{"id":84289,"date":"2018-12-11T07:00:30","date_gmt":"2018-12-11T05:00:30","guid":{"rendered":"https:\/\/www.javacodegeeks.com\/?p=84289"},"modified":"2018-12-06T13:59:21","modified_gmt":"2018-12-06T11:59:21","slug":"map-postgresql-jpa-entity-hibernate","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2018\/12\/map-postgresql-jpa-entity-hibernate.html","title":{"rendered":"How to map PostgreSQL Enums to JPA entity properties using Hibernate"},"content":{"rendered":"

Introduction<\/h2>\n

The open-source hibernate-types<\/code><\/a> project allows you to map JSON, ARRAY, YearMonth<\/code>, Month<\/code> or database-specific columns (e.g. INET addresses).<\/p>\n

In this article, we are going to see how you can map a PostgreSQL Enum type to a Java array when using JPA and Hibernate.<\/p>\n

Maven dependency<\/h2>\n

First of all, you need to set up the following Maven dependency in your project pom.xml<\/code> configuration file:<\/p>\n

<dependency>\r\n    <groupId>com.vladmihalcea<\/groupId>\r\n    <artifactId>hibernate-types-52<\/artifactId>\r\n    <version>2.3.5<\/version>\r\n<\/dependency><\/pre>\n
If you\u2019re using older versions of Hibernate, check out the hibernate-types<\/code> GitHub repository<\/a> for more info about the matching dependency for your current Hibernate version.<\/p>\n
Domain Model<\/h2>\n
Let\u2019s assume we have the following sensor_state<\/code> PostgreSQL enum in our database schema:<\/p>\n
CREATE TYPE sensor_state AS ENUM (\r\n    'ONLINE',\r\n    'OFFLINE',\r\n    'UNKNOWN'\r\n);<\/pre>\n
Our application needs to store Events in the following database table:<\/p>\n
CREATE TABLE event (\r\n  id bigint NOT NULL,\r\n  sensor_names text[],\r\n  sensor_values integer[],\r\n  sensor_states sensor_state[],\r\n  CONSTRAINT event_pkey PRIMARY KEY (id)\r\n)<\/pre>\n
Notice that the sensor_names<\/code>, sensor_values<\/code> and sensor_states<\/code> columns are stored as arrays. To map the PostgreSQL array column types to Java arrays, you need a custom Hibernate type since the built-in types don\u2019t support persisting database-specific arrays.<\/p>\n
However, thanks to the hibernate-types<\/code> library you can easily map the event<\/code> table to the following Event<\/code> entity:<\/p>\n
@Entity(name = \"Event\")\r\n@Table(name = \"event\")\r\n@TypeDefs({\r\n    @TypeDef(\r\n        typeClass = StringArrayType.class,\r\n        defaultForType = String[].class\r\n    ),\r\n    @TypeDef(\r\n        typeClass = IntArrayType.class,\r\n        defaultForType = int[].class\r\n    ),\r\n    @TypeDef(\r\n        typeClass = EnumArrayType.class,\r\n        defaultForType = SensorState[].class,\r\n        parameters = {\r\n            @Parameter(\r\n                name = EnumArrayType.SQL_ARRAY_TYPE,\r\n                value = \"sensor_state\"\r\n            )\r\n        }\r\n    )\r\n})\r\npublic class Event {\r\n\r\n    @Id\r\n    private Long id;\r\n\r\n    @Column(\r\n        name = \"sensor_names\",\r\n        columnDefinition = \"text[]\"\r\n    )\r\n    private String[] sensorNames;\r\n\r\n    @Column(\r\n        name = \"sensor_values\",\r\n        columnDefinition = \"integer[]\"\r\n    )\r\n    private int[] sensorValues;\r\n\r\n    @Column(\r\n        name = \"sensor_states\",\r\n        columnDefinition = \"sensor_state[]\"\r\n    )\r\n    private SensorState[] sensorStates;\r\n\r\n    public Long getId() {\r\n        return id;\r\n    }\r\n\r\n    public Event setId(\r\n            Long id) {\r\n        this.id = id;\r\n        return this;\r\n    }\r\n\r\n    public String[] getSensorNames() {\r\n        return sensorNames;\r\n    }\r\n\r\n    public Event setSensorNames(\r\n            String[] sensorNames) {\r\n        this.sensorNames = sensorNames;\r\n        return this;\r\n    }\r\n\r\n    public int[] getSensorValues() {\r\n        return sensorValues;\r\n    }\r\n\r\n    public Event setSensorValues(\r\n            int[] sensorValues) {\r\n        this.sensorValues = sensorValues;\r\n        return this;\r\n    }\r\n\r\n    public SensorState[] getSensorStates() {\r\n        return sensorStates;\r\n    }\r\n\r\n    public Event setSensorStates(\r\n            SensorState[] sensorStates) {\r\n        this.sensorStates = sensorStates;\r\n        return this;\r\n    }\r\n}<\/pre>\n
Notice the Fluent-style API used by the Event<\/code> entity. While JPA is more strict when it comes to defining setters, Hibernate allows you to define the setters so that you can build the entity using a Fluent-style API. For more details, check out this article<\/a>.
 
<\/div> <\/div><\/p>\n
The @TypeDef<\/code> annotation is used to define the mapping between the Java array class types and their associated Hibernate types:<\/p>\n