -> {
            System.out.println("do" + ctx.path());
            ctx.result("Hello World");
        });

        // 处理异常
        app.exception(Exception.class, (e, ctx) -> {
            ctx.result("发生异常了");
        });
        // 处理异常状态
        app.error(404, ctx -> {
            ctx.html("Generic 404 message");
        });
        // 测试异常
        app.get("/exception/{e}", ctx -> {
            String msg = ctx.pathParam("e");
            if ("1".equals(msg)) {
                throw new InvalidAlgorithmParameterException("测试异常");
            } else if ("2".equals(msg)) {
                throw new ClassNotFoundException("Invalid");
            } else if ("3".equals(msg)) {
                ctx.status(404);
            } else {
                throw new Exception("Invalid algorithm parameter");
            }
        });
        //get请求{}参数解析
        app.get("/path/<path>", ctx -> ctx.result("Hello Path2 " + ctx.pathParam("path")));
        //post请求
        app.post("/json", ctx -> {
            Map<String, String> map = new HashMap<>();
            map.put("name", "张三");
            ctx.json(map);
        });
        //get请求<>参数解析
        app.get("/name/{name}", ctx -> {
            NaiveRateLimit.requestPerTimeUnit(ctx, 5, TimeUnit.MINUTES);
            ctx.result("Hello Path " + ctx.pathParam("name"));
        });
        // webscoket
        app.ws("/websocket/{path}", ws -> {
            ws.onConnect(ctx -> System.out.println("Connected"));
            ws.onMessage(ctx -> {
                System.out.println("收到消息" + ctx.message());
                ctx.send("我收到了" + ctx.message());
            });
        });
        // 前置处理器
        app.before(ctx -> System.out.println("before" + ctx.path()));
        // 后置处理器
        app.after(ctx -> System.out.println("after" + ctx.path()));
        // 启动
        app.start(7070);
    }

创建Javalin实例

使用代码

Javalin app = Javalin.create(config -> {
            System.out.println("用户配置");
        });

实现原理

实现源码

    public static Javalin create(Consumer<JavalinConfig> config) {
        // 初始化示例对象
        Javalin app = new Javalin();
        // 加载用户配置
        JavalinConfig.applyUserConfig(app, app.cfg, config); // mutates app.config and app (adds http-handlers)
        // 延迟检测服务是否正常启动
        JettyUtil.maybeLogIfServerNotStarted(app.jettyServer);
        return app;
    }

流程
在这里插入图片描述

get/post/websocket/before/after配置

使用方式

 app.get("/", ctx -> {
            System.out.println("do" + ctx.path());
            ctx.result("Hello World");
        });

实现源码

    public Javalin get(@NotNull String path, @NotNull Handler handler) {
        return addHandler(HandlerType.GET, path, handler);
    }
    public Javalin addHandler(@NotNull HandlerType httpMethod, @NotNull String path, @NotNull Handler handler) {
        return addHandler(httpMethod, path, handler, new RouteRole[0]); // no roles set for this route (open to everyone with default access manager)
    }
   public Javalin addHandler(@NotNull HandlerType handlerType, @NotNull String path, @NotNull Handler handler, @NotNull RouteRole... roles) {
        Set<RouteRole> roleSet = new HashSet<>(Arrays.asList(roles));
        javalinServlet.getMatcher().add(new HandlerEntry(handlerType, path, cfg.routing, roleSet, handler));
        eventManager.fireHandlerAddedEvent(new HandlerMetaInfo(handlerType, Util.prefixContextPath(cfg.routing.contextPath, path), handler, roleSet));
      return this;
    }

添加流程
在这里插入图片描述
get/post/websocket/before/after处理器都是这个类型，只是请求类型不一致,
http支持的请求类型有

GET, POST, PUT, PATCH, DELETE, HEAD, TRACE, CONNECT, OPTIONS, BEFORE, AFTER, INVALID;

websocket支持的请求类型有

 WS_BEFORE, WEBSOCKET, WS_AFTER

exceptionHandler配置

使用方式

        // 处理异常
        app.exception(Exception.class, (e, ctx) -> {
            ctx.result("发生异常了");
        });

实现源码

    public <T extends Exception> Javalin exception(@NotNull Class<T> exceptionClass, @NotNull ExceptionHandler<? super T> exceptionHandler) {
        javalinServlet.getExceptionMapper().getHandlers().put(exceptionClass, (ExceptionHandler<Exception>) exceptionHandler);
        return this;
    }

添加流程
在这里插入图片描述

errorHandler配置

使用方式

        // 处理异常状态
        app.error(404, ctx -> {
            ctx.html("Generic 404 message");
        });

