github原文鏈接 https://github.com/DespairYoke/java-advance颖系。創(chuàng)作不易嗅剖，請(qǐng)給個(gè)免費(fèi)的star，已表支持嘁扼。
在Servlet如何關(guān)聯(lián)spring中信粮，說過當(dāng)請(qǐng)求來后會(huì)被轉(zhuǎn)發(fā)到springDispatcherServlet類中的doService方法。
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
doDispatch(request, response);
}
轉(zhuǎn)發(fā)到doDispatch中
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
mappedHandler = getHandler(processedRequest);
}
getHandler獲取相關(guān)
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (MyHandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
可以看出趁啸，循環(huán)遍歷初始化時(shí)加載的handlerMappings蒋院。在初始化時(shí)加載是BeanNameUrlHandlerMapping和RequestMappingHandlerMapping(不知道的，可以參考上篇文章spingMvc初始HandlerMapping)莲绰。
BeanNameUrlHandlerMapping不滿條件返回null欺旧，而RequestMappingHandlerMapping滿足條件，通過getHandler返回我們想要的HandlerExecutionChain蛤签。
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
return executionChain;
}
getHandlerExecutionChain可見是對(duì)handler和request的封裝辞友，真正的處理還是如何獲取到這個(gè)handler。
具體代碼寫在了AbstractHandlerMethodMapping中
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
this.mappingRegistry.acquireReadLock();
try {
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
}
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
this.mappingRegistry.releaseReadLock();
}
}
在前文分析中震肮，handlerMethod在初始化的時(shí)候放在了称龙，mappingRegistry中，由上述代碼戳晌，可以看出是從mappingRegistry中鲫尊，匹配請(qǐng)求，并返回handlerMethod沦偎。
那我們看下lookupHandlerMethod方法吧疫向。
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<>();
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
if (!matches.isEmpty()) {
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
matches.sort(comparator);
if (logger.isTraceEnabled()) {
logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches);
}
Match bestMatch = matches.get(0);
if (matches.size() > 1) {
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
}
}
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
}
果不其然是對(duì)我們的請(qǐng)求路徑進(jìn)行最佳匹配。
這樣我們就回去到初始化handlerMapping時(shí)生成的handlerMethod豪嚎，為后續(xù)handlerAdapter做好參數(shù)準(zhǔn)備搔驼。
