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

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m (How to Configure a Reference Descriptor Using Workbench)
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[[Image:support.gif|Supported.]]
 
[[Image:support.gif|Supported.]]
 
|}
 
|}
 
  
  
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TIMESTAMP
 
TIMESTAMP
 
|}
 
|}
 
  
  
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This table lists the supported direct-to-field mapping combinations.
 
This table lists the supported direct-to-field mapping combinations.
 
  
  
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Note that some of these mappings result in a loss of precision: avoid these combinations if you require this level of precision. For example, if you create a direct-to-field mapping between a <tt>java.sql.Date</tt> attribute and a <tt>TIMESTAMPTZ</tt> database field, there is no loss of precision. However, if you create a direct-to-field mapping between a <tt>java.sql.Timestamp</tt> attribute and a <tt>DATE</tt> database field, the nanoseconds or milliseconds of the attribute are not stored in the database.
 
Note that some of these mappings result in a loss of precision: avoid these combinations if you require this level of precision. For example, if you create a direct-to-field mapping between a <tt>java.sql.Date</tt> attribute and a <tt>TIMESTAMPTZ</tt> database field, there is no loss of precision. However, if you create a direct-to-field mapping between a <tt>java.sql.Timestamp</tt> attribute and a <tt>DATE</tt> database field, the nanoseconds or milliseconds of the attribute are not stored in the database.
 
  
  
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# Click the '''General''' tab. The General tab appears.<br>'''''Direct Mapping General Tab, Database Field Option'''''<br>[[Image:mpdtfdfd.gif|Direct Mapping General Tab, Database Field Option]]
 
# Click the '''General''' tab. The General tab appears.<br>'''''Direct Mapping General Tab, Database Field Option'''''<br>[[Image:mpdtfdfd.gif|Direct Mapping General Tab, Database Field Option]]
 
#Use the '''Database Field''' field to select a field for this direct mapping. You must have previously associated the descriptor with a database table as described in [[Configuring%20a%20Relational%20Descriptor%20(ELUG)#Configuring Associated Tables|Configuring Associated Tables]].
 
#Use the '''Database Field''' field to select a field for this direct mapping. You must have previously associated the descriptor with a database table as described in [[Configuring%20a%20Relational%20Descriptor%20(ELUG)#Configuring Associated Tables|Configuring Associated Tables]].
 
  
  
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'''Note'''<nowiki>:</nowiki>  For direct-to-field mappings of an aggregate descriptor (see [[Configuring%20a%20Relational%20Descriptor%20(ELUG)|Configuring a Relational Descriptor as a Class or Aggregate Type]]), this field is for display only and cannot be changed.
 
'''Note'''<nowiki>:</nowiki>  For direct-to-field mappings of an aggregate descriptor (see [[Configuring%20a%20Relational%20Descriptor%20(ELUG)|Configuring a Relational Descriptor as a Class or Aggregate Type]]), this field is for display only and cannot be changed.
 
|}
 
|}
 +
 +
  
 
==Configuring Reference Descriptor==
 
==Configuring Reference Descriptor==
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[[Image:support.gif|Supported.]]
 
[[Image:support.gif|Supported.]]
 
|}
 
|}
 
  
  
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# Click the '''General''' tab. The General tab appears.<br>'''''General Tab, Reference Descriptor Field'''''<br>[[Image:mpgenref.gif|General Tab, Reference Descriptor Field]]
 
# Click the '''General''' tab. The General tab appears.<br>'''''General Tab, Reference Descriptor Field'''''<br>[[Image:mpgenref.gif|General Tab, Reference Descriptor Field]]
 
# Use the '''Reference Descriptor''' field to select the descriptor referenced by this relationship mapping.
 
# Use the '''Reference Descriptor''' field to select the descriptor referenced by this relationship mapping.
 
  
  
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For variable one-to-one mappings, the Reference Descriptor must be an ''interface''. See [[Configuring%20a%20Relational%20Variable%20One-to-One%20Mapping%20(ELUG)|Configuring a Relational Variable One-to-One Mapping]] for more information.
 
For variable one-to-one mappings, the Reference Descriptor must be an ''interface''. See [[Configuring%20a%20Relational%20Variable%20One-to-One%20Mapping%20(ELUG)|Configuring a Relational Variable One-to-One Mapping]] for more information.
 
|}
 
|}
 
  
  
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When you generate the deployment XML for your project, the ''mapping'' to the <tt>Employee</tt> class will be included, but not the <tt>Employee</tt> class.
 
