How to Map PostgreSQL Arrays to Java Arrays with Hibernate?

Mapping PostgreSQL Arrays to Java Arrays with Hibernate

Problem

Attempting to map a numeric PostgreSQL array to a numeric Java array using Hibernate results in an exception during database queries.

Solution

To resolve this issue, follow these steps:

1. Add Hibernate Types Maven Dependency:

<code class="xml"><dependency>
    <groupid>com.vladmihalcea</groupid>
    <artifactid>hibernate-types-52</artifactid>
    <version>${hibernate-types.version}</version>
</dependency></code>

2. Define Hibernate Type Definitions:

In your Java class, specify the custom Hibernate types you'll use to map the arrays:

<code class="java">@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;</code>

3. Create Custom Hibernate Types (Optional):

The StringArrayType and IntArrayType classes are not built-in; you need to create them as follows:

<code class="java">@TypeDef(
    name = "string-array",
    typeClass = StringArrayType.class
)
@TypeDef(
    name = "int-array",
    typeClass = IntArrayType.class
)</code>

4. Testing:

When persisting entities with array values, Hibernate will generate SQL statements that map the arrays correctly.

Example

Assuming the following table structure:

<code class="sql">CREATE TABLE event (
    id int8 not null,
    version int4,
    sensor_names text[],
    sensor_values integer[],
    primary key (id)
);</code>

You can map it to the following Java class:

<code class="java">@Entity(name = "Event")
@Table(name = "event")
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
}</code>

When inserting entities with array values, Hibernate will generate SQL statements like:

<code class="sql">INSERT INTO event (
    version,
    sensor_names,
    sensor_values,
    id
)
VALUES (
    0,
    {NULL},
    {NULL},
    0
);

INSERT INTO event (
    version,
    sensor_names,
    sensor_values,
    id
)
VALUES (
    0,
    {"Temperature","Pressure"},
    {"12","756"},
    1
);</code>

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