Consume a RESTful WS using Spring MVC and Jackson - json

Question

I would like to consume a RESTful WS using Spring and Jackson.
I'm considering a JSON stream fetched by using Facebook Graph (FC Juventus's JSON data-stream)
This is my controller:
#Controller
public class ConsumeWSController {
#RequestMapping(value = "/consumews", method = RequestMethod.GET)
public String home(Locale locale, Model model) {
logger.info("Consume a RESTful webservice.", locale);
RestTemplate restTemplate = new RestTemplate();
Page page = restTemplate.getForObject("http://graph.facebook.com/juventus", Page.class);
model.addAttribute("pageAbout", page.getAbout());
model.addAttribute("pageAwards", page.getAwards());
return "consumews";
}
}
And the Page class:
#JsonIgnoreProperties(ignoreUnknown = true)
public class Page {
private String about;
private String awards;
public String getAbout() {
return about;
}
public void setAbout(String about) {
this.about = about;
}
public String getAwards() {
return awards;
}
public void setAwards(String awards) {
this.awards = awards;
}
}
But the console returns this error:
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [my.proj.Page] and content type [application/json;charset=UTF-8]
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:894)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
How can I fix this error?

Answer 1

Make sure that you have added the correct Jackson package to your classpath. For Jackson 2 and you use Maven:
<dependency>
<groupId>com.fasterxml.jackson.jaxrs</groupId>
<artifactId>jackson-jaxrs-json-provider</artifactId>
<version>2.3.1</version>
</dependency>
Or if you use the old Jackson add:
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-jaxrs</artifactId>
<version>1.9.13</version>
</dependency>

Answer 2

You need to define Jackson as your default message converter for JSON content. This is what I do (I use GSON so this might not be the exact syntax for the Jackson message converter):
<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
<property name="messageConverters">
<list>
<bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter" />
</list>
</property>
</bean>
But since you're not defining your RestTemplate as a Spring-managed bean, you need to do it manually:
restTemplate.getMessageConverters().add(new MappingJacksonHttpMessageConverter());
PS. I see you're using the newer Jackson dependency so the proper mapper might be different in that case.