上一篇終于找到了呼叫管道方法的地方, 代碼片段:

//org/apache/catalina/connector/CoyoteAdapter#service
// Parse and set Catalina and configuration specific
// request parameters 在 Map 中決議請求
postParseSuccess = postParseRequest(req, request, res, response);
if (postParseSuccess) {
    //check valves if we support async
    //getContainer() -> StandardEngine
    request.setAsyncSupported(
            connector.getService().getContainer().getPipeline().isAsyncSupported());
    // Calling the container
    // 呼叫 StandardEngineValve#invoke(), 開始執行管道方法.    (責任鏈模式)
    // 如果有多個 valve , 這里 getFirst() 拿到的就是 first valve,
    // 然后在 first valve中, 需要呼叫 getNext().invoke(request, response) 來傳遞
    connector.getService()   // --> StandardService
            .getContainer()  // --> StandardEngine
            .getPipeline()  // --> StandardPipeLine
            .getFirst()  //獲取優先級: first > basic
            .invoke(request, response);
}

1. 從代碼上看, 只獲取了 first, 那說好的很多閥門呢? 帶著疑問, 只能去看一下 StandardPipeLine 的閥門.

2. 默認情況下, 這里的getFirst() 獲取到的是 StandardEngineValve, 其實他是 basic. 　　

StandardPipeLine 

  他有兩個 閥門屬性:  

1. basic -- 末位閥門

2. first -- 首尾閥門

除此之外, 沒找到任何閥門屬性了. 沒辦法, 只能接著看看閥門

Valve

Valve 里面定義了兩個方法:

1. public Valve getNext()

2. public void setNext(Valve valve)

看到這里, 總算明白了, 原來閥門本身, 也是一個指標, 指向了下一個閥門的位置. 使用閥門, 可以組成一個單向鏈表.

addValve()

明白了閥門是指標之后, 還需要知道, 增加閥門時的順序, 所以必須看一下 addValve() 方法.

/**
 * 加入valve時, 會放到basic最近的位子上, 具體分兩種情況:
 * 1. first為空, 則放在first上 : first -> basic
 * 2. first不為空, 則放在離basic最近的位子上
 * first -> v1 -> v2 -> basic , 此時要插入 v3, 結果是: first -> v1 -> v2 -> v3 -> basic*/
@Override
public void addValve(Valve valve) {

    // Validate that we can add this Valve
    if (valve instanceof Contained)
        ((Contained) valve).setContainer(this.container);

    // Start the new component if necessary
    if (getState().isAvailable()) {
        if (valve instanceof Lifecycle) {
            try {
                ((Lifecycle) valve).start();
            } catch (LifecycleException e) {
                log.error(sm.getString("standardPipeline.valve.start"), e);
            }
        }
    }

    // Add this Valve to the set associated with this Pipeline
    if (first == null) {
        first = valve;
        valve.setNext(basic);
    }
    else {
        Valve current = first;
        while (current != null) {
            if (current.getNext() == basic) {
                current.setNext(valve);
                valve.setNext(basic);
                break;
            }
            current = current.getNext();
        }
    }

    container.fireContainerEvent(Container.ADD_VALVE_EVENT, valve);
}

初始狀態下, first 是空的, 所有的閥門, 在新增的時候, 都是緊挨著basic的位置放的.

getFirst()

/**
 * 拿取優先級:(有頭拿頭, 沒頭拿尾)
 * 1. first存在, 則回傳first
 * 2. first不存在, 則回傳 basic
 * @return
 */
@Override
public Valve getFirst() {
    if (first != null) {
        return first;
    }

    return basic;
}

在獲取的時候, 當 first 為空時, 直接獲取 basic , 說明此時只有一個閥門

當first 不為空時, 則會拿取 first , 然后需要在 呼叫閥門的時候, 進行傳遞.

