Intro to Hibernate2:17 with Chris Ramacciotti
In this first lesson, you will get a high-level look at some of the important classes of the Hibernate library.
[MUSIC] 0:00 So we've chosen Hibernate as your ORM, 0:05 and now it's time to get a grasp of the main components we'll be interacting with. 0:07 Check it out. 0:12 We've already seen this basic graphic of a Hibernate application. 0:13 If we zoom into the Hibernate component, we see some important pieces revealed. 0:17 First is the session factory. 0:21 In Hibernate, a session factory is a fairly heavy weight object 0:24 that contains the relationships between the application and a database. 0:27 There is usually just one of these per application. 0:32 It encapsulates all the objects related to mapping pojos to database tables and 0:35 columns. 0:40 Which is contained in the metadata sources object. 0:41 A session represents an interaction with the database 0:45 in which a live connection is established. 0:47 We'll see that before performing any data operations we'll open a session. 0:50 And when we're done interacting with the data we'll immediately close the session. 0:55 These objects are lightweight and therefore, are created as needed. 0:59 A transaction represents a unit of work that must be performed on the database, 1:03 which might in compass several queries. 1:08 For example, a database transaction performing a bank account transfer 1:10 might involve deducting a hundred dollars from one account and adding it to another. 1:14 If adding the hundred dollars to the second account fails, 1:19 we want to undo the initial deduction. 1:22 Otherwise the hundred dollars vanishes. 1:25 In a transaction we begin the work, perform all the queries, and 1:28 if they succeed, we commit the transaction, which finalizes all queries. 1:32 If any part fails, we roll back the transaction which will reverse each query. 1:37 Pretty powerful stuff. 1:42 And of course, Hibernate supports this. 1:44 Finally, a criteria allows us to query the database using its mapped pojo class. 1:47 And add restrictions to further filter those results, 1:52 using methods that translate to the SQL Like or > or = operators. 1:55 At their most basic level these restrictions translate to simple or 2:02 compound where clauses. 2:06 All right, now that you've seen some of the main components of Hibernate. 2:10 Let's dive in. 2:13 Meet me in the next video to start coding. 2:14
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