When you generate the deployment XML for your project, the ''mapping'' to the <tt>Employee</tt> class will be included, but not the <tt>Employee</tt> class.
  
'''See Also'''
+
See Also:
 
: [[#Configuring Reference Descriptor|Configuring Reference Descriptor]]
 
: [[#Configuring Reference Descriptor|Configuring Reference Descriptor]]
 +
 +
  
 
==Configuring Batch Reading==
 
==Configuring Batch Reading==
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[[Image:support.gif|Supported.]]
 
[[Image:support.gif|Supported.]]
 
|}
 
|}
 
  
  
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# Click the '''General''' tab. The General tab appears.<br>'''''General Tab, Batch Reading Option'''''<br>[[Image:oogenbat.gif|General Tab, Batch Reading Option]]
 
# Click the '''General''' tab. The General tab appears.<br>'''''General Tab, Batch Reading Option'''''<br>[[Image:oogenbat.gif|General Tab, Batch Reading Option]]
 
#To specify that this mapping using batch reading, select the '''Batch Reading''' option.
 
#To specify that this mapping using batch reading, select the '''Batch Reading''' option.
 
 
  
  
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<span id="Example 33-1"></span>
 
<span id="Example 33-1"></span>
 
''''' Query Optimization Using Batching'''''
 
''''' Query Optimization Using Batching'''''
 +
<source lang="java">
 
  public void customize(ClassDescriptor descriptor) {  
 
  public void customize(ClassDescriptor descriptor) {  
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
     phoneNumbersMapping =
+
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("phones");  
        (OneToManyMapping)descriptor.getMappingForAttributeName("phones");  
+
 
     phoneNumbersMapping.useBatchReading();
 
     phoneNumbersMapping.useBatchReading();
 
  }
 
  }
 
+
</source>
  
  
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[[Image:support.gif|Supported.]]
 
[[Image:support.gif|Supported.]]
 
|}
 
|}
 
  
  
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| id="r2c1-t12" headers="r1c1-t12" align="left" | '''Query Key'''
 
| id="r2c1-t12" headers="r1c1-t12" align="left" | '''Query Key'''
 
| headers="r2c1-t12 r1c2-t12" align="left" |
 
| headers="r2c1-t12 r1c2-t12" align="left" |
Specify the query key to order by. Click '''Add''' to add query keys to, or '''Remove''' to remove query keys from the ordering operation.Click '''Up''' or '''Down''' to change the sort order of selected query keys.
+
Specify the query key to order by.  
 +
 
 +
Click '''Add''' to add query keys to, or '''Remove''' to remove query keys from the ordering operation.
 +
 
 +
Click '''Up''' or '''Down''' to change the sort order of selected query keys.
 
|- align="left" valign="top"
 
|- align="left" valign="top"
 
| id="r3c1-t12" headers="r1c1-t12" align="left" | '''Order'''
 
| id="r3c1-t12" headers="r1c1-t12" align="left" | '''Order'''
 
| headers="r3c1-t12 r1c2-t12" align="left" | Specify if EclipseLink orders the selected query key in '''Ascending''' or '''Descending''' (alphabetical) order.
 
| headers="r3c1-t12 r1c2-t12" align="left" | Specify if EclipseLink orders the selected query key in '''Ascending''' or '''Descending''' (alphabetical) order.
 
|}
 
|}
 
  
  
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<span id="'Example 33-2"></span>
 
<span id="'Example 33-2"></span>
 
''''' Configuring Query Key Order'''''
 
''''' Configuring Query Key Order'''''
 +
<source lang="java">
 
  public void customize(ClassDescriptor descriptor) {
 
  public void customize(ClassDescriptor descriptor) {
 
   
 
   
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
 
   
 
   
     phoneNumbersMapping =
+
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("phones");  
        (OneToManyMapping)descriptor.getMappingForAttributeName("phones");  
+
 
   
 
   
 
     phoneNumbersMapping.addAscendingOrdering("areaCode");  
 
     phoneNumbersMapping.addAscendingOrdering("areaCode");  
 
   
 
   
     ExpressionBuilder phone =  
+
     ExpressionBuilder phone = phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
        phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
+
 
