分析下springmvc的HandlerMapping映射的抽象类
初始化操作
通过initApplicationContext()方法进行初始化，其一般是由父类执行ApplicationContextAware#setApplicationContext()方法间接调用，源码奉上
protected void initApplicationContext() throws BeansException {
//供子类扩展添加拦截器，目前spring没有自行实现
extendInterceptors(this.interceptors);
//搜寻springmvc中的MappedInterceptors保存至adaptedInterceptors集合
detectMappedInterceptors(this.adaptedInterceptors);
//将interceptors集合添加至adaptedInterceptors集合中
initInterceptors();
}
主要目的是获取springmvc上下文中的拦截器集合，此处特指MappedInterceptor
AbstractHandlerMapping#getHandler()-获取处理链对象
源码奉上
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//getHandlerInternal(request)方法为抽象方法，供子类实现
//获取到的handler对象一般为bean/HandlerMethod
Object handler = getHandlerInternal(request);
//上述找不到则使用默认的处理类，没有设定则返回null，则会返回前台404错误
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
//创建处理链对象
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
//针对cros跨域请求的处理，此处就不分析了
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
由以上代码分析可知，需要观察下如何获取handler对象以及创建HandlerExecutionChain处理链对象
AbstractHandlerMethodMapping#getHandlerInternal()-针对HandlerMethod的获取
主要是解析@Controller注解类中的@RequestMapping方法得到其中的HandlerMethod对象作为返回的Handler
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
//获取访问的路径，一般类似于request.getServletPath()返回不含contextPath的访问路径
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);//获取读锁
this.mappingRegistry.acquireReadLock();
try {
//获取HandlerMethod作为handler对象,这里涉及到路径匹配的优先级
//优先级：精确匹配>最长路径匹配>扩展名匹配
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
//HandlerMethod内部含有bean对象，其实指的是对应的Controller
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
//释放读锁
this.mappingRegistry.releaseReadLock();
}
}
AbstractUrlHandlerMapping#getHandlerInternal()-针对beanName的获取
源码奉上，此处的逻辑就较为简单了
protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
//从handlerMap查找路径对应的beanName
Object handler = lookupHandler(lookupPath, request);
if (handler == null) {
// We need to care for the default handler directly, since we need to
// expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.
Object rawHandler = null;
if ("/".equals(lookupPath)) {
rawHandler = getRootHandler();
}
if (rawHandler == null) {
rawHandler = getDefaultHandler();
}
if (rawHandler != null) {
// Bean name or resolved handler?
if (rawHandler instanceof String) {
String handlerName = (String) rawHandler;
rawHandler = getApplicationContext().getBean(handlerName);
}
validateHandler(rawHandler, request);
handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);
}
}return handler;
}
AbstractHandlerMapping#getHandlerExecutionChain()-创建处理链对象
先附上HandlerExecutionChain的内部属性
//真实处理请求对象
private final Object handler; //拦截器集合
private HandlerInterceptor[] interceptors; //拦截器集合
private List<HandlerInterceptor> interceptorList; //拦截器开始下标，默认正序执行
private int interceptorIndex = -1;
再奉上创建处理链对象的源码
//此处的handler可为HandlerMethod/beanName
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
处理链的创建基本就是 带有handler对象以及添加拦截器对象集合，用于后期的拦截
HandlerExecutionChain处理链内部含有handler对象，可为
@RequestMapping对应的HandlerMethod对象，也可为springmvc上下文的beanNameHandlerExecutionChain处理链内部主要包含拦截器对象，其可从springmvc上下文获取
HandlerInterceptor/MappedHandlerInterceptor类型作为内部集合；当然此处获得拦截器集合也是根据路径匹配获取的，比如
mvc:interceptor指定的或者mvc:resource指定的