实现源码

    public Javalin error(int status, @NotNull String contentType, @NotNull Handler handler) {
        javalinServlet.getErrorMapper().addHandler(status, contentType, handler);
        return this;
    }

添加流程
在这里插入图片描述

权限管理配置

使用方式

// Set the access-manager that Javalin should use
config.accessManager((handler, ctx, routeRoles) -> {
    MyRole userRole = getUserRole(ctx);
    if (routeRoles.contains(userRole)) {
        handler.handle(ctx);
    } else {
        ctx.status(401).result("Unauthorized");
    }
});

Role getUserRole(Context ctx) {
    // determine user role based on request.
    // typically done by inspecting headers, cookies, or user session
}

enum Role implements RouteRole {
    ANYONE, ROLE_ONE, ROLE_TWO, ROLE_THREE;
}

app.get("/un-secured",   ctx -> ctx.result("Hello"),   Role.ANYONE);
app.get("/secured",      ctx -> ctx.result("Hello"),   Role.ROLE_ONE);

实现源码

    fun accessManager(accessManager: AccessManager) { pvt.accessManager = accessManager }

设置流程
在这里插入图片描述

启动流程

使用方式

// 启动
app.start(7070);

源码

    public Javalin start(int port) {
        // 设置端口号
        jettyServer.setServerPort(port);
        // 启动服务
        return start();
    }

start()

public Javalin start() {
        // 记录启动开始时间
        long startupTimer = System.currentTimeMillis();
        // 如果已经启动了就报错
        if (jettyServer.started) {
            String message = "Server already started. If you are trying to call start() on an instance " +
                "of Javalin that was stopped using stop(), please create a new instance instead.";
            throw new IllegalStateException(message);
        }
        // 标识服务已经启动
        jettyServer.started = true;
        // 检测日志组件是否引入
        Util.printHelpfulMessageIfLoggerIsMissing();
        // 触发服务启动中事件
        eventManager.fireEvent(JavalinEvent.SERVER_STARTING);
        try {
            // 打印服务启动中
            JavalinLogger.startup("Starting Javalin ...");
            // 启动jetty服务
            jettyServer.start(javalinJettyServlet);
            // 打印javlin和java版本
            Util.logJavalinVersion();
            // 打印服务已经启动和耗时
            JavalinLogger.startup("Javalin started in " + (System.currentTimeMillis() - startupTimer) + "ms \\o/");
            // 发布服务已启动事件
            eventManager.fireEvent(JavalinEvent.SERVER_STARTED);
        } catch (Exception e) {
            // 打印服务启动异常
            JavalinLogger.error("Failed to start Javalin");
            // 发布服务启动失败事件
            eventManager.fireEvent(JavalinEvent.SERVER_START_FAILED);
            // 如果jetty已启动成功了，则停止服务
            if (Boolean.TRUE.equals(jettyServer.server().getAttribute("is-default-server"))) {
                stop();// stop if server is default server; otherwise, the caller is responsible to stop
            }
            if (e.getMessage() != null && e.getMessage().contains("Failed to bind to")) {
                // 端口冲突
                throw new JavalinBindException("Port already in use. Make sure no other process is using port " + Util.getPort(e) + " and try again.", e);
            } else if (e.getMessage() != null && e.getMessage().contains("Permission denied")) {
                // 权限不足
                throw new JavalinBindException("Port 1-1023 require elevated privileges (process must be started by admin).", e);
            }
            // 其他异常
            throw new JavalinException(e);
        }
        return this;
    }

其中核心逻辑在jettyServer.start(javalinJettyServlet);中
jettyServer.start(javalinJettyServlet);

