java - 使用 Hibernate 和 JPA 持久化 JSON 对象

Question

我试图在 Spring 启动时在 MySQL 数据库中存储一个 JSON 对象。我知道我做错了什么，但我无法弄清楚它是什么，因为我对 Spring 相当陌生。

我有一个休息端点，在那里我获得了以下 JSON 对象(通过 HTTP PUT)，我需要将它存储在数据库中，以便用户可以稍后(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 号码 的 key 在对象中可能会有所不同，由于该要求，我正在使用 HashMap捕捉 Controller 中的对象。

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

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

        return "OK";

    }

正如你在方法中看到的，我可以迭代 HashMap并坚持每个 Animal db 中的对象。但我正在寻找一种方法来坚持整个 HashMap在一个记录中。我做了一些阅读，他们建议我使用 @ManyToMany映射。

谁能指出我坚持 HashMap 的方向以不同的方式？ (或者使用 @ManyToMany 是唯一正确的方法吗？)

Answer 1

Maven 依赖
您需要做的第一件事是设置以下Hibernate Types项目中的 Maven 依赖项 pom.xml配置文件:

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

领域模型
假设您有以下实体:

@Entity(name = "Book")
@Table(name = "book")
@TypeDef(
    typeClass = JsonType.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用于指示 Hibernate 映射 JsonNode对象使用 JsonType 由 Hibernate Types 项目提供。
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
)

您还可以重新加载并修改它:

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 照顾 UPDATE给你的声明:

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