Package org.apache.commons.beanutils2.converters

Class AbstractConverter<D>

java.lang.Object
org.apache.commons.beanutils2.converters.AbstractConverter<D>
Type Parameters:
D - The default value type.
All Implemented Interfaces:
Converter<D>
Direct Known Subclasses:
ArrayConverter, BooleanConverter, CharacterConverter, ClassConverter, ColorConverter, DateTimeConverter, DimensionConverter, DurationConverter, EnumConverter, FileConverter, InetAddressConverter, LocaleConverter, LocalTimeConverter, MonthDayConverter, NumberConverter, OffsetTimeConverter, PathConverter, PatternConverter, PeriodConverter, PointConverter, StringConverter, URIConverter, URLConverter, UUIDConverter, YearConverter, YearMonthConverter, ZoneIdConverter, ZoneOffsetConverter
public abstract class AbstractConverter<D> extends Object implements Converter<D>
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

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.

Since:
1.8.0

  • Constructor Details

    • AbstractConverter

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

    • AbstractConverter

      public AbstractConverter(D defaultValue)
      Constructs 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 Details

    • toLowerCase

      protected static String toLowerCase(Object value)
      Converts the given object to a lower-case string.
      Parameters:
      value - the input string.
      Returns:
      the given string trimmed and converter to lower-case.

    • toString

      protected static String toString(Object value)
      Converts the given object to a lower-case string.
      Parameters:
      value - the input string.
      Returns:
      the given string trimmed and converter to lower-case.

    • toTrim

      protected static String toTrim(Object value)
      Converts the given object to a lower-case string.
      Parameters:
      value - the input string.
      Returns:
      the given string trimmed and converter to lower-case.

    • conversionException

      protected ConversionException conversionException(Class<?> type, Object value)
      Creates a standard conversion exception with a message indicating that the passed in value cannot be converted to the desired target type.
      Parameters:
      type - the target type
      value - the value to be converted
      Returns:
      a ConversionException with a standard message
      Since:
      1.9

    • convert

      public <R> R convert(Class<R> type, Object value)
      Converts the input object into an output object of the specified type.
      Specified by:
      convert in interface Converter<D>
      Type Parameters:
      R - the result 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)
      Returns the first element from an Array (or Collection) or the value unchanged if not an Array (or Collection). N.B. This needs to be overridden 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)
      Converts the input object into a String.

      N.B.This implementation simply uses the value's toString() method and should be overridden 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:
      IllegalArgumentException - if an error occurs converting to a String

    • convertToType

      protected abstract <R> R convertToType(Class<R> type, Object value) throws Throwable
      Converts the input object into an output object of the specified type.

      Typical implementations will provide a minimum of String --&gt; type conversion.

      Type Parameters:
      R - Target type of the 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)
      Gets 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<D> getDefaultType()
      Gets the default type this Converter handles.
      Returns:
      The default type this Converter handles.

    • handleError

      protected <T> T handleError(Class<T> type, Object value, Throwable cause)
      Handles Conversion Errors.

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

      Type Parameters:
      T - Target type of the conversion.
      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 <T> T handleMissing(Class<T> type)
      Handles missing values.

      If a default value has been specified, then it is returned (after a cast to the desired target class); otherwise a ConversionException is thrown.

      Type Parameters:
      T - the desired target type
      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()
      Tests 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(D defaultValue)
      Sets 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()
      Converts this instance to a String.
      Overrides:
      toString in class Object
      Returns:
      A String representation of this converter