   fun start(wsAndHttpServlet: JavalinJettyServlet) {
        // 如果未设置端口则设置为8080端口
        if (serverPort == -1 && cfg.pvt.server == null) {
            serverPort = 8080
            JavalinLogger.startup("No port specified, starting on port $serverPort. Call start(port) to change ports.")
        }
        // 初始化默认sessionHandler管理session
        cfg.pvt.sessionHandler = cfg.pvt.sessionHandler ?: defaultSessionHandler()
        val nullParent = null // javalin handlers are orphans
        // 定义jetty请求处理器
        val wsAndHttpHandler = object : ServletContextHandler(nullParent, Util.normalizeContextPath(cfg.routing.contextPath), SESSIONS) {
            override fun doHandle(target: String, jettyRequest: Request, request: HttpServletRequest, response: HttpServletResponse) {
                request.setAttribute("jetty-target-and-request", Pair(target, jettyRequest)) // used in JettyResourceHandler
                nextHandle(target, jettyRequest, request, response)
            }
        }.apply {
            this.sessionHandler = cfg.pvt.sessionHandler
            cfg.pvt.servletContextHandlerConsumer?.accept(this)
            // 设置所有路径处理器
            addServlet(ServletHolder(wsAndHttpServlet), "/*")
            // 初始化websocket处理器
            JettyWebSocketServletContainerInitializer.configure(this) { _, _ ->
                /* we don't want to configure WebSocketMappings during ServletContext initialization phase */
            }
        }
        // 初始化jetty服务，并设置处理器
        server().apply {
            handler = if (handler == null) wsAndHttpHandler else handler.attachHandler(wsAndHttpHandler)
            if (connectors.isEmpty()) { // user has not added their own connectors, we add a single HTTP connector
                connectors = arrayOf(defaultConnector(this))
            }
        }.start()
        // 打印javalin logo
        logJavalinBanner(cfg.showJavalinBanner)
        // 打印是否使用Loom(Java虚拟线程)
        LoomUtil.logIfLoom(server())

        // 初始化资源处理器
        (cfg.pvt.resourceHandler as? JettyResourceHandler)?.init() // we want to init this here to get logs in order

        // 打印服务使用的ip和端口
        server().connectors.filterIsInstance<ServerConnector>().forEach {
            JavalinLogger.startup("Listening on ${it.protocol}://${it.host ?: "localhost"}:${it.localPort}${cfg.routing.contextPath}")
        }
        // 非http服务打印绑定的端口
        server().connectors.filter { it !is ServerConnector }.forEach {
            JavalinLogger.startup("Binding to: $it")
        }
        // 设置服务启动的端口号
        serverPort = (server().connectors[0] as? ServerConnector)?.localPort ?: -1
    }

启动流程
在这里插入图片描述

请求处理流程

处理请求的入口
JavalinJettyServlet.service
这个类既处理http也处理websocket

override fun service(req: HttpServletRequest, res: HttpServletResponse) { // this handles both http and websocket
        // 判断是否有websocket请求标识
        if (req.getHeader(Header.SEC_WEBSOCKET_KEY) == null) { // this isn't a websocket request
            // http请求处理
            return httpServlet.service(req, res) // treat as normal HTTP request
        }
        // 去除项目路径前缀
        val requestUri = req.requestURI.removePrefix(req.contextPath)
        // 查找url对应后端处理器
        val entry = wsPathMatcher.findEndpointHandlerEntry(requestUri) ?: return res.sendError(404, "WebSocket handler not found")
        // 构建请求处理的上下文
        val upgradeContext = JavalinServletContext(
            req = req,
            res = res,
            cfg = cfg,
            matchedPath = entry.path,
            pathParamMap = entry.extractPathParams(requestUri),
        )
        // 校验权限
        if (!allowedByAccessManager(entry, upgradeContext)) return res.sendError(HttpStatus.UNAUTHORIZED.code, HttpStatus.UNAUTHORIZED.message)
        // 设置上下文
        req.setAttribute(upgradeContextKey, upgradeContext)
        // 设置协议头
        setWsProtocolHeader(req, res)
        // 处理websocket请求
        super.service(req, res) // everything is okay, perform websocket upgrade
    }

从源码可以知道http请求又调了JavalinServlet.service进行处理，websocket
掉jetty进行处理，会回调这个类型configure方法，因为这类继承了JettyWebSocketServlet类。
接下来先介绍http请求处理部分
JavalinServlet.service

override fun service(request: HttpServletRequest, response: HttpServletResponse) {
        try {
            // 构建请求处理的上下文
            val ctx = JavalinServletContext(req = request, res = response, cfg = cfg)
            // 定义请求处理的任务列表添加函数，添加到头部还是尾部
            val submitTask: (SubmitOrder, Task) -> Unit = { order, task ->
                when (order) {
                    FIRST -> ctx.tasks.offerFirst(task)
                    LAST -> ctx.tasks.add(task)
                }
            }
            // 去除项目的上下文路径
            val requestUri = ctx.path().removePrefix(ctx.contextPath())
            // 生成请求处理的任务列表（生成任务的最终顺序如下表）
            cfg.pvt.servletRequestLifecycle.forEach { it.createTasks(submitTask, this, ctx, requestUri) }
            // 处理请求
            ctx.handleSync()
        } catch (throwable: Throwable) {
            // 兜底异常处理
            exceptionMapper.handleUnexpectedThrowable(response, throwable)
        }
    }

