org.springframework.web.context.ConfigurableWebApplicationContext Java Examples

/**
 * Instantiate the WebApplicationContext for this servlet, either a default
 * {@link org.springframework.web.context.support.XmlWebApplicationContext}
 * or a {@link #setContextClass custom context class}, if set.
 * <p>This implementation expects custom contexts to implement the
 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
 * interface. Can be overridden in subclasses.
 * <p>Do not forget to register this servlet instance as application listener on the
 * created context (for triggering its {@link #onRefresh callback}, and to call
 * {@link org.springframework.context.ConfigurableApplicationContext#refresh()}
 * before returning the context instance.
 * @param parent the parent ApplicationContext to use, or {@code null} if none
 * @return the WebApplicationContext for this servlet
 * @see org.springframework.web.context.support.XmlWebApplicationContext
 */
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
	Class<?> contextClass = getContextClass();
	if (this.logger.isDebugEnabled()) {
		this.logger.debug("Servlet with name '" + getServletName() +
				"' will try to create custom WebApplicationContext context of class '" +
				contextClass.getName() + "'" + ", using parent context [" + parent + "]");
	}
	if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
		throw new ApplicationContextException(
				"Fatal initialization error in servlet with name '" + getServletName() +
				"': custom WebApplicationContext class [" + contextClass.getName() +
				"] is not of type ConfigurableWebApplicationContext");
	}
	ConfigurableWebApplicationContext wac =
			(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

	wac.setEnvironment(getEnvironment());
	wac.setParent(parent);
	wac.setConfigLocation(getContextConfigLocation());

	configureAndRefreshWebApplicationContext(wac);

	return wac;
}
 

@Override
public void initialize()
        throws ContainerInitializationException {
    Timer.start("SPRINGBOOT_COLD_START");

    SpringApplication app = new SpringApplication(
            springBootInitializer,
            ServerlessServletEmbeddedServerFactory.class,
            SpringBootServletConfigurationSupport.class
    );
    if (springProfiles != null && springProfiles.length > 0) {
        ConfigurableEnvironment springEnv = new StandardEnvironment();
        springEnv.setActiveProfiles(springProfiles);
        app.setEnvironment(springEnv);
    }
    ConfigurableApplicationContext applicationContext = app.run();

    ((ConfigurableWebApplicationContext)applicationContext).setServletContext(getServletContext());
    AwsServletRegistration reg = (AwsServletRegistration)getServletContext().getServletRegistration(DISPATCHER_SERVLET_REGISTRATION_NAME);
    if (reg != null) {
        reg.setLoadOnStartup(1);
    }
    super.initialize();
    initialized = true;
    Timer.stop("SPRINGBOOT_COLD_START");
}
 

/**
 * Instantiate the WebApplicationContext for this servlet, either a default
 * {@link org.springframework.web.context.support.XmlWebApplicationContext}
 * or a {@link #setContextClass custom context class}, if set.
 * <p>This implementation expects custom contexts to implement the
 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
 * interface. Can be overridden in subclasses.
 * <p>Do not forget to register this servlet instance as application listener on the
 * created context (for triggering its {@link #onRefresh callback}, and to call
 * {@link org.springframework.context.ConfigurableApplicationContext#refresh()}
 * before returning the context instance.
 * @param parent the parent ApplicationContext to use, or {@code null} if none
 * @return the WebApplicationContext for this servlet
 * @see org.springframework.web.context.support.XmlWebApplicationContext
 */
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
	Class<?> contextClass = getContextClass();
	if (this.logger.isDebugEnabled()) {
		this.logger.debug("Servlet with name '" + getServletName() +
				"' will try to create custom WebApplicationContext context of class '" +
				contextClass.getName() + "'" + ", using parent context [" + parent + "]");
	}
	if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
		throw new ApplicationContextException(
				"Fatal initialization error in servlet with name '" + getServletName() +
				"': custom WebApplicationContext class [" + contextClass.getName() +
				"] is not of type ConfigurableWebApplicationContext");
	}
	ConfigurableWebApplicationContext wac =
			(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

	wac.setEnvironment(getEnvironment());
	wac.setParent(parent);
	wac.setConfigLocation(getContextConfigLocation());

