使用JPA删除实体的问题
UPDATE
我的朋友做了相同的代码行，他的行很正常。 会是什么呢？ 我使用NetBeans 7.0.1，他的是6.9.1。 我的GlassFish是3.1，他是3.0.1
更新结束
@Inheritance(strategy= InheritanceType.JOINED) @Entity @Table(name = "vehicle") @DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.INTEGER) @NamedQueries({ @NamedQuery(name = "Vehicle.findAll", query = "SELECT v FROM Vehicle v")}) public class Vehicle implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id") private Integer id; @JoinColumn(name = "color_id") @ManyToOne(optional = false) private Color color; public Vehicle() { } //Getters and Setters } --- @Entity @Table(name = "car") @DiscriminatorValue("1") @NamedQueries({ @NamedQuery(name = "Car.findAll", query = "SELECT c FROM Car c")}) public class Car extends Vehicle implements Serializable { private static final long serialVersionUID = 1L; @Column(name = "airbag") private Boolean airbag; public Car() { } //Getters and Setters } 当我试图删除一辆汽车时，它会抛出一个exception，并且在Stacktrace中有一个UPDATE查询，如果我想删除它是非常奇怪的。
你们有没有想过这里会发生什么？
Car car = em.find(Car.class, id); em.remove(car);
堆：
Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'color_id' cannot be null Error Code: 1048 Call: UPDATE vehicle SET color_id = ? WHERE (id = ?) bind => [2 parameters bound] Query: DeleteObjectQuery(br.com.something.entity.Vehicle[ id=3 ]) at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:324) at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:840) at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeNoSelect(DatabaseAccessor.java:906) at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:592) at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:535) at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:1702) at org.eclipse.persistence.sessions.server.ClientSession.executeCall(ClientSession.java:253) at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:207) at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:193) at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.updateObject(DatasourceCallQueryMechanism.java:749)
也许你需要一个关于汽车和颜色之间关系的CascadeType？