private 
     static 
     final 
     boolean gsonPresent =
    
   

   

    

   
   

    

     			ClassUtils.isPresent(
     "com.google.gson.Gson", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
    
   


 所以我们只要把Jackson2或者GSON加入工程的class path，Spring就会自动把GsonHttpMessageConverter加进来。 
 
1）我们在POM中添加以下依赖
 
 

 

   

    

   
   

    
        
     <dependency>
    
   

   

    

   
   

    
            
     <groupId>com.fasterxml.jackson.core
     </groupId>
    
   

   

    

   
   

    
            
     <artifactId>jackson-databind
     </artifactId>
    
   

   

    

   
   

    
            
     <version>2.6.1
     </version>
    
   

   

    

   
   

    
        
     </dependency>
    
   


 或者 
 
 

 

   

    

   
   

    
	
     <dependency>
    
   

   

    

   
   

    
		
     <groupId>com.google.code.gson
     </groupId>
    
   

   

    

   
   

    
		
     <artifactId>gson
     </artifactId>
    
   

   

    

   
   

    
		
     <version>2.3.1
     </version>
    
   

   

    

   
   

    
	
     </dependency>
    
   


 2）在XmlOrJsonController.java中添加getEmployeeJson（）方法 
 
 

 

   

    

   
   

    
	
     @RequestMapping(value=
     "/json/{name}", method=RequestMethod.GET)
    
   

   

    

   
   

    
	
     @ResponseBody
    
   

   

    

   
   

    
	
     public Employee getEmployeeJson(@PathVariable String name) {
    
   

   

    

   
   

    
		
     return 
     new Employee(name, 
     16000);
    
   

   

    

   
   

    

     	}
    
   


 
和getEmployeeXml（）相比，这里唯一的不同是返回对象变成了Employee，因为Employee类上没有@XmlRootElement注解，所以Spring不会选择Jaxb2RootElementHttpMessageConverter。又因为Accept属性中包含了*/*，表示接受任意格式返回数据，所以GsonHttpMessageConverter的canWrite()方法返回true.这样Spring就会选择MappingJackson2HttpMessageConverter或者GsonHttpMessageConverter来进行数据转换。
 

 

 至此，我们知道请求头中的Accept属性是一个很关键的东西，我们可以根据这个在Controller中写一个方法，根据Accept的值自动返回XML或者JSON数据。
 
 

 

   

    

   
   

    
	
     /**
    
   

   

    

   
   

    

     	 * 根据request header中的Accept自动选择返回XML or JSON 
    
   

   

    

   
   

    

     	 */
    
   

   

    

   
   

    
	
     @RequestMapping(value=
     "/{name}", method=RequestMethod.GET)
    
   

   

    

   
   

    
	
     @ResponseBody
    
   

   

    

   
   

    
	
     public Employee getEmployee(@PathVariable String name) {
    
   

   

    

   
   

    
		
     return 
     new EmployeeX(name, 
     16000);
    
   

   

    

   
   

    

     	}
    
   


 因为浏览器的Accept值不方便修改，我们自己写客户端来调用。 
 
 

 

   

    

   
   

    

     package learning.webapp;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import java.io.IOException;
    
   

   

    

   
   

    

     import java.io.InputStream;
    
   

   

    

   
   

    

     import java.net.URI;
    
   

   

    

   
   

    

     import java.net.URISyntaxException;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import org.junit.Test;
    
   

   

    

   
   

    

     import org.springframework.http.HttpEntity;
    
   

   

    

   
   

    

     import org.springframework.http.HttpHeaders;
    
   

   

    

   
   

    

     import org.springframework.http.HttpMethod;
    
   

   

    

   
   

    

     import org.springframework.http.client.ClientHttpRequest;
    
   

   

    

   
   

    

     import org.springframework.http.client.ClientHttpResponse;
    
   

   

    

   
   

    

     import org.springframework.http.client.SimpleClientHttpRequestFactory;
    
   

   

    

   
   

    

     import org.springframework.web.client.RestTemplate;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     public 
     class XmlOrJasonControllerTest {
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    
	
     @Test
    
   

   

    

   
   

    
	
     public void testJsonResponse() throws IOException, URISyntaxException {
    
   

   

    

   
   

    

     		String url = 
     "http://localhost:8080/employees/Jack";
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     		ClientHttpRequest request = 
     new SimpleClientHttpRequestFactory().createRequest(
     new URI(url), HttpMethod.GET);
    
   

   

    

   
   

    

     		request.getHeaders().set(
     "Accept", 
     "application/json");
    
   

   

    

   
   

    

     		ClientHttpResponse response = request.execute();
    
   

   

    

   
   

    

     		InputStream is = response.getBody();
    
   

   

    

   
   

    
		
     byte bytes[] = 
     new 
     byte[(
     int) response.getHeaders().getContentLength()];
    
   

   

    

   
   

    

     		is.read(bytes);
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     		String jsonData = 
     new String(bytes);
    
   

   

    

   
   

    

     		System.out.println(jsonData);
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    
	
     @Test
    
   

   

    

   
   

    
	
     public void testXmlResponse() throws IOException, URISyntaxException {
    
   

   

    

   
   

    

     		String url = 
     "http://localhost:8080/employees/Jack";
    
   

   

    

   
   

    
		
     // response headers 中包含Transfer-Encoding:chunked，没有content length,
    
   

   

    

   
   

    

     		HttpHeaders requestHeaders = 
     new HttpHeaders();
    
   

   

    

   
   

    

     		requestHeaders.set(
     "Accept", 
     "application/xml");
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     		RestTemplate restTemplate = 
     new RestTemplate();
    
   

   

    

   
   

    

     		HttpEntity<Object> httpEntity = 
     new HttpEntity<Object>(requestHeaders);
    
   

   

    

   
   

    

     		String xmlData = restTemplate.exchange(url, HttpMethod.GET, httpEntity, String.class).getBody();
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     		System.out.println(xmlData);
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    

     }
    
   



 

 
[参考资料]
 
1）http://www.cnblogs.com/fangjian0423/p/springMVC-xml-json-convert.html
 
2）http://my.oschina.net/lichhao/blog/172562