   
 
   
 
     phoneNumbersMapping.getSelectionQuery().addOrdering(
 
     phoneNumbersMapping.getSelectionQuery().addOrdering(
 
         phone.get("type").toUpperCase().ascending());
 
         phone.get("type").toUpperCase().ascending());
 
  }
 
  }
   
+
  </source>
 
+
  
  
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Using Workbench, you can either import this table from your database or create it. If you import tables from the database (see [[Using%20Workbench%20(ELUG)|Importing Tables from a Database]]), EclipseLink creates references that correspond to existing database constraints (if supported by the driver). You can also define references in EclipseLink without creating similar constraints on the database.
 
Using Workbench, you can either import this table from your database or create it. If you import tables from the database (see [[Using%20Workbench%20(ELUG)|Importing Tables from a Database]]), EclipseLink creates references that correspond to existing database constraints (if supported by the driver). You can also define references in EclipseLink without creating similar constraints on the database.
 
  
  
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+
See Also:
'''See Also'''
+
 
: [[#Configuring Table and Field References (Foreign and Target Foreign Keys)|Configuring Table and Field References (Foreign and Target Foreign Keys)]]
 
: [[#Configuring Table and Field References (Foreign and Target Foreign Keys)|Configuring Table and Field References (Foreign and Target Foreign Keys)]]
 
  
  
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<span id="Example 33-3"></span>
 
<span id="Example 33-3"></span>
 
''''' Adding Complex Join to a Mapping'''''
 
''''' Adding Complex Join to a Mapping'''''
 +
<source lang="java">
 
  public void customize(ClassDescriptor descriptor) {
 
  public void customize(ClassDescriptor descriptor) {
 
   
 
   
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
     phoneNumbersMapping =
+
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("cellPhones");
        (OneToManyMapping)descriptor.getMappingForAttributeName("cellPhones");
+
 
    
 
    
     ExpressionBuilder phone =  
+
     ExpressionBuilder phone = phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
        phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
+
 
   
 
   
 
     phoneNumbersMapping.addTargetForeignKeyFieldName("PHONE.EMP_ID", "EMP.ID");
 
     phoneNumbersMapping.addTargetForeignKeyFieldName("PHONE.EMP_ID", "EMP.ID");
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         and(phone.getField("PHONE.TYPE').equal("CELL")));  
 
         and(phone.getField("PHONE.TYPE').equal("CELL")));  
 
  }
 
  }
 
+
</source>
 
+
  
 
{| class="Note oac_no_warn" width="80%" border="1" frame="hsides" rules="groups" cellpadding="3" frame="hsides" rules="groups"
 
{| class="Note oac_no_warn" width="80%" border="1" frame="hsides" rules="groups" cellpadding="3" frame="hsides" rules="groups"
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'''Note:''' You can provide the same functionality by using a descriptor amendment method (see [[Customizing%20the%20EclipseLink%20Application%20(ELUG)#Using the Descriptor Amendment Methods|Using the Descriptor Amendment Methods]]).
 
'''Note:''' You can provide the same functionality by using a descriptor amendment method (see [[Customizing%20the%20EclipseLink%20Application%20(ELUG)#Using the Descriptor Amendment Methods|Using the Descriptor Amendment Methods]]).
 
|}
 
|}
 +
  
  
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For more information about joins, see [[Introduction%20to%20EclipseLink%20Expressions%20(ELUG)|Expressions for Joining and Complex Relationships]].
 
For more information about joins, see [[Introduction%20to%20EclipseLink%20Expressions%20(ELUG)|Expressions for Joining and Complex Relationships]].
 
  
  
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# To use joining with this relationship, select the '''Use Joining''' option.
 
# To use joining with this relationship, select the '''Use Joining''' option.
  
'''See Also'''
+
See Also:
 
: [[#Configuring Joining at the Mapping Level|Configuring Joining at the Mapping Level]]
 
: [[#Configuring Joining at the Mapping Level|Configuring Joining at the Mapping Level]]
 
  
  
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<span id="Example 33-4"></span>
 
<span id="Example 33-4"></span>
 
''''' Adding Join at the Mapping Level'''''
 
''''' Adding Join at the Mapping Level'''''
 +
<source lang="java">
 
  public void customize(ClassDescriptor descriptor) {
 
  public void customize(ClassDescriptor descriptor) {
 
   
 
   
 
     OneToManyMapping addressMapping = new OneToManyMapping();
 
     OneToManyMapping addressMapping = new OneToManyMapping();
     addressMapping =
+
     addressMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("address");
        (OneToManyMapping)descriptor.getMappingForAttributeName("address");
+
 
     addressMapping.useJoining();
 
     addressMapping.useJoining();
 
     ...
 
