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Documentation > WebObjects 4.5 >
EOAdaptor Reference
Inherits
from: NSObject
Implements: EOPropertyListEncoding
Package: com.apple.yellow.eoaccess
Class Description
An EOAttribute represents a column, field or property in a
database, and associates an internal name with an external name
or expression by which the property is known to the database. The
property an EOAttribute represents may be a meaningful value, such
as a salary or a name, or it may be an arbitrary value used for
identification but with no real-world applicability (ID numbers
and foreign keys for relationships fall into this category). An
EOAttribute also maintains type information for binding values to
the instance variables of objects.
EOAttributes are also used to represent arguments for EOStoredProcedures.
You usually define attributes in your EOModel with the EOModeler
application, which is documented in Enterprise Objects
Framework Tools and Techniques. Your code probably won't
need to programmatically interact with EOAttribute unless you're
working at the adaptor level. See "Creating Attributes" for information
on creating your own attribute objects.
Fore detailed discussion of using attribute objects to map
database data types to Java objects, see "Mapping from Database to Objects" and "Working with Custom Data Types" .
EOAttributes can also alter the way values are selected, inserted,
and updated in the database by defining special format strings;
see "SQL Statement Formats" for
more information.
Constants
EOAttribute defines the following int constants
as possible return values for the EOAttribute method adaptorValueType.
The return value indicates the data type that will be fetched from
the database for the receiving attribute.
EOAttribute defines the additional int constants
to be used by factoryMethodArgumentType and setFactoryMethodArgumentType to specify
the type of argument that should be passed to the attribute's "factory
method". For more information, see "Working with Custom Data Types" .
EOAttribute also defines int constants
to represent parameter direction for EOAttributes that represent arguments
to a stored procedure. For more information, see the parameterDirection method description.
Interfaces Implemented
EOPropertyListEncoding
awakeWithPropertyList
encodeIntoPropertyList
Method Types
- Constructors
- EOAttribute
- Accessing the entity
- entity
- parent
- Accessing the name
- setName
- name
- validateName
- beautifyName
- Accessing date information
- serverTimeZone
- setServerTimeZone
- Accessing external definitions
- setColumnName
- columnName
- setDefinition
- definition
- setExternalType
- externalType
- Accessing value type
information
- setValueClassName
- valueClassName
- setValueType
- valueType
- setAllowsNull
- allowsNull
- setPrecision
- precision
- setScale
- scale
- setWidth
- width
- validateValue:
- Converting to adaptor
value types
- adaptorValueByConvertingAttributeValue
- adaptorValueType
- Working with custom value
types
- setValueFactoryMethodName
- valueFactoryMethod
- valueFactoryMethodName
- setFactoryMethodArgumentType
- factoryMethodArgumentType
- setAdaptorValueConversionMethodName
- adaptorValueConversionMethod
- adaptorValueConversionMethodName
- archiveDataForObject
- Accessing attribute characteristics
- setReadOnly
- isReadOnly
- isDerived
- isFlattened
- Accessing SQL statement
formats
- setReadFormat
- readFormat
- setWriteFormat
- writeFormat
- Accessing the user dictionary
- setUserInfo
- userInfo
- Working with stored procedures
- setParameterDirection
- parameterDirection
- storedProcedure
- Working with prototypes
- overridesPrototypeDefinitionForKey
- prototype
- prototypeName
- setPrototype
Constructors
public EOAttribute(
NSDictionary propertyList,
Object owner)
Creates a new EOAttribute initialized
from propertyList-a dictionary
containing only property list data types (that is, String, NSDictionary,
NSArray, and NSData objects). This constructor is used by EOModeler
when it reads in a Model from a file, for example. The owner argument
should be the EOAttribute's EOEntity or EOStoredProcedure. EOAttributes
created from a property list must receive an awakeWithPropertyList message immediately
after creation before they are fully functional, but the awake... message
should be deferred until the all of the other objects in the model
have also been created.
Static Methods
public static NSData archiveDataForObject(NSObject anObject)
Return anObject's
value as a NSData object whose bytes can be stored in an external
repository.
Instance Methods
public Object adaptorValueByConvertingAttributeValue(Object value)
Ensures that value is
either a String, Number, NSData, or NSDate, converting it if necessary.