	configureAndRefreshWebApplicationContext(wac);

	return wac;
}
 

/**
 * Allows loading/override of custom bean definitions from sakai.home
 *
 * <p>The pattern is the 'servlet_name-context.xml'</p>
 *
 * @param sc current servlet context
 * @param wac the new WebApplicationContext
 */
@Override
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
	super.customizeContext(sc, wac);
	if (wac != null) {
		final String servletName = sc.getServletContextName();
		String location = getHomeBeanDefinitionIfExists(servletName);
		if (StringUtils.isNotBlank(location)) {
			String[] configLocations = wac.getConfigLocations();
			String[] newLocations = Arrays.copyOf(configLocations, configLocations.length + 1);
			newLocations[configLocations.length] = "file:" + location;
			wac.setConfigLocations(newLocations);
			log.info("Servlet {} added an additional bean config location [{}]", servletName, location);
		}
	}
}
 

/**
 * Instantiate the WebApplicationContext for this servlet, either a default
 * {@link org.springframework.web.context.support.XmlWebApplicationContext}
 * or a {@link #setContextClass custom context class}, if set.
 * <p>This implementation expects custom contexts to implement the
 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
 * interface. Can be overridden in subclasses.
 * <p>Do not forget to register this servlet instance as application listener on the
 * created context (for triggering its {@link #onRefresh callback}, and to call
 * {@link org.springframework.context.ConfigurableApplicationContext#refresh()}
 * before returning the context instance.
 * @param parent the parent ApplicationContext to use, or {@code null} if none
 * @return the WebApplicationContext for this servlet
 * @see org.springframework.web.context.support.XmlWebApplicationContext
 */
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
	Class<?> contextClass = getContextClass();
	if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
		throw new ApplicationContextException(
				"Fatal initialization error in servlet with name '" + getServletName() +
				"': custom WebApplicationContext class [" + contextClass.getName() +
				"] is not of type ConfigurableWebApplicationContext");
	}
	ConfigurableWebApplicationContext wac =
			(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

	wac.setEnvironment(getEnvironment());
	wac.setParent(parent);
	String configLocation = getContextConfigLocation();
	if (configLocation != null) {
		wac.setConfigLocation(configLocation);
	}
	configureAndRefreshWebApplicationContext(wac);

	return wac;
}
 

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
    Class<?> contextClass = getContextClass();
    if (this.logger.isDebugEnabled()) {
        this.logger.debug("Servlet with name '" + getServletName() +
                "' will try to create custom WebApplicationContext context of class '" +
                contextClass.getName() + "'" + ", using parent context [" + parent + "]");
    }
    if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
        throw new ApplicationContextException(
                "Fatal initialization error in servlet with name '" + getServletName() +
                "': custom WebApplicationContext class [" + contextClass.getName() +
                "] is not of type ConfigurableWebApplicationContext");
    }
    ConfigurableWebApplicationContext wac =
            (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
    
    wac.setParent(parent);
    if (wac.getParent() == null) {
        ApplicationContext rootContext = (ApplicationContext) getServletContext().getAttribute("JetStreamRoot");
        wac.setParent(rootContext);
    }
    wac.setConfigLocation(getContextConfigLocation());
    configureAndRefreshWebApplicationContext(wac);
    return wac;
}
 

@Test
public void should_cancel_register_task_on_context_close() {
	ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
	ThreadPoolTaskScheduler scheduler = mock(ThreadPoolTaskScheduler.class);
	RegistrationApplicationListener listener = new RegistrationApplicationListener(registrator, scheduler);

	ScheduledFuture<?> task = mock(ScheduledFuture.class);
	when(scheduler.scheduleAtFixedRate(isA(Runnable.class), eq(Duration.ofSeconds(10)))).then((invocation) -> task);

	listener.onApplicationReady(new ApplicationReadyEvent(mock(SpringApplication.class), null,
			mock(ConfigurableWebApplicationContext.class)));
	verify(scheduler).scheduleAtFixedRate(isA(Runnable.class), eq(Duration.ofSeconds(10)));

	listener.onClosedContext(new ContextClosedEvent(mock(WebApplicationContext.class)));
	verify(task).cancel(true);
}
 