StandardEngineValve

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

    // Select the Host to be used for this Request
    Host host = request.getHost();
    if (host == null) {
        response.sendError
            (HttpServletResponse.SC_BAD_REQUEST,
             sm.getString("standardEngine.noHost",
                          request.getServerName()));
        return;
    }
    if (request.isAsyncSupported()) {
        request.setAsyncSupported(host.getPipeline().isAsyncSupported());
    }

    // Ask this Host to process this request
    //呼叫 StandardHostValve#invoke() 方法
    host.getPipeline()   //-->StandardPipeline
            .getFirst()  //--> AccessLogValve --> ErrorReportValve --> StandardHostValve
            .invoke(request, response);

}

StandardEngineValve 作為管道的 basic(末位) , 肩負著呼叫子節點的管道方法. 這里啟動了 StandardHostValve

AccessLogValve 

//org.apache.catalina.valves.AbstractAccessLogValve#invoke
public void invoke(Request request, Response response) throws IOException,
        ServletException {
    if (tlsAttributeRequired) {
        // The log pattern uses TLS attributes. Ensure these are populated
        // before the request is processed because with NIO2 it is possible
        // for the connection to be closed (and the TLS info lost) before
        // the access log requests the TLS info. Requesting it now causes it
        // to be cached in the request.
        request.getAttribute(Globals.CERTIFICATES_ATTR);
    }
    if (cachedElements != null) {
        for (CachedElement element : cachedElements) {
            element.cache(request);
        }
    }
    getNext().invoke(request, response);
}

ErrorReportValve 

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

    // Perform the request
    getNext().invoke(request, response);

    if (response.isCommitted()) {
        if (response.setErrorReported()) {
            // Error wasn't previously reported but we can't write an error
            // page because the response has already been committed. Attempt
            // to flush any data that is still to be written to the client.
            try {
                response.flushBuffer();
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
            }
            // Close immediately to signal to the client that something went
            // wrong
            response.getCoyoteResponse().action(ActionCode.CLOSE_NOW,
                    request.getAttribute(RequestDispatcher.ERROR_EXCEPTION));
        }
        return;
    }

    Throwable throwable = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);

    // If an async request is in progress and is not going to end once this
    // container thread finishes, do not process any error page here.
    if (request.isAsync() && !request.isAsyncCompleting()) {
        return;
    }

    if (throwable != null && !response.isError()) {
        // Make sure that the necessary methods have been called on the
        // response. (It is possible a component may just have set the
        // Throwable. Tomcat won't do that but other components might.)
        // These are safe to call at this point as we know that the response
        // has not been committed.
        response.reset();
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
    }

    // One way or another, response.sendError() will have been called before
    // execution reaches this point and suspended the response. Need to
    // reverse that so this valve can write to the response.
    response.setSuspended(false);

    try {
        report(request, response, throwable);
    } catch (Throwable tt) {
        ExceptionUtils.handleThrowable(tt);
    }
}

這里是先進行了傳遞, 然后根據后面執行的結果, 再進行一些錯誤處理.

StandardHostValve

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

    // Select the Context to be used for this Request.   context --> StandardContext
    Context context = request.getContext();
    if (context == null) {
        return;
    }

    if (request.isAsyncSupported()) {
        request.setAsyncSupported(context.getPipeline().isAsyncSupported());
    }

    boolean asyncAtStart = request.isAsync();

    try {
        context.bind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);
　　　　　//fireRequestInitEvent 最侄訓呼叫 Servlet 監聽器 ServletRequestListener#requestInitialized()
        if (!asyncAtStart && !context.fireRequestInitEvent(request.getRequest())) {
            // Don't fire listeners during async processing (the listener
            // fired for the request that called startAsync()).
            // If a request init listener throws an exception, the request
            // is aborted.
            return;
        }

