静态资源如何访问
可以直接访问静态资源,因为有SimpleUrlHandlerMapping
处理。
EnableWebMvcConfiguration的resourceHandlerMapping
自动配置EnableWebMvcConfiguration
的resourceHandlerMapping
调用的时候:
ResourceHandlerRegistry的resourceHandlerMapping
最后创建一个SimpleUrlHandlerMapping
,里面有两个映射,定义了两种资源路径:
然后在他在初始化之前处理的setApplicationContext
方法中注册了两个映射:
注册到handlerMap
中:
log
信息也有:
实验
比如我直接请求resources\static\test.html
:
直接在浏览器
AbstractUrlHandlerMapping的lookupHandler
我们来看看原理,获取处理器映射器的时候就到这个方法里,其实就是进行uri的匹配,匹配到了再解析uri
参数,最后封装成执行链加入拦截器返回。
@Nullable
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
// 直接能匹配上
Object handler = this.handlerMap.get(urlPath);
if (handler != null) {//如果存在的话
// Bean name or resolved handler?
if (handler instanceof String) {//只是名字的话要实例化
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
return buildPathExposingHandler(handler, urlPath, urlPath, null);
}
// Pattern match? uri模式匹配
List<String> matchingPatterns = new ArrayList<>();
for (String registeredPattern : this.handlerMap.keySet()) {//遍历进行匹配
if (getPathMatcher().match(registeredPattern, urlPath)) {
matchingPatterns.add(registeredPattern);//匹配上就添加进去
}
else if (useTrailingSlashMatch()) {
if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {
matchingPatterns.add(registeredPattern + "/");
}
}
}
String bestMatch = null;
Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);
if (!matchingPatterns.isEmpty()) {//不为空的话排序
matchingPatterns.sort(patternComparator);
if (logger.isTraceEnabled() && matchingPatterns.size() > 1) {
logger.trace("Matching patterns " + matchingPatterns);
}
bestMatch = matchingPatterns.get(0);//取第一个
}
if (bestMatch != null) {//存在就获取对应的处理器
handler = this.handlerMap.get(bestMatch);
if (handler == null) {
if (bestMatch.endsWith("/")) {//如果以/结尾的话就把/去掉再看有没映射的处理器
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 + "]");
}
}
// Bean name or resolved handler?
if (handler instanceof String) {//处理器只是名字的话要实例化
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
validateHandler(handler, request);
String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);//取出匹配的资源,出掉最开始的/
// uri参数,比如restful风格的
Map<String, String> uriTemplateVariables = new LinkedHashMap<>();
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.isTraceEnabled() && uriTemplateVariables.size() > 0) {
logger.trace("URI variables " + uriTemplateVariables);
}
return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables);//封装执行链加入拦截器一起返回
}
// No handler found...
return null;
}
buildPathExposingHandler
创建执行链,然后加入一个PathExposingHandlerInterceptor
拦截器,如果有uri参数的话还要加入UriTemplateVariablesHandlerInterceptor
拦截器,其实就是设置一些请求属性,暴露给请求。
最后还会加一个跨域的拦截器:
ResourceHttpRequestHandler的handleRequest执行处理器
重点就是获取资源,然后写出去。
@Override
public void handleRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 获取资源
Resource resource = getResource(request);
if (resource == null) {//找不到
logger.debug("Resource not found");
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
}
...
// 获取资源媒体类型
MediaType mediaType = getMediaType(request, resource);
...
ServletServerHttpResponse outputMessage = new ServletServerHttpResponse(response);
if (request.getHeader(HttpHeaders.RANGE) == null) {
Assert.state(this.resourceHttpMessageConverter != null, "Not initialized");
setHeaders(response, resource, mediaType);//设置头信息
this.resourceHttpMessageConverter.write(resource, mediaType, outputMessage);//写出去
}
else {
...
}
}
}
下篇说怎么获取资源和写出去的。
好了,今天就到这里了,希望对学习理解有帮助,大神看见勿喷,仅为自己的学习理解,能力有限,请多包涵。