If value needs to be converted, adaptorValueByConvertingAttributeValue uses
the adaptor conversion method to convert value to
one of these four primitive types. If the attribute hasn't a specific
adaptor conversion method, and the type to be fetched from the database
is AdaptorBytesType, archiveDataForObject will be
invoked to convert the attribute value.See
Also: adaptorValueConversionMethod, adaptorValueType
public NSSelector adaptorValueConversionMethod()
Returns the method used to convert a custom
class into one of the primitive types that the adaptor knows how
to manipulate: String, Number, NSData, or NSDate. The return value
of this method is derived from the attribute's adaptor value conversion
method name. If that name doesn't map to a valid selector in the Java run-time, null is
returned.See Also: adaptorValueByConvertingAttributeValue, adaptorValueConversionMethodName
public String adaptorValueConversionMethodName()
Returns the name of the method used to convert
a custom class into one of the primitive types that the adaptor
knows how to manipulate: String, Number, NSData, or NSDate.See
Also: adaptorValueByConvertingAttributeValue
public int adaptorValueType()
Returns a constant that indicates the data type
that will be fetched from the database. Currently, this method returns
one of the following values:
| Constant |
Description |
AdaptorNumberType |
A number value |
AdaptorCharactersType |
A string of characters |
AdaptorBytesType |
Raw bytes |
AdaptorDateType |
A date |
See Also: factoryMethodArgumentType
public boolean allowsNull()
Returns true to indicate that the attribute
can have a null value, false otherwise. If the attribute maps directly
to a column in the database, it also is used to determine whether
the database column can have a NULL value.See
Also: setAllowsNull
public void beautifyName()
Makes the attribute name conform to a standard
convention. Names that conform to this style are all lower-case
except for the initial letter of each embedded word other than the
first, which is upper case. Thus, "NAME" becomes "name",
and "FIRST_NAME" becomes "firstName". This method is used
in reverse-engineering an EOModel.See Also: nameForExternalName (EOEntity), validateName, beautifyNames (EOModel)
public String columnName()
Returns the name of the column in the database
that corresponds to this attribute, or null if the attribute isn't
simple (that is, if it's derived or flattened). An adaptor uses
this name to identify the column corresponding to the attribute.
Your application should never need to use this name. Note that columnName and definition are mutually
exclusive; if one returns a value, the other returns null.See
Also: , externalType
public String definition()
Returns a derived or flattened attribute's
definition, or null if the attribute is simple. An attribute's definition
is either a value expression defining a derived attribute, such
as "salary * 12", or a data path for a flattened attribute,
such as "toAuthor.name". Note that columnName and definition are
mutually exclusive; if one returns a value, the other returns null.See
Also: externalType, setDefinition
public EOEntity entity()
Returns the entity that owns the attribute,
or null if this attribute is acting as an argument for a stored procedure.See
Also: storedProcedure
public String externalType()
Returns the attribute's type as understood
by the database; for example, a Sybase "varchar" or an Oracle
"NUMBER".See Also: columnName, setExternalType
public int factoryMethodArgumentType()
Returns the type of argument that should be
passed to the "factory method"-which is invoked by the attribute
to create an attribute value for a custom class. This method returns
one of the following values:
| Constant |
Argument Type |
FactoryMethodArgumentIsData |
NSData |
FactoryMethodArgumentIsString |
String |
FactoryMethodArgumentIsBytes |
raw bytes |
See Also: valueFactoryMethod, setFactoryMethodArgumentType
public boolean isDerived()
Returns false if the attribute corresponds exactly
to one column in the table associated with its entity, and true if
it doesn't. For example, an attribute with a definition of "otherAttributeName
+ 1" is derived.Note that flattened attributes are also
considered as derived attributes.
See
Also: isFlattened, definition
public boolean isFlattened()
Returns true if the attribute is flattened, false otherwise.
A flattened attribute is one that's accessed through an entity's
relationships but belongs to another entity.Note that flattened
attributes are also considered to be derived attributes.
See
Also: isDerived, definition
public boolean isReadOnly()
Returns true if the value of the attribute can't
be modified, false if it can.See Also: setReadOnly
public String name()
Returns the attribute's name.See
Also: columnName, definition, setName
public boolean overridesPrototypeDefinitionForKey(String key)
Returns false if the requested key gets its
value from the prototype attribute. If the attribute has an override,
then this method returns true. Valid values for key include "columnName," "valueClass," and
so on.See Also: prototype
public int parameterDirection()
Returns the parameter direction for attributes
that are arguments to a stored procedure. This method returns one
of the following values:
| Constant |
Description |
Void |
No parameters |
InParameter |
Input only parameters |
OutParameter |
Output only parameters |
InOutParameter |
Bidirectional parameters (input and output) |
See Also: storedProcedure, storedProcedureForOperation (EOEntity), setParameterDirection
public Object parent()
Returns the attribute's parent, which is either
an EOEntity or an EOStoredProcedure. Use this method when you need
to find the model for an attribute.
public int precision()
Returns the precision of the database representation
for attributes with a value class of Number or java.math.BigDecimal.See
Also: scale
public EOAttribute prototype()
Returns the prototype attribute that is used
to define default settings for the receiver.See
Also: overridesPrototypeDefinitionForKey
public String prototypeName()
Returns the name of the prototype attribute
of the receiver.See Also: prototype
public String readFormat()
Returns a format string of the appropriate type
that can be used when building an expression that contains the value
of the attribute.See Also: setReadFormat, writeFormat
public int scale()
Returns the scale of the database representation
for attributes with a value class of Number or java.math.BigDecimal.
