@Entity
@Table(name="user_account_entity")
@JsonDeserialize(using = UserAccountDeserializer.class)
@JsonSerialize(using = UserAccountSerializer.class)
public class UserAccountEntity implements UserDetails {

    @Id
    private String id;

    private String username;

    private String password;

    public UserAccountEntity(final String username, final String password) {
        this.password = password.trim();
        this.username = username.trim();
    }
    //....
}

public class UserAccountDeserializer extends JsonDeserializer<UserAccountEntity> {

    @Override
    public UserAccountEntity deserialize(JsonParser jp,
            DeserializationContext ctxt) throws IOException,
            JsonProcessingException {
        JsonNode node = jp.getCodec().readTree(jp);
        final String username = node.get("username").asText();
        final String password = node.get("password").asText();
        return new UserAccountEntity(username, password);
    }

}