![]() ![]() ![]() Simple IDs can be generated automatically (surrogate IDs), and this is the most common way for handling ID values. Usually, we use simple IDs for our JPA entities. The “simple” ID is represented by a single field in an entity, the composite one – by a separate class that contains a set of fields that identify an entity. What options do we have?įirst, we can define an ID of a “simple” or a “composite” structure. But for the article, we will continue to use the terms ID and primary key interchangeably. We need to map the ID to column(s) that uniquely identify each row. Note: The ID does not have to map to the column(s) defined as the table primary key. This is one of the key concepts allowing developers to focus mainly on the business logic, while most of the boilerplate operations are being handled by a JPA implementation itself, and IDs are a vital part of this process. This way, developers can fetch JPA entities from the database, work with them and save them later without calling any insert or update statements. Therefore, the JPA specification requires developers to define a field or a set of fields to establish the one-to-one association between an entity instance and a particular DB record. It introduces entities - Java objects that are rigidly tied to their records in the database. Usually, this mapping is managed manually as a part of the business logic. At this application-to-database level of communications, there is no direct link between objects in the application and records stored in the database. To save or update data, we need to compose another insert or update statement. To obtain a dataset, developers run a select statement that returns corresponding tuples. While working with JDBC, we communicate with a database using its own language - native SQL queries. JDBC and relational databases do not require primary or unique keys for a table. Why is that? Introduction: why do we need IDs in JPA Entities at all? According to the JPA specification, Entity is a Java class that meets the following requirements:Īs you can see, ID is required. ![]()
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