org.codehaus.jackson.JsonGenerationException: Can not write number, expecting field name - json

Question

Hi i am working on a spring mvc application well i need to Serialize an object in order to pass it with an ajax Post.
my bean class :
#JsonSerialize(using = AgentSer.class)
public class AgentCust implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Long personneID;
private String nom;
private String prenom;
private String matriculation;
private String marche;
private String compte;
private String phone, mail, chat;
public String getMarche() {
return marche;
}
public void setMarche(String marche) {
this.marche = marche;
}
public String getCompte() {
return compte;
}
public void setCompte(String compte) {
this.compte = compte;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getMail() {
return mail;
}
public void setMail(String mail) {
this.mail = mail;
}
public String getChat() {
return chat;
}
public void setChat(String chat) {
this.chat = chat;
}
public Long getPersonneID() {
return personneID;
}
public void setPersonneID(Long personneID) {
this.personneID = personneID;
}
public String getNom() {
return nom;
}
public void setNom(String nom) {
this.nom = nom;
}
public String getPrenom() {
return prenom;
}
public void setPrenom(String prenom) {
this.prenom = prenom;
}
public String getMatriculation() {
return matriculation;
}
public void setMatriculation(String matriculation) {
this.matriculation = matriculation;
}
}
and the class that will serialize my bean :
public class AgentSer extends JsonSerializer<AgentCust> {
#Override
public void serialize(AgentCust value, JsonGenerator jgen, SerializerProvider arg2) throws IOException, JsonProcessingException {
// TODO Auto-generated method stub
jgen.writeStartObject();
jgen.writeNumber(value.getPersonneID());
jgen.writeString(value.getMatriculation());
jgen.writeString(value.getNom());
jgen.writeString(value.getPrenom());
jgen.writeString(value.getCompte());
jgen.writeString(value.getMarche());
jgen.writeString(value.getChat());
jgen.writeString(value.getMail());
jgen.writeString(value.getPhone());
jgen.writeEndObject();
}
}
in my controller i use my class like that:
AgentCust ags ;
// i set values here .
ObjectMapper mapper = new ObjectMapper();
String json = "";
try {
json = mapper.writeValueAsString(ags);
} catch (Exception e) {
System.out.println(e);
}
but at the end i get that :
org.codehaus.jackson.JsonGenerationException: Can not write number, expecting field name
any help please.

Answer 1

Why are you using a custom serializer(which is wrong as it doesn't include the field names). You are really complicating your life.
You can set the serialization options like this (you can also set them in a static block):
final ObjectMapper mapper = new ObjectMapper();
/*
you can set them globally in a static block and reuse the mapper...
performance gain
*/
mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
mapper.configure(SerializationFeature.WRITE_EMPTY_JSON_ARRAYS, false);
mapper.setSerializationInclusion(Include.NON_NULL);
The rest of the code is the same(just add a constructor in your AgentCust.class to avoid some mapping errors):
AgentCust ags = new AgentCust();
ags.setChat("chat1");
ags.setCompte("compte1");
ags.setMail("mail1");
ags.setMarche("marche1");
ags.setMatriculation("matriculation1");
ags.setNom("nom1");
ags.setPersonneID(123456L);
ags.setPhone("phone1");
ags.setPrenom("prenom1");
String json = "";
try {
json = mapper.writeValueAsString(ags);
} catch (JsonProcessingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(json);
Another strange thing is that you're serializing the pojo as String. Why not JsonNode or ObjectNode?
public static ObjectNode convObjToONode(Object o) {
StringWriter stringify = new StringWriter();
ObjectNode objToONode = null;
try {
mapper.writeValue(stringify, o);
objToONode = (ObjectNode) mapper.readTree(stringify.toString());
} catch (JsonMappingException e) {
Logger.error("ERROR MAPPING JSON from object!", e);
} catch (JsonGenerationException e) {
Logger.error("ERROR GENERATING JSON from object!", e);
} catch (IOException e) {
Logger.error("ERROR IO when writing JSON from object!", e);
}
Logger.debug("Object as ObjectNode : " + objToONode);
return objToONode;
}