     ...
 
  }
 
  }
 
+
</source>
 
+
  
 
{| class="Note oac_no_warn" width="80%" border="1" frame="hsides" rules="groups" cellpadding="3" frame="hsides" rules="groups"
 
{| class="Note oac_no_warn" width="80%" border="1" frame="hsides" rules="groups" cellpadding="3" frame="hsides" rules="groups"
Line 884: Line 870:
  
 
[[Category: EclipseLink User's Guide]]
 
[[Category: EclipseLink User's Guide]]
[[Category: Draft]]
+
[[Category: Release 1]]
 
[[Category: Task]]
 
[[Category: Task]]
 
[[Category: ORM]]
 
[[Category: ORM]]

Latest revision as of 09:42, 20 May 2009

Contents

Related Topics

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

This table lists the types of relational mappings that you can configure and provides a cross-reference to the type-specific chapter that lists the configurable options supported by that type.


If you are creating... See...

Direct-to-Field Mapping

Configuring a Relational Direct-to-Field Mapping

Transformation Mapping

Configuring a Relational Transformation Mapping

Direct-to-XMLType Mapping

Configuring a Relational Direct-to-XMLType Mapping

One-to-One Mapping

Configuring a Relational One-to-One Mapping

Variable One-to-One Mapping

Configuring a Relational Variable One-to-One Mapping

One-to-Many Mapping

Configuring a Relational One-to-Many Mapping

Many-to-Many Mapping

Configuring a Relational Many-to-Many Mapping

Aggregate Collection Mapping

Configuring a Relational Aggregate Collection Mapping

Direct Collection Mapping

Configuring a Relational Direct Collection Mapping

Direct Map Mapping

Configuring a Relational Direct Map Mapping

Aggregate Object Mapping

Configuring a Relational Aggregate Object Mapping


For more information, see the following:


[edit] Configuring Common Relational Mapping Options

This table lists the configurable options shared by two or more relational mapping types.


Option to Configure Workbench Java

Database field

Supported

Supported

Reference descriptor

Supported

Supported

Container policy

Supported

Supported

Method or direct field access

Supported

Supported

Default null value

Supported

Supported

Read-only mapping

Supported

Supported

Indirection (lazy loading)

Supported

Supported

Private or Independent relationships

Supported

Supported

Mapping comments

Supported

Supported

Serialized object converter

Supported

Supported

Type conversion converter

Supported

Supported

Object type conversion

Supported

Supported

Bidirectional relationship

Supported

Supported

Batch reading

Supported

Supported

Query key order

Supported

Supported

Table and field references

Supported

Supported

Joining

Supported

Supported


[edit] Configuring a Database Field

You can associate an object attribute with a database field.

This table summarizes which relational mappings support this option.


Mapping Using the Workbench How to Use Java

Direct-to-Field Mapping

Supported.

Supported.

Direct-to-XMLType Mapping

Supported.

Supported.


When choosing the database field, you must consider Java and database field type compatibility.

EclipseLink supports the following Java types:

  • java.lang: Boolean, Float, Integer, String, Double, Long, Short, Byte, Byte[ ], Character, Character[ ]; all the primitives associated with these classes
  • java.math: BigInteger, BigDecimal
  • java.sql: Date, Time, Timestamp
  • java.util: Date, Calendar

While executing reads, the mappings in the Relational Mapping Support for Reference Descriptor table perform the simple one-way data conversions that the Type Conversions Provided by Direct-to-Field Mappings table describes. For two-way or more complex conversions, You must use converters).

The mappings in this table also allow you to specify a null value. This may be required if primitive types are used in the object, and the database field allows null values. For more information, see Configuring a Default Null Value at the Mapping Level.


