使用Hibernate和JPA持久化JSON对象

Question

我试图在spring启动时将JSON对象存储在MySQL数据库中。我知道我做错了事，但是我无法弄清楚到底是什么原因，因为我对Spring还很陌生。

我有一个休息端点，在这里我通过HTTP PUT获取以下JSON对象，并且需要将其存储在数据库中，以便用户以后可以通过HTTP GET获取它。

{
  "A": {
    "Name": "Cat",
    "Age": "1"
  },
  "B": {
    "Name": "Dog",
    "Age": "2"
  },
  "C": {
    "Name": "Horse",
    "Age": "1"
  }
}

请注意，在上述情况下，对象 中* 键 的 数量 可能会有所不同，由于该要求，我正在使用a 来捕获控制器中的对象。

*HashMap

@RequestMapping(method = RequestMethod.POST)
    public String addPostCollection(@RequestBody HashMap<String, Animal> hp) {

        hp.forEach((x, y) -> {
            postRepository.save(hp.get(x));
        });

        return "OK";

    }

如您在方法中所看到的，我可以迭代HashMap并将每个Animal对象保留在db中。但是我正在寻找一种将整个HashMap记录保持在单个记录中的方法。我读了一些书，他们建议我使用@ManyToMany映射。

谁能指出我以HashMap不同的方式坚持下去的方向？（或者正在使用@ManyToMany唯一正确的方法来执行此操作？）

Answer 1

这是一个非常常见的要求，因此我决定写一篇非常详细的文章，介绍使用JPA和Hibernate时映射JSON列类型的最佳方法。

Maven依赖

您需要做的第一件事是在项目配置文件中设置以下Hibernate
Types
Maven依赖项pom.xml：

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-52</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

领域模型

假设您具有以下实体：

@Entity(name = "Book")
@Table(name = "book")
@TypeDef(
    typeClass = JsonBinaryType.class, 
    defaultForType = JsonNode.class
)
public class Book {

    @Id
    @GeneratedValue
    private Long id;

    @NaturalId
    private String isbn;

    @Column(columnDefinition = "jsonb")
    private JsonNode properties;

    //Getters and setters omitted for brevity
}

请注意，@TypeDef用来指示Hibernate JsonNode使用JsonBinaryTypeHibernate
Types项目提供的内容来映射对象。

测试时间

现在，如果您保存实体：

Book book = new Book();
book.setIsbn( "978-9730228236" );
book.setProperties(
    JacksonUtil.toJsonNode(
        "{" +
        "   \"title\": \"High-Performance Java Persistence\"," +
        "   \"author\": \"Vlad Mihalcea\"," +
        "   \"publisher\": \"Amazon\"," +
        "   \"price\": 44.99" +
        "}"
    )
);

entityManager.persist( book );

Hibernate将生成以下SQL语句：

INSERT INTO
    book 
(
    isbn, 
    properties, 
    id
) 
VALUES
(
    '978-9730228236', 
    '{"title":"High-Performance Java Persistence","author":"Vlad Mihalcea","publisher":"Amazon","price":44.99}',  
    1
)

您还可以将其加载回并修改它：

Session session = entityManager.unwrap( Session.class );

Book book = session
    .bySimpleNaturalId( Book.class )
    .load( "978-9730228236" );

LOGGER.info( "Book details: {}", book.getProperties() );

book.setProperties(
    JacksonUtil.toJsonNode(
        "{" +
        "   \"title\": \"High-Performance Java Persistence\"," +
        "   \"author\": \"Vlad Mihalcea\"," +
        "   \"publisher\": \"Amazon\"," +
        "   \"price\": 44.99," +
        "   \"url\": \"https://www.amazon.com/High-Performance-Java-Persistence-Vlad-Mihalcea/dp/973022823X/\"" +
        "}"
    )
);

Hibernate UPDATE为您处理以下声明：

SELECT  b.id AS id1_0_
FROM    book b
WHERE   b.isbn = '978-9730228236'

SELECT  b.id AS id1_0_0_ ,
        b.isbn AS isbn2_0_0_ ,
        b.properties AS properti3_0_0_
FROM    book b
WHERE   b.id = 1

-- Book details: {"price":44.99,"title":"High-Performance Java Persistence","author":"Vlad Mihalcea","publisher":"Amazon"}

UPDATE
    book 
SET
    properties = '{"title":"High-Performance Java Persistence","author":"Vlad Mihalcea","publisher":"Amazon","price":44.99,"url":"https://www.amazon.com/High-Performance-Java-Persistence-Vlad-Mihalcea/dp/973022823X/"}'
WHERE
    id = 1