HandlerMapping
# RequestMapping加载策略
DispatcherServlet#initHandlerMappings
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
// detectAllHandlerMappings默认true
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {
//也可以将detectAllHandlerMappings设置为false，并自己指定`name=handlerMapping`的`HandleMapping`
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}
// 如果没有配置HandlerMapping，从resources/org/springframework/web/servlet/DispatcherServlet.properties中读取默认配置
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerMappings declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
}
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DispatcherServlet#getDefaultStrategies
private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties";
private static final Properties defaultStrategies;
static {
// Load default strategy implementations from properties file.
// This is currently strictly internal and not meant to be customized
// by application developers.
try {
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
}
}
protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
String key = strategyInterface.getName();
String value = defaultStrategies.getProperty(key);
if (value != null) {
String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
List<T> strategies = new ArrayList<>(classNames.length);
for (String className : classNames) {
try {
Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
Object strategy = createDefaultStrategy(context, clazz);
strategies.add((T) strategy);
}
//catch error ...
}
return strategies;
}
else {
return new LinkedList<>();
}
}
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默认策略对应的类写在DispatcherServlet.properties中
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\
org.springframework.web.servlet.function.support.RouterFunctionMapping
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实践中一般使用的是@Controller和@RequestMapping来指定请求处理方法，所以以RequestMappingHandlerMapping来分析
该类实现了一些Aware接口和InitializingBean接口，在Bean实例化过程中会被调用。
# 注册拦截器
ApplicationObjectSupport#setApplicationContext
public final void setApplicationContext(@Nullable ApplicationContext context) throws BeansException {
if (context == null && !isContextRequired()) {
// Reset internal context state.
this.applicationContext = null;
this.messageSourceAccessor = null;
}
else if (this.applicationContext == null) {
// Initialize with passed-in context.
if (!requiredContextClass().isInstance(context)) {
throw new ApplicationContextException(
"Invalid application context: needs to be of type [" + requiredContextClass().getName() + "]");
}
this.applicationContext = context;
this.messageSourceAccessor = new MessageSourceAccessor(context);
initApplicationContext(context);
}
else {
// Ignore reinitialization if same context passed in.
if (this.applicationContext != context) {
throw new ApplicationContextException(
"Cannot reinitialize with different application context: current one is [" +
this.applicationContext + "], passed-in one is [" + context + "]");
}
}
}
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AbstractHandlerMapping#initApplicationContext
protected void initApplicationContext() throws BeansException {
//留给子类扩展
extendInterceptors(this.interceptors);
//初始化拦截器
detectMappedInterceptors(this.adaptedInterceptors);
initInterceptors();
}
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AbstractHanlerMapping#detectMappedInterceptors
protected void detectMappedInterceptors(List<HandlerInterceptor> mappedInterceptors) {
mappedInterceptors.addAll(
BeanFactoryUtils.beansOfTypeIncludingAncestors(
obtainApplicationContext(), MappedInterceptor.class, true, false).values());
}
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# 注册请求处理类
RequesMappingtHandlerMapping#afterPropertiesSet
public void afterPropertiesSet() {
this.config = new RequestMappingInfo.BuilderConfiguration();
this.config.setUrlPathHelper(getUrlPathHelper());
this.config.setPathMatcher(getPathMatcher());
this.config.setSuffixPatternMatch(useSuffixPatternMatch());
this.config.setTrailingSlashMatch(useTrailingSlashMatch());
this.config.setRegisteredSuffixPatternMatch(useRegisteredSuffixPatternMatch());
this.config.setContentNegotiationManager(getContentNegotiationManager());
super.afterPropertiesSet();
}
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AbstractHandlerMethodMapping#afterPropertiesSet
public void afterPropertiesSet() {
initHandlerMethods();
}
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AbstractHandlerMethodMapping#initHandlerMethods
protected void initHandlerMethods() {
//获取容器中Bean，实例化
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}
