---

---

Host接口

public interface Host extends Container {


    // ----------------------------------------------------- Manifest Constants


    /**
     * The ContainerEvent event type sent when a new alias is added
     * by <code>addAlias()</code>.
     */
    public static final String ADD_ALIAS_EVENT = "addAlias";


    /**
     * The ContainerEvent event type sent when an old alias is removed
     * by <code>removeAlias()</code>.
     */
    public static final String REMOVE_ALIAS_EVENT = "removeAlias";


    // ------------------------------------------------------------- Properties


    /**
     * Return the application root for this Host.  This can be an absolute
     * pathname, a relative pathname, or a URL.
     */
    public String getAppBase();


    /**
     * Set the application root for this Host.  This can be an absolute
     * pathname, a relative pathname, or a URL.
     *
     * @param appBase The new application root
     */
    public void setAppBase(String appBase);


    /**
     * Return the value of the auto deploy flag.  If true, it indicates that 
     * this host's child webapps should be discovred and automatically 
     * deployed.
     */
    public boolean getAutoDeploy();


    /**
     * Set the auto deploy flag value for this host.
     * 
     * @param autoDeploy The new auto deploy flag
     */
    public void setAutoDeploy(boolean autoDeploy);


    /**
     * Set the DefaultContext
     * for new web applications.
     *
     * @param defaultContext The new DefaultContext
     */
    public void addDefaultContext(DefaultContext defaultContext);


    /**
     * Retrieve the DefaultContext for new web applications.
     */
    public DefaultContext getDefaultContext();


    /**
     * Return the canonical, fully qualified, name of the virtual host
     * this Container represents.
     */
    public String getName();


    /**
     * Set the canonical, fully qualified, name of the virtual host
     * this Container represents.
     *
     * @param name Virtual host name
     *
     * @exception IllegalArgumentException if name is null
     */
    public void setName(String name);


    // --------------------------------------------------------- Public Methods


    /**
     * Import the DefaultContext config into a web application context.
     *
     * @param context web application context to import default context
     */
    public void importDefaultContext(Context context);


    /**
     * Add an alias name that should be mapped to this same Host.
     *
     * @param alias The alias to be added
     */
    public void addAlias(String alias);


    /**
     * Return the set of alias names for this Host.  If none are defined,
     * a zero length array is returned.
     */
    public String[] findAliases();


    /**
     * Return the Context that would be used to process the specified
     * host-relative request URI, if any; otherwise return <code>null</code>.
     *
     * @param uri Request URI to be mapped
     */
    public Context map(String uri);


    /**
     * Remove the specified alias name from the aliases for this Host.
     *
     * @param alias Alias name to be removed
     */
    public void removeAlias(String alias);


}

---

StandardHost实现类

    /**
     * Create a new StandardHost component with the default basic Valve.
     */
    public StandardHost() {

        super();
        pipeline.setBasic(new StandardHostValve());

    }

      <Host name="www.dhy.com"  appBase="dhy"
            unpackWARs="true" autoDeploy="true">
        <context path="/xpy" docBase="xpy" ></context>
      </Host>

Deployer接口具体是干啥的，大家看了上面的xml配置，估计就会明白了。

Host对应一个域名，该域名在操作系统层面的文件系统中映射到一个目录，该目录下可以有很多子目录，这些子目录会挨个映射到当前Host下面所管理的context容器上去

   /**
     * Start this host
     */
    public synchronized void start() throws LifecycleException {

        // Set error report valve
        if ((errorReportValveClass != null)
            && (!errorReportValveClass.equals(""))) {
            try {
                Valve valve = (Valve) Class.forName(errorReportValveClass)
                    .newInstance();
                addValve(valve);
            } catch (Throwable t) {
                log(sm.getString
                    ("standardHost.invalidErrorReportValveClass", 
                     errorReportValveClass));
            }
        }

        // Set dispatcher valve
        addValve(new ErrorDispatcherValve());

        super.start();

    }

    /**
     * The Java class name of the default error reporter implementation class 
     * for deployed web applications.
     */
    private String errorReportValveClass =
        "org.apache.catalina.valves.ErrorReportValve";

这里Host的start初始化方法主要就是添加了两个关于错误日志处理的阀门，随后调用父类ContainerBase的start方法，启动相关组件，调用子容器的start初始化方法，因为这些逻辑都是通用的，因此都放到了父类的start方法中实现

父类ContainerBase的start方法
    /**
     * Prepare for active use of the public methods of this Component.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents it from being started
     */
    @Override
    public synchronized void start() throws LifecycleException {

        // Validate and update our current component state
        if (started)
            throw new LifecycleException
                (sm.getString("containerBase.alreadyStarted", logName()));

        // Notify our interested LifecycleListeners
        lifecycle.fireLifecycleEvent(BEFORE_START_EVENT, null);

        addDefaultMapper(this.mapperClass);
        started = true;