The returned value can be negative.See Also: precision, setScale
public NSTimeZone serverTimeZone()
Returns the time zone assumed for NSDates in
the database server, or the local time zone if one hasn't been
set. An EOAdaptorChannel automatically converts dates between the
time zones used by the server and the client when fetching and saving
values. Applies only to attributes that represent dates.See
Also: setServerTimeZone
public void setAdaptorValueConversionMethodName(String conversionMethodName)
Sets to conversionMethodName the
name of the method used to convert a custom class into one of the primitive
types that the adaptor knows how to manipulate: String, Number,
NSData, or NSDate.See Also: adaptorValueConversionMethodName
public void setAllowsNull(boolean allowsNull)
Sets according to allowsNull whether
or not the attribute can have a nullvalue. If the attribute maps directly
to a column in the database, it also controls whether the database
column can have a NULL value.See Also: allowsNull
public void setColumnName(String columnName)
Sets to columnName the
name of the attribute used in communication with the database server.
An adaptor uses this name to identify the column corresponding to
the attribute; this name must match the name of a column in the
database table corresponding to the attribute's entity.This
method makes a derived or flattened attribute simple; the definition is released
and the column name takes its place for use with the server.
| setColumnName and setDefinition are
closely related. Only one can be set at any given time. Invoking
either of these methods causes the other value to be set to null |
See Also: columnName
public void setDefinition(String definition)
Sets to definition the
attribute's definition as recognized by the database server. definition should
be either a value expression defining a derived attribute, such
as "salary * 12", or a data path for a flattened attribute,
such as "toAuthor.name".Prior to invoking this method,
the attribute's entity must have been set by adding the attribute
to an entity. This method will not function correctly if the attribute's
entity has not been set.
This method converts a simple
attribute into a derived or flattened attribute; the columnName is removed and
the definition takes its place for use with the server.
| setColumnName and setDefinition are
closely related. Only one can be set at any given time. Invoking
either of these methods causes the other value to be set to null. |
See Also: definition
public void setExternalType(String typeName)
Sets to typeName the
type used for the attribute in the database adaptor; for example,
a Sybase "varchar" or an Oracle7 "NUMBER". Each adaptor
defines the set of types that can be supplied to setExternalType.
The external type you specify for a given attribute must correspond
to the type used in the database server.See
Also: setDefinition, externalType
public void setFactoryMethodArgumentType(int argumentType)
Sets the type of argument that should be passed
to the "factory method"-which is invoked by the receiver to
create a value for a custom class. Factory methods can accept Strings,
NSDatas, or raw bytes; specify an argumentType as FactoryMethodArgumentIsString, FactoryMethodArgumentIsData,
or FactoryMethodArgumentIsBytes as
appropriate.See Also: setValueFactoryMethodName, factoryMethodArgumentType
public void setName(String name)
Sets the attribute's name to name. Throws
an exception if name is already in
use by another attribute or relationship of the same entity, or
if name is not a valid attribute
name.See Also: validateName, name
public void setParameterDirection(int parameterDirection)
Sets the parameter direction for attributes
that are arguments to a stored procedure. parameterDirection should
be one of the following values:See
Also: setStoredProcedure (EOEntity), parameterDirection
public void setPrecision(int precision)
Sets to precision the
precision of the database representation for attributes with a value
class of Number or java.math.BigDecimal.See
Also: setScale, precision
public void setPrototype(EOAttribute prototype)
Sets the prototype attribute. This overrides
any existing settings in the attribute.See
Also: prototype
public void setReadFormat(String aString)
Sets the format string that's used to format
the attribute's value for SELECT statements. In aString,
%P is replaced by the attribute's external name. The read
format string is used whenever the attribute is referenced in a
select list or qualifier.
