org.apache.commons.beanutils.converters
Class AbstractConverter

java.lang.Object
  extended by 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:

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


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