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"));});// webscoketapp.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

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

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

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

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

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 = 8080JavalinLogger.startup("No port specified, starting on port $serverPort. Call start(port) to change ports.")}// 初始化默认sessionHandler管理sessioncfg.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 JettyResourceHandlernextHandle(target, jettyRequest, request, response)}}.apply {this.sessionHandler = cfg.pvt.sessionHandlercfg.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 connectorconnectors = arrayOf(defaultConnector(this))}}.start()// 打印javalin logologJavalinBanner(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

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 = trueuserFutureSupplier = nulltasks.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 everythingcfg.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 JavalinServletContextreq.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

 @OnWebSocketConnectfun 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)}@OnWebSocketMessagefun 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)}@OnWebSocketMessagefun 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)}@OnWebSocketClosefun 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()}@OnWebSocketErrorfun 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)}

采用注解形式定义一系列websocket操作
请求处理流程

总结

至此，主要处理流程都介绍完毕，还有部分异步请求的处理下次再更新。最后附上Jetty核心组件结构图