用SpringMVC源码解析之配置加载SpringServletContainerInitializer
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@Override
public void onStartup(Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
throws ServletException {
List<WebApplicationInitializer> initializers = new LinkedList<WebApplicationInitializer>();
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) waiClass.newInstance());
}
catch（Throwable ex）{
throw new ServletException（“无法实例化WebApplicationInitializer类”，ex）;
}
}
}
}
如果（initializers.isEmpty（））{
servletContext.log（ “检测到的无弹簧WebApplicationInitializer类型上的类路径”）;
返回;
}
servletContext.log（initializers.size（）+ “类路径上检测到的弹簧WebApplicationInitializers”）;
AnnotationAwareOrderComparator.sort（初始化）;
for（WebApplicationInitializer initializer：initializers）{
initializer.onStartup（servletContext）;
}
/ [mw_shl_code]
[color=#000][font=sans-serif][size=16px]进入到DispatcherServlet初始化器org.springframework.web.servlet.support.AbstractDispatcherServletInitializer＃onStartup这个方法[/size][/font][/color]
[mw_shl_code=applescript,true] @Override
public void onStartup(ServletContext servletContext) throws ServletException {
//调用上下文加载器初始化类的onStartup方法
super.onStartup(servletContext);
//注册DispatcherServlet
registerDispatcherServlet(servletContext);
}
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进入到这个方法org.springframework.web.context.AbstractContextLoaderInitializer#onStartup，执行ContextLoader初始化器
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@Override
public void onStartup(ServletContext servletContext) throws ServletException {
registerContextLoaderListener(servletContext);
}
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进入到这个方法org.springframework.web.context.AbstractContextLoaderInitializer#registerContextLoaderListener，注册ContextLoader监听器
[mw_shl_code = applescript，true] protected void registerContextLoaderListener（ServletContext servletContext）{
//获取上层应用上下文对象 - >
WebApplicationContext rootAppContext = createRootApplicationContext（）;
if（rootAppContext！= null）{
//创建上下文加载监听器
ContextLoaderListener listener = new ContextLoaderListener（rootAppContext）;
listener.setContextInitializers（getRootApplicationContextInitializers（））;
//把上下文加载监听器加载到servlet容器
servletContext.addListener（listener）;
}
else {
logger.debug（“没有注册ContextLoaderListener，因为”+
“createRootApplicationContext（）没有返回应用程序上下文”）;
}
} [/ mw_shl_code]
进入到这个方法org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer#createRootApplicationContext
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@Override
protected WebApplicationContext createRootApplicationContext() {
//从子类实现中或者从@Configuration、@Component注解配置中获取配置类
Class<?>[] configClasses = getRootConfigClasses();
if (!ObjectUtils.isEmpty(configClasses)) {
// 如果没有配置就默认初始化基于注解的web应用上下文类
AnnotationConfigWebApplicationContext rootAppContext = new AnnotationConfigWebApplicationContext();
rootAppContext.register(configClasses);
return rootAppContext;
}
else {
return null;
}
}
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进入到这个方法org.springframework.web.context.AbstractContextLoaderInitializer#getRootApplicationContextInitializers
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protected ApplicationContextInitializer<?>[] getRootApplicationContextInitializers() {
return null;
}
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返回到这个方法org.springframework.web.servlet.support.AbstractDispatcherServletInitializer#onStartup这一行
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// 注册DispatcherServlet
registerDispatcherServlet(servletContext);
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进入到这个方法org.springframework.web.servlet.support.AbstractDispatcherServletInitializer#registerDispatcherServlet
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protected void registerDispatcherServlet(ServletContext servletContext) {
//获取servletName，默认名称是dispatcher
String servletName = getServletName（）;
Assert.hasLength（servletName，“getServletName（）不能返回空或null”）;
//创建servlet程序上下文 - >
WebApplicationContext servletAppContext = createServletApplicationContext（）;
Assert.notNull（servletAppContext，
“createServletApplicationContext（）没有返回
servlet [”+ servletName +“]”）的应用程序“+ ”上下文;
//创建DispatcherServlet
FrameworkServlet dispatcherServlet = createDispatcherServlet（servletAppContext）;
//注册的servlet上下文初始化器，这里是模板实现
dispatcherServlet.setContextInitializers（getServletApplicationContextInitializers（））;
//添加的DispatcherServlet到的servlet容器
ServletRegistration.Dynamic registration = servletContext.addServlet（servletName，dispatcherServlet）;
Assert.notNull（注册，
“无法注册名称为'的servlet +”+ servletName +“'。”+
“检查是否有另一个以相同名称注册的servlet。”）;
registration.setLoadOnStartup（1）;
//获取servletMapping实现，这里是抽象实现，注册映射
registration.addMapping（getServletMappings（））;
//设置是否支持异步，默认支持
registration.setAsyncSupported（isAsyncSupported（））;
//获取servletFilter，这里是模板实现
Filter [] filters = getServletFilters（）;
if（！ObjectUtils.isEmpty（filters））{
for（Filter filter：filters）{
//注册过滤器 - >
registerServletFilter（servletContext，filter）;
//定制化注册，默认是模板实现
customizeRegistration(registration);
}
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进入到这个方法org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer#createServletApplicationContext
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@Override
protected WebApplicationContext createServletApplicationContext() {
//创建基于注解的web应用上下文
AnnotationConfigWebApplicationContext servletAppContext = new AnnotationConfigWebApplicationContext();
//从子类实现中或者从@Configuration、@Component注解配置中获取配置类
Class<?>[] configClasses = getServletConfigClasses();
if (!ObjectUtils.isEmpty(configClasses)) {
// 注册@Configuration配置的配置加载类到AnnotationConfigWebApplicationContext
servletAppContext.register(configClasses);
}
return servletAppContext;
}
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进入到这个方法org.springframework.web.servlet.support.AbstractDispatcherServletInitializer#registerServletFilter
[mw_shl_code=applescript,true]protected FilterRegistration.Dynamic registerServletFilter(ServletContext servletContext, Filter filter) {
//获取filteName
String filterName = Conventions.getVariableName(filter);
//添加filter到servlet容器
Dynamic registration = servletContext.addFilter(filterName, filter);
//如果filter注册失败
if (registration == null) {
int counter = -1;
while (counter == -1 || registration == null) {
counter++;
//添加filter#0 到servlet容器
registration = servletContext.addFilter(filterName + "#" + counter, filter);
//提示有同样的名字的过滤器已注册过
Assert.isTrue（计数器<100，
“无法注册过滤器'”+过滤器+“'。”+
“可能已经注册了相同的过滤器实例吗？”）;
}
}
//是否支持异步，默认是
registration.setAsyncSupported（isAsyncSupported（））;
registration.addMappingForServletNames（getDispatcherTypes（），false，getServletName（））;
退货登记;
} [/ mw_shl_code]
原文 - 微信公众号：天河聊架构