Type Conversions Provided by Direct-to-Field Mappings

Java type Database type

Integer, Float, Double, Byte, Short, BigDecimal, BigInteger, int, float, double, byte, short

NUMBER, NUMERIC, DECIMAL, FLOAT, DOUBLE, INT, SMALLINT, BIT, BOOLEAN

Boolean, boolean

BOOLEAN, BIT, SMALLINT, NUMBER, NUMERIC, DECIMAL, FLOAT, DOUBLE, INT

String

VARCHAR, CHAR, VARCHAR2, CLOB, TEXT, LONG, LONG VARCHAR, MEMOThe following types apply only to Oracle9: NVARCHAR2, NCLOB, NCHAR

byte[ ]

BLOB, LONG RAW, IMAGE, RAW, VARBINARY, BINARY, LONG VARBINARY

Time

TIME

java.sql.Date

DATE

Timestamp, java.util.Date, Calendar

TIMESTAMP


Support for oracle.sql.TimeStamp

EclipseLink provides additional support for mapping Java date and time data types to Oracle Database DATE, TIMESTAMP, and TIMESTAMPTZ data types when you use the Oracle JDBC driver with Oracle9i Database Server or later and the Oracle9Platform in EclipseLink.

In a direct-to-field mapping, you are not required to specify the database type of the field value; EclipseLink determines the appropriate data type conversion.

This table lists the supported direct-to-field mapping combinations.


Supported Oracle Database Date and Time Direct-to-Field Mappings

Java Type Database Type Description

java.sql.Time

TIMESTAMP

Full bidirectional support.

TIMESTAMPTZ

Full bidirectional support.

DATE

Full bidirectional support.

java.sql.Date

TIMESTAMP

Full bidirectional support.

TIMESTAMPTZ

Full bidirectional support.

DATE

Full bidirectional support.

java.sql.Timestamp

TIMESTAMP

Full bidirectional support.

TIMESTAMPTZ

Full bidirectional support.

DATE

Nanoseconds are not stored in the database.

java.util.Date

TIMESTAMP

Full bidirectional support.

TIMESTAMPTZ

Full bidirectional support.

DATE

Milliseconds are not stored in the database.

java.util.Calendar

TIMESTAMP

Native SQL or binding gives Calendar timezone.

Note: The TIMESTAMP database value has no timezone – the Calendar object provides the local timezone by default. If the database is not in this timezone, you must obtain the database timezone by some other means and update the Calendarobject accordingly. For this reason, TIMESTAMPTZ may be a better choice.

TIMESTAMPTZ

Native SQL or binding stores timezone; standard SQL is based on the local timezone.

DATE

Neither timezone nor milliseconds are stored in the database.


Note that some of these mappings result in a loss of precision: avoid these combinations if you require this level of precision. For example, if you create a direct-to-field mapping between a java.sql.Date attribute and a TIMESTAMPTZ database field, there is no loss of precision. However, if you create a direct-to-field mapping between a java.sql.Timestamp attribute and a DATE database field, the nanoseconds or milliseconds of the attribute are not stored in the database.


[edit] How to Configure a Database Field Using Workbench

Use this procedure to select a specific database field for a direct mapping.

  1. Select the direct mapping attribute in the Navigator. Its properties appear in the Editor.
  2. Click the General tab. The General tab appears.
    Direct Mapping General Tab, Database Field Option
    Direct Mapping General Tab, Database Field Option
  3. Use the Database Field field to select a field for this direct mapping. You must have previously associated the descriptor with a database table as described in Configuring Associated Tables.


Note: For direct-to-field mappings of an aggregate descriptor (see Configuring a Relational Descriptor as a Class or Aggregate Type), this field is for display only and cannot be changed.


[edit] Configuring Reference Descriptor

In relational mappings that extend org.eclipse.persistence.mappings.ForeignReferenceMapping, attributes reference other EclipseLink descriptors–not the data source. You can select any descriptor in the project.

This table summarizes which relational mappings support this option.


Mapping Using the Workbench How to Use Java

One-to-one

Supported.

Supported.

Variable one-to-one

Supported.

Supported.

One-to-many

Supported.

Supported.

Many-to-many

Supported.

Supported.

Aggregate collection

Unsupported.

Supported.

Aggregate object

Supported.

Supported.


[edit] How to Configure a Reference Descriptor Using Workbench

To specify a reference descriptor for a relational mapping, 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, Reference Descriptor Field
    General Tab, Reference Descriptor Field
  3. Use the Reference Descriptor field to select the descriptor referenced by this relationship mapping.