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AbstractHandlerMethodMapping#getCandidateBeanNames
protected String[] getCandidateBeanNames() {
//是否获取父容器Bean，默认false
return (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
obtainApplicationContext().getBeanNamesForType(Object.class));
}
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AbstractHandlerMethodMapping#processCandidateBean
protected void processCandidateBean(String beanName) {
Class<?> beanType = null;
try {
//实例化
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);
}
}
//isHandler选取要处理的类型 交由之类实现
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}
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子类实现匹配请求处理类的方法
RequestMappingHandlerMapping#isHandler
//处理Controller和RequestMapping注解标注的类
protected boolean isHandler(Class<?> beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}
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AbstractHandlerMethodMapping#detectHandlerMethods
protected void detectHandlerMethods(Object handler) {
//如果是bean名称，再获取一遍
Class<?> handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
Class<?> userType = ClassUtils.getUserClass(handlerType);
//获取请求处理方法的map key=目标方法，value=请求路径、类型等信息
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup<T>) method -> {
try {
//解析方法上的RequestMapping注解请求路径、类型等信息
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);
//注册URL与对应处理方法
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
}
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子类实现获取handler中处理请求方法的方法
RequestMappingHandlerMapping#getMappingForMethod
protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
info = typeInfo.combine(info);
}
String prefix = getPathPrefix(handlerType);
if (prefix != null) {
info = RequestMappingInfo.paths(prefix).options(this.config).build().combine(info);
}
}
return info;
}
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RequestMappingHandlerMapping#createRequestMappingInfo
private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
RequestCondition<?> condition = (element instanceof Class ?
getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
}
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RequestMappingHandlerMapping#createRequestMapping
protected RequestMappingInfo createRequestMappingInfo(
RequestMapping requestMapping, @Nullable RequestCondition<?> customCondition) {
RequestMappingInfo.Builder builder = RequestMappingInfo
.paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))
.methods(requestMapping.method())
.params(requestMapping.params())
.headers(requestMapping.headers())
.consumes(requestMapping.consumes())
.produces(requestMapping.produces())
.mappingName(requestMapping.name());
if (customCondition != null) {
builder.customCondition(customCondition);
}
return builder.options(this.config).build();
}
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可以发现大部分都是框架定义好的模板方法，RequestMappingHandlerMapping就是实现预留给子类实现的方法，通过处理Controller,RequestMapping注解,得到请求处理类，以及可处理请求的相关参数。
AbstractHandlerMethodMapping#registerHandlerMathod
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
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MappingRegistry是AbstractHandlerMethodMapping的内部类，内置多个map,存储请求与处理方法的映射关系。
MappingRegistry#register
public void register(T mapping, Object handler, Method method) {
// Assert that the handler method is not a suspending one.
if (KotlinDetector.isKotlinType(method.getDeclaringClass())) {
Class<?>[] parameterTypes = method.getParameterTypes();
if ((parameterTypes.length > 0) && "kotlin.coroutines.Continuation".equals(parameterTypes[parameterTypes.length - 1].getName())) {
throw new IllegalStateException("Unsupported suspending handler method detected: " + method);
}
}
this.readWriteLock.writeLock().lock();
try {
//封装
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
//校验不能重复添加
validateMethodMapping(handlerMethod, mapping);
//绑定URL与处理方法的映射 URL->mapping->(handler,method)
this.mappingLookup.put(mapping, handlerMethod);
List<String> directUrls = getDirectUrls(mapping);
for (String url : directUrls) {
this.urlLookup.add(url, mapping);
}
String name = null;
if (getNamingStrategy() != null) {
//命名策略生成路径信息可以作为URL的替代
name = getNamingStrategy().getName(handlerMethod, mapping);
addMappingName(name, handlerMethod);
}
//跨域设置
CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
if (corsConfig != null) {
this.corsLookup.put(handlerMethod, corsConfig);
}
//封装
this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
}
finally {
this.readWriteLock.writeLock().unlock();
}
}
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上次更新: 2023/04/09, 16:34:32