springMVC源码分析--AbstractHandlerMethodMapping获取url和HandlerMethod对应关系（十）

在之前的博客 springMVC源码分析--AbstractHandlerMapping（二）中我们介绍了AbstractHandlerMethodMapping的父类AbstractHandlerMapping，其定义了抽象方法getHandlerInternal(HttpServletRequest request)，我看一下其在AbstractHandlerMethodMapping中的实现。

在AbstractHandlerMethodMapping中getHandlerInternal的实现如下：
//根据request来获取HandlerMethod
@Override
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
//获取请求连接
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
if (logger.isDebugEnabled()) {
logger.debug("Looking up handler method for path " + lookupPath);
}
//读锁
this.mappingRegistry.acquireReadLock();
try {
//获取HandlerMethod
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
if (logger.isDebugEnabled()) {
if (handlerMethod != null) {
logger.debug("Returning handler method [" + handlerMethod + "]");
}
else {
logger.debug("Did not find handler method for [" + lookupPath + "]");
}
}
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
this.mappingRegistry.releaseReadLock();
}
}具体的实现是在lookupHandlerMethod中，最终是在mappingRegistry中获取HandlerMethod，mappingRegistry可以看似是一个Map结构（其实其包含了3个map），包含了url和HandlerMethod的对应关系。

protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<Match>();
//从mappingRegistry中获取directPathMatches匹配关系
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);
}
//最终返回HandlerMethod
if (!matches.isEmpty()) {
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
Collections.sort(matches, 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);
}
}

以下几个方法是在查找url和HandlerMethod的过程中一些帮助实现。

private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
for (T mapping : mappings) {
T match = getMatchingMapping(mapping, request);
if (match != null) {
matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
}
}
}
//在子类中实现
protected abstract T getMatchingMapping(T mapping, HttpServletRequest request);

protected abstract Comparator<T> getMappingComparator(HttpServletRequest request);

protected void handleMatch(T mapping, String lookupPath, HttpServletRequest request) {
request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, lookupPath);
}
//在子类中实现
protected HandlerMethod handleNoMatch(Set<T> mappings, String lookupPath, HttpServletRequest request)
throws Exception {

return null;
}