SpringMVC源码解读 - HandlerMapping - RequestMappingHandlerMapping初始化

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RequestMappingHandlerMapping ,用于注解@Controller,@RequestMapping来定义controller.

 1 @Controller 2 @RequestMapping(value = "books") 3 public class BookController { 4  5     @RequestMapping(value = "/{id}") 6     @ResponseBody 7     public String getBook(@PathVariable("id") String id) { 8         // ... 9         return id;10     }11 }

初始化时,3个类的大致分工如下:

　　AbstractHandlerMethodMapping定义整个算法流程;

　　RequestMappingInfoHandlerMapping提供匹配条件RequestMappingInfo的解析处理;

　　RequestMappingHandlerMapping根据@RequestMapping注解生成 RequestMappingInfo,同时提供isHandler实现

整个初始化工作由AbstractHandlerMethodMapping的initHandlerMethods主导.

　　1. 使用BeanFactoryUtils扫描应用下的Object或者直接从容器中获取Object

　　2. 迭代类,分别判断isHandler判断目标类是否Handler

　　　　2.1 RequestMappingHandlerMapping.isHandler根据@Controller或@RequestMapping注解判断(有任意一个)

　　3. 对handler解析出所有需要分发的方法detectHandlerMethods

　　　　3.1 获取原始的Class<?>

　　　　3.2 使用HandlerMethodSelector.selectMethods过滤具体handler method,预留getMappingForMethod模板方法给子类

　　　　　　RequestMappingHandlerMapping.getMappingForMethod根据类,方法上的RequestMapping注解生成匹配条件RequestMappingInfo

　　　　3.3 对过滤到的每个method进行注册registerHandlerMethod

　　　　　　a, 使用createHandlerMethod封装处理器为HandlerMethod

　　　　　　b, 判断之前是否已经匹配条件对应的处理器是否冲突(相同的匹配条件只能有一个对应的处理器)

　　　　　　c, 设置匹配条件到handler method的映射关系

　　　　　　d, 从匹配条件中解析出url,并注册到urlMap(url到匹配条件的映射),这边由RequestMappingInfoHandlerMapping.getMappingPathPatterns实现

　　4. 对HandlerMethod进行初始化handlerMethodsInitialized,其实现在什么都没做

在讲初始化之前,我们先来聊聊使用到的一些概念

　　1. 映射关系,url到匹配条件RequestMappingInfo,匹配条件到HandlerMethod

　　2. 特殊的MultiValueMap,特别在value是个List

　　3. 使用到注解@Controller,@RequestMapping

　　4. 封装处理器信息的HandlerMethod

　　5. 封装各类匹配条件的RequestMappingInfo(诸如pattern,http method,request parameter等)

　　6. RequestCondition记录匹配条件

1. 进行request分发前,需要在初始化时准备好映射关系,这边AbstractHandlerMethodMapping中有两个属性保存了映射关系

// AbstractHandlerMethodMapping

1     // 匹配条件到HandlerMethod的映射2     private final Map<T, HandlerMethod> handlerMethods = new LinkedHashMap<T, HandlerMethod>();3     // url到匹配条件的映射4     private final MultiValueMap<String, T> urlMap = new LinkedMultiValueMap<String, T>();

2. 这边的MultiValueMap其实挺简单,就是map的值是个list

1 public interface MultiValueMap<K, V> extends Map<K, List<V>> {2   // ...      3 }

3. 我们再来看看这边使用到的两个注解:

// @Controller

 1     // org.springframework.stereotype.Controller 2 @Target({ElementType.TYPE}) 3 @Retention(RetentionPolicy.RUNTIME) 4 @Documented 5 @Component 6 public @interface Controller { 7  8     /** 9      * The value may indicate a suggestion for a logical component name,10      * to be turned into a Spring bean in case of an autodetected component.11      * @return the suggested component name, if any12      */13     String value() default "";14 15 }

// @RequestMapping

 1     // org.springframework.web.bind.annotation.RequestMapping 2     @Target({ElementType.METHOD, ElementType.TYPE}) 3     @Retention(RetentionPolicy.RUNTIME) 4     @Documented 5     @Mapping 6     public @interface RequestMapping { 7  8         /** 9          * url路径,如/myPath/*.do10          */11         String[] value() default {};12 13         /**14          * HTTP request methods 如:GET, POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE.15          */16         RequestMethod[] method() default {};17 18         /**19          * requeset parameter 有3种匹配方式,是否包含某个参数,参数值相等,参数值不等于某个值,如myParam!=myValue20          */21         String[] params() default {};22 23         /**24          * request的header25          */26         String[] headers() default {};27 28         /**29          * request的MediaType30          */31         String[] consumes() default {};32 33         /**34          * response的MediaType35          */36         String[] produces() default {};37 38     }39 }