        // Ask this Context to process this request. Requests that are
        // already in error must have been routed here to check for
        // application defined error pages so DO NOT forward them to the the
        // application for processing.
        try {
            if (!response.isErrorReportRequired()) {
                //StandardContextValve#invoke()
                context.getPipeline()   //-->StandardPipeline
                        .getFirst()   //--> NonLoginAuthenticator --> StandardContextValve
                        .invoke(request, response);
            }
        } catch (Throwable t) {
            ExceptionUtils.handleThrowable(t);
            container.getLogger().error("Exception Processing " + request.getRequestURI(), t);
            // If a new error occurred while trying to report a previous
            // error allow the original error to be reported.
            if (!response.isErrorReportRequired()) {
                request.setAttribute(RequestDispatcher.ERROR_EXCEPTION, t);
                throwable(request, response, t);
            }
        }

        // Now that the request/response pair is back under container
        // control lift the suspension so that the error handling can
        // complete and/or the container can flush any remaining data
        response.setSuspended(false);

        Throwable t = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);

        // Protect against NPEs if the context was destroyed during a
        // long running request.
        if (!context.getState().isAvailable()) {
            return;
        }

        // Look for (and render if found) an application level error page
        if (response.isErrorReportRequired()) {
            // If an error has occurred that prevents further I/O, don't waste time
            // producing an error report that will never be read
            AtomicBoolean result = new AtomicBoolean(false);
            response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, result);
            if (result.get()) {
                if (t != null) {
                    throwable(request, response, t);
                } else {
                    status(request, response);
                }
            }
        }

        if (!request.isAsync() && !asyncAtStart) {
　　　　　　　//最侄訓呼叫 Servlet 監聽器 ServletRequestListener#requestDestroyed()
            context.fireRequestDestroyEvent(request.getRequest());
        }
    } finally {
        // Access a session (if present) to update last accessed time, based
        // on a strict interpretation of the specification
        if (ACCESS_SESSION) {
            request.getSession(false);
        }

        context.unbind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);
    }
}

StandardHostValve 作為末位valve, 同樣的, 肩負著啟動子節點的管道.

NonLoginAuthenticator

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

    if (log.isDebugEnabled()) {
        log.debug("Security checking request " + request.getMethod() + " " +
                request.getRequestURI());
    }

    // Have we got a cached authenticated Principal to record?
    if (cache) {
        Principal principal = request.getUserPrincipal();
        if (principal == null) {
            Session session = request.getSessionInternal(false);
            if (session != null) {
                principal = session.getPrincipal();
                if (principal != null) {
                    if (log.isDebugEnabled()) {
                        log.debug("We have cached auth type " + session.getAuthType() +
                                " for principal " + principal);
                    }
                    request.setAuthType(session.getAuthType());
                    request.setUserPrincipal(principal);
                }
            }
        }
    }

    boolean authRequired = isContinuationRequired(request);

    Realm realm = this.context.getRealm();
    // Is this request URI subject to a security constraint?
    SecurityConstraint[] constraints = realm.findSecurityConstraints(request, this.context);

    AuthConfigProvider jaspicProvider = getJaspicProvider();
    if (jaspicProvider != null) {
        authRequired = true;
    }

    if (constraints == null && !context.getPreemptiveAuthentication() && !authRequired) {
        if (log.isDebugEnabled()) {
            log.debug("Not subject to any constraint");
        }
        getNext().invoke(request, response);
        return;
    }

    // Make sure that constrained resources are not cached by web proxies
    // or browsers as caching can provide a security hole
    if (constraints != null && disableProxyCaching &&
            !"POST".equalsIgnoreCase(request.getMethod())) {
        if (securePagesWithPragma) {
            // Note: These can cause problems with downloading files with IE
            response.setHeader("Pragma", "No-cache");
            response.setHeader("Cache-Control", "no-cache");
        } else {
            response.setHeader("Cache-Control", "private");
        }
        response.setHeader("Expires", DATE_ONE);
    }

    if (constraints != null) {
        // Enforce any user data constraint for this security constraint
        if (log.isDebugEnabled()) {
            log.debug("Calling hasUserDataPermission()");
        }
        if (!realm.hasUserDataPermission(request, response, constraints)) {
            if (log.isDebugEnabled()) {
                log.debug("Failed hasUserDataPermission() test");
            }
            /*
             * ASSERT: Authenticator already set the appropriate HTTP status
             * code, so we do not have to do anything special
             */
            return;
        }
    }

