spring web
源码
@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {
/**
* Delegate the {@code ServletContext} to any {@link WebApplicationInitializer}
* implementations present on the application classpath.
* <p>Because this class declares @{@code HandlesTypes(WebApplicationInitializer.class)},
* Servlet 3.0+ containers will automatically scan the classpath for implementations
* of Spring's {@code WebApplicationInitializer} interface and provide the set of all
* such types to the {@code webAppInitializerClasses} parameter of this method.
* <p>If no {@code WebApplicationInitializer} implementations are found on the classpath,
* this method is effectively a no-op. An INFO-level log message will be issued notifying
* the user that the {@code ServletContainerInitializer} has indeed been invoked but that
* no {@code WebApplicationInitializer} implementations were found.
* <p>Assuming that one or more {@code WebApplicationInitializer} types are detected,
* they will be instantiated (and <em>sorted</em> if the @{@link
* org.springframework.core.annotation.Order @Order} annotation is present or
* the {@link org.springframework.core.Ordered Ordered} interface has been
* implemented). Then the {@link WebApplicationInitializer#onStartup(ServletContext)}
* method will be invoked on each instance, delegating the {@code ServletContext} such
* that each instance may register and configure servlets such as Spring's
* {@code DispatcherServlet}, listeners such as Spring's {@code ContextLoaderListener},
* or any other Servlet API componentry such as filters.
* @param webAppInitializerClasses all implementations of
* {@link WebApplicationInitializer} found on the application classpath
* @param servletContext the servlet context to be initialized
* @see WebApplicationInitializer#onStartup(ServletContext)
* @see AnnotationAwareOrderComparator
*/
@Override
public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
throws ServletException {
List<WebApplicationInitializer> initializers = new LinkedList<>();
if (webAppInitializerClasses != null) {
for (Class<?> waiClass : webAppInitializerClasses) {
// Be defensive: Some servlet containers provide us with invalid classes,
// no matter what @HandlesTypes says...
if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
try {
initializers.add((WebApplicationInitializer)
ReflectionUtils.accessibleConstructor(waiClass).newInstance());
}
catch (Throwable ex) {
throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
}
}
}
}
if (initializers.isEmpty()) {
servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
return;
}
servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
AnnotationAwareOrderComparator.sort(initializers);
for (WebApplicationInitializer initializer : initializers) {
initializer.onStartup(servletContext);
}
}
}
WebApplicationInitializer 有4个实现类
1. AbstractContextLoaderInitializer
public abstract class AbstractContextLoaderInitializer implements WebApplicationInitializer {
/** Logger available to subclasses */
protected final Log logger = LogFactory.getLog(getClass());
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
registerContextLoaderListener(servletContext); //注册 监听器
}
/**
* Register a {@link ContextLoaderListener} against the given servlet context. The
* {@code ContextLoaderListener} is initialized with the application context returned
* from the {@link #createRootApplicationContext()} template method.
* @param servletContext the servlet context to register the listener against
*/
protected void registerContextLoaderListener(ServletContext servletContext) {
WebApplicationContext rootAppContext = createRootApplicationContext(); //创建web根容器
if (rootAppContext != null) {
ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);
listener.setContextInitializers(getRootApplicationContextInitializers());
servletContext.addListener(listener); //添加监听器
}
else {
logger.debug("No ContextLoaderListener registered, as " +
"createRootApplicationContext() did not return an application context");
}
}
/**
* Create the "<strong>root</strong>" application context to be provided to the
* {@code ContextLoaderListener}.
* <p>The returned context is delegated to
* {@link ContextLoaderListener#ContextLoaderListener(WebApplicationContext)} and will
* be established as the parent context for any {@code DispatcherServlet} application
* contexts. As such, it typically contains middle-tier services, data sources, etc.
* @return the root application context, or {@code null} if a root context is not
* desired
* @see org.springframework.web.servlet.support.AbstractDispatcherServletInitializer
*/
@Nullable
protected abstract WebApplicationContext createRootApplicationContext();
/**
* Specify application context initializers to be applied to the root application
* context that the {@code ContextLoaderListener} is being created with.
