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Difference between revisions of "Configuring a Relational Direct Collection Mapping (ELUG)"

m (Configuring Direct Value Field)
m (Introduction to Relational Direct Collection Mapping Configuration)
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This example shows how to create a direct collection mapping and add it to a descriptor using Java code.
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<span id="Example 36-1"></span>
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''''' Direct Collection Mapping'''''
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<pre>
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public void customize(ClassDescriptor descriptor) {
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    DirectCollectionMapping mapping = new DirectCollectionMapping(); 
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    // configure mapping
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    ...
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    // add mapping to descriptor
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    descriptor.addMapping(mapping);
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}
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</pre>
  
 
For more information, see the following:
 
For more information, see the following:
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* [[Introduction%20to%20Relational%20Mappings%20(ELUG)#Direct Collection Mapping|Direct Collection Mapping]]
 
* [[Introduction%20to%20Relational%20Mappings%20(ELUG)#Direct Collection Mapping|Direct Collection Mapping]]
 
* [[Configuring%20a%20Relational%20Mapping%20(ELUG)|Configuring a Relational Mapping]]
 
* [[Configuring%20a%20Relational%20Mapping%20(ELUG)|Configuring a Relational Mapping]]
 
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* [[Creating%20and%20Configuring%20Mappings%20(ELUG)|Creating and Configuring Mappings]]
For information on using JPA to configure direct collection mappings, see [[Using%20EclipseLink%20JPA%20Extensions%20(ELUG)#How to Use the @BasicCollection Annotation|How to Use the @BasicCollection Annotation]].
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For information on using JPA to configure direct collection mappings, see [[Using%20EclipseLink%20JPA%20Extensions%20(ELUG)#How to Use the @BasicCollection Annotation|How to Use the @BasicCollection Annotation]].
  
 
==Configuring Target Table==
 
==Configuring Target Table==

Revision as of 12:05, 30 November 2007

This section describes the various components that you must configure in order to use a relational direct collection mapping.

For information on how to configure EclipseLink mappings options common to two or more mapping types, see Configuring a Mapping.

For information on how to create EclipseLink mappings, see Creating a Mapping.

Configurable Options for Relational Direct Collection Mapping lists the configurable options for a relational direct collection mapping.


Introduction to Relational Direct Collection Mapping Configuration

This table lists the configurable options for a relational direct collection mapping.


Configurable Options for Relational Direct Collection Mapping

Option Workbench Java

Target table (see #Configuring Target Table)

Supported

Supported

Direct value field (see #Configuring Direct Value Field)

Supported

Supported

Method or direct field access (see Configuring a Type Conversion Converter)

Supported

Supported

Read-only mapping (see Configuring Read-Only Mappings)

Supported

Supported

Batch reading (see Configuring Batch Reading)

Supported

Supported

Indirection (lazy loading) (see Configuring Mapping Comments)

Supported

Supported

Container policy (see Configuring Mapping Comments)

Supported

Supported

Mapping comments (see Configuring Mapping Comments)

Supported

Supported

Serialized object converter (see Configuring a Serialized Object Converter)

Supported

Supported

Type conversion converter (see Configuring a Type Conversion Converter)

Supported

Supported

Object type converter (see Configuring an Object Type Converter)

Supported

Supported

Table and field references (see Configuring Joining at the Mapping Level)

Supported

Supported


This example shows how to create a direct collection mapping and add it to a descriptor using Java code.

Direct Collection Mapping

public void customize(ClassDescriptor descriptor) { 
    DirectCollectionMapping mapping = new DirectCollectionMapping();  

    // configure mapping
    ... 

    // add mapping to descriptor
    descriptor.addMapping(mapping);
}

For more information, see the following:


For information on using JPA to configure direct collection mappings, see How to Use the @BasicCollection Annotation.

Configuring Target Table

Each direct collection stores reference information in a target table. In Figure 32-6, the RESPONS table contains the primary key and object of the instance owning the collection. You must create this table in your database.


How to Configure a Target Table Using Workbench

To specify the direct collection specifics, use this procedure:

  1. Select the mapped attribute in the Navigator. Its properties appear in the Editor.
  2. Click the General tab. The General tab appears.
    General Tab, Target Table Options
    General Tab, Target Table Options

Use the Target Table list to select the table that contains the reference fields for the direct collection mapping.



How to Configure a Target Table Using Java

Direct collection mappings store collections of Java objects that are not EclipseLink-enabled. Direct collections usually store Java types, such as String.

Direct collection mappings are instances of the DirectCollectionMapping class and require the following elements:

  • The attribute mapped, set by using the setAttributeName method.
  • The database table that holds the values to be stored in the collection, set by using the setReferenceTableName method.
  • The field in the reference table from which the values are read and placed into the collection; this is called the direct field. Set it using the setDirectFieldName method.
  • The foreign key information, which you specify using the setReferenceKeyFieldName method and passing the name of the field that is a foreign reference to the primary key of the source object

Note: If the target primary key is composite, call the addReferenceKeyFieldName method for each of the fields that make up the key.


Configuring a Simple Direct Collection Mapping

public void customize(ClassDescriptor descriptor) { 
    DirectCollectionMapping directCollectionMapping = 
                                    new DirectCollectionMapping();
    directCollectionMapping.setAttributeName ("responsibilitiesList");
    directCollectionMapping.setReferenceTableName ("RESPONS"); // target table
    directCollectionMapping.setDirectFieldName ("DESCRIP");
    directCollectionMapping.setReferenceKeyFieldName ("EMP_ID");
    directCollectionMapping.useCollectionClass (Collection.class); // default

    // add this mapping to descriptor
    descriptor.addMapping (directCollectionMapping);
}

In addition to the API that Configuring a Simple Direct Collection Mapping illustrates, other common API for use with direct collection mappings include the following:


  • useBasicIndirection: implements EclipseLink value holder indirection.
  • useTransparentCollection: if you use transparent indirection, this element places a special collection in the source object's attribute.
  • dontUseIndirection: implements no indirection.

For more information about the available methods for DirectCollectionMapping, see the EclipseLink API Reference.

Configuring Direct Value Field

The direct value field, located in the reference table, stores the primitive data value. In Figure 32-6, the DESCRIP field stores the collection.


How to Configure a Direct Value Field Using Workbench

To specify the direct collection specifics, use this procedure:

  1. Select the mapped attribute in the Navigator. Its properties appear in the Editor.
  2. Click the General tab. The General tab appears.
    General Tab, Direct Value Field
    General Tab, Direct Value Field

Use the Direct Value Field list to select the field from the Target Table table that contains the object of the collection.



How to Configure Direct Value Field Using Java

Configuring a Simple Direct Collection Mapping demonstrates how to create and configure a direct collection mapping, including the setting of a direct field. The example also shows how to add this mapping to the descriptor.



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