处理器适配器和映射器

Spring MVC 有许多默认配置，如下：

# spring-webmvc-4.2.4.RELEASE.jar!/org/springframework/web/servlet/DispatcherServlet.properties
org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver

org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver
# 处理器映射器
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
    org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping
# 处理器适配器
org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
    org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter

org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\
    org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
    org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver

org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator

org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver

org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager

查看处理器映射器和处理器适配器类的源码会发现这两个类是已过期的，如下：

// org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping：处理器映射器
/**
 * Implementation of the {@link org.springframework.web.servlet.HandlerMapping}
 * interface that maps handlers based on HTTP paths expressed through the
 * {@link RequestMapping} annotation at the type or method level.
 *
 * <p>Registered by default in {@link org.springframework.web.servlet.DispatcherServlet}
 * on Java 5+. <b>NOTE:</b> If you define custom HandlerMapping beans in your
 * DispatcherServlet context, you need to add a DefaultAnnotationHandlerMapping bean
 * explicitly, since custom HandlerMapping beans replace the default mapping strategies.
 * Defining a DefaultAnnotationHandlerMapping also allows for registering custom
 * interceptors:
 *
 * <pre class="code">
 * &lt;bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"&gt;
 *   &lt;property name="interceptors"&gt;
 *     ...
 *   &lt;/property&gt;
 * &lt;/bean&gt;</pre>
 *
 * Annotated controllers are usually marked with the {@link Controller} stereotype
 * at the type level. This is not strictly necessary when {@link RequestMapping} is
 * applied at the type level (since such a handler usually implements the
 * {@link org.springframework.web.servlet.mvc.Controller} interface). However,
 * {@link Controller} is required for detecting {@link RequestMapping} annotations
 * at the method level if {@link RequestMapping} is not present at the type level.
 *
 * <p><b>NOTE:</b> Method-level mappings are only allowed to narrow the mapping
 * expressed at the class level (if any). HTTP paths need to uniquely map onto
 * specific handler beans, with any given HTTP path only allowed to be mapped
 * onto one specific handler bean (not spread across multiple handler beans).
 * It is strongly recommended to co-locate related handler methods into the same bean.
 *
 * <p>The {@link AnnotationMethodHandlerAdapter} is responsible for processing
 * annotated handler methods, as mapped by this HandlerMapping. For
 * {@link RequestMapping} at the type level, specific HandlerAdapters such as
 * {@link org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter} apply.
 *
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @since 2.5
 * @see RequestMapping
 * @see AnnotationMethodHandlerAdapter
 * @deprecated as of Spring 3.2, in favor of
 * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping RequestMappingHandlerMapping}
 */
@Deprecated
public class DefaultAnnotationHandlerMapping extends AbstractDetectingUrlHandlerMapping {
// org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter：处理器适配器
/**
 * Implementation of the {@link org.springframework.web.servlet.HandlerAdapter} interface
 * that maps handler methods based on HTTP paths, HTTP methods, and request parameters
 * expressed through the {@link RequestMapping} annotation.
 *
 * <p>Supports request parameter binding through the {@link RequestParam} annotation.
 * Also supports the {@link ModelAttribute} annotation for exposing model attribute
 * values to the view, as well as {@link InitBinder} for binder initialization methods
 * and {@link SessionAttributes} for automatic session management of specific attributes.
 *
 * <p>This adapter can be customized through various bean properties.
 * A common use case is to apply shared binder initialization logic through
 * a custom {@link #setWebBindingInitializer WebBindingInitializer}.
 *
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @author Sam Brannen
 * @since 2.5
 * @see #setPathMatcher
 * @see #setMethodNameResolver
 * @see #setWebBindingInitializer
 * @see #setSessionAttributeStore
 * @deprecated as of Spring 3.2, in favor of
 * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter RequestMappingHandlerAdapter}
 */
@Deprecated
public class AnnotationMethodHandlerAdapter extends WebContentGenerator
        implements HandlerAdapter, Ordered, BeanFactoryAware {

从注释中可以看到让我们使用新的处理器映射器和处理器适配器类，而我们只需要将这两个类的实例交给 Spring 管理，Spring MVC 就会默认使用上这两个类，配置如下：

<!-- springmvc.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans.xsd
           http://www.springframework.org/schema/mvc
           http://www.springframework.org/schema/mvc/spring-mvc.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context.xsd">
    <!--配置控制器扫描-->
    <context:component-scan base-package="com.zze.springmvc.web.controller"/>
    <!--配置处理器映射器-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"/>
    <!--配置处理器适配器-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>
</beans>

而这样配置显然不够简洁，Spring MVC 还为我们提供了一个更简洁的配置方式，如下：

<!-- springmvc.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans.xsd
           http://www.springframework.org/schema/mvc
           http://www.springframework.org/schema/mvc/spring-mvc.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context.xsd">
    <!--配置控制器扫描-->
    <context:component-scan base-package="com.zze.springmvc.web.controller"/>
    <!--配置注解驱动，相当于同时使用最新处理器映射器和处理器适配器-->
    <mvc:annotation-driven/>
</beans>

从 spring 3.1 版本开始，废除了 DefaultAnnotationHandlerMapping 的使用，推荐使用 RequestMappingHandlerMapping 完成注解式处理器映射。
从 spring 3.1 版本开始，废除了 AnnotationMethodHandlerAdapter 的使用，推荐使用 RequestMappingHandlerAdapter 完成注解式处理器适配。
映射器与适配器必需配套使用，如果映射器使用了推荐的 RequestMappingHandlerMapping，适配器也必需使用推荐的 RequestMappingHandlerAdapter。

视图解析器

在 Spring 核心配置文件中配置上如下视图解析器：

<!--视图解析器-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/jsp/"/>
    <property name="suffix" value=".jsp"/>
</bean>

此时 Controller 返回的 viewName 如果是 userlist，那么它实际上会转发到 /WEB-INF/jsp/userlist.jsp。

目录CONTENT

SpringMVC(2)之配置相关

处理器适配器和映射器

视图解析器

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