springmvc-web.xml配置
<servlet>
<servlet-name>dispatch</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--springmvc配置文件加载路径-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring/mvc/*.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
<async-supported>true</async-supported>
</servlet>
<servlet-mapping>
<servlet-name>dispatch</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
DispatcherServlet类结构
查看源码可以得知类结构如下
本文将对Dispatcher的父类作下向导，方便读者以及博主自我查阅
HttpServletBean-web服务抽象类
具体的介绍可以详看官方注释，这里我们只关注它的init方法，代码如下
//开始初始化springmvc servlet，并实例化相应的PropertyValues供子类调用
public final void init() throws ServletException {
if (logger.isDebugEnabled()) {
logger.debug("Initializing servlet '" + getServletName() + "'");
}
// Set bean properties from init parameters.
try {
//此处便是读取<servlet>节点中的<init-param>参数保存至MutablePropertyValues#propertyValueList集合中
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
//默认为空
initBeanWrapper(bw);
//将bean与属性关联
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
throw ex;
}
// Let subclasses do whatever initialization they like.供子类复写
initServletBean();
if (logger.isDebugEnabled()) {
logger.debug("Servlet '" + getServletName() + "' configured successfully");
}
}
FrameworkServlet-结合spring的web抽象类
官方简单的解释为：Spring的web基本servlet框架，通过基于javaBean解决方式来集合Spring的application context上下文。
- ApplicationContextAware接口
该接口的使用主要是为当前类可以拥有spring application context上下文类，可方便的获取bean对象，内部只有一个接口方法setApplicationContext(ApplicationContext app)，在FrameworkServlet中的实现
public void setApplicationContext(ApplicationContext applicationContext) {
//由spring调用并进行相应的applicationContext的注入
if (this.webApplicationContext == null && applicationContext instanceof WebApplicationContext) {
this.webApplicationContext = (WebApplicationContext) applicationContext;
this.webApplicationContextInjected = true;
}
}
doService()-抽象接口
主要是供子类去实现处理servlet的请求复写
initServletBean()方法，完善功能
@Override
protected final void initServletBean() throws ServletException {
//打印我们熟悉的日志
getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
if (this.logger.isInfoEnabled()) {
this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
}
//对该方法的初始化时间作下统计
long startTime = System.currentTimeMillis();
try {
//此处的初始化操作类似于ContextLoader#initWebApplicationContext
this.webApplicationContext = initWebApplicationContext();
//供子类调用去初始化另外的功能
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");
}
}
- 承接
initServletBean()方法的initWebApplicationContext()，代码如下
protected WebApplicationContext initWebApplicationContext() {
//一般来说,spring初始化时间比springmvc要早，所以rootContext一般都存在
WebApplicationContext rootContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
//先检查spring是否已经注入了webApplicationContext，其中的刷新操作类似于`ContextLoader#initWebApplicationContext`，初次调用此处为空
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()) {
if (cwac.getParent() == null) {
//springmvc的父类为spring上下文
cwac.setParent(rootContext);
}
//此处方法不同于`ContextLoader`的相同方法
configureAndRefreshWebApplicationContext(cwac);
}
}
}
//再而尝试从ServletContext的`contextAttribute`对应的值去获取
if (wac == null) {
wac = findWebApplicationContext();
}
//不然则创建新的webApplicationContext
if (wac == null) {
wac = createWebApplicationContext(rootContext);
}
//springmvc的第一次刷新
if (!this.refreshEventReceived) {
//调用子类的onRefresh(wac)方法初始化springmvc
onRefresh(wac);
}
//保存至servletContext属性中
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;
}
FrameworkServlet#createWebApplicationContext()-springmvc创建上下文对象
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
//默认为XmlWebApplicationContext.class也可指定contextClass属性在web.xml
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);
//设置springmvc的配置文件即 contextConfigLocation属性
wac.setConfigLocation(getContextConfigLocation());
//此处与ContextLoader#configureAndRefreshWebApplicationContext()类似
configureAndRefreshWebApplicationContext(wac);
return wac;
}
- 承接createWebApplicationContext方法的
FrameworkServlet#configureAndRefreshWebApplicationContext()-springmvc的刷新处理，不同于spring
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
//设置id属性
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
if (this.contextId != null) {
wac.setId(this.contextId);
}
else { wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(getServletContext().getContextPath()) + "/" + getServletName());
}
}
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
//默认的namespace为getServletName()+"-servlet"
wac.setNamespace(getNamespace());
wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
}
//空方法
postProcessWebApplicationContext(wac);
//读取web.xml中的`context-param`节点中的globalInitializerClasses、contextInitializerClasses并初始化
applyInitializers(wac);
//刷新，此处可见Spring源码情操陶冶-AbstractApplicationContext博文
wac.refresh();
}