/**
 * Allows loading/override of custom bean definitions from sakai.home
 *
 * <p>The pattern is the 'servlet_name-context.xml'</p>
 *
 * @param sc current servlet context
 * @param wac the new WebApplicationContext
 */
@Override
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
	super.customizeContext(sc, wac);
	if (wac != null) {
		final String servletName = sc.getServletContextName();
		String location = getHomeBeanDefinitionIfExists(servletName);
		if (StringUtils.isNotBlank(location)) {
			String[] configLocations = wac.getConfigLocations();
			String[] newLocations = Arrays.copyOf(configLocations, configLocations.length + 1);
			newLocations[configLocations.length] = "file:" + location;
			wac.setConfigLocations(newLocations);
			log.info("Servlet {} added an additional bean config location [{}]", servletName, location);
		}
	}
}
 

protected WebApplicationContext createWebApplicationContext(ServletContext sc, ApplicationContext parent)
{
	GenericWebApplicationContext wac = (GenericWebApplicationContext) BeanUtils.instantiateClass(GenericWebApplicationContext.class);

	// Assign the best possible id value.
	wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + contextPath);

	wac.setParent(parent);
	wac.setServletContext(sc);
	wac.refresh();

	return wac;
}
 

/**
 * Creates a new container handler with the given reader and writer objects
 *
 * @param requestTypeClass The class for the incoming Lambda event
 * @param requestReader An implementation of `RequestReader`
 * @param responseWriter An implementation of `ResponseWriter`
 * @param securityContextWriter An implementation of `SecurityContextWriter`
 * @param exceptionHandler An implementation of `ExceptionHandler`
 */
public SpringLambdaContainerHandler(Class<RequestType> requestTypeClass,
                                    Class<ResponseType> responseTypeClass,
                                    RequestReader<RequestType, HttpServletRequest> requestReader,
                                    ResponseWriter<AwsHttpServletResponse, ResponseType> responseWriter,
                                    SecurityContextWriter<RequestType> securityContextWriter,
                                    ExceptionHandler<ResponseType> exceptionHandler,
                                    ConfigurableWebApplicationContext applicationContext,
                                    InitializationWrapper init) {
    super(requestTypeClass, responseTypeClass, requestReader, responseWriter, securityContextWriter, exceptionHandler);
    Timer.start("SPRING_CONTAINER_HANDLER_CONSTRUCTOR");
    appContext = applicationContext;
    setInitializationWrapper(init);
    Timer.stop("SPRING_CONTAINER_HANDLER_CONSTRUCTOR");
}
 

@Order(0)
@Bean(initMethod="start", destroyMethod="stop")
public Server httpServer(
        @Value("${http.hostname}") String hostname,
        @Value("${http.port}") int port,
        ConfigurableWebApplicationContext webApplicationContext) {

    // set up servlets
    ServletHandler servlets = new ServletHandler();
    ServletContextHandler context = new ServletContextHandler(ServletContextHandler.NO_SESSIONS | ServletContextHandler.NO_SECURITY);
    context.setErrorHandler(null);
    context.setWelcomeFiles(new String[] { "/" });

    // set up spring with the servlet context
    setServletContext(context.getServletContext());

    // configure the spring mvc dispatcher
    DispatcherServlet dispatcher = new DispatcherServlet(webApplicationContext);

    // map application servlets
    context.addServlet(new ServletHolder(dispatcher), "/");

    servlets.setHandler(context);

    // create the server
    InetSocketAddress address = StringUtils.isBlank(hostname) ? new InetSocketAddress(port) : new InetSocketAddress(hostname, port);
    Server server = new Server();
    ServerConnector connector = new ServerConnector(server);
    connector.setHost(address.getHostName());
    connector.setPort(address.getPort());
    server.setConnectors(new Connector[]{ connector });
    server.setHandler(servlets);

    return server;
}
 

private Collection<ObjectMapper> getObjectMappers(ConfigurableWebApplicationContext webApplicationContext) {
    Map<String, JacksonMessageSerDe> serdes = webApplicationContext.getBeansOfType(JacksonMessageSerDe.class);
    if(serdes.isEmpty()){
        return Collections.emptyList();
    }
    return Collections2.transform(serdes.values(), new Function<JacksonMessageSerDe, ObjectMapper>() {
        @Nullable
        @Override
        public ObjectMapper apply(@Nullable JacksonMessageSerDe serDe) {
            return serDe.getObjectMapper();
        }
    });
}
 

