3. Spring4.0之@RestController

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4.0重要的一个新的改进是@RestController注解，它继承自@Controller注解。4.0之前的版本，Spring MVC的组件都使用@Controller来标识当前类是一个控制器servlet。

使用这个特性，我们可以开发REST服务的时候不需要使用@Controller而专门的@RestController。

当你实现一个RESTful web services的时候，response将一直通过response body发送。为了简化开发，Spring 4.0提供了一个专门版本的controller。下面我们来看看@RestController实现的定义：

@Target(value=TYPE)
@Retention(value=RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController

官方文档解释:

A convenience annotation that is itself annotated with @Controller and @ResponseBody. Types that carry this annotation are treated as controllers where @RequestMapping methods assume @ResponseBody semantics by default.
注解本身使用@Controller和@ResponseBody注解。使用了这个注解的类会被看作一个controller-使用@RequestMapping的方法有一个默认的@ResponseBody注解。

@ResponseBody – As of version 4.0 this annotation can also be added on the type level in which case is inherited and does not need to be added on the method level.
@ResponseBody也可以加到类一级，通过继承方法一级不需要添加。

UserDetials.java:

package javabeat.net.rest;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class UserDetails {
private String userName;
private String emailId;

@XmlAttribute
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}

@XmlAttribute
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
}

SpringRestControllerDemo.java

package javabeat.net.rest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SpringRestControllerDemo {
@Autowired UserDetails userDetails;
@RequestMapping(value="/springcontent",
method=RequestMethod.GET,produces={"application/xml", "application/json"})
@ResponseStatus(HttpStatus.OK)
public UserDetails getUser() {
UserDetails userDetails = new UserDetails();
userDetails.setUserName("Krishna");
userDetails.setEmailId("krishna@gmail.com");
return userDetails;
}

@RequestMapping(value="/springcontent.htm", method=RequestMethod.GET)
@ResponseStatus(HttpStatus.OK)
public String getUserHtml() {
//Test HTML view
return "example";
}
}

dispatcher-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
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-4.0.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-4.0.xsd">

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

<bean id="userDetails" class="javabeat.net.rest.UserDetails"/>
<mvc:annotation-driven content-negotiation-manager="contentManager"/>
<bean id="contentManager"
class="org.springframework.web.accept.ContentNegotiationManagerFactoryBean">
<property name="favorPathExtension" value="true"/>
<property name="ignoreAcceptHeader" value="true" />
<property name="defaultContentType" value="text/html" />
<property name="useJaf" value="false"/>
<property name="mediaTypes">
<map>
<entry key="json" value="application/json" />
<entry key="html" value="text/html" />
<entry key="xml" value="application/xml" />
</map>
</property>
</bean>
<bean id="jspViewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>

</beans>

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