* @since 4.2
* @see #createRootApplicationContext()
* @see ContextLoaderListener#setContextInitializers
*/
@Nullable
protected ApplicationContextInitializer<?>[] getRootApplicationContextInitializers() {
return null;
}
}
2 . AbstractDispatcherServletInitializer
public abstract class AbstractDispatcherServletInitializer extends AbstractContextLoaderInitializer {
public static final String DEFAULT_SERVLET_NAME = "dispatcher";
public AbstractDispatcherServletInitializer() {
}
public void onStartup(ServletContext servletContext) throws ServletException {
super.onStartup(servletContext);
this.registerDispatcherServlet(servletContext);
}
protected void registerDispatcherServlet(ServletContext servletContext) {
String servletName = this.getServletName();
Assert.hasLength(servletName, "getServletName() must not return null or empty");
WebApplicationContext servletAppContext = this.createServletApplicationContext();
Assert.notNull(servletAppContext, "createServletApplicationContext() must not return null");
FrameworkServlet dispatcherServlet = this.createDispatcherServlet(servletAppContext);
Assert.notNull(dispatcherServlet, "createDispatcherServlet(WebApplicationContext) must not return null");
dispatcherServlet.setContextInitializers(this.getServletApplicationContextInitializers());
Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet); //添加servlet
if (registration == null) {
throw new IllegalStateException("Failed to register servlet with name '" + servletName + "'. Check if there is another servlet registered under the same name.");
} else {
registration.setLoadOnStartup(1);
registration.addMapping(this.getServletMappings()); //添加mapping
registration.setAsyncSupported(this.isAsyncSupported());
Filter[] filters = this.getServletFilters();
if (!ObjectUtils.isEmpty(filters)) {
Filter[] var7 = filters;
int var8 = filters.length;
for(int var9 = 0; var9 < var8; ++var9) {
Filter filter = var7[var9];
this.registerServletFilter(servletContext, filter);
}
}
this.customizeRegistration(registration);
}
}
protected String getServletName() {
return "dispatcher";
}
protected abstract WebApplicationContext createServletApplicationContext();
protected FrameworkServlet createDispatcherServlet(WebApplicationContext servletAppContext) {
return new DispatcherServlet(servletAppContext);
}
@Nullable
protected ApplicationContextInitializer<?>[] getServletApplicationContextInitializers() {
return null;
}
protected abstract String[] getServletMappings();
@Nullable
protected Filter[] getServletFilters() {
return null;
}
protected javax.servlet.FilterRegistration.Dynamic registerServletFilter(ServletContext servletContext, Filter filter) {
String filterName = Conventions.getVariableName(filter);
javax.servlet.FilterRegistration.Dynamic registration = servletContext.addFilter(filterName, filter);
if (registration == null) {
for(int counter = 0; registration == null; ++counter) {
if (counter == 100) {
throw new IllegalStateException("Failed to register filter with name '" + filterName + "'. Check if there is another filter registered under the same name.");
}
registration = servletContext.addFilter(filterName + "#" + counter, filter); //添加filter
}
}
registration.setAsyncSupported(this.isAsyncSupported());
registration.addMappingForServletNames(this.getDispatcherTypes(), false, new String[]{this.getServletName()});
return registration;
}
private EnumSet<DispatcherType> getDispatcherTypes() {
return this.isAsyncSupported() ? EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.INCLUDE, DispatcherType.ASYNC) : EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.INCLUDE);
}
protected boolean isAsyncSupported() {
return true;
}
protected void customizeRegistration(Dynamic registration) {
}
}
3 AbstractAnnotationConfigDispatcherServletInitializer
public abstract class AbstractAnnotationConfigDispatcherServletInitializer extends AbstractDispatcherServletInitializer {
public AbstractAnnotationConfigDispatcherServletInitializer() {
}
@Nullable
protected WebApplicationContext createRootApplicationContext() {
Class<?>[] configClasses = this.getRootConfigClasses();
if (!ObjectUtils.isEmpty(configClasses)) {
AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext(); //类似spring 中配置文件
context.register(configClasses);
return context;
} else {
return null;
}
}
protected WebApplicationContext createServletApplicationContext() {
AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
Class<?>[] configClasses = this.getServletConfigClasses();
if (!ObjectUtils.isEmpty(configClasses)) {
context.register(configClasses);
}
return context;
}
@Nullable
protected abstract Class<?>[] getRootConfigClasses();
@Nullable
protected abstract Class<?>[] getServletConfigClasses();
}
public abstract class AbstractContextLoaderInitializer implements WebApplicationInitializer { /** Logger available to subclasses */protected final Log logger = LogFactory.getLog(getClass());@Overridepublic void onStartup(ServletContext servletContext) throws ServletException { registerContextLoaderListener(servletContext);} /** * Register a {@link ContextLoaderListener} against the given servlet context. The * {@code ContextLoaderListener} is initialized with the application context returned * from the {@link #createRootApplicationContext()} template method. * @param servletContext the servlet context to register the listener against */protected void registerContextLoaderListener(ServletContext servletContext) { WebApplicationContext rootAppContext = createRootApplicationContext(); if (rootAppContext != null) { ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);listener.setContextInitializers(getRootApplicationContextInitializers());servletContext.addListener(listener);} else { logger.debug("No ContextLoaderListener registered, as " + "createRootApplicationContext() did not return an application context");} } /** * Create the "<strong>root</strong>" application context to be provided to the * {@code ContextLoaderListener}. * <p>The returned context is delegated to * {@link ContextLoaderListener#ContextLoaderListener(WebApplicationContext)} and will * be established as the parent context for any {@code DispatcherServlet} application * contexts. As such, it typically contains middle-tier services, data sources, etc. * @return the root application context, or {@code null} if a root context is not * desired * @see org.springframework.web.servlet.support.AbstractDispatcherServletInitializer */@Nullableprotected abstract WebApplicationContext createRootApplicationContext();/** * Specify application context initializers to be applied to the root application * context that the {@code ContextLoaderListener} is being created with. * @since 4.2 * @see #createRootApplicationContext() * @see ContextLoaderListener#setContextInitializers */@Nullableprotected ApplicationContextInitializer<?>[] getRootApplicationContextInitializers() { return null;}}