        // Start our subordinate components, if any
        if ((loader != null) && (loader instanceof Lifecycle))
            ((Lifecycle) loader).start();
        if ((logger != null) && (logger instanceof Lifecycle))
            ((Lifecycle) logger).start();
        if ((manager != null) && (manager instanceof Lifecycle))
            ((Lifecycle) manager).start();
        if ((cluster != null) && (cluster instanceof Lifecycle))
            ((Lifecycle) cluster).start();
        if ((realm != null) && (realm instanceof Lifecycle))
            ((Lifecycle) realm).start();
        if ((resources != null) && (resources instanceof Lifecycle))
            ((Lifecycle) resources).start();

        // Start our Mappers, if any
        Mapper mappers[] = findMappers();
        for (int i = 0; i < mappers.length; i++) {
            if (mappers[i] instanceof Lifecycle)
                ((Lifecycle) mappers[i]).start();
        }

        // Start our child containers, if any
        Container children[] = findChildren();
        for (int i = 0; i < children.length; i++) {
            if (children[i] instanceof Lifecycle)
                ((Lifecycle) children[i]).start();
        }

        // Start the Valves in our pipeline (including the basic), if any
        if (pipeline instanceof Lifecycle)
            ((Lifecycle) pipeline).start();

        // Notify our interested LifecycleListeners
        lifecycle.fireLifecycleEvent(START_EVENT, null);

        // Notify our interested LifecycleListeners
        lifecycle.fireLifecycleEvent(AFTER_START_EVENT, null);

    }

---

ContainerBase类的invoke方法因为是通用逻辑抽取，因此实现是固定的:

    public void invoke(Request request, Response response)
        throws IOException, ServletException {
        //调用当前容器管道中的阀门进行处理
        pipeline.invoke(request, response);

    }

---

StandardHostValve类

StandardHostValve的invoke方法如下:

   public void invoke(Request request, Response response,
                       ValveContext valveContext)
        throws IOException, ServletException {

        // Validate the request and response object types
        if (!(request.getRequest() instanceof HttpServletRequest) ||
            !(response.getResponse() instanceof HttpServletResponse)) {
            return;     // NOTE - Not much else we can do generically
        }

        // Select the Context to be used for this Request
        StandardHost host = (StandardHost) getContainer();
        //根据map方法找到当前请求对应的context对象
        Context context = (Context) host.map(request, true);
        if (context == null) {
            ((HttpServletResponse) response.getResponse()).sendError
                (HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                 sm.getString("standardHost.noContext"));
            return;
        }

        // Bind the context CL to the current thread
        Thread.currentThread().setContextClassLoader
            (context.getLoader().getClassLoader());

         //如果存在session的话，更新最后一次访问的时间
        // Update the session last access time for our session (if any)
        HttpServletRequest hreq = (HttpServletRequest) request.getRequest();
        String sessionId = hreq.getRequestedSessionId();
        if (sessionId != null) {
            Manager manager = context.getManager();
            if (manager != null) {
                Session session = manager.findSession(sessionId);
                if ((session != null) && session.isValid())
                    session.access();
            }
        }

        // Ask this Context to process this request
        //将当前请求接着传递给找到的context对象进行处理
        context.invoke(request, response);

    }

---

这里调用的其实是父类ContainerBase的map方法:

    public Container map(Request request, boolean update) {

        // Select the Mapper we will use
        Mapper mapper = findMapper(request.getRequest().getProtocol());
        if (mapper == null)
            return (null);

        // Use this Mapper to perform this mapping
        //这里最终调用的是StandardHostMapper的map方法，下面再分析，这里最终传入的其实就是请求URI中的context路径部分
        return (mapper.map(request, update));

    }

StandardHost类的map方法:

    public Context map(String uri) {

        if (debug > 0)
            log("Mapping request URI '" + uri + "'");
        if (uri == null)
            return (null);

        // Match on the longest possible context path prefix
        if (debug > 1)
            log("  Trying the longest context path prefix");
        Context context = null;
        //拿到当前请求context路径部分
        String mapuri = uri;
        while (true) {
            //去子容器中找到该context
            context = (Context) findChild(mapuri);
            if (context != null)
                break;
            int slash = mapuri.lastIndexOf('/');
            if (slash < 0)
                break;
            mapuri = mapuri.substring(0, slash);
        }

        // If no Context matches, select the default Context
        if (context == null) {
            if (debug > 1)
                log("  Trying the default context");
            context = (Context) findChild("");
        }

        // Complain if no Context has been selected
        if (context == null) {
            log(sm.getString("standardHost.mappingError", uri));
            return (null);
        }

        // Return the mapped Context (if any)
        if (debug > 0)
            log(" Mapped to context '" + context.getPath() + "'");
        return (context);

    }

---

StandardHostWrapper类

说明继承了ContainerBase的容器，只要调用了父类的start方法，就会添加一个默认的映射器

    protected void addDefaultMapper(String mapperClass) {

        // Do we need a default Mapper?
        if (mapperClass == null)
            return;
        if (mappers.size() >= 1)
            return;

        // Instantiate and add a default Mapper
        try {
            Class clazz = Class.forName(mapperClass);
            Mapper mapper = (Mapper) clazz.newInstance();
            mapper.setProtocol("http");
            addMapper(mapper);
        } catch (Exception e) {
            log(sm.getString("containerBase.addDefaultMapper", mapperClass),
                e);
        }

