generate and print barcodes c# Sets, bags, lists, and maps of value types in Java

Generator Quick Response Code in Java Sets, bags, lists, and maps of value types

Sets, bags, lists, and maps of value types
QR Code ISO/IEC18004 Creation In Java
Using Barcode printer for Java Control to generate, create QR Code JIS X 0510 image in Java applications.
www.OnBarcode.com
Decoding QR Code In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
A java.util.SortedMap can be mapped with <map> element, and the sort attribute can be set to either a comparator or natural ordering for in-memory sorting. Initialize the collection with a java.util.TreeMap instance. Arrays are supported by Hibernate with <primitive-array> (for Java primitive value types) and <array> (for everything else). However, they re rarely used in domain models, because Hibernate can t wrap array properties. You lose lazy loading without bytecode instrumentation, and optimized dirty checking, essential convenience and performance features for persistent collections.
Make Denso QR Bar Code In Java
Using Barcode maker for Java Control to generate, create QR Code image in Java applications.
www.OnBarcode.com
Painting QR Code In Java
Using Barcode creation for Java Control to generate, create QR image in Java applications.
www.OnBarcode.com
The JPA standard doesn t name all these options. The possible standard collection property types are Set, List, Collection, and Map. Arrays aren t considered. Furthermore, the JPA specification only specifies that collection properties hold references to entity objects. Collections of value types, such as simple String instances, aren t standardized. However, the specification document already mentions that future versions of JPA will support collection elements of embeddable classes (in other words, value types). You ll need vendor-specific support if you want to map collections of value types with annotations. Hibernate Annotations include that support, and we d expect many other JPA vendors support the same. If you want to map collection interfaces and implementations not directly supported by Hibernate, you need to tell Hibernate about the semantics of your custom collections. The extension point in Hibernate is called PersistentCollection; usually you extend one of the existing PersistentSet, PersistentBag, or PersistentList classes. Custom persistent collections are not very easy to write and we don t recommend doing this if you aren t an experienced Hibernate user. An example can be found in the Hibernate test suite source code, as part of your Hibernate download package. We now go through several scenarios, always implementing the collection of item images. You map it first in XML and then with Hibernate s support for collection annotations. For now, assume that the image is stored somewhere on the filesystem and that you keep just the filename in the database. How images are stored and loaded with this approach isn t discussed; we focus on the mapping.
PDF417 Creation In Java
Using Barcode encoder for Java Control to generate, create PDF-417 2d barcode image in Java applications.
www.OnBarcode.com
Printing DataMatrix In Java
Using Barcode generation for Java Control to generate, create ECC200 image in Java applications.
www.OnBarcode.com
Mapping a set
Encode PDF-417 2d Barcode In Java
Using Barcode encoder for Java Control to generate, create PDF417 image in Java applications.
www.OnBarcode.com
Making ITF In Java
Using Barcode generator for Java Control to generate, create Interleaved 2 of 5 image in Java applications.
www.OnBarcode.com
The simplest implementation is a Set of String image filenames. First, add a collection property to the Item class:
Quick Response Code Creator In VS .NET
Using Barcode drawer for VS .NET Control to generate, create QR Code image in .NET framework applications.
www.OnBarcode.com
QR-Code Creator In None
Using Barcode encoder for Font Control to generate, create Quick Response Code image in Font applications.
www.OnBarcode.com
Mapping collections and entity associations
Draw PDF 417 In None
Using Barcode creation for Font Control to generate, create PDF-417 2d barcode image in Font applications.
www.OnBarcode.com
Barcode Drawer In Visual Studio .NET
Using Barcode maker for Reporting Service Control to generate, create Barcode image in Reporting Service applications.
www.OnBarcode.com
private Set images = new HashSet(); ... public Set getImages() { return this.images; } public void setImages(Set images) { this.images = images; }
EAN-13 Decoder In VB.NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Reading PDF 417 In Visual C#.NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Now, create the following mapping in the Item s XML metadata:
QR Generator In None
Using Barcode drawer for Font Control to generate, create QR-Code image in Font applications.
www.OnBarcode.com
Read Code 3 Of 9 In VS .NET
Using Barcode reader for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
<set name="images" table="ITEM_IMAGE"> <key column="ITEM_ID"/> <element type="string" column="FILENAME" not-null="true"/> </set>
Barcode Encoder In Java
Using Barcode maker for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Barcode Maker In Java
Using Barcode creation for BIRT reports Control to generate, create Barcode image in BIRT applications.
www.OnBarcode.com
The image filenames are stored in a table named ITEM_IMAGE, the collection table. From the point of view of the database, this table is a separate entity, a separate table, but Hibernate hides this for you. The <key> element declares the foreign key column in the collection table that references the primary key ITEM_ID of the owning entity. The <element> tag declares this collection as a collection of value type instances in this case, of strings. A set can t contain duplicate elements, so the primary key of the ITEM_IMAGE collection table is a composite of both columns in the <set> declaration: ITEM_ID and FILENAME. You can see the schema in figure 6.1.
Universal Product Code Version A Encoder In None
Using Barcode generator for Software Control to generate, create GS1 - 12 image in Software applications.
www.OnBarcode.com
Print European Article Number 13 In Java
Using Barcode generation for Android Control to generate, create GS1 - 13 image in Android applications.
www.OnBarcode.com
Figure 6.1 Table structure and example data for a collection of strings
It doesn t seem likely that you would allow the user to attach the same image more than once, but let s suppose you did. What kind of mapping would be appropriate in that case
Mapping an identifier bag
An unordered collection that permits duplicate elements is called a bag. Curiously, the Java Collections framework doesn t include a bag implementation. However, the java.util.Collection interface has bag semantics, so you only need a matching implementation. You have two choices:
Sets, bags, lists, and maps of value types
Write the collection property with the java.util.Collection interface, and, on declaration, initialize it with an ArrayList of the JDK. Map the collection in Hibernate with a standard <bag> or <idbag> element. Hibernate has a built-in PersistentBag that can deal with lists; however, consistent with the contract of a bag, it ignores the position of elements in the ArrayList. In other words, you get a persistent Collection. Write the collection property with the java.util.List interface, and, on declaration, initialize it with an ArrayList of the JDK. Map it like the previous option, but expose a different collection interface in the domain model class. This approach works but isn t recommended, because clients using this collection property may think the order of elements is always preserved, which isn t the case if it s mapped as a <bag> or <idbag>.
We recommend the first option. Change the type of images in the Item class from Set to Collection, and initialize it with an ArrayList:
private Collection images = new ArrayList(); ... public Collection getImages() { return this.images; } public void setImages(Collection images) { this.images = images; }
Note that the setter method accepts a Collection, which can be anything in the JDK collection interface hierarchy. However, Hibernate is smart enough to replace this when persisting the collection. (It also relies on an ArrayList internally, like you did in the declaration of the field.) You also have to modify the collection table to permit duplicate FILENAMEs; the table needs a different primary key. An <idbag> mapping adds a surrogate key column to the collection table, much like the synthetic identifiers you use for entity classes:
<idbag name="images" table="ITEM_IMAGE"> <collection-id type="long" column="ITEM_IMAGE_ID"> <generator class="sequence"/> </collection-id> <key column="ITEM_ID"/> <element type="string" column="FILENAME" not-null="true"/> </idbag>
Copyright © OnBarcode.com . All rights reserved.