Spring Boot and Spring Data Rest

Question

I want to use Spring Data Rest in my Spring Boot project but I am running into difficulty. I am using Spring boot version 2.0.0.M2. I also tried version 1.5.4.RELEASE but got the same error

I am using the following imports in my pom

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.apache.tomcat</groupId>
                <artifactId>tomcat-jdbc</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-rest</artifactId>
    </dependency>

My DB object is as follows

    @Entity
@Table(name = "T_PUBLICATION")
public class PublicationDBO implements Serializable{

    private static final long serialVersionUID = -8883649751668748295L;

    @Id
    @Column(name = "id")
    private Long id;    
    @Column(name = "publication_name")
    private String publicationName; 
    @Column(name = "number_of_pages")
    private Long numberOfPages; 
    @Column(name = "storage_key")
    private String storageKey;  
    @Column(name = "processing_complete")
    private Boolean processingComplete; 
    @Column(name = "date_added")
    private LocalDateTime dateAdded;    
    @Column(name = "date_updated")
    private LocalDateTime dateUpdated;

}

Database SQL (MySQL DB)

CREATE TABLE `T_PUBLICATION` (
  `id` int(11) NOT NULL,
  `publication_name` varchar(255) NOT NULL,
  `number_of_pages` int(11) NOT NULL,
  `storage_key` varchar(255) NOT NULL,
  `processing_complete` tinyint(1) NOT NULL,
  `date_added` datetime NOT NULL,
  `date_updated` datetime NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Repository Class

    import org.springframework.data.repository.PagingAndSortingRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;

import com.dao.vo.PublicationDBO;

@RepositoryRestResource(collectionResourceRel = "publication", path = "publication")
public interface PublicationRepository extends PagingAndSortingRepository<PublicationDBO, Long>{

}

When I tried to access the endpoints for Spring Data and this object - I get the following error

2017-07-17 16:03:28 [http-nio-8080-exec-1] DEBUG org.hibernate.SQL - select publicatio0_.id as id1_1_0_, publicatio0_.date_added as date_add2_1_0_, publicatio0_.date_updated as date_upd3_1_0_, publicatio0_.number_of_pages as number_o4_1_0_, publicatio0_.processing_complete as processi5_1_0_, publicatio0_.publication_name as publicat6_1_0_, publicatio0_.storage_key as storage_7_1_0_ from T_PUBLICATION publicatio0_ where publicatio0_.id=?
Hibernate: select publicatio0_.id as id1_1_0_, publicatio0_.date_added as date_add2_1_0_, publicatio0_.date_updated as date_upd3_1_0_, publicatio0_.number_of_pages as number_o4_1_0_, publicatio0_.processing_complete as processi5_1_0_, publicatio0_.publication_name as publicat6_1_0_, publicatio0_.storage_key as storage_7_1_0_ from T_PUBLICATION publicatio0_ where publicatio0_.id=?
2017-07-17 16:03:28 [http-nio-8080-exec-1] WARN  o.s.w.s.m.s.DefaultHandlerExceptionResolver - Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: java.lang.String cannot be cast to java.lang.Long; nested exception is com.fasterxml.jackson.databind.JsonMappingException: java.lang.String cannot be cast to java.lang.Long (through reference chain: org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$PersistentEntityResourceSerializer$1["content"]->com.dao.vo.PublicationDBO["publicationName"])
2017-07-17 16:03:28 [http-nio-8080-exec-1] WARN  o.s.w.s.m.s.DefaultHandlerExceptionResolver - Resolved exception caused by Handler execution: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: java.lang.String cannot be cast to java.lang.Long; nested exception is com.fasterxml.jackson.databind.JsonMappingException: java.lang.String cannot be cast to java.lang.Long (through reference chain: org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$PersistentEntityResourceSerializer$1["content"]->com.dao.vo.PublicationDBO["publicationName"])

Note: I tried the JPA calls using a standard service class and they worked first time so the entity mapping to my database tables is correct

Can anyone offer any assistance on why this is happening? I have checked my database mappings and they appear to be ok

Thanks Damien

Answer 1

According to this post -https://github.com/spring-projects/spring-boot/issues/9756 Changing the Spring Boot version from 2.0.0.M1 to 2.0.0.BUILD-SNAPSHOT has resolved the issue

Answer 2

I think you are not sending 'id' as part of your JSON. You might have probably assumed id is auto created, and assumed you don't have to send. If it is the case (i.e. you don't want to send id in your JSON object) add @JsonIgnore to id in your Entity definition. If you do, you will not get Id field included in the return object when you query as well. If you want id, send a null or "" (empty string) in your JSON. Sometimes, Spring boot may ignore these empty fields. There should be another @Json... annotation to instruct it to not to ignore null/empty values. I could not get it top of my head, you have to Google it.