java barcode generator Lazy properties in Java

Painting Denso QR Bar Code in Java Lazy properties

Lazy properties
QR-Code Encoder In Java
Using Barcode creation for Java Control to generate, create QR Code 2d barcode image in Java applications.
www.OnBarcode.com
Scan QR Code In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
"; id = " + e.getEntityId()); } }
Drawing Barcode In Java
Using Barcode creation for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
Paint Barcode In Java
Using Barcode creation for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
Your next step is to tell Hibernate to use your listener class:
Data Matrix Maker In Java
Using Barcode creation for Java Control to generate, create DataMatrix image in Java applications.
www.OnBarcode.com
Code 128 Encoder In Java
Using Barcode printer for Java Control to generate, create Code128 image in Java applications.
www.OnBarcode.com
<hibernate-configuration> <session-factory> <listener type="load" class="com.manning.hq.ch11.MyLoadEventListener"/> </session-factory> </hibernate-configuration>
Barcode Creator In Java
Using Barcode generator for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
Making UCC - 14 In Java
Using Barcode maker for Java Control to generate, create GTIN - 14 image in Java applications.
www.OnBarcode.com
Note that you re registering the listeners in the hibernate.cfg.xml file, not a mapping definition. Now, when an Event instance is loaded, the following is output to the log file:
QR Code Reader In VB.NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
QR-Code Printer In VS .NET
Using Barcode printer for Reporting Service Control to generate, create Quick Response Code image in Reporting Service applications.
www.OnBarcode.com
INFO Object loaded: Event; id = 4
Generating Barcode In None
Using Barcode creation for Software Control to generate, create Barcode image in Software applications.
www.OnBarcode.com
Recognize QR Code 2d Barcode In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Instead of just dumping something to the log file, you could have implemented a security manager to make sure only certain users can load Event instances. Another way to use events is for debugging. Suppose you have a collection that isn t getting populated as you expect. You can create an implementation of InitializeCollectionEventListener to log when a given collection is initialized. Events are an interesting way to debug and manage your Hibernate applications. For example, your event-handling code could also integrate with Java Management Extensions (JMX) to create an administrative console. In the next section, we ll discuss another new feature in Hibernate 3: lazy properties.
Read Code 128 Code Set C In Visual Basic .NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Decoding Barcode In .NET Framework
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
11.7 Lazy properties
Barcode Creation In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create Barcode image in ASP.NET applications.
www.OnBarcode.com
PDF 417 Recognizer In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
A common request from developers using Hibernate is the ability to lazily populate properties of persistent classes, similar to lazy
Barcode Generation In VB.NET
Using Barcode drawer for .NET framework Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
Barcode Recognizer In VB.NET
Using Barcode Control SDK for .NET framework Control to generate, create, read, scan barcode image in .NET applications.
www.OnBarcode.com
What s new in Hibernate 3
Creating EAN13 In None
Using Barcode printer for Font Control to generate, create EAN / UCC - 13 image in Font applications.
www.OnBarcode.com
UPC-A Encoder In Java
Using Barcode generation for Android Control to generate, create GTIN - 12 image in Android applications.
www.OnBarcode.com
collections. For instance, say you have an Event class that you want to display to a user. Your display doesn t include the start and end times of the Event, so there s no reason to populate it. This can be a powerful feature, but you need to see how it has been implemented in comparison to lazy collections. Lazy population is fairly easy with collections, since Hibernate can transparently provide its own implementations of the collection interfaces. With properties, Hibernate can t step in at runtime to intercept each property because most of the properties are concrete classes, not interfaces. Instead, Hibernate must perform some compile-time processing, called instrumentation. Instrumentation is the process of modifying bytecode to add additional operations, typically for debugging or testing purposes. Hibernate inserts instrumentation to intercept calls to lazy properties. When the interception is made, the property is populated transparently. To create a lazy property, simply add the lazy attribute to the <property> element:
<property name="startDate" type="date" lazy="true"/>
Next, process your bytecode with an Ant task provided by Hibernate:
<taskdef name="instrument" classname="org.hibernate.tools.instrument.InstrumentTask" classpathref="project.class.path"/> <instrument> <fileset dir="${build.dest}"> <include name="**/*.class"/> </fileset> </instrument>
The bytecode is modified to its current directory. If you ve configured your classes to have lazy properties but the classes haven t had instrumentation added, Hibernate transparently disables the feature for that class.
Summary
While lazy properties require the extra step of adding instrumentation to bytecode, they allow you to be very specific when retrieving objects. The only thing to remember is that lazy properties, like lazy collections, require the Session to be open when the properties are populated.
11.8 Summary
With Hibernate s increasing adoption in enterprise applications, each new release must add features and address problems found in previous releases. Hibernate 3 is meant to address some of the shortcomings in previous releases, particularly in working with legacy databases. Other features, such as filters and dynamic classes, are designed to make developing with Hibernate easier. Dynamic classes allow you to persist simple Maps of values. One of the main advantages of working with Maps is their flexibility: you can put any object into a Map and persist it. You aren t required to create explicit property accessors, as with POJOs. Another feature we examined, lazy properties, allows the developer to specify properties that are not populated when the object is retrieved from the database. We also looked at filters, which return objects that pass certain criteria. Filters can be enabled or disabled at runtime, and can be passed parameters. The features in Hibernate 3 should make it easier to quickly manage object persistence for any Java application, including legacy applications.
Copyright © OnBarcode.com . All rights reserved.