使用Spring＆Jackson将从Oracle Apex检索到的Json转换为POJO的异常

Question

we have a rest web service with Oracle 11g and Apex on the server side. On the client side we are developing for android, and using Spring 1.0.1 and Jackson 2.2.3 libraries to manage the requests of the rest webservices and convert the json data back into a pojo.

It works very well when the webservice is a "query". The resultset-Json data is converted in an array of Pojos without problem. But when we try to do the same with a oracle procedure, it fails with an exception.

The Json data returned by the procedure is the following:

{"item":"{\r\n  \"user\" : \"{john}\",\r\n  \"profile\" : \"nothing\"\r\n}"}

I tried an online Json validator, and the Json data appears to be valid. In the header you can also see that the type is "application/json".

The pojo object is as follows:

   public class User {

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    private String user;

    public String getProfile() {
        return profile;
    }

    public void setProfile(String profile) {
        this.profile = profile;
    }

    private String profile;
}

The code that calls the webservice and tries to convert json to pojo is the following (copied from the spring examples):

RestTemplate restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
User users = restTemplate.getForObject(url, User.class);

And at last, the exception when it tries to do "getForObject":

org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [com.xxx.xxx] and content type [text/plain;charset=iso-8859-1]

I tried to do the same with the Gson library instead the Jackson library, and the same exception is trown. Now I'm blocked since a couple of days...

Any ideas? What I'm doing wrong?

Thanks in advance,

Answer 1

The problem is with the JSON you are returning and the class you have declared. Your JSON structure is {"item":"{\\r\\n \\"user\\" : \\"{john}\\",\\r\\n \\"profile\\" : \\"nothing\\"\\r\\n}"} which doesn't map to the User class. The Json Structure that maps to the user class is {\\r\\n \\"user\\" : \\"{john}\\",\\r\\n \\"profile\\" : \\"nothing\\"\\r\\n}

So you will have to either change the JSON response in the Rest Service.

Or add a new class structure like this

public class UserItem {
 User user;
 //the usual setter getter
}

Then the Rest Call will be like this :

RestTemplate restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
UserItem item = restTemplate.getForObject(url, UserItem .class);
User user = item.getUser();