Java笔记Spring（七）

DispatcherServlet初始化，继续分析日志

主要部分：

1 23-May-2018 17:47:55.457 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.DispatcherServlet.initServletBean FrameworkServlet 'dispatcher': initialization started
2 23-May-2018 17:47:55.463 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.context.support.XmlWebApplicationContext.prepareRefresh Refreshing WebApplicationContext for namespace 'dispatcher-servlet': startup date [Wed May 23 17:47:55 CST 2018]; parent: Root WebApplicationContext
3 23-May-2018 17:47:55.464 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions Loading XML bean definitions from ServletContext resource [/WEB-INF/dispatcher-servlet2.xml]
4 23-May-2018 17:47:56.298 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.register Mapped "{[/user/get],methods=[GET],produces=[text/plain;charset=utf-8]}" onto public java.lang.String com.example.demo.controller.UserController.get(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
5 23-May-2018 17:47:56.424 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.initControllerAdviceCache Looking for @ControllerAdvice: WebApplicationContext for namespace 'dispatcher-servlet': startup date [Wed May 23 17:47:55 CST 2018]; parent: Root WebApplicationContext
6 23-May-2018 17:47:56.504 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.initControllerAdviceCache Looking for @ControllerAdvice: WebApplicationContext for namespace 'dispatcher-servlet': startup date [Wed May 23 17:47:55 CST 2018]; parent: Root WebApplicationContext
7 23-May-2018 17:47:56.686 INFO [RMI TCP Connection(3)-127.0.0.1] org.springframework.web.servlet.DispatcherServlet.initServletBean FrameworkServlet 'dispatcher': initialization completed in 1228 ms

public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware {

    /**
     * Overridden method of {@link HttpServletBean}, invoked after any bean properties
     * have been set. Creates this servlet's WebApplicationContext.
     */
    @Override
    protected final void initServletBean() throws ServletException {
        getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
        if (this.logger.isInfoEnabled()) {
            this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
        }
        long startTime = System.currentTimeMillis();

        try {
            this.webApplicationContext = initWebApplicationContext();
            initFrameworkServlet();
        }
        catch (ServletException ex) {
            this.logger.error("Context initialization failed", ex);
            throw ex;
        }
        catch (RuntimeException ex) {
            this.logger.error("Context initialization failed", ex);
            throw ex;
        }

        if (this.logger.isInfoEnabled()) {
            long elapsedTime = System.currentTimeMillis() - startTime;
            this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
                    elapsedTime + " ms");
        }
    }

    /**
     * Initialize and publish the WebApplicationContext for this servlet.
     * <p>Delegates to {@link #createWebApplicationContext} for actual creation
     * of the context. Can be overridden in subclasses.
     * @return the WebApplicationContext instance
     * @see #FrameworkServlet(WebApplicationContext)
     * @see #setContextClass
     * @see #setContextConfigLocation
     */
    protected WebApplicationContext initWebApplicationContext() {
        WebApplicationContext rootContext =
                WebApplicationContextUtils.getWebApplicationContext(getServletContext());
        WebApplicationContext wac = null;

        if (this.webApplicationContext != null) {
            // A context instance was injected at construction time -> use it
            wac = this.webApplicationContext;
            if (wac instanceof ConfigurableWebApplicationContext) {
                ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
                if (!cwac.isActive()) {
                    // The context has not yet been refreshed -> provide services such as
                    // setting the parent context, setting the application context id, etc
                    if (cwac.getParent() == null) {
                        // The context instance was injected without an explicit parent -> set
                        // the root application context (if any; may be null) as the parent
                        cwac.setParent(rootContext);
                    }
                    configureAndRefreshWebApplicationContext(cwac);
                }
            }
        }
        if (wac == null) {
            // No context instance was injected at construction time -> see if one
            // has been registered in the servlet context. If one exists, it is assumed
            // that the parent context (if any) has already been set and that the
            // user has performed any initialization such as setting the context id
            wac = findWebApplicationContext();
        }
        if (wac == null) {
            // No context instance is defined for this servlet -> create a local one
            wac = createWebApplicationContext(rootContext);
        }

