Class AbstractConverter
- All Implemented Interfaces:
Converter
- Direct Known Subclasses:
ArrayConverter
,BooleanConverter
,CharacterConverter
,ClassConverter
,DateTimeConverter
,FileConverter
,NumberConverter
,StringConverter
,URLConverter
Converter
implementation that provides the structure
for handling conversion to and from a specified type.
This implementation provides the basic structure for
converting to/from a specified type optionally using a default
value or throwing a ConversionException
if a
conversion error occurs.
Implementations should provide conversion to the specified
type and from the specified type to a String
value
by implementing the following methods:
convertToString(value)
- convert to a String (default implementation uses the objectstoString()
method).convertToType(Class, value)
- convert to the specified type
The default value has to be compliant to the default type of this
converter - which is enforced by the generic type parameter. If a
conversion is not possible and a default value is set, the converter
tries to transform the default value to the requested target type.
If this fails, a ConversionException
if thrown.
- Since:
- 1.8.0
- Version:
- $Id$
-
Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final String
Debug logging message to indicate default value configurationprivate Object
The default value specified to our Constructor, if any.private org.apache.commons.logging.Log
Logging for this instance.private static final String
Current package nameprivate boolean
Should we return the default value on conversion errors? -
Constructor Summary
ConstructorsConstructorDescriptionConstruct a Converter that throws aConversionException
if an error occurs.AbstractConverter
(Object defaultValue) Construct a Converter that returns a default value if an error occurs. -
Method Summary
Modifier and TypeMethodDescriptionprotected ConversionException
conversionException
(Class<?> type, Object value) Generates a standard conversion exception with a message indicating that the passed in value cannot be converted to the desired target type.<T> T
Convert the input object into an output object of the specified type.protected Object
convertArray
(Object value) Return the first element from an Array (or Collection) or the value unchanged if not an Array (or Collection).private <T> T
convertToDefaultType
(Class<T> targetClass, Object value) Performs a conversion to the default type.protected String
convertToString
(Object value) Convert the input object into a String.protected abstract <T> T
convertToType
(Class<T> type, Object value) Convert the input object into an output object of the specified type.protected Object
getDefault
(Class<?> type) Return the default value for conversions to the specified type.protected abstract Class
<?> Return the default type thisConverter
handles.protected <T> T
handleError
(Class<T> type, Object value, Throwable cause) Handle Conversion Errors.protected <T> T
handleMissing
(Class<T> type) Handle missing values.boolean
Indicates whether a default value will be returned or exception thrown in the event of a conversion error.(package private) org.apache.commons.logging.Log
log()
Accessor method for Log instance.protected void
setDefaultValue
(Object defaultValue) Set the default value, converting as required.toString()
Provide a String representation of this converter.(package private) String
Provide a String representation of ajava.lang.Class
.
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Field Details
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DEFAULT_CONFIG_MSG
Debug logging message to indicate default value configuration- See Also:
-
PACKAGE
Current package name- See Also:
-
log
private transient org.apache.commons.logging.Log logLogging for this instance. -
useDefault
private boolean useDefaultShould we return the default value on conversion errors? -
defaultValue
The default value specified to our Constructor, if any.
-
-
Constructor Details
-
AbstractConverter
public AbstractConverter()Construct a Converter that throws aConversionException
if an error occurs. -
AbstractConverter
Construct a Converter that returns a default value if an error occurs.- Parameters:
defaultValue
- The default value to be returned if the value to be converted is missing or an error occurs converting the value.
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Method Details
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isUseDefault
public boolean isUseDefault()Indicates whether a default value will be returned or exception thrown in the event of a conversion error.- Returns:
true
if a default value will be returned for conversion errors orfalse
if aConversionException
will be thrown.
-
convert
Convert the input object into an output object of the specified type.- Specified by:
convert
in interfaceConverter
- Type Parameters:
T
- the target type of the conversion- Parameters:
type
- Data type to which this value should be convertedvalue
- The input value to be converted- Returns:
- The converted value.
- Throws:
ConversionException
- if conversion cannot be performed successfully and no default is specified.
-
convertToString
Convert the input object into a String.N.B.This implementation simply uses the value's
toString()
method and should be overriden if a more sophisticated mechanism for conversion to a String is required.- Parameters:
value
- The input value to be converted.- Returns:
- the converted String value.
- Throws:
Throwable
- if an error occurs converting to a String
-
convertToType
Convert the input object into an output object of the specified type.Typical implementations will provide a minimum of
String --> type
conversion.- Type Parameters:
T
- Target type of the conversion.- Parameters:
type
- Data type to which this value should be converted.value
- The input value to be converted.- Returns:
- The converted value.
- Throws:
Throwable
- if an error occurs converting to the specified type
-
convertArray
Return the first element from an Array (or Collection) or the value unchanged if not an Array (or Collection). N.B. This needs to be overriden for array/Collection converters.- Parameters:
value
- The value to convert- Returns:
- The first element in an Array (or Collection) or the value unchanged if not an Array (or Collection)
-
handleError
Handle Conversion Errors.If a default value has been specified then it is returned otherwise a ConversionException is thrown.
- Type Parameters:
T
- Target type of the conversion.- Parameters:
type
- Data type to which this value should be converted.value
- The input value to be convertedcause
- The exception thrown by theconvert
method- Returns:
- The default value.
- Throws:
ConversionException
- if no default value has been specified for thisConverter
.
-
handleMissing
Handle missing values.If a default value has been specified, then it is returned (after a cast to the desired target class); otherwise a ConversionException is thrown.
- Type Parameters:
T
- the desired target type- Parameters:
type
- Data type to which this value should be converted.- Returns:
- The default value.
- Throws:
ConversionException
- if no default value has been specified for thisConverter
.
-
setDefaultValue
Set the default value, converting as required.If the default value is different from the type the
Converter
handles, it will be converted to the handled type.- Parameters:
defaultValue
- The default value to be returned if the value to be converted is missing or an error occurs converting the value.- Throws:
ConversionException
- if an error occurs converting the default value
-
getDefaultType
Return the default type thisConverter
handles.- Returns:
- The default type this
Converter
handles.
-
getDefault
Return the default value for conversions to the specified type.- Parameters:
type
- Data type to which this value should be converted.- Returns:
- The default value for the specified type.
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toString
Provide a String representation of this converter. -
log
org.apache.commons.logging.Log log()Accessor method for Log instance.The Log instance variable is transient and accessing it through this method ensures it is re-initialized when this instance is de-serialized.
- Returns:
- The Log instance.
-
toString
Provide a String representation of ajava.lang.Class
.- Parameters:
type
- Thejava.lang.Class
.- Returns:
- The String representation.
-
convertToDefaultType
Performs a conversion to the default type. This method is called if we do not have a target class. In this case, the T parameter is not set. Therefore, we can cast to it (which is required to fulfill the contract of the method signature).- Type Parameters:
T
- the type of the result object- Parameters:
targetClass
- the target class of the conversionvalue
- the value to be converted- Returns:
- the converted value
-
conversionException
Generates a standard conversion exception with a message indicating that the passed in value cannot be converted to the desired target type.- Parameters:
type
- the target typevalue
- the value to be converted- Returns:
- a
ConversionException
with a standard message - Since:
- 1.9
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