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Tag Archives: JPA

JPA Tutorial – The ULTIMATE Guide (PDF Download)

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EDITORIAL NOTE: The Java Persistence API (JPA) is a Java programming language application programming interface specification that describes the management of relational data in applications using Java Platform, Standard Edition and Java Platform, Enterprise Edition. JPA has become the de-facto standard to write application code that interacts with Databases. For this reason we have provided an abundance of tutorials here ...

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A beginner’s guide to Java Persistence locking

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Implicit locking In concurrency theory, locking is used for protecting mutable shared data against hazardous data integrity anomalies. Because lock management is a very complex problem, most applications rely on their data provider implicit locking techniques. Delegating the whole locking responsibility to the database system can both simplify application development and prevent concurrency issues, such as deadlocking. Deadlocks can still ...

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EAGER fetching is a code smell

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Introduction Hibernate fetching strategies can really make a difference between an application that barely crawls and a highly responsive one. In this post I’ll explain why you should prefer query based fetching instead of global fetch plans. Fetching 101 Hibernate defines four association retrieving strategies:     Fetching Strategy Description Join The association is OUTER JOINED in the original SELECT ...

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5 ways to initialize lazy relations and when to use them

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Lazy loading of relations between entities is a well established best practice in JPA. Its main goal is to retrieve only the requested entities from the database and load the related entities only if needed. That is a great approach, if we only need the requested entities. But it creates additional work and can be the cause of performance problems, ...

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JPA Entity Graphs

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One of the latest features in JPA 2.1 is the ability to specify fetch plans using Entity Graphs. This is useful since it allows you to customise the data that is retrieved with a query or find operation. When working with mid to large size applications is common to display data from the same entity in different and many ways. ...

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JPA Tutorial: Mapping Entities – Part 3

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In my last article I showed two different ways to read/write persistent entity state – field and property. When field access mode is used, JPA directly reads the state values from the fields of an entity using reflection. It directly translates the field names into database column names if we do not specify the column names explicitly.  In case of property access mode, ...

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JPA Tutorial: Mapping Entities – Part 2

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In my last post I showed a simple way of persisting an entity. I explained the default approach that JPA uses to determine the default table for an entity. Let’s assume that we want to override this default name. We may like to do so because the data model has been designed and fixed before and the table names do ...

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Preventing lost updates in long conversations

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Introduction All database statements are executed within the context of a physical transaction, even when we don’t explicitly declare transaction boundaries (BEGIN/COMMIT/ROLLBACK). Data integrity is enforced by the ACID properties of database transactions. Logical vs Physical transactions An logical transaction is an application-level unit of work that may span over multiple physical (database) transactions. Holding the database connection open throughout ...

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JPA tutorial: Mapping Entities – Part 1

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In this article I will discuss about the entity mapping procedure in JPA. As for my examples I will use the same schema that I used in one of my previous articles. In my two previous articles I explained how to set up JPA in a Java SE environment. I do not intend to write the setup procedure for a ...

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