        if (!this.refreshEventReceived) {
            // Either the context is not a ConfigurableApplicationContext with refresh
            // support or the context injected at construction time had already been
            // refreshed -> trigger initial onRefresh manually here.
            onRefresh(wac);// 都会执行一次
        }

        if (this.publishContext) {
            // Publish the context as a servlet context attribute.
            String attrName = getServletContextAttributeName();
            getServletContext().setAttribute(attrName, wac);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
                        "' as ServletContext attribute with name [" + attrName + "]");
            }
        }

        return wac;
    }

    protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
        if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
            // The application context id is still set to its original default value
            // -> assign a more useful id based on available information
            if (this.contextId != null) {
                wac.setId(this.contextId);
            }
            else {
                // Generate default id...
                wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
                        ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
            }
        }

        wac.setServletContext(getServletContext());
        wac.setServletConfig(getServletConfig());
        wac.setNamespace(getNamespace());// 通过设置namespace的方式，使得日志displayName不同
        wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));

        // The wac environment's #initPropertySources will be called in any case when the context
        // is refreshed; do it eagerly here to ensure servlet property sources are in place for
        // use in any post-processing or initialization that occurs below prior to #refresh
        ConfigurableEnvironment env = wac.getEnvironment();
        if (env instanceof ConfigurableWebEnvironment) {
            ((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
        }

        postProcessWebApplicationContext(wac);
        applyInitializers(wac);
        wac.refresh();
    }
}

initWebApplicationContext与ContextLoader中的initWebApplicationContext方式极其相似，ContextLoader是默认创建了XmlWebApplicationContext的实例，而这里获得的同样也是XmlWebApplicationContext的实例对象，实际是同一个对象。

同样，LoadBeanDefinitions获取的是web.xml中配置在servlet标签下init-param中key-value

    public static <T> Map<String, T> beansOfTypeIncludingAncestors(
            ListableBeanFactory lbf, Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
            throws BeansException {

        Assert.notNull(lbf, "ListableBeanFactory must not be null");// lbf = new DefaultListableBeanFactory();
        Map<String, T> result = new LinkedHashMap<String, T>(4);
        result.putAll(lbf.getBeansOfType(type, includeNonSingletons, allowEagerInit));
        if (lbf instanceof HierarchicalBeanFactory) {
            HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
            if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
                Map<String, T> parentResult = beansOfTypeIncludingAncestors(
                        (ListableBeanFactory) hbf.getParentBeanFactory(), type, includeNonSingletons, allowEagerInit);
                for (Map.Entry<String, T> entry : parentResult.entrySet()) {
                    String beanName = entry.getKey();
                    if (!result.containsKey(beanName) && !hbf.containsLocalBean(beanName)) {
                        result.put(beanName, entry.getValue());
                    }
                }
            }
        }
        return result;
    }

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
        implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
    @Override
    public <T> Map<String, T> getBeansOfType(Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
            throws BeansException {

        String[] beanNames = getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
        Map<String, T> result = new LinkedHashMap<String, T>(beanNames.length);
        for (String beanName : beanNames) {
            try {
                result.put(beanName, getBean(beanName, type));
            }
            catch (BeanCreationException ex) {
                Throwable rootCause = ex.getMostSpecificCause();
                if (rootCause instanceof BeanCurrentlyInCreationException) {
                    BeanCreationException bce = (BeanCreationException) rootCause;
                    if (isCurrentlyInCreation(bce.getBeanName())) {
                        if (this.logger.isDebugEnabled()) {
                            this.logger.debug("Ignoring match to currently created bean '" + beanName + "': " +
                                    ex.getMessage());
                        }
                        onSuppressedException(ex);
                        // Ignore: indicates a circular reference when autowiring constructors.
                        // We want to find matches other than the currently created bean itself.
                        continue;
                    }
                }
                throw ex;
            }
        }
        return result;
    }

