HandlerMapping处理器映射器
作用是根据request找到相应的处理器Handler和Interceptors，然后封装成HandlerExecutionChain对象返回
HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
实现类
HandlerMapping帮助DispatcherServlet进行web请求的url到具体处理类的匹配，用来根据请求的url查找Handler，内部维护的Map<String, Object>映射，springmvc提供了不同的映射器实现不同的映射方式，例如：配置文件方式，实现接口方式，注解方式等
private final Map<String, Object> handlerMap = new LinkedHashMap<String, Object>();
spring自带了多个处理器映射实现
-
BeanNameUrlHandlerMapping 根据控制器Bean的名字将控制器映射到URL -
ControllerBeanNameHandlerMapping 与BeanNameUrlHandlerMapping类似 -
ControllerClassNameHandlerMapping 通过使用控制器的类名作为URL基础将控制器映射到URL -
DefaultAnnotationHandlerMapping 将请求映射给使用@RequestMapping注解的控制器和控制器方法 -
SimplerUrlHandlerMapping 使用定义在Spring应用上下文的集合将控制器映射到URL -
RequestMappingHandlerMapping SpringMVC3.1新增的，在springMVC3.1之前，DefaultAnnotationHandlerMapping会在类级别上选中一个控制器，然后通过AnnotationMethodHandlerAdapter定位到具体要调用的方法；而在SpringMVC3.1之后，这些操作全都放生在RequestMappingHandlerMapping中，从类级别和方法级别的@RequestMapping注解中获取到路径映射信息，使得在HandlerInterceptor中获取到的处理器肯定是一个HandlerMethod类型
配置
<!-- 开启注解 -->
<mvc:annotation-driven/>
<bean id="defaultAnnotationHandlerMapping" class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
mvc:annotation-driven配置的作用
-
<mvc:annotation-driven/>会自动注册RequestMappingHandlerMapping、RequestMappingHandlerAdater、ExceptionHandlerExceptionResolver三个bean -
支持使用ConversionService实例对表单参数进行类型转换 -
支持使用@NumberFormatannotation、@DataTimeFormat注解完成数据类型的格式化 -
支持使用@Vaild注解对JavaBean实例进行JSR 303验证 -
支持使用@RequestBody和@ResponseBody注解
RequestMappingHandlerMapping源码
由于一般都使用<mvc:annotation-driven/>进行配置，所以就以RequestMappingHandlerMapping为例进行讲解
创建
RequestMappingHandlerMapping实现了ApplicationContextAware接口，会执行setApplicationContext
// 调用链路 org.springframework.context.support.ApplicationObjectSupport#setApplicationContext ——>org.springframework.context.support.ApplicationObjectSupport#initApplicationContext(org.springframework.context.ApplicationContext) -->org.springframework.web.servlet.handler.AbstractHandlerMapping#initApplicationContext
// org.springframework.web.servlet.handler.AbstractHandlerMapping#initApplicationContext
protected void initApplicationContext() throws BeansException {
// 扩展interceptors的方法，空实现
extendInterceptors(this.interceptors);
// 将容器中的所有MappedInterceptor类型的bean添加到mappedInterceptors中
detectMappedInterceptors(this.adaptedInterceptors);
// 初始化Interceptor，将interceptors中的对象添加到adaptedInterceptors中
initInterceptors();
}
RequestMappingHandlerMapping实现了InitializingBean接口，会执行afterPropertiesSet
// org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#afterPropertiesSet
public void afterPropertiesSet() {
initHandlerMethods();
}
// org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#initHandlerMethods
protected void initHandlerMethods() {
// 拿到容器中的bean，筛选出Handler
String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
getApplicationContext().getBeanNamesForType(Object.class));
for (String beanName : beanNames) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
Class<?> beanType = null;
try {
beanType = getApplicationContext().getType(beanName);
}
catch (Throwable ex) {
}
// (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class)); 判断
if (beanType != null && isHandler(beanType)) {
// 将访问地址、Method进行映射
detectHandlerMethods(beanName);
}
}
}
handlerMethodsInitialized(getHandlerMethods());
}
访问
在进行访问的时候会通过org.springframework.web.servlet.DispatcherServlet#getHandler方法来遍历handlerMappings
HandlerExecutionChain handler = hm.getHandler(request);
来调用HandlerMapping的getHandler方法
// org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandler
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
// 找到Handler，根据地址找到对应的方法
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
// 如果找到的handler是一个字符串，可能是beanName，从bean容器中查找
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
// 为handler生成执行链，即为HandlerExecutionChain对象添加interceptor
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
// 跨域处理
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;
}
getHandlerInternal
// org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerInternal
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();
}
}
getHandlerExecutionChain
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
https://zhhll.icu/2021/框架/springmvc/底层剖析/2.HandlerMapping/
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