Jetty源码导读一：启动过程

启动过程总体流程

Server > ThreadPool 、Handler > Connector

Server

启动过程，主要做了以下的事情:

检查，如果 ErrorHandler 没有，则创建一个
注册和启动关闭钩子
启动除了 Connector 的其他所有组件 ThreadPool 、Handler

最后启动 Connector

// Server.java @Override protected void doStart() throws Exception { // 1.如果 ErrorHandler 没有，则创建一个 if (_errorHandler == null) _errorHandler = getBean(ErrorHandler.class); if (_errorHandler == null) setErrorHandler(new ErrorHandler()); if (_errorHandler instanceof ErrorHandler.ErrorPageMapper) LOG.warn("ErrorPageMapper not supported for Server level Error Handling"); _errorHandler.setServer(this);

1    //2.If the Server should be stopped when the jvm exits, register
2    //with the shutdown handler thread.
3    if (getStopAtShutdown())
4        ShutdownThread.register(this);
5
6    //3. Register the Server with the handler thread for receiving
7    //remote stop commands
8    ShutdownMonitor.register(this);
9    //Start a thread waiting to receive "stop" commands.
10    ShutdownMonitor.getInstance().start(); // initialize
11
12    // 4.启动 Server, 将会启动除了 Connector 的其他所有组件
13    MultiException mex = new MultiException();
14    try
15    {
16        super.doStart();
17    }
18    catch (Throwable e)
19    {
20        mex.add(e);
21    }
22
23    // 5.最后启动 Connector
24    if (mex.size() == 0)
25    {
26        for (Connector connector : _connectors)
27        {
28            try
29            {
30                connector.start();
31            }
32            catch (Throwable e)
33            {
34                mex.add(e);
35            }
36        }
37    }
38
39    if (isDumpAfterStart())
40        dumpStdErr();
41
42    mex.ifExceptionThrow();
43
44    LOG.info(String.format("Started @%dms", Uptime.getUptime()));
45}

比如 embedded-jetty-jsp

1         server = new Server();
2
3        // Define ServerConnector
4        ServerConnector connector = new ServerConnector(server);
5        connector.setPort(port);
6        server.addConnector(connector);
7
8         // Create Servlet context
9        ServletContextHandler servletContextHandler = new ServletContextHandler(ServletContextHandler.SESSIONS);
10        servletContextHandler.setContextPath("/");
11        servletContextHandler.setResourceBase(baseUri.toASCIIString());
12
13        // Since this is a ServletContextHandler we must manually configure JSP support.
14        enableEmbeddedJspSupport(servletContextHandler);
15    
16        // Add Application Servlets
17        servletContextHandler.addServlet(DateServlet.class, "/date/");
18        // Create Example of mapping jsp to path spec
19        ServletHolder holderAltMapping = new ServletHolder();
20        holderAltMapping.setName("foo.jsp");
21        holderAltMapping.setForcedPath("/test/foo/foo.jsp");
22        servletContextHandler.addServlet(holderAltMapping, "/test/foo/");
23    
24        // Default Servlet (always last, always named "default")
25        ServletHolder holderDefault = new ServletHolder("default", DefaultServlet.class);
26        holderDefault.setInitParameter("resourceBase", baseUri.toASCIIString());
27        holderDefault.setInitParameter("dirAllowed", "true");
28        servletContextHandler.addServlet(holderDefault, "/");
29        server.setHandler(servletContextHandler);
30
31        // Start Server
32        server.start();
33
34
35

Connector

Connector 的实现类 ServerConnector 中，有一个_acceptors的数组，在 Connector 启动的时候, 会根据_acceptors数组的长度创建对应数量的 Acceptor，而 Acceptor 的个数可以配置。

启动 HttpConnectionFactory, SelectorManager 等
根据_acceptors数组的长度创建对应数量的 Acceptor，并启动

// AbstractConnector.java @Override protected void doStart() throws Exception { ... // 启动 HttpConnectionFactory, SelectorManager 等 super.doStart(); ...
```
1    for (int i = 0; i < _acceptors.length; i++)
2    {
3        Acceptor a = new Acceptor(i);
4        addBean(a);
5        getExecutor().execute(a);
6    }
7}
```

Acceptor 本质是一个线程。

1// ServerConnector.java
2    @Override
3    public void accept(int acceptorID) throws IOException
4    {
5        ServerSocketChannel serverChannel = _acceptChannel;
6        if (serverChannel != null && serverChannel.isOpen())
7        {
8            // 阻塞等待客户端的连接
9            SocketChannel channel = serverChannel.accept();
10            // 连接成功
11            accepted(channel);
12        }
13    }
14     
15    // 这里已经连接成功
16    private void accepted(SocketChannel channel) throws IOException
17    {
18        channel.configureBlocking(false);
19        Socket socket = channel.socket();
20        configure(socket);
21        // _manager 是 SelectorManager 实例，里面管理了所有的 Selector 实例
22        _manager.accept(channel);
23    }
24
25
26

SelectorManager

SelectorManager 启动的时候，会把所有的 ManagedSelector 启动了。

1// SelectorManager.java
2    @Override
3    protected void doStart() throws Exception
4    {
5        _lease = ThreadPoolBudget.leaseFrom(getExecutor(), this, _selectors.length);
6        for (int i = 0; i < _selectors.length; i++)
7        {
8            ManagedSelector selector = newSelector(i);
9            _selectors[i] = selector;
10            addBean(selector);
11        }
12        super.doStart();
13    }
14
15
16

ManagedSelector 启动的时候，会启动 SelectorProducer （使用策略 EatWhatYouKill ）

1// ManagedSelector.java
2    public ManagedSelector(SelectorManager selectorManager, int id)
3    {
4        _selectorManager = selectorManager;
5        _id = id;
6        SelectorProducer producer = new SelectorProducer();
7        Executor executor = selectorManager.getExecutor();
8        _strategy = new EatWhatYouKill(producer, executor);
9        addBean(_strategy, true);
10        setStopTimeout(5000);
11    }
12    
13    @Override
14    protected void doStart() throws Exception
15    {
16        super.doStart();
17        _selector = _selectorManager.newSelector();
18
19        // The producer used by the strategies will never
20        // be idle (either produces a task or blocks).
21
22        // The normal strategy obtains the produced task, schedules
23        // a new thread to produce more, runs the task and then exits.
24        _selectorManager.execute(_strategy::produce);
25
26        // Set started only if we really are started
27        Start start = new Start();
28        submit(start);
29        start._started.await();
30    }
31
32
33

Jetty源码导读一：启动过程

启动过程总体流程

Server

Connector

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