SpringMVC源码解析- HandlerAdapter初始化-白红宇

SpringMVC源码解析- HandlerAdapter初始化

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发布时间：2019-06-18

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HandlerAdapter初始化时,主要是进行注解解析器初始化注册;返回值处理类初始化;全局注解@ControllerAdvice内容读取并缓存.

　　注解解析器初始化注册:@ModelAttribute(往model中添加属性)

　　注解解析器初始化注册:@InitBinder(用于注册校验器,参数编辑器等)　　

　　返回值处理returnValueHandlers初始化

　　全局的@ControllerAdvice注解使用类的@ModelAttribute 和 @InitBinder信息读取并缓存

注:具体解析器的分析还是看后续文章吧,要不文章跟裹脚布似的.

注解@ModelAttritue解析器初始化并注册

我们先看下@ModelAttribute注解的使用吧:

　　1. 在注解中定义属性名,方法返回值

　　2. 通过model直接设置

　　3. 暂时没搞定

1     // 在注解中定义属性名,方法返回值 2     @ModelAttribute("clazzName") 3     public String setModel() { 4         return this.getClass().getName(); 5     } 6     // 通过model直接设置 7     @ModelAttribute 8     public void setModel1(Model model){ 9         model.addAttribute("movie", "who");10     }11     // 暂时没搞定12     @ModelAttribute()13     public String setModel2(){14         return "actor";15     }

新建解析器时的逻辑:

　　1 如果没有配置,直接读取默认实现

　　　　这边默认实现多达24种+自定义实现,主要分为4类解析器:基于注解,基于类型,自定义,号称解析全部

　　2 通过Composite封装,并注册

　　　　解析策略实在太多,这边封装一个HandlerMethodArgumentResolverComposite,迭代解析器委托处理(有点责任链的味道)

先看初始化解析器,并注册的代码:

1 package org.springframework.web.servlet.mvc.method.annotation; 2 public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter implements BeanFactoryAware, 3         InitializingBean { 4     public void afterPropertiesSet() { 5         if (this.argumentResolvers == null) { 6             List
     
       resolvers = getDefaultArgumentResolvers(); 7             this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers); 8         } 9         // ...10     }11     private List
      
        getDefaultArgumentResolvers() {12         List
       
         resolvers = new ArrayList
        
         ();13 14         // Annotation-based argument resolution 基于注解的解析器15         resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));16         resolvers.add(new RequestParamMapMethodArgumentResolver());17         resolvers.add(new PathVariableMethodArgumentResolver());18         resolvers.add(new PathVariableMapMethodArgumentResolver());19         resolvers.add(new MatrixVariableMethodArgumentResolver());20         resolvers.add(new MatrixVariableMapMethodArgumentResolver());21         resolvers.add(new ServletModelAttributeMethodProcessor(false));22         resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters()));23         resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters()));24         resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));25         resolvers.add(new RequestHeaderMapMethodArgumentResolver());26         resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory()));27         resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));28 29         // Type-based argument resolution 基于类型的解析器30         resolvers.add(new ServletRequestMethodArgumentResolver());31         resolvers.add(new ServletResponseMethodArgumentResolver());32         resolvers.add(new HttpEntityMethodProcessor(getMessageConverters()));33         resolvers.add(new RedirectAttributesMethodArgumentResolver());34         resolvers.add(new ModelMethodProcessor());35         resolvers.add(new MapMethodProcessor());36         resolvers.add(new ErrorsMethodArgumentResolver());37         resolvers.add(new SessionStatusMethodArgumentResolver());38         resolvers.add(new UriComponentsBuilderMethodArgumentResolver());39 40         // Custom arguments 自定义解析器41         if (getCustomArgumentResolvers() != null) {42             resolvers.addAll(getCustomArgumentResolvers());43         }44 45         // Catch-all 全能的解析器46         resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));47         resolvers.add(new ServletModelAttributeMethodProcessor(true));48 49         return resolvers;50     }51 }

然后是HandlerMethodArgumentResolverComposite迭代具体解析器委托处理的代码:

GOF对责任链意图的定义是:

　　使多个对象都有机会iu处理请求,从而避免请求的发送者和接受者直接的耦合关系.将这些对象连成一条链,并沿这条链传递该请求,直到有一个对象处理它为止.

　　从百度百科盗了个类图,来类比下:

上面是标准的责任链,下面是HandlerMethodReturnValueHandler部分类图

1 package org.springframework.web.method.support; 2 public class HandlerMethodArgumentResolverComposite implements HandlerMethodArgumentResolver { 3     public Object resolveArgument( 4             MethodParameter parameter, ModelAndViewContainer mavContainer, 5             NativeWebRequest webRequest, WebDataBinderFactory binderFactory) 6             throws Exception { 7  8         HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter); 9         return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);10     }11     public boolean supportsParameter(MethodParameter parameter) {12         return getArgumentResolver(parameter) != null;13     }14     private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {15         HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);16         if (result == null) {17             for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) {18                 if (methodArgumentResolver.supportsParameter(parameter)) {19                     result = methodArgumentResolver;20                     this.argumentResolverCache.put(parameter, result);21                     break;22                 }23             }24         }25         return result;26     }27     // ...28 }

注解@InitBinder解析器初始化

先看@InitBinder注解的使用吧:

1     /** 2      * 使用WebDataBinder实现日期校验 3      * @param dataBinder 4      */ 5     @InitBinder 6     public void dateFormat(WebDataBinder dataBinder){ 7         SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd"); 8         dateFormat.setLenient(false); 9         dataBinder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat,false));10     }

这边的代码逻辑其实跟@ModelAttribute解析器初始化的逻辑是一样的,就不具体分析,只是这边初始化使用的解析器是不一样的.至于差异的原因,暂时还不知道,哪位有兴趣可以帮忙科普科普.

