码迷,mamicode.com
首页 > 移动开发 > 详细

Spring MVC的handlermapping之RequestMappingHandlerMapping初始化

时间:2018-03-29 12:01:08      阅读:217      评论:0      收藏:0      [点我收藏+]

标签:注册   ant   length   sele   匹配   lin   一个   映射   control   

RequestMappingHandlerMapping:这个handlerMapping是基于注解的
同样,先上类图:

技术分享图片

通过类图可以看到,同样是继承父类 AbstractHandlerMapping来进行拦截器的初始化工作,实际上处理自己逻辑的只有下面三个类;
需要注意的是RequestMappingHandlerMapping初始化并不是重写initApplicationContext()方法 ,而是通过实现InitializingBean接口来进行初始工作的。

备注:InitializingBean接口为bean提供了初始化方法的方式,它只包括afterPropertiesSet方法,凡是实现该接口的类,在初始化bean的时候会执行该方法。
来看AbstractHandlerMethodMapping 中关键的代码:
 1     public void afterPropertiesSet() { //实现了InitializingBean接口的方法,进行初始化的入口。
 2         this.initHandlerMethods();
 3     }
 4 
 5     protected void initHandlerMethods() {
 6         if (this.logger.isDebugEnabled()) {
 7             this.logger.debug("Looking for request mappings in application context: " + this.getApplicationContext());
 8         }
 9      //扫描应用下所有Object类
10         String[] beanNames = this.detectHandlerMethodsInAncestorContexts ? BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.getApplicationContext(), Object.class) : this.getApplicationContext().getBeanNamesForType(Object.class);
11         String[] arr$ = beanNames;
12         int len$ = beanNames.length;
13 
14         for(int i$ = 0; i$ < len$; ++i$) {
15             String beanName = arr$[i$];
16             if (this.isHandler(this.getApplicationContext().getType(beanName))) { //ishandler由子类实现,是个钩子方法,让子类实现自己的逻辑
17                 this.detectHandlerMethods(beanName);
18             }
19         }
20 
21         this.handlerMethodsInitialized(this.getHandlerMethods());//初始化处理器对象,目前是钩子方法,但是也没有子类实现这个方法
22     }

isHandler方法是在RequestMappingHandlerMapping中实现的

1     protected boolean isHandler(Class<?> beanType) { //非常简单, 就是看这个类有没有Controller或者RequestMapping注解,有一个就行
2         return AnnotationUtils.findAnnotation(beanType, Controller.class) != null || AnnotationUtils.findAnnotation(beanType, RequestMapping.class) != null;
3     }

回到AbstractHandlerMethodMapping看:

 1     protected void detectHandlerMethods(Object handler) { //开始注册handler
 2         Class<?> handlerType = handler instanceof String ? this.getApplicationContext().getType((String)handler) : handler.getClass();
 3         final Class<?> userType = ClassUtils.getUserClass(handlerType);
      //这块是获取handelr的所有方法,但是有一个过滤器,就是把有匹配条件的的method获取到
4 Set<Method> methods = HandlerMethodSelector.selectMethods(userType, new MethodFilter() { 5 public boolean matches(Method method) { 6 return AbstractHandlerMethodMapping.this.getMappingForMethod(method, userType) != null;//getMappingForMethod钩子方法,子类实现 7 } 8 }); 9 Iterator i$ = methods.iterator(); 10 //遍历method 进行注册。 11 while(i$.hasNext()) { 12 Method method = (Method)i$.next(); 13 T mapping = this.getMappingForMethod(method, userType); 14 this.registerHandlerMethod(handler, method, mapping); 15 } 16 17 }

来看getMappingForMethod的实现,是在RequestMappingHandlerMapping实现的

 1     protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) { 
 2         RequestMappingInfo info = null; //获取方法上的RequestMapping注解信息
 3         RequestMapping methodAnnotation = (RequestMapping)AnnotationUtils.findAnnotation(method, RequestMapping.class);
 4         if (methodAnnotation != null) {
 5             RequestCondition<?> methodCondition = this.getCustomMethodCondition(method);
 6             info = this.createRequestMappingInfo(methodAnnotation, methodCondition); 构造匹配条件
         // 获取类上的面RequestHandlerMapping注解信息
7 RequestMapping typeAnnotation = (RequestMapping)AnnotationUtils.findAnnotation(handlerType, RequestMapping.class); 8 if (typeAnnotation != null) { 9 RequestCondition<?> typeCondition = this.getCustomTypeCondition(handlerType); 10 info = this.createRequestMappingInfo(typeAnnotation, typeCondition).combine(info); 构造匹配条件,同方法的进行合并 11 } 12 } 13 14 return info; 15 }

备注下;RequestMappingInfo 实际上是匹配条件的一个抽象对象,包含了url,method,param,header...等等

来看注册方法前,先看一下处理器是保存在哪的;

1 public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean {
2     //这块实际上是两个map保存的,泛型实际上就是RequestMappingInfo,这个就是匹配条件 HanlderMethod是封装了处理器全部信息的封装类
3     private final Map<T, HandlerMethod> handlerMethods = new LinkedHashMap(); //存的是 key:匹配条件 value: 处理器
4     private final MultiValueMap<String, T> urlMap = new LinkedMultiValueMap(); //key: url value: 匹配条件

这块讲一下MultiValueMap

public interface MultiValueMap<K, V> extends Map<K, List<V>> //实际上就是个 value是个list的map
 1     protected void registerHandlerMethod(Object handler, Method method, T mapping) {
 2         HandlerMethod handlerMethod;
 3         if (handler instanceof String) {
 4             String beanName = (String)handler;
 5             handlerMethod = new HandlerMethod(beanName, this.getApplicationContext(), method);
 6         } else {
 7             handlerMethod = new HandlerMethod(handler, method);
 8         }
 9 
10         HandlerMethod oldHandlerMethod = (HandlerMethod)this.handlerMethods.get(mapping);
11         if (oldHandlerMethod != null && !oldHandlerMethod.equals(handlerMethod)) { //不允许存在一个mapping对应多个handlerMethod
12             throw new IllegalStateException("Ambiguous mapping found. Cannot map ‘" + handlerMethod.getBean() + "‘ bean method \n" + handlerMethod + "\nto " + mapping + ": There is already ‘" + oldHandlerMethod.getBean() + "‘ bean method\n" + oldHandlerMethod + " mapped.");
13         } else {
14             this.handlerMethods.put(mapping, handlerMethod); //存放第一个映射集合
15             if (this.logger.isInfoEnabled()) {
16                 this.logger.info("Mapped \"" + mapping + "\" onto " + handlerMethod);
17             }
18 
19             Set<String> patterns = this.getMappingPathPatterns(mapping); //获取方法的URL
20             Iterator i$ = patterns.iterator();
21 
22             while(i$.hasNext()) {
23                 String pattern = (String)i$.next();
24                 if (!this.getPathMatcher().isPattern(pattern)) { //依次放入第二个映射集合
25                     this.urlMap.add(pattern, mapping);
26                 }
27             }
28 
29         }
30     }

到此为止,RequestMappingHandlerMapping就初始化完成了。

疑问:  为什么非注解映射器都是通过重写initApplication方法,而注解映射器是通过实现iniliazingBean接口来初始化,这样的好处是什么?

欢迎探讨

Spring MVC的handlermapping之RequestMappingHandlerMapping初始化

标签:注册   ant   length   sele   匹配   lin   一个   映射   control   

原文地址:https://www.cnblogs.com/haoerlv/p/8668635.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!