public abstract class AbstractConverter extends Object implements Converter
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 objects toString()
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.
| Constructor and Description |
|---|
AbstractConverter()
Construct a Converter that throws a
ConversionException if an error occurs. |
AbstractConverter(Object defaultValue)
Construct a Converter that returns a default
value if an error occurs.
|
| Modifier and Type | Method and Description |
|---|---|
protected 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(Class<T> type,
Object value)
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).
|
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<?> |
getDefaultType()
Return the default type this
Converter 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 |
isUseDefault()
Indicates whether a default value will be returned or exception
thrown in the event of a conversion error.
|
protected void |
setDefaultValue(Object defaultValue)
Set the default value, converting as required.
|
String |
toString()
Provide a String representation of this converter.
|
public AbstractConverter()
ConversionException if an error occurs.public AbstractConverter(Object defaultValue)
defaultValue - The default value to be returned
if the value to be converted is missing or an error
occurs converting the value.public boolean isUseDefault()
true if a default value will be returned for
conversion errors or false if a ConversionException
will be thrown.public <T> T convert(Class<T> type, Object value)
convert in interface ConverterT - the target type of the conversiontype - Data type to which this value should be convertedvalue - The input value to be convertedConversionException - if conversion cannot be performed
successfully and no default is specified.protected String convertToString(Object value) throws Throwable
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.
value - The input value to be converted.Throwable - if an error occurs converting to a Stringprotected abstract <T> T convertToType(Class<T> type, Object value) throws Throwable
Typical implementations will provide a minimum of
String --> type conversion.
T - Target type of the conversion.type - Data type to which this value should be converted.value - The input value to be converted.Throwable - if an error occurs converting to the specified typeprotected Object convertArray(Object value)
value - The value to convertprotected <T> T handleError(Class<T> type, Object value, Throwable cause)
If a default value has been specified then it is returned otherwise a ConversionException is thrown.
T - Target type of the conversion.type - Data type to which this value should be converted.value - The input value to be convertedcause - The exception thrown by the convert methodConversionException - if no default value has been
specified for this Converter.protected <T> T handleMissing(Class<T> type)
If a default value has been specified, then it is returned (after a cast to the desired target class); otherwise a ConversionException is thrown.
T - the desired target typetype - Data type to which this value should be converted.ConversionException - if no default value has been
specified for this Converter.protected void setDefaultValue(Object defaultValue)
If the default value is different from the type the
Converter handles, it will be converted
to the handled type.
defaultValue - The default value to be returned
if the value to be converted is missing or an error
occurs converting the value.ConversionException - if an error occurs converting
the default valueprotected abstract Class<?> getDefaultType()
Converter handles.Converter handles.protected Object getDefault(Class<?> type)
type - Data type to which this value should be converted.protected ConversionException conversionException(Class<?> type, Object value)
type - the target typevalue - the value to be convertedConversionException with a standard messageCopyright © 2000–2019 The Apache Software Foundation. All rights reserved.