Class ArrayConverter

  • All Implemented Interfaces:
    Converter

    public class ArrayConverter
    extends AbstractConverter
    Generic Converter implementation that handles conversion to and from array objects.

    Can be configured to either return a default value or throw a ConversionException if a conversion error occurs.

    The main features of this implementation are:

    • Element Conversion - delegates to a Converter, appropriate for the type, to convert individual elements of the array. This leverages the power of existing converters without having to replicate their functionality for converting to the element type and removes the need to create a specifc array type converters.
    • Arrays or Collections - can convert from either arrays or Collections to an array, limited only by the capability of the delegate Converter.
    • Delimited Lists - can Convert to and from a delimited list in String format.
    • Conversion to String - converts an array to a String in one of two ways: as a delimited list or by converting the first element in the array to a String - this is controlled by the setOnlyFirstToString(boolean) parameter.
    • Multi Dimensional Arrays - it is possible to convert a String to a multi-dimensional arrays, by embedding ArrayConverter within each other - see example below.
    • Default Value
      • No Default - use the ArrayConverter(Class, Converter) constructor to create a converter which throws a ConversionException if the value is missing or invalid.
      • Default values - use the ArrayConverter(Class, Converter, int) constructor to create a converter which returns a default value. The defaultSize parameter controls the default value in the following way:
        • defaultSize < 0 - default is null
        • defaultSize = 0 - default is an array of length zero
        • defaultSize > 0 - default is an array with a length specified by defaultSize (N.B. elements in the array will be null)

    Parsing Delimited Lists

    This implementation can convert a delimited list in String format into an array of the appropriate type. By default, it uses a comma as the delimiter but the following methods can be used to configure parsing:
    • setDelimiter(char) - allows the character used as the delimiter to be configured [default is a comma].
    • setAllowedChars(char[]) - adds additional characters (to the default alphabetic/numeric) to those considered to be valid token characters.

    Multi Dimensional Arrays

    It is possible to convert a String to mulit-dimensional arrays by using ArrayConverter as the element Converter within another ArrayConverter.

    For example, the following code demonstrates how to construct a Converter to convert a delimited String into a two dimensional integer array:

        // Construct an Integer Converter
        IntegerConverter integerConverter = new IntegerConverter();
    
        // Construct an array Converter for an integer array (i.e. int[]) using
        // an IntegerConverter as the element converter.
        // N.B. Uses the default comma (i.e. ",") as the delimiter between individual numbers
        ArrayConverter arrayConverter = new ArrayConverter(int[].class, integerConverter);
    
        // Construct a "Matrix" Converter which converts arrays of integer arrays using
        // the pre-ceeding ArrayConverter as the element Converter.
        // N.B. Uses a semi-colon (i.e. ";") as the delimiter to separate the different sets of numbers.
        //      Also the delimiter used by the first ArrayConverter needs to be added to the
        //      "allowed characters" for this one.
        ArrayConverter matrixConverter = new ArrayConverter(int[][].class, arrayConverter);
        matrixConverter.setDelimiter(';');
        matrixConverter.setAllowedChars(new char[] {','});
    
        // Do the Conversion
        String matrixString = "11,12,13 ; 21,22,23 ; 31,32,33 ; 41,42,43";
        int[][] result = (int[][])matrixConverter.convert(int[][].class, matrixString);
     
    Since:
    1.8.0
    Version:
    $Id: ArrayConverter.java 1746219 2016-05-31 05:05:09Z ggregory $
    • Constructor Summary

      Constructors 
      Constructor Description
      ArrayConverter​(java.lang.Class<?> defaultType, Converter elementConverter)
      Construct an array Converter with the specified component Converter that throws a ConversionException if an error occurs.
      ArrayConverter​(java.lang.Class<?> defaultType, Converter elementConverter, int defaultSize)
      Construct an array Converter with the specified component Converter that returns a default array of the specified size (or null) if an error occurs.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected java.lang.Object convertArray​(java.lang.Object value)
      Returns the value unchanged.
      protected java.util.Collection<?> convertToCollection​(java.lang.Class<?> type, java.lang.Object value)
      Converts non-array values to a Collection prior to being converted either to an array or a String.
      protected java.lang.String convertToString​(java.lang.Object value)
      Handles conversion to a String.
      protected <T> T convertToType​(java.lang.Class<T> type, java.lang.Object value)
      Handles conversion to an array 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.
      void setAllowedChars​(char[] allowedChars)
      Set the allowed characters to be used for parsing a delimited String.
      void setDelimiter​(char delimiter)
      Set the delimiter to be used for parsing a delimited String.
      void setOnlyFirstToString​(boolean onlyFirstToString)
      Indicates whether converting to a String should create a delimited list or just convert the first value.
      java.lang.String toString()
      Provide a String representation of this array converter.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    • Constructor Detail

