使用Maven管理的依賴庫，

在pom.xml的 dependencies 裡面配置Spring和jackson的依賴，配置後，會自動載入，spring context core aop 等其他spring依賴包新增 jackson-databind 後，jackson-core, jackson-annotations也會自動依賴

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>4.3.4.RELEASE</version>
		</dependency>

		<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.8.5</version>
		</dependency>
 

儲存，更新Maven，自動載入依賴庫
建立MvcController，內容如下

@Controller
@RequestMapping("/mvc")
public class MvcController {

	@RequestMapping(value="/json", method=RequestMethod.GET)
	public @ResponseBody User getUserJson() {
		User user = new User();
		user.setUsername("使用者名稱");
		user.setPassword("密碼");
		
		return user;
	}
}
 

web.xml內容如下

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>Tx-advice</display-name>
  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:applicationContext.xml</param-value>
  </context-param>
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>
  <servlet>
  	<servlet-name>springMVC</servlet-name>
  	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  	<init-param>
  		<param-name>contextConfigLocation</param-name>
  		<param-value>classpath:springmvc-servlet.xml</param-value>
  	</init-param>
  	<load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
  	<servlet-name>springMVC</servlet-name>
  	<url-pattern>/</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>
 

applicationContext.xml內容如下

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:util="http://www.springframework.org/schema/util" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
       http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/context  
    http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx.xsd
    http://www.springframework.org/schema/util
    http://www.springframework.org/schema/util/spring-util.xsd
    http://www.springframework.org/schema/mvc
    http://www.springframework.org/schema/mvc/spring-mvc.xsd">

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

</beans>

springmvc-servlet.xml內容如下

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:util="http://www.springframework.org/schema/util" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
       http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/context  
    http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx.xsd
    http://www.springframework.org/schema/util
    http://www.springframework.org/schema/util/spring-util.xsd
    http://www.springframework.org/schema/mvc
    http://www.springframework.org/schema/mvc/spring-mvc.xsd">

	<context:component-scan base-package="com.ing.controller"></context:component-scan>
	<mvc:default-servlet-handler />
	
	<bean id="internalResourceViewResolver"
		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix" value="/WEB-INF/jsp/"></property>
		<property name="suffix" value=".jsp"></property>
	</bean>

	<mvc:annotation-driven></mvc:annotation-driven>

</beans>

配置完成之後，啟動專案，訪問http://localhost:8080/webdemo/mvc/json，正確返回json資料。

如果想返回XML資料，在實體類上面使用 @XmlRootElement 註解即可，貼出實體類User的原始碼

package com.ing.po;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class User {
	private String username;
	private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}

再訪問原來返回json資料的網址，返回的就是XML格式的資料了


總結：其實Spring4.0之後的版本返回json資料的配置很簡單，只要加入jackson的依賴庫，在controller裡面的對映器方法前使用@ResponseBody註解即可。
如果想返回xml資料，不用新增其他的jar包，只需要在實體類加入 @XmlRootElement 註解類，在controller裡面的對映器方法前使用@ResponseBody註解即可。