使用@Controller注解为什么要配置<mvc:annotation-driven />

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Java代码  

1. <context:component-scan base-package="com"></context:component-scan>  

Java代码  

1. <servlet>  
2.     <servlet-name>mvc</servlet-name>  
3.     <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
4.     <load-on-startup>1</load-on-startup>  
5. </servlet>  
6. <servlet-mapping>  
7.     <servlet-name>mvc</servlet-name>  
8.     <url-pattern>*.do</url-pattern>  
9. </servlet-mapping>  

Java代码  

1. <context:component-scan base-package="com"></context:component-scan>  
2. <mvc:annotation-driven/>  
3. <mvc:resources mapping="/styles/**" location="/WEB-INF/resource/styles/"/>  
4. <mvc:default-servlet-handler/>  

Java代码  

1. <servlet>  
2.     <servlet-name>mvc</servlet-name>  
3.     <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
4.     <load-on-startup>1</load-on-startup>  
5. </servlet>  
6. <servlet-mapping>  
7.     <servlet-name>mvc</servlet-name>  
8.     <url-pattern>/</url-pattern>  
9. </servlet-mapping>  

是什么原因造成这种区别的呢？为什么一开始没用<mvc:annotation-driven/>的时候可以，添加了默认servlet之后就不行了呢？ 

回答

------------------------------------------------

This tag registers the DefaultAnnotationHandlerMapping and AnnotationMethodHandlerAdapter beans that are required for Spring MVC to dispatch requests to Controllers. 
这个标签注册了Spring MVC分发请求到控制器所必须的DefaultAnnotationHandlerMapping和AnnotationMethodHandlerAdapter实例

The tag configures those two beans with sensible defaults based on what is present in your classpath. 
标签配置的这2个实例可以根据classpath中的内容默认提供以下功能：

The defaults are:
1. Support for Spring 3‘s Type ConversionService in addition to JavaBeans PropertyEditors during Data Binding. 
A ConversionService instance produced by the org.springframework.format.support.FormattingConversionServiceFactoryBean is used by default. 
This can be overriden by setting the conversion-service attribute.
支持spring3的javaBeans属性编辑器数据绑定时的类型转换服务。
类型转换服务实例默认为org.springframework.format.support.FormattingConversionServiceFactoryBean。
可以覆盖conversion-service属性来指定类型转换服务实例类。

2. Support for formatting Number fields using the @NumberFormat annotation
支持@NumberFormat 注解格式化数字类型字段。

3. Support for formatting Date, Calendar, Long, and Joda Time fields using the @DateTimeFormat annotation, if Joda Time 1.3 or higher is present on the classpath.
@DateTimeFormat注解格式化 Date, Calendar, Long和 Joda Time（如classpath下存在Joda Time 1.3或更高版本）字段

4. Support for validating @Controller inputs with @Valid, if a JSR-303 Provider is present on the classpath. 
The validation system can be explicitly configured by setting the validator attribute.
支持@Valid注解验证控制器数据，classpath中需JSR-303的**。
可以使用setting明确的配置

5. Support for reading and writing XML, if JAXB is present on the classpath.
支持读写xml，classpath中需JAXB 。

6. Support for reading and writing JSON, if Jackson is present on the classpath.
支持读写json，classpath中需Jackson 。

A typical usage is shown below:
下边是用法：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
<!-- JSR-303 support will be detected on classpath and enabled automatically -->
<mvc:annotation-driven/>
</beans>

求上述1-6的使用例子。

总结：

要使用spring mvc中的@Controller注解，就必须要配置<mvc:annotation-driven />，否则org.springframework.web.servlet.DispatcherServlet无法找到控制器并把请求分发到控制器。

使用@Controller注解为什么要配置<mvc:annotation-driven />

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原文地址：http://my.oschina.net/liting/blog/524726