      • ArrayConverter

        public ArrayConverter​(java.lang.Class<?> defaultType,
                              Converter elementConverter)
        Construct an array Converter with the specified component Converter that throws a ConversionException if an error occurs.
        Parameters:
        defaultType - The default array type this Converter handles
        elementConverter - Converter used to convert individual array elements.
      • ArrayConverter

        public ArrayConverter​(java.lang.Class<?> defaultType,
                              Converter elementConverter,
                              int defaultSize)
        Construct an array Converter with the specified component Converter that returns a default array of the specified size (or null) if an error occurs.
        Parameters:
        defaultType - The default array type this Converter handles
        elementConverter - Converter used to convert individual array elements.
        defaultSize - Specifies the size of the default array value or if less than zero indicates that a null default value should be used.
    • Method Detail

      • setDelimiter

        public void setDelimiter​(char delimiter)
        Set the delimiter to be used for parsing a delimited String.
        Parameters:
        delimiter - The delimiter [default ',']
      • setAllowedChars

        public void setAllowedChars​(char[] allowedChars)
        Set the allowed characters to be used for parsing a delimited String.
        Parameters:
        allowedChars - Characters which are to be considered as part of the tokens when parsing a delimited String [default is '.' and '-']
      • setOnlyFirstToString

        public void setOnlyFirstToString​(boolean onlyFirstToString)
        Indicates whether converting to a String should create a delimited list or just convert the first value.
        Parameters:
        onlyFirstToString - true converts only the first value in the array to a String, false converts all values in the array into a delimited list (default is true
      • getDefaultType

        protected java.lang.Class<?> getDefaultType()
        Return the default type this Converter handles.
        Specified by:
        getDefaultType in class AbstractConverter
        Returns:
        The default type this Converter handles.
      • convertToString

        protected java.lang.String convertToString​(java.lang.Object value)
                                            throws java.lang.Throwable
        Handles conversion to a String.
        Overrides:
        convertToString in class AbstractConverter
        Parameters:
        value - The value to be converted.
        Returns:
        the converted String value.
        Throws:
        java.lang.Throwable - if an error occurs converting to a String
      • convertToType

        protected <T> T convertToType​(java.lang.Class<T> type,
                                      java.lang.Object value)
                               throws java.lang.Throwable
        Handles conversion to an array of the specified type.
        Specified by:
        convertToType in class AbstractConverter
        Type Parameters:
        T - Target type of the conversion.
        Parameters:
        type - The 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)
        Returns the value unchanged.
        Overrides:
        convertArray in class AbstractConverter
        Parameters:
        value - The value to convert
        Returns:
        The value unchanged
      • convertToCollection

        protected java.util.Collection<?> convertToCollection​(java.lang.Class<?> type,
                                                              java.lang.Object value)
        Converts non-array values to a Collection prior to being converted either to an array or a String.

        • Collection values are returned unchanged
        • Number, Boolean and Date values returned as a the only element in a List.
        • All other types are converted to a String and parsed as a delimited list.
        N.B. The method is called by both the convertToType(Class, Object) and convertToString(Object) methods for non-array types.
        Parameters:
        type - The type to convert the value to
        value - value to be converted
        Returns:
        Collection elements.
      • getDefault

        protected java.lang.Object getDefault​(java.lang.Class<?> type)
        Return the default value for conversions to the specified type.
        Overrides:
        getDefault in class AbstractConverter
        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 array converter.
        Overrides:
        toString in class AbstractConverter
        Returns:
        A String representation of this array converter