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 java.lang.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: 555824 $ $Date: 2007-07-13 01:27:15 +0100 (Fri, 13 Jul 2007) $

Field Summary
private static java.lang.String DEFAULT_CONFIG_MSG
          Debug logging message to indicate default value configuration
private  java.lang.Class defaultType
          The default type this Converter handles.
private  java.lang.Object defaultValue
          The default value specified to our Constructor, if any.
private  org.apache.commons.logging.Log log
          Logging for this instance.
private static java.lang.String PACKAGE
          Current package name
private  boolean useDefault
          Should we return the default value on conversion errors?
 
Constructor Summary
AbstractConverter(java.lang.Class defaultType)
          Construct a Converter that throws a ConversionException if an error occurs.
AbstractConverter(java.lang.Class defaultType, java.lang.Object defaultValue)
          Construct a Converter that returns a default value if an error occurs.
 
Method Summary
 java.lang.Object convert(java.lang.Class type, java.lang.Object value)
          Convert the input object into an output object of the specified type.
protected  java.lang.Object convertArray(java.lang.Object value)
          Return the first element from an Array (or Collection) or the value unchanged if not an Array (or Collection).
protected  java.lang.String convertToString(java.lang.Object value)
          Convert the input object into a String.
protected abstract  java.lang.Object convertToType(java.lang.Class type, java.lang.Object value)
          Convert the input object into an output object of the specified type.
protected  java.lang.Object getDefault(java.lang.Class type)
          Return the default value for conversions to the specified type.
protected  java.lang.Class getDefaultType()
          Return the default type this Converter handles.
protected  java.lang.Object handleError(java.lang.Class type, java.lang.Object value, java.lang.Throwable cause)
          Handle Conversion Errors.
protected  java.lang.Object handleMissing(java.lang.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.
(package private)  org.apache.commons.logging.Log log()
          Accessor method for Log instance.
(package private)  java.lang.Class primitive(java.lang.Class type)
          Change primitve Class types to the associated wrapper class.
protected  void setDefaultValue(java.lang.Object defaultValue)
          Set the default value, converting as required.
 java.lang.String toString()
          Provide a String representation of this converter.
(package private)  java.lang.String toString(java.lang.Class type)
          Provide a String representation of a java.lang.Class.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

DEFAULT_CONFIG_MSG

private static final java.lang.String DEFAULT_CONFIG_MSG
Debug logging message to indicate default value configuration

See Also:
Constant Field Values

PACKAGE

private static final java.lang.String PACKAGE
Current package name

See Also:
Constant Field Values

log

private transient org.apache.commons.logging.Log log
Logging for this instance.


defaultType

private java.lang.Class defaultType
The default type this Converter handles.


useDefault

private boolean useDefault
Should we return the default value on conversion errors?


defaultValue

private java.lang.Object defaultValue
The default value specified to our Constructor, if any.

Constructor Detail

AbstractConverter

public AbstractConverter(java.lang.Class defaultType)
Construct a Converter that throws a ConversionException if an error occurs.

Parameters:
defaultType - The default type this Converter handles

AbstractConverter

public AbstractConverter(java.lang.Class defaultType,
                         java.lang.Object defaultValue)
Construct a Converter that returns a default value if an error occurs.

Parameters:
defaultType - The default type this Converter handles
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 java.lang.Object convert(java.lang.Class type,
                                java.lang.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 java.lang.String convertToString(java.lang.Object value)
                                    throws java.lang.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:
java.lang.Throwable - if an error occurs converting to a String

convertToType

protected abstract java.lang.Object convertToType(java.lang.Class type,
                                                  java.lang.Object value)
                                           throws java.lang.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:
java.lang.Throwable - if an error occurs converting to the specified type

convertArray

protected java.lang.Object convertArray(java.lang.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 java.lang.Object handleError(java.lang.Class type,
                                       java.lang.Object value,
                                       java.lang.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 java.lang.Object handleMissing(java.lang.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(java.lang.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 java.lang.Class getDefaultType()
Return the default type this Converter handles.

Returns:
The default type this Converter handles.

getDefault

protected java.lang.Object getDefault(java.lang.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 java.lang.String toString()
Provide a String representation of this converter.

Overrides:
toString in class java.lang.Object
Returns:
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.

primitive

java.lang.Class primitive(java.lang.Class type)
Change primitve Class types to the associated wrapper class.

Parameters:
type - The class type to check.
Returns:
The converted type.

toString

java.lang.String toString(java.lang.Class type)
Provide a String representation of a java.lang.Class.

Parameters:
type - The java.lang.Class.
Returns:
The String representation.


Copyright (c) 2001-2007 - Apache Software Foundation