@Override
public void initialize(ConfigurableWebApplicationContext configurableWebApplicationContext) {
    ConfigurableEnvironment environment = configurableWebApplicationContext.getEnvironment();
    if (environment.getSystemEnvironment().containsKey("MONGODB_PORT_27017_TCP_ADDR") &&
            environment.getSystemEnvironment().containsKey("MONGODB_PORT_27017_TCP_PORT")) {
        environment.setActiveProfiles("docker");
    }
    if (!hasActiveProfile(environment)) {
        environment.setActiveProfiles("production");
    }
    LOGGER.info("Active profiles are {}", StringUtils.join(environment.getActiveProfiles(), ","));
}
 

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());
	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();
}
 

@Override
@Nonnull
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
    if (this.logger.isDebugEnabled()) {
        this.logger.debug(
                String.format("Servlet with name '%s' will try to create custom WebApplicationContext context of class '%s', using parent context [%s]",
                        getServletName(), CubaXmlWebApplicationContext.class.getName(), parent));
    }
    ConfigurableWebApplicationContext wac = new CubaXmlWebApplicationContext() {
        @Override
        protected ResourcePatternResolver getResourcePatternResolver() {
            return new SingleAppResourcePatternResolver(this, libFolder);
        }
    };

    String contextConfigLocation = getContextConfigLocation();
    if (contextConfigLocation == null) {
        throw new RuntimeException("Unable to determine context config location");
    }

    wac.setEnvironment(getEnvironment());
    wac.setParent(parent);
    wac.setConfigLocation(contextConfigLocation);

    configureAndRefreshWebApplicationContext(wac);

    return wac;
}
 

@Test
@SuppressWarnings("deprecation")
public void nullMessageSource() throws JspException {
	PageContext pc = createPageContext();
	ConfigurableWebApplicationContext ctx = (ConfigurableWebApplicationContext)
			RequestContextUtils.getWebApplicationContext(pc.getRequest(), pc.getServletContext());
	ctx.close();

	MessageTag tag = new MessageTag();
	tag.setPageContext(pc);
	tag.setCode("test");
	tag.setVar("testvar2");
	tag.doStartTag();
	assertEquals("Correct doEndTag return value", Tag.EVAL_PAGE, tag.doEndTag());
}
 

@Override
public void initialize(ConfigurableWebApplicationContext configurableWebApplicationContext) {
    ConfigurableEnvironment environment = configurableWebApplicationContext.getEnvironment();
    if (environment.getSystemEnvironment().containsKey("MONGODB_PORT_27017_TCP_ADDR") &&
            environment.getSystemEnvironment().containsKey("MONGODB_PORT_27017_TCP_PORT")) {
        environment.setActiveProfiles("docker");
    }
    if (!hasActiveProfile(environment)) {
        environment.setActiveProfiles("production");
    }
    LOGGER.info("Active profiles are {}", StringUtils.join(environment.getActiveProfiles(), ","));
}
 

@Override
protected void customizeContext(ServletContext servletContext, ConfigurableWebApplicationContext configurableWebApplicationContext) {
    super.customizeContext(servletContext, configurableWebApplicationContext);

    ResteasyDeployment deployment = (ResteasyDeployment) servletContext.getAttribute(ResteasyDeployment.class.getName());
    if (deployment == null) {
        throw new RuntimeException(Messages.MESSAGES.deploymentIsNull());
    }

    SpringBeanProcessor processor = new SpringBeanProcessor(deployment);
    configurableWebApplicationContext.addBeanFactoryPostProcessor(processor);
    configurableWebApplicationContext.addApplicationListener(processor);
}
 

