JPA: @ElementCollection and InheritanceType.TABLE_PER_CLASS -> Duplicate column name

java, jpa

Solution

Okay, I've just found out what was wrong!

In such a scenario I'd built you should couldn't use the @CollectionTable(name="ENTITY_PARAMS") annotation.

So, by just using... @ElementCollection @MapKeyColumn (name = "PARAM_KEY") @Column(name = "PARAM_VALUE") private Map parameters;

Every works fine, and the resulting tables (in MySQL) are:

CREATE TABLE Sensor_PARAMETERS (
    Sensor_ID BIGINT NOT NULL,
    PARAM_VALUE VARCHAR(255),
    PARAM_KEY VARCHAR(255)
)

and

CREATE TABLE Entity_PARAMETERS (
    Entity_ID BIGINT NOT NULL,
    PARAM_VALUE VARCHAR(255),
    PARAM_KEY VARCHAR(255)
)

So, without that attribute everything works fine.... Hope, nobody needs this post. Even if: "Congratulation, you found the answer!" ;-)

Problem

I've created the following scenario: ``` @javax.persistence.Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) public class MyEntity implements Serializable{ @Id @GeneratedValue protected Long id; ... @ElementCollection @CollectionTable(name="ENTITY_PARAMS") @MapKeyColumn (name = "ENTITY_KEY") @Column(name = "ENTITY_VALUE") protected Map<String, String> parameters; ... } ``` As well as: ``` @javax.persistence.Entity public class Sensor extends MyEntity{ @Id @GeneratedValue protected Long id; ... // so here "protected Map<String, String> parameters;" is inherited !!!! ... } ``` So running this example, no tables are created and i get the following message: ``` WARNUNG: Got SQLException executing statement "CREATE TABLE ENTITY_PARAMS (Entity_ID BIGINT NOT NULL, ENTITY_VALUE VARCHAR(255), ENTITY_KEY VARCHAR(255), Sensor_ID BIGINT NOT NULL, ENTITY_VALUE VARCHAR(255))": com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Duplicate column name 'ENTITY_VALUE' ``` I also tried overriding the attributes on the Sensor class... ``` @AttributeOverrides({ @AttributeOverride(name = "ENTITY_KEY", column = @Column(name = "SENSOR_KEY")), @AttributeOverride(name = "ENTITY_VALUE", column = @Column(name = "SENSOR_VALUE")) }) ``` ... but the same error. EDIT: Okay, I'd found out that with the Inheritance strategy "JOINED" as well as with "SINGLE_TABLE" everything works fine. Also it seems that it has nothing to do with the EclipseLink version - I tried 1.3 and 2.0.1. END_EDIT Can anybody help me?

Original source