org.apache.commons.beanutils.converters
Class AbstractConverter

java.lang.Object
  org.apache.commons.beanutils.converters.AbstractConverter

All Implemented Interfaces:

Converter

Direct Known Subclasses:

ArrayConverter, BooleanConverter, CharacterConverter, ClassConverter, DateTimeConverter, FileConverter, NumberConverter, StringConverter, URLConverter

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:

• convertToString(value) - convert to a String (default implementation uses the objects toString() method).
• convertToType(Class, value) - convert to the specified type

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

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

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

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

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.

convert

public Object convert(Class type,
                      Object value)

Convert the input object into an output object of the specified type.

Specified by:

convert in interface Converter

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.

convertToString

protected String convertToString(Object value)
                          throws Throwable

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)
                                 throws Throwable

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

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)

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.

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

getDefaultType

protected abstract Class getDefaultType()

Return the default type this Converter handles.

Returns:

The default type this Converter handles.

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.

toString

public String toString()

Provide a String representation of this converter.

Overrides:

toString in class Object

Returns:

A String representation of this converter