@Override
protected void customizeContext(final ServletContext servletContext, final ConfigurableWebApplicationContext applicationContext) {
    super.customizeContext(servletContext, applicationContext);

    final String[] newLocations = cloudStackContext.getConfigLocationsForWeb(configuredParentName, applicationContext.getConfigLocations());

    applicationContext.setConfigLocations(newLocations);
}
 

/**
 * Creates a default SpringLambdaContainerHandler initialized with the `AwsProxyRequest` and `AwsProxyResponse` objects and sets the given profiles as active
 * @param applicationContext A custom ConfigurableWebApplicationContext to be used
 * @param profiles The spring profiles to activate
 * @return An initialized instance of the `SpringLambdaContainerHandler`
 * @throws ContainerInitializationException When the Spring framework fails to start.
 */
public static SpringLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> getAwsProxyHandler(ConfigurableWebApplicationContext applicationContext, String... profiles)
        throws ContainerInitializationException {
    return new SpringProxyHandlerBuilder<AwsProxyRequest>()
            .defaultProxy()
            .initializationWrapper(new InitializationWrapper())
            .springApplicationContext(applicationContext)
            .profiles(profiles)
            .buildAndInitialize();
}
 

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());
	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();
}
 

@Override
public void initialize(ConfigurableWebApplicationContext ctx) {
    // vars are searched in order: spring > jvm > env > app.prop > airsonic.prop > default consts
    // spring: java -jar pkg.jar --var=foo
    // jvm: java -jar -Dvar=foo pkg.jar
    // env: SET var=foo; java -jar pkg.jar

    Map<String, String> migratedProps = SettingsService.getMigratedPropertyKeys();

    // Migrate each property source key to its latest name
    // PropertySource precedence matters. Higher migrates first, lower will skip migration if key has already migrated
    // At lookup time, migrated properties have lower precedence (so more specific properties can override migrated properties)
    // Example for same start: env (higher precedence) and file (lower) need to migrate A -> B and both have A
    //  - env migrates A -> B, file skips chain (migration keys already present)
    //  - Lookup(A) will find env[A] (higher precedence)
    //  - Lookup(B) will find migrated[env[A]] since B does not exist in env and file, and migrated has env[A] (skipped file)
    // Example 1 for in-the-middle chain migration: env has C and file has A in migration A -> B -> C -> D
    //  - env migrates C -> D, file migrates A -> B (skips rest of the chain)
    //  - Lookup(A) finds file[A]
    //  - Lookup(B) finds migrated[file[A]]
    //  - Lookup(C) finds env[C]
    //  - Lookup(D) finds migrated[env[C]]
    // Example 2 for in-the-middle chain migration: env has A and file has C in migration A -> B -> C -> D
    //  - env migrates A -> B -> C -> D, file skips chain (migration keys already present)
    //  - Lookup(A) finds env[A]
    //  - Lookup(B) finds migrated[env[A]]
    //  - Lookup(C) finds file[C] (higher precedence than migrated[env[C]])
    //  - Lookup(D) finds migrated[env[A]]
    ctx.getEnvironment().getPropertySources().forEach(ps -> SettingsService.migratePropertySourceKeys(migratedProps, ps, MIGRATED));
    ctx.getEnvironment().getPropertySources().addLast(new MapPropertySource("migrated-properties", MIGRATED));

    // Migrate external property file
    SettingsService.migratePropFileKeys(migratedProps, ConfigurationPropertiesService.getInstance());
    ctx.getEnvironment().getPropertySources().addLast(new ConfigurationPropertySource("airsonic-properties", ConfigurationPropertiesService.getInstance().getConfiguration()));

    // Set default constants - only set if vars are blank so their PS need to be set first (or blank vars will get picked up first on look up)
    SettingsService.setDefaultConstants(ctx.getEnvironment(), DEFAULT_CONSTANTS);
    ctx.getEnvironment().getPropertySources().addFirst(new MapPropertySource("default-constants", DEFAULT_CONSTANTS));
}
 

