Spring-boot + Hibernate + JPA with transient fields

Question

This is my first question, but I have been looking for a solution for 2 days, with no success. In my project, I have a User entity with a transient property:

@Transient
@JsonProperty
private List<String> files;

I have no setter, and getter is:

public List<String> getFiles() {
    /* Call one static method */
}

Executing the application with NetBeans in debug, works fine, and from javascript, I can get the getFiles results, using user.fotos. But when I generate .jar file, and I execute the application with command java -jar app.jar, by calling one Rest function that must return one User object, I get this exception:

2015-10-28 14:39:35.963  WARN 27836 --- [nio-7777-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: (was java.lang.NullPointerException) (through reference chain: com.pfc.soriano.wsdbmodel.entity.User["files"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.pfc.soriano.wsdbmodel.entity.User["files"])
2015-10-28 14:39:35.963  WARN 27836 --- [nio-7777-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Handler execution resulted in exception: Could not write content: (was java.lang.NullPointerException) (through reference chain: com.pfc.soriano.wsdbmodel.entity.User["files"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.pfc.soriano.wsdbmodel.entity.User["files"])

My question is: What is Netbeans doing different from command line java -jar, which makes it work fine?

so you get an NPE, and ? only you know what line of what code that is ... — Neil Stockton, Oct 28 '15 at 16:21
What do you need to know, Neil? From method getFiles(), I'm calling one static method: `public static Collection getImages(String prefix, String path) { List result = new ArrayList<>(); File directorio = new File(path); TruequeFiltro filtro = new TruequeFiltro(prefix); for (File file : directorio.listFiles(filtro)) { result.add(file.getName()); } return result; }` — Nacho Soriano, Oct 28 '15 at 18:06
You have an NPE, so work out which line, then work out WHAT is null, then fix it. — Neil Stockton, Oct 28 '15 at 18:26
I don't need to do anything in order to get NPE. I have one UserController, with `@Autowired UserDao userDao;` and this method: ` @RequestMapping(value = "findById", method = RequestMethod.POST) @ResponseBody public User findById(@Param("id") Long id) { return userDao.findOne(id); } `. UserDao is defined as: `@RepositoryRestResource(collectionResourceRel = "users", itemResourceRel = "users") public interface UserDao extends JpaRepository { ` When I call from javascript with ajax the method findById, I obtain the exception that appears in my first comment. — Nacho Soriano, Oct 28 '15 at 18:53
If I run the application with netbeans, everything works fine. If I run the application with `java -jar app.jar` command, nothing works. And if I delete the transient field `files` and getter and setter, everything works fine using netbeans or command line. — Nacho Soriano, Oct 28 '15 at 19:07

score 2 · Accepted Answer · edited May 23 '17 at 12:08

Trying to find some documentation more, I found this: JPA Transient Annotation and JSON

Thanks to Damien, finally I have my project working fine: Main Application.java:

@SpringBootApplication
public class Application extends WebMvcConfigurerAdapter {

    /* Here we register the Hibernate4Module into an ObjectMapper, then set this custom-configured ObjectMapper
     * to the MessageConverter and return it to be added to the HttpMessageConverters of our application*/
    public MappingJackson2HttpMessageConverter jacksonMessageConverter() {
        MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();

        ObjectMapper mapper = new ObjectMapper();
        Hibernate4Module hm = new Hibernate4Module();
        hm.disable(Hibernate4Module.Feature.USE_TRANSIENT_ANNOTATION);
        mapper.registerModule(hm);

        messageConverter.setObjectMapper(mapper);
        return messageConverter;
    }

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add(jacksonMessageConverter());
        super.configureMessageConverters(converters);
    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

User entity Class:

@Entity
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "ID")
    private Long id;
    @Transient
    Collection<String> files;

    public Long getId() {
        files = Utils.getImages("" + id, "src/main/webapp/user/");
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Collection<String> getFiles() {
        return files;
    }

    public void setFiles(Collection<String> files) {
        this.files = files;
    }
}

UserDAO interface:

@RepositoryRestResource(collectionResourceRel = "users", itemResourceRel = "users")
public interface UserDAO extends JpaRepository<User, Long> {

}

UserController:

@Controller
@RequestMapping(value = "user")
public class UserController {

    @Autowired
    UserDAO userDAO;

    @RequestMapping(value = "findById", method = RequestMethod.POST)
    @ResponseBody
    public User findById(@Param("id") Long id) {
        return userDAO.findOne(id);
    }
}

Javascript function:

function loadUser(id) {
    $.ajax({
        type: "POST",
        url: serviceBaseUrl + "user/findById",
        data: {id: id},
        contentType: "application/x-www-form-urlencoded; charset=UTF-8",
        success: function (data, textStatus, jqXHR) {
            if(data) {
                alert(data.files);
                /* DO SOMETHING ELSE */
            }
        },
        error: function (jqXHR, textStatus, errorThrown) {
            console.log(jqXHR.responseJSON.message);
        }
    });
}

The result is that javascript show me an alert with the file names that exists on the server.

Spring-boot + Hibernate + JPA with transient fields

1 Answers1