Note: For aggregate mappings the Reference Descriptor must be an aggregate. See Configuring a Relational Descriptor as a Class or Aggregate Type for more information.

For variable one-to-one mappings, the Reference Descriptor must be an interface. See Configuring a Relational Variable One-to-One Mapping for more information.


You can specify a reference descriptor that is not in the current Workbench project. For example, to create a mapping to an Employee class that does not exist in the current project, do the following:

  1. Add the Employee class to your current project. See Working with Projects.
  2. Create the relationship mapping to the Employee descriptor.
  3. Deactivate the Employee descriptor. See Active and Inactive Descriptors.

When you generate the deployment XML for your project, the mapping to the Employee class will be included, but not the Employee class.

See Also:

Configuring Reference Descriptor


[edit] Configuring Batch Reading

Batch reading can be used in most of the relational mappings. This feature should be used only if it is known that the related objects are always required with the source object.

This table summarizes which relational mappings support this option.


Mapping Using the Workbench Using Java

One-to-one

Supported.

Supported.

One-to-many

Supported.

Supported.

Many-to-many

Supported.

Supported.

Direct collection

Supported.

Supported.

Direct map

Supported.

Supported.

Aggregate object

Unsupported.

Supported.


[edit] How to Configure Batch Reading Using Workbench

To use batch reading in a relationship mapping, 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, Batch Reading Option
    General Tab, Batch Reading Option
  3. To specify that this mapping using batch reading, select the Batch Reading option.


[edit] How to Configure Batch Reading Using Java

This example shows how to use a DescriptorCustomizer class to add batch reading to a mapping.

Query Optimization Using Batching

 public void customize(ClassDescriptor descriptor) { 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("phones"); 
     phoneNumbersMapping.useBatchReading();
 }


[edit] Configuring Query Key Order

You can configure EclipseLink to maintain collections in order by query key.

This table summarizes which relational mappings support this option.


Mapping Using the Workbench Using Java

Many-to-many

Supported.

Supported.

One-to-many

Supported.

Supported.

Aggregate collection

Unsupported.

Supported.


[edit] How to Configure Query Key Order Using Workbench

To specify the order of a mapping's query keys, use this procedure:

  1. Select the mapped attribute in the Navigator. Its properties appear in the Editor.
  2. Click the Ordering tab. The Ordering tab appears.
    Ordering Tab
    Ordering Tab
  3. Complete the Ordering options on the tab.
Field Description
Query Key

Specify the query key to order by.

Click Add to add query keys to, or Remove to remove query keys from the ordering operation.

Click Up or Down to change the sort order of selected query keys.

Order Specify if EclipseLink orders the selected query key in Ascending or Descending (alphabetical) order.


[edit] How to Configure Query Key Order Using Java

This example shows how to use the DescriptorCustomizer class to add complex ordering to a mapping.

Configuring Query Key Order

 public void customize(ClassDescriptor descriptor) {
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
 
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("phones"); 
 
     phoneNumbersMapping.addAscendingOrdering("areaCode"); 
 
     ExpressionBuilder phone = phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
 
     phoneNumbersMapping.getSelectionQuery().addOrdering(
         phone.get("type").toUpperCase().ascending());
 }


Note: You can provide the same functionality by using a descriptor amendment method (see Using the Descriptor Amendment Methods).


[edit] Configuring Table and Field References (Foreign and Target Foreign Keys)

A foreign key is a combination of one or more database columns that reference a unique key, usually the primary key, in another table. Foreign keys can be any number of fields (similar to a primary key), all of which are treated as a unit. A foreign key and the parent key it references must have the same number and type of fields.

Mappings that extend org.eclipse.persistence.mappings.ForeignReferenceMapping use foreign keys to find information in the database so that the target object(s) can be instantiated. For example, if every Employee has an attribute address that contains an instance of Address (which has its own descriptor and table) then, the one-to-one mapping for the address attribute would specify foreign key information to find an Address for a particular Employee.

EclipseLink classifies foreign keys into two categories in mappings–foreign keys and target foreign keys:

  • In a foreign key, the key is found in the table associated with the mapping's own descriptor. For example, an Employee foreign key to ADDRESS would be in the EMPLOYEE table.
  • In a target foreign key, the reference is from the target object's table back to the key from the mapping's descriptor's table. For example, the ADDRESS table would have a foreign key to EMPLOYEE.