    @Override
    public String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
        if (!isConfigurationFrozen() || type == null || !allowEagerInit) {
            return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);
        }
        Map<Class<?>, String[]> cache =
                (includeNonSingletons ? this.allBeanNamesByType : this.singletonBeanNamesByType);
        String[] resolvedBeanNames = cache.get(type);
        if (resolvedBeanNames != null) {
            return resolvedBeanNames;
        }
        resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true);
        if (ClassUtils.isCacheSafe(type, getBeanClassLoader())) {
            cache.put(type, resolvedBeanNames);
        }
        return resolvedBeanNames;
    }

    private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
        List<String> result = new ArrayList<String>();

        // Check all bean definitions. private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
        for (String beanName : this.beanDefinitionNames) {// 集中中的值来自与自动扫描装配 component-scan
            // Only consider bean as eligible if the bean name
            // is not defined as alias for some other bean.
            if (!isAlias(beanName)) {
                try {
                    RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                    // Only check bean definition if it is complete.
                    if (!mbd.isAbstract() && (allowEagerInit ||
                            ((mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading())) &&
                                    !requiresEagerInitForType(mbd.getFactoryBeanName()))) {
                        // In case of FactoryBean, match object created by FactoryBean.
                        boolean isFactoryBean = isFactoryBean(beanName, mbd);
                        BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
                        boolean matchFound =
                                (allowEagerInit || !isFactoryBean ||
                                        (dbd != null && !mbd.isLazyInit()) || containsSingleton(beanName)) &&
                                (includeNonSingletons ||
                                        (dbd != null ? mbd.isSingleton() : isSingleton(beanName))) &&
                                isTypeMatch(beanName, type);
                        if (!matchFound && isFactoryBean) {
                            // In case of FactoryBean, try to match FactoryBean instance itself next.
                            beanName = FACTORY_BEAN_PREFIX + beanName;
                            matchFound = (includeNonSingletons || mbd.isSingleton()) && isTypeMatch(beanName, type);
                        }
                        if (matchFound) {
                            result.add(beanName);
                        }
                    }
                }
                catch (CannotLoadBeanClassException ex) {
                    if (allowEagerInit) {
                        throw ex;
                    }
                    // Probably contains a placeholder: let's ignore it for type matching purposes.
                    if (this.logger.isDebugEnabled()) {
                        this.logger.debug("Ignoring bean class loading failure for bean '" + beanName + "'", ex);
                    }
                    onSuppressedException(ex);
                }
                catch (BeanDefinitionStoreException ex) {
                    if (allowEagerInit) {
                        throw ex;
                    }
                    // Probably contains a placeholder: let's ignore it for type matching purposes.
                    if (this.logger.isDebugEnabled()) {
                        this.logger.debug("Ignoring unresolvable metadata in bean definition '" + beanName + "'", ex);
                    }
                    onSuppressedException(ex);
                }
            }
        }

        // Check manually registered singletons too.
        for (String beanName : this.manualSingletonNames) {
            try {
                // In case of FactoryBean, match object created by FactoryBean.
                if (isFactoryBean(beanName)) {
                    if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {
                        result.add(beanName);
                        // Match found for this bean: do not match FactoryBean itself anymore.
                        continue;
                    }
                    // In case of FactoryBean, try to match FactoryBean itself next.
                    beanName = FACTORY_BEAN_PREFIX + beanName;
                }
                // Match raw bean instance (might be raw FactoryBean).
                if (isTypeMatch(beanName, type)) {
                    result.add(beanName);
                }
            }
            catch (NoSuchBeanDefinitionException ex) {
                // Shouldn't happen - probably a result of circular reference resolution...
                if (logger.isDebugEnabled()) {
                    logger.debug("Failed to check manually registered singleton with name '" + beanName + "'", ex);
                }
            }
        }

        return StringUtils.toStringArray(result);
    }
}