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Setting and Tuning of JPA Queries

); Flushing changes to the database before every query execution affects performance significantly. Therefore, when performance is important, this issue has to be considered. Lock Mode (setLockMode) ObjectDB

GROUP BY and HAVING clauses

OF c.continents GROUP BY c.currency Because grouping is performed in this query on a path

FROM clause (JPQL / Criteria API)

could also cause performance problems. For example, let's look at the following query execution

Storing JPA Entity Objects

. Storing a large amount of entity objects can also be performed by multiple transactions: em

Obtaining a JPA Database Connection

, update, and delete should only be performed within an active transaction. Given an EntityManager, em

Database Server

. For instance, you can increase the maximum JVM heap size and improve performance by using HotSpot JVM

Chapter 1 - Quick Tour

This chapter demonstrates basic ObjectDB and JPA concepts by introducing a simple example program. After reading this chapter you should be able to write basic programs that create, open and close ObjectDB databases and perform basic CRUD operations (Create/Store, Retrieve, Update and Delete

Step 4: Add a Servlet Class

(request, response); } } GuestServlet performs the following operations on every http request

Step 3: Define an EJB Session Bean

Operations on the database will be performed by an instance of a session bean (EJB) class that we will define in this step: Open the [New Session Bean] dialog box by right clicking the guest package node (in the [Projects] window), selecting New > Other... > Java EE (or Enterprise JavaBeans

Step 4: Add a Servlet Class

performs the following operations on every http request: The EntityManagerFactory is retrieved from

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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