1 package org.springframework.web.servlet.mvc.method.annotation; 2 public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter implements BeanFactoryAware, 3         InitializingBean { 4     private List
     
       getDefaultInitBinderArgumentResolvers() { 5         List
      
        resolvers = new ArrayList
       
        (); 6  7         // Annotation-based argument resolution 基于注解的解析器 8         resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false)); 9         resolvers.add(new RequestParamMapMethodArgumentResolver());10         resolvers.add(new PathVariableMethodArgumentResolver());11         resolvers.add(new PathVariableMapMethodArgumentResolver());12         resolvers.add(new MatrixVariableMethodArgumentResolver());13         resolvers.add(new MatrixVariableMapMethodArgumentResolver());14         resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));15 16         // Type-based argument resolution 基于类型的解析器17         resolvers.add(new ServletRequestMethodArgumentResolver());18         resolvers.add(new ServletResponseMethodArgumentResolver());19 20         // Custom arguments 自定义解析器21         if (getCustomArgumentResolvers() != null) {22             resolvers.addAll(getCustomArgumentResolvers());23         }24 25         // Catch-all 全能的解析器26         resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));27 28         return resolvers;29     }30     // ...31 }

返回值处理returnValueHandlers初始化

用于将handler处理器的返回值封装成ModelAndView.

这边的处理逻辑跟@ModelAttribute注解解析器的初始化高度雷同,我们还是看看使用的HandlerMethodReturnValueHandler接口

接口的定义方式也是高度雷同,一个api问是否支持,一个api进行具体处理.

1 package org.springframework.web.method.support;2 public interface HandlerMethodReturnValueHandler {3     boolean supportsReturnType(MethodParameter returnType);4     void handleReturnValue(Object returnValue,5                            MethodParameter returnType,6                            ModelAndViewContainer mavContainer,7                            NativeWebRequest webRequest) throws Exception;8 9 }

分类貌似也有一定的相似.

1 package org.springframework.web.servlet.mvc.method.annotation; 2 public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter implements BeanFactoryAware, 3         InitializingBean { 4     private List
     
       getDefaultReturnValueHandlers() { 5         List
      
        handlers = new ArrayList
       
        (); 6  7         // Single-purpose return value types 单一目的 8         handlers.add(new ModelAndViewMethodReturnValueHandler()); 9         handlers.add(new ModelMethodProcessor());10         handlers.add(new ViewMethodReturnValueHandler());11         handlers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.contentNegotiationManager));12         handlers.add(new CallableMethodReturnValueHandler());13         handlers.add(new DeferredResultMethodReturnValueHandler());14         handlers.add(new AsyncTaskMethodReturnValueHandler(this.beanFactory));15 16         // Annotation-based return value types 基于注解17         handlers.add(new ModelAttributeMethodProcessor(false));18         handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.contentNegotiationManager));19 20         // Multi-purpose return value types 多目的21         handlers.add(new ViewNameMethodReturnValueHandler());22         handlers.add(new MapMethodProcessor());23 24         // Custom return value types 自定义25         if (getCustomReturnValueHandlers() != null) {26             handlers.addAll(getCustomReturnValueHandlers());27         }28 29         // Catch-all    又是全能30         if (!CollectionUtils.isEmpty(getModelAndViewResolvers())) {31             handlers.add(new ModelAndViewResolverMethodReturnValueHandler(getModelAndViewResolvers()));32         }33         else {34             handlers.add(new ModelAttributeMethodProcessor(true));35         }36 37         return handlers;38     }39 }

全局的@ControllerAdvice注解使用类的@ModelAttribute 和 @InitBinder信息读取并缓存

@ControllerAdvice注解主要是为了解决以下的场景问题:

　　如果@ModelAttribute或@InitBinder注解如果需要在很多地方使用,怎么办?

　　使用集成的话,由于java的单继承会限制父类,不够灵活.

使用时只需要如下添加注解就可以

1 @ControllerAdvice()2 public class AdviceController {3     // ...4 }

源码解析时,是通过InitializingBean的afterPropertiesSet调用initControllerAdviceCache初始化的解析器.

查找使用注解@ControllerAdivce的类时,通过spring迭代容器过滤容器中全部的类,找到使用ControllerAdvice.class的类并注册.

