hibernate-annotations | 易学教程

What is a IncompatibleClassChangeError exception in Java?

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问题 i am working on a small application and I am trying to use Hibernate Annotations to map my entities. I wanted to test if everything is alright when i got this exception : Exception in thread "main" java.lang.ExceptionInInitializerError at fr.cc2i.intervention.dao.main.Main$HibernateUtil.<clinit>(Main.java:48) at fr.cc2i.intervention.dao.main.Main.test(Main.java:21) at fr.cc2i.intervention.dao.main.Main.main(Main.java:32) Caused by: java.lang.IncompatibleClassChangeError: Implementing class at

hibernate two tables per one entity

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问题 I have one entity - User . It is described by User.class . Hibernate creates one table per entity, so when I call session.save(user) , my data is always saved to this table. Now I need another table for data of same User type, and I need to save my entity to that table only. Data structure (something like this): table users_1_table{ string id; string username; } table users_2_table{ string id; string username; } work with this : session.save(user1,"users_1_table") session.save(user2,"users_2

Hibernate annotation or XML configuration

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问题 I have started a new project with Hibernate. Is Hibernate annotation a better choice or is Hibernate XML mapping better? I have used Hibernate with XML configuration, but I have no idea about annotation. are there any issues while going for annotation based implementation? is maintenance of an application easier or more complicated with annotation based? which one is better (that is, annotation or XML mapping) and which one is is widely used? Why? If I use a different database at a different

Java: Hibernate @OneToOne mapping

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问题 I\'m trying to get Hibernate @OneToOne annotations working and not having much success here... Let\'s say I\'ve got a table called status that looks like this: +------------------------------------------------+ | status | +------------------------------------------------+ | id | frn_user_id | frn_content_id | status | +----+-------------+----------------+------------+ | 1 | 111 | 0 | \"active\" | +----+-------------+----------------+------------+ | 2 | 0 | 222 | \"inactive\" | +----+---------

Confusion: @NotNull vs @Column(nullable = false)

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When they appear on a field/getter of an @Entity , what is the difference between them? (I persist the Entity through Hibernate ). What framework and/or specification each one of them belongs to? @NotNull is located within javax.validation.constraints . In the javax.validation.constraints.NotNull javadoc it says The annotated element must not be null but it does not speak of the element's representation in the database, so why would I add the constraint nullable=false to the column? Ryan Stewart @NotNull is a JSR 303 Bean Validation annotation. It has nothing to do with database constraints

mappedBy reference an unknown target entity property

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问题 I am having an issue in setting up a one to many relationship in my annotated object. I have the following: @MappedSuperclass public abstract class MappedModel { @Id @GeneratedValue(strategy=GenerationType.AUTO) @Column(name=\"id\",nullable=false,unique=true) private Long mId; then this @Entity @Table(name=\"customer\") public class Customer extends MappedModel implements Serializable { /** * */ private static final long serialVersionUID = -2543425088717298236L; /** The collection of stores.

Hibernate/persistence without @Id

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问题 I have a database view that yields a result set that has no true primary key. I want to use Hibernate/Persistence to map this result set onto Java objects. Of course, because there is no PK, I cannot decorate any field with @Id . When deploying, Hibernate complains about the missing @Id . How can I work around this? 回答1: If there's a combination of columns that makes a row unique, model a primary key class around the combination of columns. If there isn't, you're basically out of luck -- but

can someone please explain me @MapsId in hibernate?

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问题 Can someone please explain to me @MapsId in hibernate? I\'m having a hard time understanding it. It would be great if one could explain it with an example and in what kind of use cases is it most applicable? 回答1: Here is a nice explanation from Object DB. Designates a ManyToOne or OneToOne relationship attribute that provides the mapping for an EmbeddedId primary key, an attribute within an EmbeddedId primary key, or a simple primary key of the parent entity. The value element specifies the

Confusion: @NotNull vs @Column(nullable = false)

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问题 When they appear on a field/getter of an @Entity , what is the difference between them? (I persist the Entity through Hibernate ). What framework and/or specification each one of them belongs to? @NotNull is located within javax.validation.constraints . In the javax.validation.constraints.NotNull javadoc it says The annotated element must not be null but it does not speak of the element\'s representation in the database, so why would I add the constraint nullable=false to the column? 回答1: