I am trying to store a JSON object in MySQL database in spring boot. I know I am doing something wrong but I a can't figure out what it is because I am fairly new to Spring.
I have a rest endpoint where I get the following JSON object (via HTTP PUT) and I need to store it in database so that the user can fetch it later (via HTTP GET).
{
"A": {
"Name": "Cat",
"Age": "1"
},
"B": {
"Name": "Dog",
"Age": "2"
},
"C": {
"Name": "Horse",
"Age": "1"
}
}
Note that in the above case The number of keys in the object may vary, Due to that requirement I am using a HashMap to catch the object in the controller.
@RequestMapping(method = RequestMethod.POST)
public String addPostCollection(@RequestBody HashMap<String, Animal> hp) {
hp.forEach((x, y) -> {
postRepository.save(hp.get(x));
});
return "OK";
}
As you can see in the method, I can iterate the HashMap and persist each Animal object in db. But I am looking for a way to persist the entire HashMap in a single record. I have did some reading and they suggest me to use a @ManyToMany mapping.
Can anyone point me in a direction to persist the HashMap in a different way? (or is using the @ManyToMany the only and right way to do this?)
This is a very common requirement, so I decided to write a very detailed article, about the best way to map JSON column types when using JPA and Hibernate.
Maven dependency
The first thing you need to do is to set up the following Hibernate Types Maven dependency in your project pom.xml configuration file:
<dependency>
<groupId>com.vladmihalcea</groupId>
<artifactId>hibernate-types-52</artifactId>
<version>${hibernate-types.version}</version>
</dependency>
Domain model
Let's assume you have the following entity:
@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
}
Notice the @TypeDef is used to instruct Hibernate to map the JsonNode object using the JsonBinaryType offered by the Hibernate Types project.
Testing time
Now, if you save an entity:
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 is going to generate the following SQL statement:
INSERT INTO
book
(
isbn,
properties,
id
)
VALUES
(
'978-9730228236',
'{"title":"High-Performance Java Persistence","author":"Vlad Mihalcea","publisher":"Amazon","price":44.99}',
1
)
And you can also load it back and modify it:
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 taking caare of the UPDATE statement for you:
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