1. Introduction. The OneToMany relationship is the most common JPA association and foreign key is controlled by the child-side directly including unidirectional and bidirectional association. This note presents how to configure bidirectional @OneToMany association 2. Bidirectional ManyToOne / OneToMany Relationships. Assuming that: Event entity references a single instance of User entity User entity references a… Read More »
In JPA, two types of the @OneToOne relationships are bidirectional and unidirectional. In each type, we can use different mapping approaches: One-to-one association that maps a foreign key column. One-to-one association where both source and target share the same primary key values. One-to-one association from an embeddable class to another entity. 1. Bidirectional OneToOne association… Read More »
1. Introduction. Retrieved data with paging and storing is a basic feature of any application. This can be handled by database side (page and sort in a stored procedure, or native SQL query), and Spring Data JPA via use QueryDSL or Specifications. The note will present how to implement QueryDSL with Optional in Java 8.… Read More »
1. Pre-requisites Should read first there types of mapping below: Single-table strategy Joined-tables strategy Table-per-class strategy 2. Summary mapping strategies Table 1: Summary of OO hierarchy inheritance mapping strategies (source: EJB3 in Action) References: D. Pan, R. Rahman, R. Cuprak, M. Remijan, “Mapping inheritance”, In EJB3 in Action,pp.292-293, Manning, Second Edition, 2014
1. Table-per-class strategy Table-per-class strategy is similar to joined-tables strategy because each entity in domain model gets its own table. One significant difference is no relationship between the tables, which doesn’t take advantage of power of relational database at all. Following the stock market example in join-table-strategy and single-table-strategy , we are there different tables namely product, bonds, shares but product_code, description, version… Read More »
1. Joined-tables strategy Follow up the Single-table strategy for mapping inheritance with JPA, this strategy stores all financial products in a single table. In contrast, the joined table strategy creates separate tables for each entity in the domain model. This means that the financial product is the parent table and it holds common data for… Read More »
1. Stock Market Example Get started on our real market example with investors who want to buy or sell shares on the marketplace of which they are participants. Actually, stockbrokers (brokers) will do trading on behalf of their clients. But, there are different financial products: shares, loan, option, bond, hibrid, future, and so on. So… Read More »