Caution: Make sure you fully understand the distinction between foreign key and target foreign key before defining a mapping.

The table reference is the database table that contains the foreign key references.

This table summarizes which relational mappings support this option.


Mapping Using the Workbench Using Java

One-to-one

Supported.

Supported.

One-to-many

Supported.

Supported.

Many-to-many

Supported.

Supported.

Aggregate collection

Unsupported.

Supported.

Direct collection

Supported.

Supported.

Direct map

Supported.

Supported.


Using Workbench, you can either import this table from your database or create it. If you import tables from the database (see Importing Tables from a Database), EclipseLink creates references that correspond to existing database constraints (if supported by the driver). You can also define references in EclipseLink without creating similar constraints on the database.


[edit] How to Configure Table and Field References (Foreign and Target Foreign Keys) Using Workbench

To specify a table for a mapping reference, use this procedure:

  1. Select the mapped attribute in the Navigator. Its properties appear in the Editor.
  2. Click the Table Reference tab. The Reference tab appears.
    Table Reference Tab, Table Reference Field
    Table Reference Tab, Table Reference Field
  3. Complete the fields on the Table Reference tab.

Use the following information to select the field references on the tab:


Field Description
Table Reference Select an existing table, or click New to create a new table reference.
Source and Target Field

Click Add to create new foreign key reference. To delete an existing key pair reference, select the Source and Target fields and click Remove.

Source Field Select the database field from the source table for this foreign key reference.
Target Field Select the database field from the target table for this foreign key reference.
Target Foreign Key Specify whether or not the reference is from the target object's table back to the key from the mapping's descriptor's table.


See Also:

Configuring Table and Field References (Foreign and Target Foreign Keys)


[edit] How to Configure Table and Field References (Foreign and Target Foreign Keys) Using Java

Use the addTargetForeignKeyFieldName method (and pass the name of the field name of the target foreign key and the source of the primary key in the source table) to specify foreign key information.

For composite source primary keys, use the addTargetForeignKeyFieldName method for each of the fields that comprise the primary key.

This esxample shows how to use the DescriptorCustomizer class to add complex join to a mapping.


Adding Complex Join to a Mapping

 public void customize(ClassDescriptor descriptor) {
 
     OneToManyMapping phoneNumbersMapping = new OneToManyMapping();
     phoneNumbersMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("cellPhones");
 
     ExpressionBuilder phone =  phoneNumbersMapping.getSelectionQuery().getExpressionBuilder();
 
     phoneNumbersMapping.addTargetForeignKeyFieldName("PHONE.EMP_ID", "EMP.ID");
 
     phoneNumbersMapping.getSelectionQuery(
         phone.getField("PHONE.EMP_ID").equal(phone.getParameter("EMP.ID").
         and(phone.getField("PHONE.TYPE').equal("CELL"))); 
 }

Note: You can provide the same functionality by using a descriptor amendment method (see Using the Descriptor Amendment Methods).


[edit] Configuring Joining at the Mapping Level

EclipseLink supports configuring an inner or outer join at the mapping level for a ForeignReferenceMapping. When a class that owns the mapping is read, the EclipseLink runtime will always get the class and the target of the reference mapping with one database hit.

Use this feature only if the target object is always required with the source object, or when indirection (lazy loading) is not used. For more information, see Indirection (Lazy Loading).

You can also configure join reading at the query level. For more information, see Join Reading and Object-Level Read Queries.

For more information about joins, see Expressions for Joining and Complex Relationships.


[edit] How to Configure Joining at the Mapping Level Using Workbench

To use joining in a relationship mapping, 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, Use Joining Option
    General Tab, Use Joining Option
  3. To use joining with this relationship, select the Use Joining option.

See Also:

Configuring Joining at the Mapping Level


[edit] How to Configure Joining at the Mapping Level Using Java

This example shows how to use the DescriptorCustomizer class to add complex join at the mapping level.


Adding Join at the Mapping Level

 public void customize(ClassDescriptor descriptor) {
 
     OneToManyMapping addressMapping = new OneToManyMapping();
     addressMapping = (OneToManyMapping)descriptor.getMappingForAttributeName("address");
     addressMapping.useJoining();
     ...
 }

Note: You can provide the same functionality by using a descriptor amendment method (see Using the Descriptor Amendment Methods).



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