# Custom input validation with JAX-RS and JSON-B (Java EE 8)

The state of a POJO (Plain Old JSON Object :-) can be validated after retrieval:

public class Developer {

    public String language;
    public int age;
    //optional field
    public String description;

    public void validate() {
        if (!language.endsWith("va") && age 


The DevelopersResource accepts the input, then calls Developer#validate:



@Path("developers")
public class DevelopersResource {

    @POST
    public String newDeveloper(Developer developer) {
        developer.validate();
        return developer.language + " " + developer.age;
    }
}    



    Test:
    

curl -i -XPOST -d'{"language":"java","age":42}'  -H"Content-type: application/json" -H"Accept: application/json" (...))/jsonb-validation/resources/developers


    returns


HTTP/1.1 200 OK
X-Powered-By: Servlet/4.0
Content-Type: application/json
Date: Fri, 14 Dec 2018 08:40:24 GMT
Content-Language: en-US
Content-Length: 7

java 42%      


    however
    
curl -i -XPOST -d'{"language":"basic"}'  -H"Content-type: application/json" -H"Accept: application/json" http://localhost:9080/jsonb-validation/resources/developers

    yields:


HTTP/1.1 400 Bad Request
X-Powered-By: Servlet/4.0
reason: Learn something cool
Date: Fri, 14 Dec 2018 08:42:43 GMT
Content-Length: 0
Content-Language: en-US
Connection: Close    


ThinWAR size: 4.7kB, deployed with: WAD



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