    // Since authenticate modifies the response on failure,
    // we have to check for allow-from-all first.
    boolean hasAuthConstraint = false;
    if (constraints != null) {
        hasAuthConstraint = true;
        for (int i = 0; i < constraints.length && hasAuthConstraint; i++) {
            if (!constraints[i].getAuthConstraint()) {
                hasAuthConstraint = false;
            } else if (!constraints[i].getAllRoles() &&
                    !constraints[i].getAuthenticatedUsers()) {
                String[] roles = constraints[i].findAuthRoles();
                if (roles == null || roles.length == 0) {
                    hasAuthConstraint = false;
                }
            }
        }
    }

    if (!authRequired && hasAuthConstraint) {
        authRequired = true;
    }

    if (!authRequired && context.getPreemptiveAuthentication()) {
        authRequired =
                request.getCoyoteRequest().getMimeHeaders().getValue("authorization") != null;
    }

    if (!authRequired && context.getPreemptiveAuthentication() &&
            HttpServletRequest.CLIENT_CERT_AUTH.equals(getAuthMethod())) {
        X509Certificate[] certs = getRequestCertificates(request);
        authRequired = certs != null && certs.length > 0;
    }

    JaspicState jaspicState = null;

    if ((authRequired || constraints != null) && allowCorsPreflightBypass(request)) {
        if (log.isDebugEnabled()) {
            log.debug("CORS Preflight request bypassing authentication");
        }
        getNext().invoke(request, response);
        return;
    }

    if (authRequired) {
        if (log.isDebugEnabled()) {
            log.debug("Calling authenticate()");
        }

        if (jaspicProvider != null) {
            jaspicState = getJaspicState(jaspicProvider, request, response, hasAuthConstraint);
            if (jaspicState == null) {
                return;
            }
        }

        if (jaspicProvider == null && !doAuthenticate(request, response) ||
                jaspicProvider != null &&
                        !authenticateJaspic(request, response, jaspicState, false)) {
            if (log.isDebugEnabled()) {
                log.debug("Failed authenticate() test");
            }
            /*
             * ASSERT: Authenticator already set the appropriate HTTP status
             * code, so we do not have to do anything special
             */
            return;
        }

    }

    if (constraints != null) {
        if (log.isDebugEnabled()) {
            log.debug("Calling accessControl()");
        }
        if (!realm.hasResourcePermission(request, response, constraints, this.context)) {
            if (log.isDebugEnabled()) {
                log.debug("Failed accessControl() test");
            }
            /*
             * ASSERT: AccessControl method has already set the appropriate
             * HTTP status code, so we do not have to do anything special
             */
            return;
        }
    }

    // Any and all specified constraints have been satisfied
    if (log.isDebugEnabled()) {
        log.debug("Successfully passed all security constraints");
    }
    getNext().invoke(request, response);

    if (jaspicProvider != null) {
        secureResponseJspic(request, response, jaspicState);
    }
}

這個閥門是進行tomcat身份驗證的.

StandardContextValve

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

    // Disallow any direct access to resources under WEB-INF or META-INF
    MessageBytes requestPathMB = request.getRequestPathMB();
    if ((requestPathMB.startsWithIgnoreCase("/META-INF/", 0))
            || (requestPathMB.equalsIgnoreCase("/META-INF"))
            || (requestPathMB.startsWithIgnoreCase("/WEB-INF/", 0))
            || (requestPathMB.equalsIgnoreCase("/WEB-INF"))) {
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
        return;
    }

    // Select the Wrapper to be used for this Request
    Wrapper wrapper = request.getWrapper();
    if (wrapper == null || wrapper.isUnavailable()) {
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
        return;
    }

