android java qr code generator The complete Hibernate mapping catalog in Java

Draw QR Code in Java The complete Hibernate mapping catalog

APPENDIX
Denso QR Bar Code Generation In Java
Using Barcode generation for Java Control to generate, create QR Code 2d barcode image in Java applications.
www.OnBarcode.com
QR-Code Recognizer In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
The complete Hibernate mapping catalog
Making EAN128 In Java
Using Barcode drawer for Java Control to generate, create EAN 128 image in Java applications.
www.OnBarcode.com
ECC200 Encoder In Java
Using Barcode generation for Java Control to generate, create Data Matrix image in Java applications.
www.OnBarcode.com
Event
Create 1D Barcode In Java
Using Barcode generation for Java Control to generate, create Linear Barcode image in Java applications.
www.OnBarcode.com
Drawing QR-Code In Java
Using Barcode creation for Java Control to generate, create QR-Code image in Java applications.
www.OnBarcode.com
ConferenceEvent
Code 128 Code Set B Creation In Java
Using Barcode encoder for Java Control to generate, create ANSI/AIM Code 128 image in Java applications.
www.OnBarcode.com
UCC - 14 Printer In Java
Using Barcode generator for Java Control to generate, create UCC - 14 image in Java applications.
www.OnBarcode.com
NetworkEvent
Print Quick Response Code In Objective-C
Using Barcode generation for iPad Control to generate, create QR Code image in iPad applications.
www.OnBarcode.com
Decoding Denso QR Bar Code In VB.NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Figure A.11 Subclasses: Event with child ConferenceEvent and NetworkEvent
Generate Data Matrix In Java
Using Barcode creation for Eclipse BIRT Control to generate, create ECC200 image in Eclipse BIRT applications.
www.OnBarcode.com
Scanning Quick Response Code In Visual C#
Using Barcode decoder for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
A.11.1 Table-per-class hierarchy strategy
ANSI/AIM Code 128 Generator In C#.NET
Using Barcode encoder for .NET Control to generate, create Code 128 image in Visual Studio .NET applications.
www.OnBarcode.com
EAN-13 Generator In None
Using Barcode generation for Font Control to generate, create EAN-13 Supplement 5 image in Font applications.
www.OnBarcode.com
To create a subclass (basic <subclass>), you need at least two classes: a superclass and a subclass. You have to mark them with the correct tags, and you need to specify a discriminator type so Hibernate knows what class each row is. Here are the classes:
Barcode Scanner In Java
Using Barcode Control SDK for BIRT Control to generate, create, read, scan barcode image in BIRT applications.
www.OnBarcode.com
Encoding UPCA In None
Using Barcode generation for Online Control to generate, create Universal Product Code version A image in Online applications.
www.OnBarcode.com
/** * @hibernate.class table="events" discriminator-value="Event" * @hibernate.discriminator column="class_name" */ public class Event implements Serializable { private Long id; /** * @hibernate.id generator-class="native" column="id" */ public Long getId() { return id; } public void setId(Long id) { this.id = id; } } /** * @hibernate.subclass discriminator-value="ConferenceEvent" */ public class ConferenceEvent extends Event{ } /** * @hibernate.subclass discriminator-value="NetworkingEvent" */ public class NetworkingEvent extends Event{ }
Quick Response Code Creation In None
Using Barcode generation for Font Control to generate, create Quick Response Code image in Font applications.
www.OnBarcode.com
GTIN - 128 Generation In None
Using Barcode drawer for Font Control to generate, create USS-128 image in Font applications.
www.OnBarcode.com
Subclasses
GS1 - 12 Drawer In VB.NET
Using Barcode printer for VS .NET Control to generate, create UCC - 12 image in VS .NET applications.
www.OnBarcode.com
Drawing Barcode In Visual Studio .NET
Using Barcode encoder for .NET Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
The parent class, Event, defines the column that will hold the discriminator value. Each subclass (as well as Event) has a different value that it will store in that column. When Hibernate loads a row, it looks at the value of the column and knows whether to instantiate an Event or a NetworkingEvent. Also, the id field demonstrates that the subclasses don t need to do anything other than extend Event. The superclass Event holds all the details.
<class name="com.manning.hq.apdxA.Event" table="events"> <id name="id" column="id" type="java.lang.Long"> <generator class="native" /> </id> <subclass name="com.manning.hq.apdxA.ConferenceEvent" discriminator-value=" ConferenceEvent " /> <subclass name="com.manning.hq.apdxA.NetworkingEvent" discriminator-value="NetworkingEvent" /> </class>
As you can see, all the subclass mappings go into the Event.hbm.xml file; no ConferenceEvent.hbm.xml will exist. Subclasses can have their own properties, which will be defined inside the <subclass> element.
Table schema
One table holds all of the events, distinguished by the value in the class_name column.
events id class_name
A.11.2 Table-per-subclass strategy
A joined subclass (<joined-subclass> element) works a bit differently from the <subclass> mapping. There will be a single top-level table, which holds all of the ids, and a table for every subclass. Since each subclass has its own table, Hibernate doesn t need a discriminator column to determine the class type. Expanding our object model,
APPENDIX
The complete Hibernate mapping catalog
assume that there are several types of Rooms, including a SuiteRoom and a PenthouseRoom:
/** * @hibernate.class table="rooms" */ public class Room implements Serializable { private Long id; /** * @hibernate.id generator-class="native" column="id" * @return */ public Long getId() { return id; } public void setId(Long id) { this.id = id; } } /** * * @hibernate.joined-subclass table="suite_room" * @hibernate.joined-subclass-key column="room_id" */ public class SuiteRoom extends Room { } /** * * @hibernate.joined-subclass table="penthouse_room" * @hibernate.joined-subclass-key column="room_id" */ public class PenthouseRoom extends Room { }
From the listing above, you can see that Room doesn t need the discriminator value. Instead, each joined subclass has to specify a key column, which joins back to the superclass table, in this case, room_id. And while it s currently not stated in the XDoclet documentation, a table attribute is available that lets you specify which table the subclasses map to.
<class name="com.manning.hq.apdxA.Room" table="rooms"> <id name="id" column="id" type="java.lang.Long">
Subclasses
<generator class="native" /> </id> <joined-subclass name="com.manning.hq.apdxA.SuiteRoom" table="suite_room"> <key column="room_id" /> </joined-subclass> <joined-subclass name="com.manning.hq.apdxA.PenthouseRoom" table="penthouse_room"> <key column="room_id" /> </joined-subclass> </class>
If the subclasses had their own properties (which they likely would in a real example), they d be defined normally with <property> elements, and they d go right under the <key> element inside the subclass.
Table schema
For this relation three tables are needed: one for the parent, and one for each of the two subclasses.
rooms id id suite_room room_id id penthouse_room room_id
A.11.3 Table-per-concrete-class strategy: any
The next inheritance strategy is one that is not commonly used. The table-per-concrete-class strategy makes use of the <any> mapping. Each concrete class has its own table, but unlike the <joined-subclass> there s no single table maintaining a common set of keys. So if each table could theoretically have its own row 1, how does another table create a foreign key to it Essentially, it needs what we refer to as a compound foreign key, with one column to store the name of table and one to store the foreign key. The fact that an object could join to any row in any table means conventional joins don t work. Therefore, several selects are needed to do what normal joins can do in one, so performance will be somewhat worse.
Copyright © OnBarcode.com . All rights reserved.