处理器类型	是否跳过异常
BEFORE	是
HTTP	是
ERROR	否
AFTER	否

再看下处理请求部分

    private fun JavalinServletContext.handleSync() {
        while (userFutureSupplier == null && tasks.isNotEmpty()) {
            // 取出第一个任务
            val task = tasks.poll()
            // 判断是否发生过异常且是否跳过异常
            if (exceptionOccurred && task.skipIfExceptionOccurred) {
                continue
            }
            // 处理任务
            handleTask(task.handler)
        }
        when {
            // 异步处理的请求
            userFutureSupplier != null -> handleUserFuture()
            // 非异步处理的请求，写入结果并打印日志
            else -> writeResponseAndLog()
        }
    }
      private fun <R> JavalinServletContext.handleTask(handler: TaskHandler<R>): R? =
        try {
            handler.handle()
        } catch (throwable: Throwable) {
            exceptionOccurred = true
            userFutureSupplier = null
            tasks.offerFirst(Task(skipIfExceptionOccurred = false) { exceptionMapper.handle(this, throwable) })
            null
        }

然后在看下websocket的处理过程
首先调用configure完成连接初始化
JavalinJettyServlet.configure

    // websocket初始化连接
    override fun configure(factory: JettyWebSocketServletFactory) { // this is called once, before everything
        cfg.pvt.wsFactoryConfig?.accept(factory)
        factory.setCreator(JettyWebSocketCreator { req, _ -> // this is called when a websocket is created (after [service])
            val preUpgradeContext = req.httpServletRequest.getAttribute(upgradeContextKey) as JavalinServletContext
            req.httpServletRequest.setAttribute(upgradeContextKey, preUpgradeContext.changeBaseRequest(req.httpServletRequest))
            val session = req.session as? Session?
            req.httpServletRequest.setAttribute(upgradeSessionAttrsKey, session?.attributeNames?.asSequence()?.associateWith { session.getAttribute(it) })
            // 初始化连接
            return@JettyWebSocketCreator WsConnection(wsPathMatcher, wsExceptionMapper, cfg.pvt.wsLogger)
        })
    }

重点看下WsConnection类

 @OnWebSocketConnect
    fun onConnect(session: Session) {
        // websocket连接初始化
        val ctx = WsConnectContext(sessionId, session)
        tryBeforeAndEndpointHandlers(ctx) { it.wsConfig.wsConnectHandler?.handleConnect(ctx) }
        tryAfterHandlers(ctx) { it.wsConfig.wsConnectHandler?.handleConnect(ctx) }
        wsLogger?.wsConnectHandler?.handleConnect(ctx)
    }

    @OnWebSocketMessage
    fun onMessage(session: Session, message: String) {
        // 收到文本消息
        val ctx = WsMessageContext(sessionId, session, message)
        tryBeforeAndEndpointHandlers(ctx) { it.wsConfig.wsMessageHandler?.handleMessage(ctx) }
        tryAfterHandlers(ctx) { it.wsConfig.wsMessageHandler?.handleMessage(ctx) }
        wsLogger?.wsMessageHandler?.handleMessage(ctx)
    }

    @OnWebSocketMessage
    fun onMessage(session: Session, buffer: ByteArray, offset: Int, length: Int) {
        // 收到二进制消息
        val ctx = WsBinaryMessageContext(sessionId, session, buffer, offset, length)
        tryBeforeAndEndpointHandlers(ctx) { it.wsConfig.wsBinaryMessageHandler?.handleBinaryMessage(ctx) }
        tryAfterHandlers(ctx) { it.wsConfig.wsBinaryMessageHandler?.handleBinaryMessage(ctx) }
        wsLogger?.wsBinaryMessageHandler?.handleBinaryMessage(ctx)
    }

    @OnWebSocketClose
    fun onClose(session: Session, statusCode: Int, reason: String?) {
        // 连接关闭
        val ctx = WsCloseContext(sessionId, session, statusCode, reason)
        tryBeforeAndEndpointHandlers(ctx) { it.wsConfig.wsCloseHandler?.handleClose(ctx) }
        tryAfterHandlers(ctx) { it.wsConfig.wsCloseHandler?.handleClose(ctx) }
        wsLogger?.wsCloseHandler?.handleClose(ctx)
        ctx.disableAutomaticPings()
    }

    @OnWebSocketError
    fun onError(session: Session, throwable: Throwable?) {
        // 发生异常
        val ctx = WsErrorContext(sessionId, session, throwable)
        tryBeforeAndEndpointHandlers(ctx) { it.wsConfig.wsErrorHandler?.handleError(ctx) }
        tryAfterHandlers(ctx) { it.wsConfig.wsErrorHandler?.handleError(ctx) }
        wsLogger?.wsErrorHandler?.handleError(ctx)
    }