    // Acknowledge the request
    try {
        response.sendAcknowledgement();
    } catch (IOException ioe) {
        container.getLogger().error(sm.getString(
                "standardContextValve.acknowledgeException"), ioe);
        request.setAttribute(RequestDispatcher.ERROR_EXCEPTION, ioe);
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        return;
    }

    if (request.isAsyncSupported()) {
        request.setAsyncSupported(wrapper.getPipeline().isAsyncSupported());
    }
    //StandardWrapperValve#invoke()
    wrapper.getPipeline()   //-->StandardPipeline
            .getFirst()   //-->StandardWrapperValve
            .invoke(request, response);
}

StandardWrapperValve

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

    // Initialize local variables we may need
    boolean unavailable = false;
    Throwable throwable = null;
    // This should be a Request attribute...
    long t1=System.currentTimeMillis();
    //增加請求次數 CAS樂觀鎖的方式
    requestCount.incrementAndGet();
    StandardWrapper wrapper = (StandardWrapper) getContainer();
    Servlet servlet = null;
    Context context = (Context) wrapper.getParent();

    // Check for the application being marked unavailable
    if (!context.getState().isAvailable()) {
        response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                       sm.getString("standardContext.isUnavailable"));
        unavailable = true;
    }

    // Check for the servlet being marked unavailable
    if (!unavailable && wrapper.isUnavailable()) {
        container.getLogger().info(sm.getString("standardWrapper.isUnavailable",
                wrapper.getName()));
        long available = wrapper.getAvailable();
        if ((available > 0L) && (available < Long.MAX_VALUE)) {
            response.setDateHeader("Retry-After", available);
            response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                    sm.getString("standardWrapper.isUnavailable",
                            wrapper.getName()));
        } else if (available == Long.MAX_VALUE) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND,
                    sm.getString("standardWrapper.notFound",
                            wrapper.getName()));
        }
        unavailable = true;
    }

    // Allocate a servlet instance to process this request
    try {
        if (!unavailable) {
            servlet = wrapper.allocate();
        }
    }
    catch (UnavailableException e) {
        container.getLogger().error(
                sm.getString("standardWrapper.allocateException",
                        wrapper.getName()), e);
        long available = wrapper.getAvailable();
        if ((available > 0L) && (available < Long.MAX_VALUE)) {
            response.setDateHeader("Retry-After", available);
            response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                       sm.getString("standardWrapper.isUnavailable",
                                    wrapper.getName()));
        } else if (available == Long.MAX_VALUE) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND,
                       sm.getString("standardWrapper.notFound",
                                    wrapper.getName()));
        }
    }
    catch (ServletException e) {
        container.getLogger().error(sm.getString("standardWrapper.allocateException",
                         wrapper.getName()), StandardWrapper.getRootCause(e));
        throwable = e;
        exception(request, response, e);
    }
    catch (Throwable e) {
        ExceptionUtils.handleThrowable(e);
        container.getLogger().error(sm.getString("standardWrapper.allocateException",
                         wrapper.getName()), e);
        throwable = e;
        exception(request, response, e);
        servlet = null;
    }

    MessageBytes requestPathMB = request.getRequestPathMB();
    DispatcherType dispatcherType = DispatcherType.REQUEST;
    if (request.getDispatcherType()==DispatcherType.ASYNC) dispatcherType = DispatcherType.ASYNC;
    request.setAttribute(Globals.DISPATCHER_TYPE_ATTR,dispatcherType);
    request.setAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR, requestPathMB);
    // Create the filter chain for this request
    // 創建過濾器鏈
    ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);