4. HandlerMethod封装了处理器相关的全部信息,如类Object,方法Method,BeanFactory,参数MethodParameter[],原始方法Method

// HandlerMethod

 1     // org.springframework.web.method.HandlerMethod 2     private final Object bean;// 因为final不可修改,所以下面每次需要修改信息时,都需要new一个 3  4     private final Method method; 5  6     private final BeanFactory beanFactory; 7  8     private final MethodParameter[] parameters; 9 10     private final Method bridgedMethod;

5. 这边匹配条件的范型只有一个实现,RequestMappingInfo.匹配条件里记录的是RequestCondition子类,用于诸如pattern,http method,request parameter等

// RequestMappingInfo

 1     // javax.servlet.http.HttpServletRequest.RequestMappingInfo 2 public final class RequestMappingInfo implements RequestCondition<RequestMappingInfo> { 3  4     private final PatternsRequestCondition patternsCondition; 5  6     private final RequestMethodsRequestCondition methodsCondition; 7  8     private final ParamsRequestCondition paramsCondition; 9 10     private final HeadersRequestCondition headersCondition;11 12     private final ConsumesRequestCondition consumesCondition;13 14     private final ProducesRequestCondition producesCondition;15 16     private final RequestConditionHolder customConditionHolder;17     // ...18 19 }

6. 最后再简单看看RequestCondition ,这边定义了3个方法

 1 package org.springframework.web.servlet.mvc.condition; 2     public interface RequestCondition<T> { 3         /** 4          * 拼接条件 5          */ 6         T combine(T other); 7  8         /** 9          * 查找匹配的条件,并返回10          */11         T getMatchingCondition(HttpServletRequest request);12 13         /**14          * 用于排序15          */16         int compareTo(T other, HttpServletRequest request);17     }

看看继承体系吧,老套路,定义接口,然后模板方法实现主要逻辑,具体算法留给子类实现,还有正事要做,还是后期再细化吧.

正文

整个初始化工作由AbstractHandlerMethodMapping的initHandlerMethods主导.copy一段,省得回去比对看

　　1. 使用BeanFactoryUtils扫描应用下的Object或者直接从容器中获取Object

　　2. 迭代类,分别判断isHandler判断目标类是否Handler

　　　　2.1 RequestMappingHandlerMapping.isHandler根据@Controller或@RequestMapping注解判断(有任意一个)

　　3. 对handler解析出所有需要分发的方法detectHandlerMethods

　　　　3.1 获取原始的Class<?>

　　　　3.2 使用HandlerMethodSelector.selectMethods过滤具体handler method,预留getMappingForMethod模板方法给子类

　　　　　　RequestMappingHandlerMapping.getMappingForMethod根据类,方法上的RequestMapping注解生成匹配条件RequestMappingInfo

　　　　3.3 对过滤到的每个method进行注册registerHandlerMethod

　　　　　　a, 使用createHandlerMethod封装处理器为HandlerMethod

　　　　　　b, 判断之前是否已经匹配条件对应的处理器是否冲突(相同的匹配条件只能有一个对应的处理器)

　　　　　　c, 设置匹配条件到handler method的映射关系

　　　　　　d, 从匹配条件中解析出url,并注册到urlMap(url到匹配条件的映射),这边由RequestMappingInfoHandlerMapping.getMappingPathPatterns实现

　　4. 对HandlerMethod进行初始化handlerMethodsInitialized,其实现在什么都没做

// AbstractHandlerMethodMapping

 1 /** 这个方法哪来的,具体看备注的InitializingBean 2      * Detects handler methods at initialization. 3      */ 4     public void afterPropertiesSet() { 5         initHandlerMethods(); 6     } 7  8     /**扫描ApplicationContext中的bean,然后筛选handler method 并注册 9      * Scan beans in the ApplicationContext, detect and register handler methods.10      * @see #isHandler(Class)11      * @see #getMappingForMethod(Method, Class)12      * @see #handlerMethodsInitialized(Map)13      */14     protected void initHandlerMethods() {15         if (logger.isDebugEnabled()) {16             logger.debug("Looking for request mappings in application context: " + getApplicationContext());17         }18 19         String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?20                 BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :21                 getApplicationContext().getBeanNamesForType(Object.class));22 23         for (String beanName : beanNames) {24             if (isHandler(getApplicationContext().getType(beanName))){25                 detectHandlerMethods(beanName);26             }27         }28         handlerMethodsInitialized(getHandlerMethods());29     }

预留给子类实现的判断handler,实际是由RequestMappingHandlerMapping实现　　

// AbstractHandlerMethodMapping

1     /**2      * Whether the given type is a handler with handler methods.3      * @param beanType the type of the bean being checked4      * @return "true" if this a handler type, "false" otherwise.5      */6     protected abstract boolean isHandler(Class<?> beanType);

// RequestMappingHandlerMapping

这边判断的逻辑很简单,类上使用Controller或RequestMapping其中至少一个注解就可以.