1 package org.springframework.web.servlet.mvc.method.annotation; 2 public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter implements BeanFactoryAware, 3         InitializingBean { 4     public void afterPropertiesSet() { 5         // ... 6         initControllerAdviceCache(); 7     } 8     private void initControllerAdviceCache() { 9         // ...10         // 扫描方式找到使用@ControllerAdvice的类11         List
     
       beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());12         Collections.sort(beans, new OrderComparator());13 14         for (ControllerAdviceBean bean : beans) {15             Set
      
        attrMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), MODEL_ATTRIBUTE_METHODS);16             if (!attrMethods.isEmpty()) {17                 this.modelAttributeAdviceCache.put(bean, attrMethods);18             }19             Set
       
         binderMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), INIT_BINDER_METHODS);20             if (!binderMethods.isEmpty()) {21                 this.initBinderAdviceCache.put(bean, binderMethods);22             }23         }24     }25 }

这边扫描获取类的方式跟之前的有所不同,我们可以细看下.

1 package org.springframework.web.method; 2 public class ControllerAdviceBean implements Ordered { 3     /** 4      * Find the names of beans annotated with 5      * {@linkplain ControllerAdvice @ControllerAdvice} in the given 6      * ApplicationContext and wrap them as {@code ControllerAdviceBean} instances. 7      */ 8     public static List
     
       findAnnotatedBeans(ApplicationContext applicationContext) { 9         List
      
        beans = new ArrayList
       
        ();10         for (String name : applicationContext.getBeanDefinitionNames()) {11             if (applicationContext.findAnnotationOnBean(name, ControllerAdvice.class) != null) { 12 beans.add(new ControllerAdviceBean(name, applicationContext)); 13  } 14  } 15 return beans; 16  } 17 }

看下两个api在接口中定义:

　　1. getBeanDefinitionNames 返回容器中定义的全部bean 的 name

　　2. findAnnotationOnBean 查找类上定义的注解,包括父类与接口

1 package org.springframework.beans.factory; 2 public interface ListableBeanFactory extends BeanFactory { 3     // ...  4     /** 5      * Return the names of all beans defined in this factory. 6      * Does not consider any hierarchy this factory may participate in, 7      * and ignores any singleton beans that have been registered by 8      * other means than bean definitions. 9      * @return the names of all beans defined in this factory,10      * or an empty array if none defined11      */12     String[] getBeanDefinitionNames();13     /**14      * Find a {@link Annotation} of {@code annotationType} on the specified15      * bean, traversing its interfaces and super classes if no annotation can be16      * found on the given class itself.17      * @param beanName the name of the bean to look for annotations on18      * @param annotationType the annotation class to look for19      * @return the annotation of the given type found, or {@code null}20      */21      A findAnnotationOnBean(String beanName, Class annotationType);22 23 }

顺便关心下@ControllerAdvice信息是如何保存的,就是对应的pojo ControllerAdviceBean:

这边只是记录bean,还没有添加添加根据类,包进行过滤匹配类的功能.

这边值得说的有3个:

　　1. 根据类是否实现Ordered接口,设置排序顺序

　　2. 扫描应用下使用ControllerAdvice注解的类就是上面说的api

　　3. 实现getBeanType获取类的类型和resolveBean获取类实例 ,这个算是advice的行为吧.作为容器的行为吧.

1 package org.springframework.web.method; 2  3 public class ControllerAdviceBean implements Ordered { 4     // 使用注解的类 5     private final Object bean; 6     private final int order; 7     private final BeanFactory beanFactory; 8  9     public ControllerAdviceBean(String beanName, BeanFactory beanFactory) { 10 // ... 11  } 12 13 public ControllerAdviceBean(Object bean) { 14 // ... 15  } 16 17 // 如果类实现Ordered,根据order的值设置排序 18 private static int initOrderFromBeanType(Class
      beanType) { 19 Order annot = AnnotationUtils.findAnnotation(beanType, Order.class); 20 return (annot != null) ? annot.value() : Ordered.LOWEST_PRECEDENCE; 21  } 22 23 private static int initOrderFromBean(Object bean) { 24 return (bean instanceof Ordered) ? ((Ordered) bean).getOrder() : initOrderFromBeanType(bean.getClass()); 25  } 26 27 /** 28 * 扫描应用下使用ControllerAdvice注解的类 29 */ 30 public static List
     
       findAnnotatedBeans(ApplicationContext applicationContext) { 31 List
      
        beans = new ArrayList
       
        (); 32 for (String name : applicationContext.getBeanDefinitionNames()) { 33 if (applicationContext.findAnnotationOnBean(name, ControllerAdvice.class) != null) { 34 beans.add(new ControllerAdviceBean(name, applicationContext)); 35  } 36  } 37 return beans; 38  } 39 40 public Class
         getBeanType() { 41 Class
         clazz = (this.bean instanceof String) 42 ? this.beanFactory.getType((String) this.bean) : this.bean.getClass(); 43 44 return ClassUtils.getUserClass(clazz); 45  } 46 47 public Object resolveBean() { 48 return (this.bean instanceof String) ? this.beanFactory.getBean((String) this.bean) : this.bean; 49  } 50 // ... 51 }