See Also: setWriteFormat, readFormat
public void setReadOnly(boolean flag)
Sets whether the value of the attribute can
be modified according to flag. Throws an exception if flag is false and
the argument is derived but not flattened.See
Also: isDerived, isFlattened, isReadOnly
public void setScale(int scale)
Sets to scale the
scale of the database representation for attributes with a value
class of Number or java.math.BigDecimal. scale can
be negative.See Also: setPrecision, scale
public void setServerTimeZone(NSTimeZone aTimeZone)
Sets to aTimeZone the
time zone used for NSDates in the database server. If aTimeZone is null then
the local time zone is used. An EOAdaptorChannel automatically converts
dates between the time zones used by the server and the client when
fetching and saving values. Applies only to attributes that represent
dates.See Also: serverTimeZone
public void setUserInfo(NSDictionary dictionary)
Sets to dictionary the
dictionary of auxiliary data, which your application can use for
whatever it needs. dictionary can
only contain property list data types (that is, NSDictionary, NSArray,
NSData, and String).See Also: userInfo
public void setValueClassName(String name)
Sets the class name for values of this attribute
to name. When an EOAdaptorChannel
fetches data for the attribute, it's presented to the application
as an instance of this class.The class need not exist in the
run-time system when this message is sent, but it must exist when
an adaptor channel performs a fetch; if the class isn't present
the result depends on the adaptor. See your adaptor's documentation
for information on how absent value classes are handled.
See
Also: setValueType, valueClassName
public void setValueFactoryMethodName(String factoryMethodName)
Sets the "factory method"-which is invoked
by the attribute to create an attribute value for a custom class-to factoryMethodName.
The factory method should be a static method returning an object
of your custom value class. Use setFactoryMethodArgumentTypeto specify
the type of argument that is to be passed to your factory method.See
Also: valueFactoryMethodName
public void setValueType(String typeName)
Sets to typeName the
conversion character (such as "i" or "d") for the data type a
Number attribute is converted to and from in your application. Value
types are scalars such as int, float,
and double. Each adaptor supports a different
set of conversion characters for numeric types. However, in most
(if not all) cases it's safe to supply a value of "i" (int)
or "d" (double).See Also: setValueClassName, valueType
public void setWidth(int length)
Sets to length the
maximum amount of bytes the attribute's value may contain. Adaptors
may use this information to allocate space for fetch buffers.See
Also: width
public void setWriteFormat(String string)
Sets the format string that's used to format
the attribute's value for INSERT or UPDATE expressions. In string,
%P is replaced by the attribute's value.See
Also: setReadFormat, writeFormat
public EOStoredProcedure storedProcedure()
Returns the stored procedure for which this
attribute is an argument. If this attribute isn't an argument to
a stored procedure but instead is owned by an entity, this method
returns null.See Also: entity
public NSDictionary userInfo()
Returns a dictionary of user data. Your application
can use this to store any auxiliary information it needs.See
Also: setUserInfo
public void validateName(String name)
Validates name and
returns null if it is a valid name, or an exception if it isn't.
A name is invalid if it has zero length; starts with a character
other than a letter, a number, or "@", "#", or "_";
or contains a character other than a letter, a number, "@",
"#", "_", or "$". A name is also invalid if the receiver's EOEntity
already has an EOAttribute with the same name, or if the model has
a stored procedure that has an argument with the same name.setName: uses
this method to validate its argument.
public Object validateValue(Object value)
Validates value by converting it to the attribute's
value type and by testing other attribute validation constraints
(such as allowsNull, width,
and so on). If, during the validation process, any coercion was performed,
the converted value is returned.See Also: adaptorValueByConvertingAttributeValue, allowsNull, valueType, valueClassName, width
public String valueClassName()
Returns the name of the class for custom value
types. When data is fetched for the attribute, it's presented
to the application as an instance of this class. This class
must be present in the run-time system when an EOAdaptorChannel
fetches data for the attribute; if the class isn't present the
result depends on the adaptor. See your adaptor's documentation for
information on how absent value classes are handled.
See
Also: valueType, setValueClassName
public NSSelector valueFactoryMethod()
Returns the factory method that's invoked
by the attribute when creating an attribute value that's of a custom
class. The value returned from this method is derived from the attribute's valueFactoryMethodName. If that name
doesn't map to a valid method in the Java run-time, this method returns null.
public String valueFactoryMethodName()
Returns the name of the factory method that's
used for creating a custom class value.See
Also: valueFactoryMethod, setValueFactoryMethodName
public String valueType()
Returns the conversion character (such as "i"
or "d") for the data type a Number attribute is converted to
and from in your application. Value types are scalars such as int, float,
and double. See
Also: valueClassName, setValueType
public int width()
Returns the maximum length (in bytes) for values
that are mapped to this attribute. Returns zero for numeric and
date types.See Also: setWidth
public String writeFormat()
Returns the format string that's used to format
the attribute's value for INSERT or UPDATE expressions. In the
returned string, %P is replaced by the attribute's value.See
Also: readFormat, setWriteFormat