1     /**2      * {@inheritDoc}3      * Expects a handler to have a type-level @{@link Controller} annotation.4      */5     @Override6     protected boolean isHandler(Class<?> beanType) {7         return ((AnnotationUtils.findAnnotation(beanType, Controller.class) != null) ||8                 (AnnotationUtils.findAnnotation(beanType, RequestMapping.class) != null));9     }

// AbstractHandlerMethodMapping

 1     /** 2      * Look for handler methods in a handler. 3      * @param handler the bean name of a handler or a handler instance 4      */ 5     protected void detectHandlerMethods(final Object handler) { 6         Class<?> handlerType = (handler instanceof String) ? 7                 getApplicationContext().getType((String) handler) : handler.getClass(); 8  9         final Class<?> userType = ClassUtils.getUserClass(handlerType);10 11         Set<Method> methods = HandlerMethodSelector.selectMethods(userType, new MethodFilter() {12             public boolean matches(Method method) {13                 return getMappingForMethod(method, userType) != null;14             }15         });16 17         for (Method method : methods) {18             T mapping = getMappingForMethod(method, userType);19             registerHandlerMethod(handler, method, mapping);20         }21     }

// AbstractHandlerMethodMapping

这边具体的实现是由RequestMappingHandlerMapping实现,根据注解生产匹配关系,这边实现类是RequestMappingInfo,就是代码有点多,慢慢看

1     /** 2      * Provide the mapping for a handler method. A method for which no3      * mapping can be provided is not a handler method.4      * @param method the method to provide a mapping for5      * @param handlerType the handler type, possibly a sub-type of the method's6      * declaring class7      * @return the mapping, or {@code null} if the method is not mapped8      */9     protected abstract T getMappingForMethod(Method method, Class<?> handlerType);

// RequestMappingHandlerMapping

 1     /** 2      * Uses method and type-level @{@link RequestMapping} annotations to create 3      * the RequestMappingInfo. 4      * 5      * @return the created RequestMappingInfo, or {@code null} if the method 6      * does not have a {@code @RequestMapping} annotation. 7      * 8      * @see #getCustomMethodCondition(Method) 9      * @see #getCustomTypeCondition(Class)10      */11     @Override12     protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {13         RequestMappingInfo info = null;14         // 读取方法上的RequestMapping注解信息15         RequestMapping methodAnnotation = AnnotationUtils.findAnnotation(method, RequestMapping.class);16         if (methodAnnotation != null) {17             // 读取自定义的条件,这边没有使用18             RequestCondition<?> methodCondition = getCustomMethodCondition(method);19             // 根据方法上的RequsetMapping注解和自定义条件,生成匹配条件.这边的匹配条件包括http method,request parameter,request header等20             info = createRequestMappingInfo(methodAnnotation, methodCondition);21             // 读取类上的RequestMapping注解信息22             RequestMapping typeAnnotation = AnnotationUtils.findAnnotation(handlerType, RequestMapping.class);23             if (typeAnnotation != null) {24                 RequestCondition<?> typeCondition = getCustomTypeCondition(handlerType);25                 // 生成类上的匹配条件,并合并方法上的26                 info = createRequestMappingInfo(typeAnnotation, typeCondition).combine(info);27             }28         }29         return info;30     }

// RequestMappingHandlerMapping

 1     /** 2      * Created a RequestMappingInfo from a RequestMapping annotation. 3      */ 4     private RequestMappingInfo createRequestMappingInfo(RequestMapping annotation, RequestCondition<?> customCondition) { 5         String[] patterns = resolveEmbeddedValuesInPatterns(annotation.value()); 6         return new RequestMappingInfo( 7                 new PatternsRequestCondition(patterns, getUrlPathHelper(), getPathMatcher(), 8                         this.useSuffixPatternMatch, this.useTrailingSlashMatch, this.fileExtensions), 9                 new RequestMethodsRequestCondition(annotation.method()),10                 new ParamsRequestCondition(annotation.params()),11                 new HeadersRequestCondition(annotation.headers()),12                 new ConsumesRequestCondition(annotation.consumes(), annotation.headers()),13                 new ProducesRequestCondition(annotation.produces(), annotation.headers(), getContentNegotiationManager()),14                 customCondition);15     }16 17     /**18      * Resolve placeholder values in the given array of patterns.19      * @return a new array with updated patterns20      */21     protected String[] resolveEmbeddedValuesInPatterns(String[] patterns) {22         if (this.embeddedValueResolver == null) {23             return patterns;24         }25         else {26             String[] resolvedPatterns = new String[patterns.length];27             for (int i=0; i < patterns.length; i++) {28                 resolvedPatterns[i] = this.embeddedValueResolver.resolveStringValue(patterns[i]);29             }30             return resolvedPatterns;31         }32     }