/**
 * Instantiate the WebApplicationContext for this servlet, either a default
 * {@link org.springframework.web.context.support.XmlWebApplicationContext}
 * or a {@link #setContextClass custom context class}, if set.
 * <p>This implementation expects custom contexts to implement the
 * {@link org.springframework.web.context.ConfigurableWebApplicationContext}
 * interface. Can be overridden in subclasses.
 * <p>Do not forget to register this servlet instance as application listener on the
 * created context (for triggering its {@link #onRefresh callback}, and to call
 * {@link org.springframework.context.ConfigurableApplicationContext#refresh()}
 * before returning the context instance.
 * @param parent the parent ApplicationContext to use, or {@code null} if none
 * @return the WebApplicationContext for this servlet
 * @see org.springframework.web.context.support.XmlWebApplicationContext
 */
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
	// 允许我们自定义容器的类型，通过 contextClass 属性进行配置
	// 但是类型必须要继承 ConfigurableWebApplicationContext，不然将会报错
	Class<?> contextClass = getContextClass();
	if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
		throw new ApplicationContextException(
				"Fatal initialization error in servlet with name '" + getServletName() +
				"': custom WebApplicationContext class [" + contextClass.getName() +
				"] is not of type ConfigurableWebApplicationContext");
	}
	// 通过反射来创建 contextClass
	ConfigurableWebApplicationContext wac =
			(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

	wac.setEnvironment(getEnvironment());
	wac.setParent(parent);
	// 获取 contextConfigLocation 属性，配置在 servlet 初始化函数中
	String configLocation = getContextConfigLocation();
	if (configLocation != null) {
		wac.setConfigLocation(configLocation);
	}
	// 初始化 Spring 环境包括加载配置环境
	configureAndRefreshWebApplicationContext(wac);

	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... 生成默认ID
			wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
					ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
		}
	}

	wac.setServletContext(getServletContext());
	wac.setServletConfig(getServletConfig());
	wac.setNamespace(getNamespace());
	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);
	// 遍历 ApplicationContextInitializer，执行 initialize 方法
	applyInitializers(wac);
	// 关键的刷新，加载配置文件及整合 parent 到 wac
	wac.refresh();
}
 

protected List<String> getTomcatContextPropertyLocations(ConfigurableApplicationContext applicationContext) {
    if (!(applicationContext instanceof ConfigurableWebApplicationContext)) {
        return Collections.emptyList();
    }
    ConfigurableWebApplicationContext webApplicationContext = (ConfigurableWebApplicationContext) applicationContext;
    List<String> locations = Lists.newArrayList();
    final String tomcatContextPropertiesFile = webApplicationContext.getServletContext().getInitParameter(contextPropertiesParameterName);
    locations.add("file:" + tomcatContextPropertiesFile);
    return locations;
}
 

@Test
public void nullMessageSource() throws JspException {
	PageContext pc = createPageContext();
	ConfigurableWebApplicationContext ctx = (ConfigurableWebApplicationContext)
			RequestContextUtils.findWebApplicationContext((HttpServletRequest) pc.getRequest(), pc.getServletContext());
	ctx.close();

	MessageTag tag = new MessageTag();
	tag.setPageContext(pc);
	tag.setCode("test");
	tag.setVar("testvar2");
	tag.doStartTag();
	assertEquals("Correct doEndTag return value", Tag.EVAL_PAGE, tag.doEndTag());
}
 

@Override
protected void customizeContext(ServletContext servletContext, ConfigurableWebApplicationContext applicationContext) {
    super.customizeContext(servletContext, applicationContext);

    String[] newLocations = cloudStackContext.getConfigLocationsForWeb(configuredParentName, applicationContext.getConfigLocations());

    applicationContext.setConfigLocations(newLocations);
}
 

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());
	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();
}
 

@Override
protected WebApplicationContext createRootApplicationContext() {
    ConfigurableWebApplicationContext ctx = ((ConfigurableWebApplicationContext) super.createRootApplicationContext());
    Objects.requireNonNull(ctx, "Something really bad is happening...");
    this.environment = ctx.getEnvironment();
    return ctx;
}
 

@Test
public void nullMessageSource() throws JspException {
	PageContext pc = createPageContext();
	ConfigurableWebApplicationContext ctx = (ConfigurableWebApplicationContext)
			RequestContextUtils.findWebApplicationContext((HttpServletRequest) pc.getRequest(), pc.getServletContext());
	ctx.close();

	MessageTag tag = new MessageTag();
	tag.setPageContext(pc);
	tag.setCode("test");
	tag.setVar("testvar2");
	tag.doStartTag();
	assertEquals("Correct doEndTag return value", Tag.EVAL_PAGE, tag.doEndTag());
}