java - Spring-boot + Hibernate + JPA 与 transient 字段

Question

这是我的第一个问题，但我已经寻找解决方案两天了，但没有成功。在我的项目中，我有一个具有 transient 属性的 User 实体:

@Transient
@JsonProperty
private List<String> files;

我没有 setter，getter 是:

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

在调试中使用 NetBeans 执行应用程序，工作正常，并且从 javascript，我可以使用 user.fotos 获取 getFiles 结果。但是，当我生成 .jar 文件，并使用命令 java -jar app.jar 执行应用程序时，通过调用一个必须返回一个 User 对象的 Rest 函数，我得到这个异常(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"])

我的问题是:Netbeans 与命令行 java -jar 有何不同，这使得它可以正常工作？

Answer 1

试图找到更多文档，我发现了这个:JPA Transient Annotation and JSON

感谢 Damien，我的项目终于可以正常运行了:主应用程序.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);
    }
}

用户实体类:

@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 接口(interface):

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

}

用户 Controller :

@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函数:

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);
        }
    });
}

结果是 JavaScript 向我显示一条警报，其中包含服务器上存在的文件名。