    }

    /**
     * The Java class name of the default Mapper class for this Container.
     */
    private String mapperClass =
        "org.apache.catalina.core.StandardHostMapper";

上面源码已经给出过了

关于这一点可以参考第12节

    public Container map(Request request, boolean update) {

        // Has this request already been mapped?
        if (update && (request.getContext() != null))
            return (request.getContext());

        // Perform mapping on our request URI
        String uri = ((HttpRequest) request).getDecodedRequestURI();
        //调用Host的map方法获得当前URI对应的context对象
        Context context = host.map(uri);

        // Update the request (if requested) and return the selected Context
        if (update) {
            request.setContext(context);
            if (context != null)
                ((HttpRequest) request).setContextPath(context.getPath());
            else
                ((HttpRequest) request).setContextPath(null);
        }
        return (context);

    }

---

为什么必须要有一个Host容器

applicationConfig方法主要是来解析web.xml配置文件的，该方法在start方法中被调用，start方法在ContextConfig监听到Context容器的启动的start事件时，被调用。

---

应用程序

connector改为关联一个Host了，然后会设置Host下面的context，host对应的域名和目录名

---

小结

Host洋洋洒洒讲了那么多，下面对Host这部分内容做一个小结先:

---

Engine接口

public interface Engine extends Container {


    // ------------------------------------------------------------- Properties


    /**
     * Return the default hostname for this Engine.
     */
    public String getDefaultHost();


    /**
     * Set the default hostname for this Engine.
     *
     * @param defaultHost The new default host
     */
    public void setDefaultHost(String defaultHost);


    /**
     * Retrieve the JvmRouteId for this engine.
     */
    public String getJvmRoute();


    /**
     * Set the JvmRouteId for this engine.
     *
     * @param jvmRouteId the (new) JVM Route ID. Each Engine within a cluster
     *        must have a unique JVM Route ID.
     */
    public void setJvmRoute(String jvmRouteId);


    /**
     * Return the <code>Service</code> with which we are associated (if any).
     */
    public Service getService();


    /**
     * Set the <code>Service</code> with which we are associated (if any).
     *
     * @param service The service that owns this Engine
     */
    public void setService(Service service);


    /**
     * Set the DefaultContext
     * for new web applications.
     *
     * @param defaultContext The new DefaultContext
     */
    public void addDefaultContext(DefaultContext defaultContext);


    /**
     * Retrieve the DefaultContext for new web applications.
     */
    public DefaultContext getDefaultContext();


    // --------------------------------------------------------- Public Methods


    /**
     * Import the DefaultContext config into a web application context.
     *
     * @param context web application context to import default context
     */
    public void importDefaultContext(Context context);


}

---

StandardEngine类

    /**
     * Create a new StandardEngine component with the default basic Valve.
     */
    public StandardEngine() {

        super();
        pipeline.setBasic(new StandardEngineValve());

    }

    /**
     * Add a child Container, only if the proposed child is an implementation
     * of Host.
     *
     * @param child Child container to be added
     */
    public void addChild(Container child) {

        if (!(child instanceof Host))
            throw new IllegalArgumentException
                (sm.getString("standardEngine.notHost"));
        super.addChild(child);

    }

    /**
     * Disallow any attempt to set a parent for this Container, since an
     * Engine is supposed to be at the top of the Container hierarchy.
     *
     * @param container Proposed parent Container
     */
    public void setParent(Container container) {

        throw new IllegalArgumentException
            (sm.getString("standardEngine.notParent"));

    }

---

StandardEngineValve类

    public void invoke(Request request, Response response,
                       ValveContext valveContext)
        throws IOException, ServletException {

        // Validate the request and response object types
        if (!(request.getRequest() instanceof HttpServletRequest) ||
            !(response.getResponse() instanceof HttpServletResponse)) {
            return;     // NOTE - Not much else we can do generically
        }

        // Validate that any HTTP/1.1 request included a host header
        HttpServletRequest hrequest = (HttpServletRequest) request;
        if ("HTTP/1.1".equals(hrequest.getProtocol()) &&
            (hrequest.getServerName() == null)) {
            ((HttpServletResponse) response.getResponse()).sendError
                (HttpServletResponse.SC_BAD_REQUEST,
                 sm.getString("standardEngine.noHostHeader",
                              request.getRequest().getServerName()));
            return;
        }

        // Select the Host to be used for this Request
        StandardEngine engine = (StandardEngine) getContainer();
        //通过request找到对应的host,不用我多说了吧，和context的步骤基本一致
        Host host = (Host) engine.map(request, true);
        if (host == null) {
            ((HttpServletResponse) response.getResponse()).sendError
                (HttpServletResponse.SC_BAD_REQUEST,
                 sm.getString("standardEngine.noHost",
                              request.getRequest().getServerName()));
            return;
        }

        // Ask this Host to process this request
        host.invoke(request, response);

    }

---

应用程序

---

小结