org.apache.commons.beanutils.converters

Class AbstractConverter

public abstract class AbstractConverter extends Object implements Converter

Base 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:

Since: 1.8.0

Version: $Revision: 640131 $ $Date: 2008-03-23 02:10:31 +0000 (Sun, 23 Mar 2008) $

Constructor Summary
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.
Method Summary
Objectconvert(Class type, Object value)
Convert the input object into an output object of the specified type.
protected ObjectconvertArray(Object value)
Return the first element from an Array (or Collection) or the value unchanged if not an Array (or Collection).
protected StringconvertToString(Object value)
Convert the input object into a String.
protected abstract ObjectconvertToType(Class type, Object value)
Convert the input object into an output object of the specified type.
protected ObjectgetDefault(Class type)
Return the default value for conversions to the specified type.
protected abstract ClassgetDefaultType()
Return the default type this Converter handles.
protected ObjecthandleError(Class type, Object value, Throwable cause)
Handle Conversion Errors.
protected ObjecthandleMissing(Class type)
Handle missing values.
booleanisUseDefault()
Indicates whether a default value will be returned or exception thrown in the event of a conversion error.
protected voidsetDefaultValue(Object defaultValue)
Set the default value, converting as required.
StringtoString()
Provide a String representation of this converter.

Constructor Detail

AbstractConverter

public AbstractConverter()
Construct a Converter that throws a ConversionException if an error occurs.

AbstractConverter

public AbstractConverter(Object defaultValue)
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.

Method Detail

convert

public Object convert(Class type, Object value)
Convert the input object into an output object of the specified type.

Parameters: type Data type to which this value should be converted value The input value to be converted

Returns: The converted value.

Throws: ConversionException if conversion cannot be performed successfully and no default is specified.

convertArray

protected Object convertArray(Object value)
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)

convertToString

protected String convertToString(Object value)
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

protected abstract Object convertToType(Class type, Object value)
Convert the input object into an output object of the specified type.

Typical implementations will provide a minimum of String --> type 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

getDefault

protected Object getDefault(Class type)
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.

getDefaultType

protected abstract Class getDefaultType()
Return the default type this Converter handles.

Returns: The default type this Converter handles.

handleError

protected Object handleError(Class type, Object value, Throwable cause)
Handle Conversion Errors.

If a default value has been specified then it is returned otherwise a ConversionException is thrown.

Parameters: type Data type to which this value should be converted. value The input value to be converted cause The exception thrown by the convert method

Returns: The default value.

Throws: ConversionException if no default value has been specified for this Converter.

handleMissing

protected Object handleMissing(Class type)
Handle missing values.

If a default value has been specified then it is returned otherwise a ConversionException is thrown.

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 this Converter.

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 or false if a ConversionException will be thrown.

setDefaultValue

protected void setDefaultValue(Object defaultValue)
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

toString

public String toString()
Provide a String representation of this converter.

Returns: A String representation of this converter

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