// AbstractHandlerMethodMapping

 1 /** 2      * Register a handler method and its unique mapping. 3      * @param handler the bean name of the handler or the handler instance 4      * @param method the method to register 5      * @param mapping the mapping conditions associated with the handler method 6      * @throws IllegalStateException if another method was already registered 7      * under the same mapping 8      */ 9     protected void registerHandlerMethod(Object handler, Method method, T mapping) {10         HandlerMethod newHandlerMethod = createHandlerMethod(handler, method);11         HandlerMethod oldHandlerMethod = handlerMethods.get(mapping);12         if (oldHandlerMethod != null && !oldHandlerMethod.equals(newHandlerMethod)) {13             throw new IllegalStateException("Ambiguous mapping found. Cannot map '" + newHandlerMethod.getBean()14                     + "' bean method \n" + newHandlerMethod + "\nto " + mapping + ": There is already '"15                     + oldHandlerMethod.getBean() + "' bean method\n" + oldHandlerMethod + " mapped.");16         }17 18         this.handlerMethods.put(mapping, newHandlerMethod);// 匹配条件requestMappingInfo 到处理器HandlerMethod19         if (logger.isInfoEnabled()) {20             logger.info("Mapped \"" + mapping + "\" onto " + newHandlerMethod);21         }22 23         Set<String> patterns = getMappingPathPatterns(mapping);24         for (String pattern : patterns) {25             if (!getPathMatcher().isPattern(pattern)) {26                 this.urlMap.add(pattern, mapping);// url到匹配条件RequestMappingInfo27             }28         }29     }

// AbstractHandlerMethodMapping

 1     /** 2      * Create the HandlerMethod instance. 3      * @param handler either a bean name or an actual handler instance 4      * @param method the target method 5      * @return the created HandlerMethod 6      */ 7     protected HandlerMethod createHandlerMethod(Object handler, Method method) { 8         HandlerMethod handlerMethod; 9         if (handler instanceof String) {10             String beanName = (String) handler;11             handlerMethod = new HandlerMethod(beanName, getApplicationContext(), method);12         }13         else {14             handlerMethod = new HandlerMethod(handler, method);15         }16         return handlerMethod;17     }

// AbstractHandlerMethodMapping

1     /**2      * Extract and return the URL paths contained in a mapping.3      */4     protected abstract Set<String> getMappingPathPatterns(T mapping);

RequestMappingInfoHandlerMapping会实现这个模板方法

// RequestMappingInfoHandlerMapping

1     /**2      * Get the URL path patterns associated with this {@link RequestMappingInfo}.3      */4     @Override5     protected Set<String> getMappingPathPatterns(RequestMappingInfo info) {6         return info.getPatternsCondition().getPatterns();7     }

备注:

1. 这边的afterPropertiesSet是因为实现了InitializingBean接口

// org.springframework.beans.factory.InitializingBean

 1 /** 2  * Interface to be implemented by beans that need to react once all their 3  * properties have been set by a BeanFactory: for example, to perform custom 4  * initialization, or merely to check that all mandatory properties have been set. 5  * 6  * <p>An alternative to implementing InitializingBean is specifying a custom 7  * init-method, for example in an XML bean definition. 8  * For a list of all bean lifecycle methods, see the BeanFactory javadocs. 9  *10  * @author Rod Johnson11  * @see BeanNameAware12  * @see BeanFactoryAware13  * @see BeanFactory14  * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName15  * @see org.springframework.context.ApplicationContextAware16  */17 public interface InitializingBean {18 19     /**20      * Invoked by a BeanFactory after it has set all bean properties supplied21      * (and satisfied BeanFactoryAware and ApplicationContextAware).22      * <p>This method allows the bean instance to perform initialization only23      * possible when all bean properties have been set and to throw an24      * exception in the event of misconfiguration.25      * @throws Exception in the event of misconfiguration (such26      * as failure to set an essential property) or if initialization fails.27      */28     void afterPropertiesSet() throws Exception;29 30 }

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