Spring MVC源碼閱讀
MVC的自動加載
@Configuration
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
// WebMvcConfigurationSupport這個Bean不存在纔會啓動 這個類的做用是若是@EnableWebMvc註解的自動裝配 兩個是互斥的
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
//優先級
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
//這些自動配置加載以後加載
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {
}
功能是java
- 啓動spring.mvc和spring.resources開頭的配置項
- 加載InternalResourceViewResolver 內部試圖資源解析器 我理解指定JSP位置的
- 加載BeanNameViewResolver 支持經過BeanName匹配的視圖解析器
- RequestMappingHandlerAdapter 適配器 註解功能的Controller適配器
- RequestMappingHandlerMapping 處理請求路徑和controller對應關係的
- WelcomePageHandlerMapping
- FormattingConversionService
- Validator
- ContentNegotiationManager
handlerMapping 處理請求和controller直接的關係
handlerAdapter 處理請求和各類controller的適配問題. 好比適配servlet 普通controller 或者註解controller.
ViewResolver 視圖解析器
HandlerInterceptor 攔截器spring
HandlerInterceptor接口
- preHandle是在找處處理handler對象的HandlerMapping以後，HandlerAdapter調度handler以前執行。
- postHandle是在HandlerAdapter調度handler以後，DispatcherServlet渲染視圖以前執行，能夠經過ModelAndView來向視圖中添加一些信息等。
- afterCompletion是在渲染視圖結束後執行，主要能夠用來進行過後的資源清理。
HandlerExecutionChain類
這個類由一個handler和若干的HandlerInterceptor構成。那麼這個類的做用就顯而易見了，就是將攔截器和handle組合起來執行。就是對handle進行了包裝。安全
public class HandlerExecutionChain {
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
// 順序執行
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
// 直到遇到一個false的
if (!interceptor.preHandle(request, response, this.handler)) {
// false 就執行triggerAfterCompletion
triggerAfterCompletion(request, response, null);
return false;
}
// 記錄false的位置
this.interceptorIndex = i;
}
}
return true;
}
/**
* Apply postHandle methods of registered interceptors.
*/
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(request, response, this.handler, mv);
}
}
}
/**
* Trigger afterCompletion callbacks on the mapped HandlerInterceptors.
* Will just invoke afterCompletion for all interceptors whose preHandle invocation
* has successfully completed and returned true.
*/
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
// 從false的位置開始. 向前遍歷順序執行.
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
}
}
MappedInterceptor接口
public final class MappedInterceptor implements HandlerInterceptor {
@Nullable
private final String[] includePatterns;
@Nullable
private final String[] excludePatterns;
private final HandlerInterceptor interceptor;
@Nullable
private PathMatcher pathMatcher;
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;
}
}
true 攔截 false 不攔截併發
若是路徑在excludePatterns中，則不攔截。若是不在，那麼若includePatterns爲空，則攔截，不然在includePatterns中才攔截。mvc
比較關鍵的兩個地方是：app
- 優先判excludePatterns
- 若includePatterns列表爲空且請求不在excludePatterns的狀況下所有攔截，不然只攔截includePatterns中的內容
HandlerMapping接口
HandlerMapping是用來處理請求與handler對象的對應關係的。cors
HandlerMapping主要包含getHandler這個方法。ide
HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
DispatcherServlet就是經過調用HandlerMapping的getHandler來進行找到request對應的handler的。post
RequestMappingHandlerMapping#afterPropertiesSet()
這個方法是在項目啓動建立Bean的時候調用的. 由於他實現了InitializingBean接口.
AbstractHandlerMethodMapping#afterPropertiesSet()->initHandlerMethods()ui
protected void initHandlerMethods() {
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}
protected String[] getCandidateBeanNames() {
return (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
obtainApplicationContext().getBeanNamesForType(Object.class));
}
protected void processCandidateBean(String beanName) {
Class<?> beanType = null;
try {
beanType = obtainApplicationContext().getType(beanName);
}
catch (Throwable ex) {
// An unresolvable bean type, probably from a lazy bean - let's ignore it.
if (logger.isTraceEnabled()) {
logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
}
}
//判斷是否Handler 標註了@Controller或者@RequestMapping
if (beanType != null && isHandler(beanType)) {
//解析controller的方法並註冊
detectHandlerMethods(beanName);
}
}
@Override
protected boolean isHandler(Class<?> beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}
protected void detectHandlerMethods(Object handler) {
//獲取到controller的class
Class<?> handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
Class<?> userType = ClassUtils.getUserClass(handlerType);
// 完成了controller中方法和RequestMappingInfo的綁定. 例如TestController類中的 tet方法 請求路徑信息的綁定
//RequestMappingInfo 表明了請求的一些信息 如:路徑信息(/test/get) method(GET)
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup<T>) method -> {
try {
return getMappingForMethod(method, userType);
}
catch (Throwable ex) {
throw new IllegalStateException("Invalid mapping on handler class [" +
userType.getName() + "]: " + method, ex);
}
});
if (logger.isTraceEnabled()) {
logger.trace(formatMappings(userType, methods));
}
methods.forEach((method, mapping) -> {
Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
//經過MappingRegistry#registry()方法註冊.
