spring mvc的拦截器的那段源代码分析
起源，研究拦截器匹配规则为什么得不到执行
@Configuration("admimWebConfig")
public class WebConfiguration implements WebMvcConfigurer {
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(getServiceAuthRestInterceptor()).
addPathPatterns(getIncludePathPatterns());
}
}
可以发现，拦截器是注入到registrations里面
public InterceptorRegistration addInterceptor(HandlerInterceptor interceptor) {
InterceptorRegistration registration = new InterceptorRegistration(interceptor);
this.registrations.add(registration);
return registration;
}
通过idea，可以看到registration只有在这个方法里用过，
protected List<Object> getInterceptors() {
return this.registrations.stream()
.sorted(INTERCEPTOR_ORDER_COMPARATOR)
.map(InterceptorRegistration::getInterceptor)
.collect(Collectors.toList());
}
然后这个方法是在WebMvcConfigurationSupport这里调用的
维护在这个类的interceptors变量里，而通过idea拦截器发现，也只有下面这个方法有返回也就是使用这个变量
protected final Object[] getInterceptors() {
if (this.interceptors == null) {
InterceptorRegistry registry = new InterceptorRegistry();
addInterceptors(registry);
registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService()));
registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));
this.interceptors = registry.getInterceptors();
}
return this.interceptors.toArray();
}
上面这个方法是WebMvcConfigurationSupport这个方法调用的
@Bean
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();
mapping.setOrder(0);
// 可以看到，是RequestMappingHandlerMapping的setInterceptors的拦截
//器调用了，也就是说，RequestMappingHandlerMapping维护了所有的拦截器
// 维护在interceptors这个变量中
mapping.setInterceptors(getInterceptors());
...
return mapping;
}
而以前分析spring mvc源码的时候，就直到，调用拦截器是在DispatchServlet的doDispatch方法里调用的
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
...
// 找到能处理这个请求的handlerMapping
// 这里找到的handlerMapping，已经初始化过了所有的拦截器
// 这里通过handlermapping，获取HandlerExecutionChain，这里会过滤掉不匹配的拦截器
mappedHandler = getHandler(processedRequest);
...
// 这里会调用拦截器
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
...
}
看调用拦截器的方法
debug发现，在这里的HandlerExecution的interceptors变量已经是过滤后的拦截器了，已经把不匹配的拦截器过滤掉了
那么这个变量interceptors到底是在哪里被赋值了呢？通过idea以及debug流程发下，没有任何地方，给interceptors赋有效的值，HandlerExecution的interceptors的值到底是怎么来的呢？
当时就很奇怪了，为什么呢？那它的值是哪来的呢？
后来通过，头构造HandlerExecution的代码，发现，忽略了一个事情，interceptors是一个集合，可以通过return 获取到这个集合，然后掉哟个add方法来改变值，而不是直接赋值改变值
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}
public HandlerInterceptor[] getInterceptors() {
if (this.interceptors == null && this.interceptorList != null) {
this.interceptors = this.interceptorList.toArray(new HandlerInterceptor[this.interceptorList.size()]);
}
return this.interceptors;
}
也就是这行代码，过滤掉了拦截器
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
//这行代码
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
// 这行代码
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
最终定位到这里，也就是这里过滤掉了不匹配的拦截器
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
// 这是我们请求的路径
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
// 这里进行匹配
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
再看过滤是怎么过滤的
会发现，首先，通过excludeUrl过滤，在excludeUrl中的，则直接过滤掉，也就是不添加这个拦截器(可是很多人会发现，添加到excludeUrl中，然后发现不起作用，这是为什么呢？看最下面的代码）
再根据includeUrl过滤，includeUrl为空的，则添加这个过滤器，意思就是，如果不自定义includeUrl，则拦截器所有。
如果includeUrl不为空，则进行匹配拦截
public boolean matches(String lookupPath, PathMatcher pathMatcher) {
PathMatcher pathMatcherToUse = (this.pathMatcher != null ? this.pathMatcher : pathMatcher);
if (!ObjectUtils.isEmpty(this.excludePatterns)) {
for (String pattern : this.excludePatterns) {
if (pathMatcherToUse.match(pattern, lookupPath)) {
return false;
}
}
}
if (ObjectUtils.isEmpty(this.includePatterns)) {
return true;
}
for (String pattern : this.includePatterns) {
if (pathMatcherToUse.match(pattern, lookupPath)) {
return true;
}
}
return false;
}
这是具体的匹配代码：AntPathMatcher类，也就是aut模式的匹配，详细的aut匹配方式，百度有很多。
关键看第一行代码
protected boolean doMatch(String pattern, String path, boolean fullMatch,
@Nullable Map<String, String> uriTemplateVariables) {
// pathSeparator路径分割符是“/”，path如果以“/”分割，而pathSeparator不以“/”分
//割，则直接返回false。也就是说，如果访问swagger-ui.html页面，这里的path
//是/swagger-ui.html，而不管配置的excludeUrl是：**swagger.html还是
//*swagger.html，都将返回false，匹配不到
if (path.startsWith(this.pathSeparator) != pattern.startsWith(this.pathSeparator)) {
return false;
}
...
return true;
}
那么AntPathMatcher匹配模式是怎样的呢？
AntPathMatcher如名使用的ant 的匹配规则,我们先看看吧.
字符wildcard 描述
? 匹配一个字符
* 匹配0个及以上字符（不包括/目录分隔符）
** 匹配0个及以上目录directories
看几个例子:
/*swagger.html 匹配/swagger.html ，*是0个或多个嘛
//swagger.html 也匹配/swagger.html **是0个或多个目录嘛
//.png 匹配/webjars/springfox-swagger-ui/images/favicon-32x32.png **匹配多层目录，*匹配多个字符
com/t?st.jsp - 匹配: com/test.jsp , com/tast.jsp , com/txst.jsp
com/.jsp - 匹配: com文件夹下的全部.jsp文件
com//test.jsp - 匹配: com文件夹和子文件夹下的全部.jsp文件,
org/springframework//.jsp - 匹配: org/springframework文件夹和子文件夹下的全部.jsp文件
org/**/servlet/bla.jsp - 匹配: org/springframework/servlet/bla.jsp , org/springframework/testing/servlet/bla.jsp , org/servlet/bla.jsp
可以写个例子测试：
public static void main(String[] args) {
pathMatcher.setCachePatterns(true);
pathMatcher.setCaseSensitive(true);
pathMatcher.setTrimTokens(true);
pathMatcher.setPathSeparator("/");
Assert.assertTrue(pathMatcher.match("/**/*swagger.html", "/swagger.html"));
Assert.assertTrue(pathMatcher.match("/**/*.png", "/webjars/springfox-swagger-ui/images/favicon-32x32.png"));
Assert.assertTrue(pathMatcher.match("a*", "ab"));
Assert.assertTrue(pathMatcher.match("a*/**/a", "ab/asdsa/a"));
Assert.assertTrue(pathMatcher.match("a*/**/a", "ab/asdsa/asdasd/a"));
Assert.assertTrue(pathMatcher.match("*", "a"));
Assert.assertTrue(pathMatcher.match("*/*", "a/a"));
}
