spring mvc <mvc:annotation-driver/>详解

To enable MVC Java config add the annotation 

@EnableWebMvc

 to
one of your 

@Configuration

 classes:

@Configuration
@EnableWebMvc
public class WebConfig {

}

To achieve the same in XML use the 

mvc:annotation-driven

 element
in your DispatcherServlet context (or in your root context if you have no DispatcherServlet context defined):

<?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.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

<mvc:annotation-driven/>

</beans>

The above registers a 

RequestMappingHandlerMapping

,
a 

RequestMappingHandlerAdapter

,
and an 

ExceptionHandlerExceptionResolver

 (among
others) in support of processing requests with annotated controller methods using annotations such as 

@RequestMapping

, 

@ExceptionHandler

,
and others.

It also enables the following:

Spring 3 style type conversion through a ConversionService instance
in addition to the JavaBeans PropertyEditors used for Data Binding.
Support for formatting Number
fields using the 

@NumberFormat

 annotation
through the 

ConversionService

.
Support for formatting 

Date

, 

Calendar

, 

Long

,
and Joda Time fields using the 

@DateTimeFormat

 annotation.
Support for validating 

@Controller

 inputs
with 

@Valid

,
if a JSR-303 Provider is present on the classpath.

HttpMessageConverter

 support
for 

@RequestBody

 method
parameters and 

@ResponseBody

 method
return values from 

@RequestMapping

 or

@ExceptionHandler

 methods.
This is the complete list of HttpMessageConverters set up by mvc:annotation-driven:

ByteArrayHttpMessageConverter

 converts
byte arrays.

StringHttpMessageConverter

 converts
strings.

ResourceHttpMessageConverter

 converts
to/from 

org.springframework.core.io.Resource

 for
all media types.

SourceHttpMessageConverter

 converts
to/from a 

javax.xml.transform.Source

.

FormHttpMessageConverter

 converts
form data to/from a 

MultiValueMap<String,
String>

.

Jaxb2RootElementHttpMessageConverter

 converts
Java objects to/from XML — added if JAXB2 is present and Jackson 2 XML extension is not present on the classpath.

MappingJackson2HttpMessageConverter

 converts
to/from JSON — added if Jackson 2 is present on the classpath.

MappingJackson2XmlHttpMessageConverter

 converts
to/from XML — added if Jackson 2 XML extension is present on the classpath.

AtomFeedHttpMessageConverter

 converts
Atom feeds — added if Rome is present on the classpath.

RssChannelHttpMessageConverter

 converts
RSS feeds — added if Rome is present on the classpath.

See Section 22.16.12,
“Message Converters” for more information about how to customize these default converters.

Jackson JSON and XML converters are created using  ObjectMapper  instances created by  Jackson2ObjectMapperBuilder  in order to provide a better default configuration. This builder customizes Jackson’s default properties with the following ones: DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES  is disabled. MapperFeature.DEFAULT_VIEW_INCLUSION  is disabled. It also automatically registers the following well-known modules if they are detected on the classpath: jackson-datatype-jdk7: support for Java 7 types like  java.nio.file.Path . jackson-datatype-joda: support for Joda-Time types. jackson-datatype-jsr310: support for Java 8 Date & Time API types. jackson-datatype-jdk8: support for other Java 8 types like  Optional .