SpringCloud解析之Zuul(一)

protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
// 这里就从上面注册好的handlerMap中获取请求urlPath对应的handler
Object handler = this.handlerMap.get(urlPath);
if (handler != null) {
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
return buildPathExposingHandler(handler, urlPath, urlPath, null);
}

// 如果获取不到，则进行正则匹配，如果还匹配不到的话，则返回null
List<String> matchingPatterns = new ArrayList<String>();
for (String registeredPattern : this.handlerMap.keySet()) {
if (getPathMatcher().match(registeredPattern, urlPath)) {
matchingPatterns.add(registeredPattern);
}
else if (useTrailingSlashMatch()) {
if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {
matchingPatterns.add(registeredPattern +"/");
}
}
}

String bestMatch = null;

// 匹配到之后，用请求urlPath对应的patternComparator，对所有匹配的url进行排序，之后获取第一个匹配的url
Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);
if (!matchingPatterns.isEmpty()) {
Collections.sort(matchingPatterns, patternComparator);
if (logger.isDebugEnabled()) {
logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);
}
bestMatch = matchingPatterns.get(0);
}
if (bestMatch != null) {

// 先根据排序后的第一个url获取对应的handler，如果没有的话则用”/”再取一次

handler = this.handlerMap.get(bestMatch);
if (handler == null) {
if (bestMatch.endsWith("/")) {
handler = this.handlerMap.get(bestMatch.substring(0, bestMatch.length() - 1));
}
if (handler == null) {
throw new IllegalStateException(
"Could not find handler for best pattern match [" + bestMatch + "]");
}
}
// 如果handler是String，则从应用上下文中获取对应的bean
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);

// 解析映射url的后半段请求uri

String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);

// 最后再确认一次bestMatch是否是最匹配请求的路由
Map<String, String> uriTemplateVariables = new LinkedHashMap<String, String>();
for (String matchingPattern : matchingPatterns) {
if (patternComparator.compare(bestMatch, matchingPattern) == 0) {
Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
Map<String, String> decodedVars = getUrlPathHelper().decodePathVariables(request, vars);
uriTemplateVariables.putAll(decodedVars);
}
}
if (logger.isDebugEnabled()) {
logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);
}

// 构建HandlerExecutionChain并返回

return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables);
}

// No handler found...
return null;
}