Can you please help me to map this class using Hibernate?
public class MyClass{
private Long id;
private String name;
private int[] values;
...
}
I'm using PostgreSQL and the column type in the table is integer[] How my array should be mapped?
Define Hibernate Mapping File The <class> elements are used to define specific mappings from a Java classes to the database tables. The Java class name is specified using the name attribute of the class element and the database table name is specified using the table attribute.
hibernate mappings are one of the key features of hibernate . they establish the relationship between two database tables as attributes in your model. that allows you to easily navigate the associations in your model and criteria queries.
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>
Assuming you have this table in your database:
create table event (
id int8 not null,
version int4,
sensor_names text[],
sensor_values integer[],
primary key (id)
)
And you want to map it like this:
@Entity(name = "Event")
@Table(name = "event")
@TypeDefs({
@TypeDef(
name = "string-array",
typeClass = StringArrayType.class
),
@TypeDef(
name = "int-array",
typeClass = IntArrayType.class
)
})
public static class Event extends BaseEntity {
@Type( type = "string-array" )
@Column(
name = "sensor_names",
columnDefinition = "text[]"
)
private String[] sensorNames;
@Type( type = "int-array" )
@Column(
name = "sensor_values",
columnDefinition = "integer[]"
)
private int[] sensorValues;
//Getters and setters omitted for brevity
}
The string-array
and int-array
are custom types which can be defined in the BaseEntity
superclass:
@TypeDefs({
@TypeDef(
name = "string-array",
typeClass = StringArrayType.class
),
@TypeDef(
name = "int-array",
typeClass = IntArrayType.class
)
})
@MappedSuperclass
public class BaseEntity {
@Id
private Long id;
@Version
private Integer version;
//Getters and setters omitted for brevity
}
The StringArrayType
and IntArrayType
are classes offered by the Hibernate Types project.
Now, when you insert a couple of entities;
Event nullEvent = new Event();
nullEvent.setId(0L);
entityManager.persist(nullEvent);
Event event = new Event();
event.setId(1L);
event.setSensorNames(
new String[] {
"Temperature",
"Pressure"
}
);
event.setSensorValues(
new int[] {
12,
756
}
);
entityManager.persist(event);
Hibernate is going to generate the following SQL statements:
INSERT INTO event (
version,
sensor_names,
sensor_values,
id
)
VALUES (
0,
NULL(ARRAY),
NULL(ARRAY),
0
)
INSERT INTO event (
version,
sensor_names,
sensor_values,
id
)
VALUES (
0,
{"Temperature","Pressure"},
{"12","756"},
1
)
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