Markus Pleines Markus Pleines - 6 months ago 60
JSON Question

org.codehaus.jackson.map.JsonMappingException: Can not instantiate value of type [simple type, class models.Job] from JSON String

i use the playframework and tried to deserialize some json into a java object.
It worked fine, exept the relationship in the model. I got the following exception


enter code hereorg.codehaus.jackson.map.JsonMappingException: Can not
instantiate value of type [simple type, class models.Job] from JSON
String; no single-String constructor/factory method (through reference
chain: models.Docfile["job"])


i thought jackson in combination with play could do that:

this is the json

{"name":"asd","filepath":"blob","contenttype":"image/png","description":"asd","job":"1"}


and this my code, nothing special:

public static Result getdata(String dataname) {
ObjectMapper mapper = new ObjectMapper();
try {
Docfile docfile = mapper.readValue((dataname), Docfile.class);
System.out.println(docfile.name);
docfile.save();

} catch (JsonGenerationException e) {

e.printStackTrace();

} catch (JsonMappingException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

return ok();
}


Hope there is help for me, thanks
Markus

UPDATE:

Docfile Bean:

package models;

import java.util.*;

import play.db.jpa.*;
import java.lang.Object.*;
import play.data.format.*;
import play.db.ebean.*;
import play.db.ebean.Model.Finder;
import play.data.validation.Constraints.*;
import play.data.validation.Constraints.Validator.*;

import javax.persistence.*;

import com.avaje.ebean.Page;

@Entity
public class Docfile extends Model {

@Id
public Long id;

@Required
public String name;

@Required
public String description;

public String filepath;

public String contenttype;

@ManyToOne
public Job job;

public static Finder<Long,Docfile> find = new Model.Finder(
Long.class, Docfile.class
);




public static List<Docfile> findbyJob(Long job) {
return find.where()
.eq("job.id", job)
.findList();
}

public static Docfile create (Docfile docfile, Long jobid) {
System.out.println(docfile);
docfile.job = Job.find.ref(jobid);
docfile.save();
return docfile;
}
}

Answer

Either you change your JSON in order to describe your "job" entity :

{
   "name":"asd",
   "filepath":"blob",
   "contenttype":"image/png",
   "description":"asd",
   "job":{
      "id":"1",
       "foo", "bar"
   }
}

or you create a constructor with a String parameter in your Job bean:

public Job(String id) {
// populate your job with its id
}
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