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
}
obtainApplicationContext().getBeanNamesForType(Object.class); 這個方法. 調用鏈是
AbstractApplicationContext#getBeanNamesForType(Object.class) -> DefaultListableBeanFactory#getBeanNamesForType(type, true(包含非單例的), true(包含提前加載的)); ->
DefaultListableBeanFactory#doGetBeanNamesForType() 從DefaultListableBeanFactory中定義的註冊表中獲取 type爲Object的類名字. 固然包含Controller.
通過這些全部的controller就都解析完成了.
registerHandlerMethod(handler, invocableMethod, mapping) controller的註冊
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
handler 值是Controller的名字. 也就是beanName. spring ioc容器中註冊的名字. 若是你沒有改過, 類的第一個字母小寫. 例如TestController. handler = testController.
invocableMethod 是能夠執行的method方法. 標記了@RequestMapping註解的
mapping RequestMappingInfo類 一個請求和handler 說使用的信息. 都在這裏. 什麼狀況路徑啊 方法啊 參數啊 header啊
handler和mapping的註冊, 內部調用了MappingRegistry類. 顧名思義. 內部持有4個註冊表和一個讀寫鎖. 這個讀寫鎖就是Controller在併發環境下 線程安全的關鍵
class MappingRegistry {
private final Map<T, MappingRegistration<T>> registry = new HashMap<>();
//RequestMappingInfo和HandlerMethod的映射關係. LinkedHashMap<> 可以保存插入順序的和遍歷順序一致的HashMap
private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<>();
//url(路徑的所有 包含Controller和方法上的path))和mappinginfo 映射關係
private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();
//類名字中提取大寫的字母及其執行方法的名字 例如TestController和要執行的方法名稱爲tet. 是方法名不是url 那麼這個key=TC#tet.
private final Map<String, List<HandlerMethod>> nameLookup = new ConcurrentHashMap<>();
private final Map<HandlerMethod, CorsConfiguration> corsLookup = new ConcurrentHashMap<>();
//讀寫鎖 提供讀寫效率並能保證線程安全
private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();
public void register(T mapping, Object handler, Method method) {
this.readWriteLock.writeLock().lock();
try {
//HandlerMethod類 就是將 beanName和BeanFactory以及要執行的method封裝成了不可變對象. 用於數據傳輸和記錄信息
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
//驗證RequestMappingInfo(不可變類)是否已經註冊過了而且仍是惟一的.
assertUniqueMethodMapping(handlerMethod, mapping);
// 註冊RequestMappingInfo和HandlerMethod的映射
this.mappingLookup.put(mapping, handlerMethod);
// 註冊URL和mapping 信息
List<String> directUrls = getDirectUrls(mapping);
for (String url : directUrls) {
this.urlLookup.add(url, mapping);
}
String name = null;
if (getNamingStrategy() != null) {
name = getNamingStrategy().getName(handlerMethod, mapping);
//nameLookup註冊
addMappingName(name, handlerMethod);
}
// 處理CrossOrigin註解
CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
if (corsConfig != null) {
this.corsLookup.put(handlerMethod, corsConfig);
}
// MappingRegistration不可變類, 將RequestMappingInfo HandlerMethod directUrls(/test/get) name(TC#tet)封裝.
this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
}
finally {
this.readWriteLock.writeLock().unlock();
}
}
}
Controller的寫是有讀寫鎖保護的.
執行也能夠稱之爲請求時處理請求和Controller.
DispatcherServlet#doDispatch 扎到了這樣的代碼
// Determine handler for the current request.
HandlerExecutionChain mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
@Nullable
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (HandlerMapping mapping : this.handlerMappings) {
HandlerExecutionChain handler = mapping.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
//AbstractHandlerMapping
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);
}
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (logger.isTraceEnabled()) {
logger.trace("Mapped to " + handler);
}
else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
logger.debug("Mapped to " + executionChain.getHandler());
}
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
@Override
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();
}
}
handlerMappings這是一個集合. 裏面存放着全部HeadlerMapping. 問題是這些HM什麼時候初始化的呢. 咱們都知道DispatcherServlet是本質是Servlet. 那麼Servlet聲明週期分 init(初始化)) service(執行邏輯) destroy(銷燬)
handlerMappings屬性的初始化必定和這個有關. DispatcherServlet類的初始化是經過Spring自動裝載完成的. init方法會去加載 在經過mappingRegistry讀取Handler的時候. 也是會加讀鎖的.
HandlerAdapter接口
在springMVC的執行流行流程中，當執行完handlerMapping獲取到request對應的HandlerExecutionChain以後，下一步就是調用HandlerAdapter執行對應的Handler。
public interface HandlerAdapter {
boolean supports(Object handler);
@Nullable
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
long getLastModified(HttpServletRequest request, Object handler);
}
supports()是用來判斷一個handler是否屬於該HandlerAdapter的，一個典型的實現方式是判斷該handler的類型，一般來講一個HandlerAdapter只支持一種類型的handler。
handle()的做用是使用給定的handler去處理請求。
getLastModified()的做用和HttpServlet中的getLastModified一致，如果handler不支持getLastModified則直接返回-1。
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