    // Call the filter chain for this request
    // NOTE: This also calls the servlet's service() method
    try {
        if ((servlet != null) && (filterChain != null)) {
            // Swallow output if needed
            if (context.getSwallowOutput()) {
                try {
                    SystemLogHandler.startCapture();
                    if (request.isAsyncDispatching()) {
                        request.getAsyncContextInternal().doInternalDispatch();
                    } else {
                        //執行過濾鏈
                        filterChain.doFilter(request.getRequest(), response.getResponse());
                    }
                } finally {
                    String log = SystemLogHandler.stopCapture();
                    if (log != null && log.length() > 0) {
                        context.getLogger().info(log);
                    }
                }
            } else {
                if (request.isAsyncDispatching()) {
                    request.getAsyncContextInternal().doInternalDispatch();
                } else {
　　　　　　　　　　　　//執行過濾器鏈方法, 最侄訓執行 Servlet 的 service 方法
                    filterChain.doFilter(request.getRequest(), response.getResponse());
                }
            }

        }
    }
    catch (ClientAbortException | CloseNowException e) {
        if (container.getLogger().isDebugEnabled()) {
            container.getLogger().debug(sm.getString(
                    "standardWrapper.serviceException", wrapper.getName(),
                    context.getName()), e);
        }
        throwable = e;
        exception(request, response, e);
    }
    catch (IOException e) {
        container.getLogger().error(sm.getString(
                "standardWrapper.serviceException", wrapper.getName(),
                context.getName()), e);
        throwable = e;
        exception(request, response, e);
    }
    catch (UnavailableException e) {
        container.getLogger().error(sm.getString(
                "standardWrapper.serviceException", wrapper.getName(),
                context.getName()), e);
        //            throwable = e;
        //            exception(request, response, e);
        wrapper.unavailable(e);
        long available = wrapper.getAvailable();
        if ((available > 0L) && (available < Long.MAX_VALUE)) {
            response.setDateHeader("Retry-After", available);
            response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                       sm.getString("standardWrapper.isUnavailable",
                                    wrapper.getName()));
        } else if (available == Long.MAX_VALUE) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND,
                        sm.getString("standardWrapper.notFound",
                                    wrapper.getName()));
        }
        // Do not save exception in 'throwable', because we
        // do not want to do exception(request, response, e) processing
    }
    catch (ServletException e) {
        Throwable rootCause = StandardWrapper.getRootCause(e);
        if (!(rootCause instanceof ClientAbortException)) {
            container.getLogger().error(sm.getString(
                    "standardWrapper.serviceExceptionRoot",
                    wrapper.getName(), context.getName(), e.getMessage()),
                    rootCause);
        }
        throwable = e;
        exception(request, response, e);
    }
    catch (Throwable e) {
        ExceptionUtils.handleThrowable(e);
        container.getLogger().error(sm.getString(
                "standardWrapper.serviceException", wrapper.getName(),
                context.getName()), e);
        throwable = e;
        exception(request, response, e);
    }
    finally {
        // Release the filter chain (if any) for this request
        if (filterChain != null) {
            //釋放過濾鏈資源
            filterChain.release();
        }

        // Deallocate the allocated servlet instance
        try {
            if (servlet != null) {
                //會受到 Servlet 池例中
                wrapper.deallocate(servlet);
            }
        } catch (Throwable e) {
            ExceptionUtils.handleThrowable(e);
            container.getLogger().error(sm.getString("standardWrapper.deallocateException",
                             wrapper.getName()), e);
            if (throwable == null) {
                throwable = e;
                exception(request, response, e);
            }
        }

        // If this servlet has been marked permanently unavailable,
        // unload it and release this instance
        try {
            if ((servlet != null) &&
                (wrapper.getAvailable() == Long.MAX_VALUE)) {
                wrapper.unload();
            }
        } catch (Throwable e) {
            ExceptionUtils.handleThrowable(e);
            container.getLogger().error(sm.getString("standardWrapper.unloadException",
                             wrapper.getName()), e);
            if (throwable == null) {
                exception(request, response, e);
            }
        }
        long t2=System.currentTimeMillis();

        long time=t2-t1;
        processingTime += time;
        if( time > maxTime) maxTime=time;
        if( time < minTime) minTime=time;
    }
}

總結

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