org.bbottema.javareflection

Class ValueConverter

java.lang.Object

org.bbottema.javareflection.ValueConverter

public final class ValueConverter
extends Object

This reflection utility class predicts (and converts) which types a specified value can be converted into. It can only do conversions of known 'common' types, which include:

• Any Number type (Integer, Character, Double, byte, etc.)
• String
• Boolean
• Character

In addition enums can be converted as well.

Author:

Benny Bottema

See Also:

ValueConverter.IncompatibleTypeException

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ValueConverter.IncompatibleTypeException This exception can be thrown in any of the conversion methods of ValueConverter, to indicate a value could not be converted into the target datatype.

Method Summary

Modifier and Type	Method and Description
static List<Class<?>>	collectCompatibleTypes(Class<?> c) Determines to which types the specified value (its type) can be converted to.
static Object	convert(Boolean value, Class<?> targetType) Attempts to convert a Boolean to the target datatype.
static Object	convert(Character value, Class<?> targetType) Attempts to convert a Character to the target datatype.
static Object	convert(Number value, Class<?> targetType) Attempts to convert a Number to the target datatype.
static Object[]	convert(Object[] args, Class<?>[] targetTypes, boolean useOriginalValueWhenIncompatible) Converts a list of values to their converted form, as indicated by the specified targetTypes.
static Object	convert(Object value, Class<?> targetType) Converts a single value into a target output datatype.
static Object	convert(String value, Class<?> targetType) Attempts to convert a String to the target datatype.
static Object	convertEnum(String value, Class<? extends Enum<?>> targetType) Attempts to convert a String to an Enum instance, by mapping to the enum's name using Enum.valueOf(Class, String).
static Object	convertNumber(String value, Class<? extends Number> numberType) Attempts to convert a String to the specified Number type.
static boolean	isCommonType(Class<?> c)
static boolean	isPrimitiveNumber(Class<?> targetType) Returns whether a Class is a primitive number.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

isCommonType

public static boolean isCommonType(Class<?> c)

Parameters:

c - The class to inspect.

Returns:

whether given type is a known common type.

collectCompatibleTypes

@Nonnull
public static List<Class<?>> collectCompatibleTypes(Class<?> c)

Determines to which types the specified value (its type) can be converted to. Most common types can be converted to most other common types and all types can be converted into a String using Object.toString().

Parameters:

c - The input type to find compatible conversion output types for

Returns:

The list with compatible conversion output types.

convert

@Nonnull
public static Object[] convert(Object[] args,
                                         Class<?>[] targetTypes,
                                         boolean useOriginalValueWhenIncompatible)
                                  throws ValueConverter.IncompatibleTypeException

Converts a list of values to their converted form, as indicated by the specified targetTypes.

Parameters:

args - The list with value to convert.

targetTypes - The output types the specified values should be converted into.

useOriginalValueWhenIncompatible - Indicates whether an exception should be thrown for inconvertible values or that the original value should be used instead.

Returns:

Array containing converted values where convertible or the original value otherwise.

Throws:

ValueConverter.IncompatibleTypeException - Thrown when unable to convert and not use the original value.

convert

@Nullable
public static Object convert(@Nullable
                                        Object value,
                                        Class<?> targetType)
                                 throws ValueConverter.IncompatibleTypeException

Converts a single value into a target output datatype. Only input/output pairs should be passed in here according to the possible conversions as determined by collectCompatibleTypes(Class).

First checks if the input and output types aren't the same. Then the conversions are checked for and done in the following order:

1. conversion to String (value.toString())
2. conversion from String (convert(String, Class))
3. conversion to any Number (convert(Number, Class))
4. conversion to Boolean (convert(Boolean, Class))
5. conversion to Character (convert(Character, Class))

Parameters:

value - The value to convert.

targetType - The target data type the value should be converted into.

Returns:

The converted value according the specified target data type.

Throws:

ValueConverter.IncompatibleTypeException - Thrown by the various convert() methods used.

convert

@Nullable
public static Object convert(@Nullable
                                        Number value,
                                        Class<?> targetType)
                                 throws ValueConverter.IncompatibleTypeException

Attempts to convert a Number to the target datatype.

NOTE: precision may be lost when converting from a wide number to a narrower number (say float to integer). These conversions are done by simply calling Number.intValue() and Number.floatValue() etc.

Conversions are as follows:

1. String: value.toString()
2. Integer: value.intValue()
3. Boolean: value.intValue() > 0
4. Float: value.floatValue()
5. Double: value.doubleValue()
6. Long: value.longValue()
7. Byte: value.byteValue()
8. Short: value.shortValue()
9. Character: Character.forDigit(value, 10) (Character.forDigit(int, int))

Parameters:

value - The number to convert.

targetType - The target datatype the number should be converted into.

Returns:

The converted number.

Throws:

ValueConverter.IncompatibleTypeException - Thrown when unable to find a compatible conversion.

convert

@Nullable
public static Object convert(@Nullable
                                        Boolean value,
                                        Class<?> targetType)
                                 throws ValueConverter.IncompatibleTypeException

Attempts to convert a Boolean to the target datatype.

Conversions are as follows:

1. Boolean (or boolean): value
2. String: value.toString()
3. Number (or primitive number): convertNumber(value ? "1" : "0") (convertNumber(String, Class))
4. Character (or character): value ? '1' : '0'

Parameters:

value - The boolean to convert.

targetType - The target datatype the boolean should be converted into.

Returns:

The converted boolean.

Throws:

ValueConverter.IncompatibleTypeException - Thrown when unable to find a compatible conversion.

convert

@Nullable
public static Object convert(@Nullable
                                        Character value,
                                        Class<?> targetType)
                                 throws ValueConverter.IncompatibleTypeException

Attempts to convert a Character to the target datatype.

Conversions are as follows:

1. String: value.toString()
2. Character (or primitive character): value
3. Number (or primitive number): convertNumber(String.valueOf(value)) (convertNumber(String, Class))
4. Boolean (or boolean): !value.equals('0')

Parameters:

value - The character to convert.

targetType - The target datatype the character should be converted into.

Returns:

The converted character.

Throws:

ValueConverter.IncompatibleTypeException - Thrown when unable to find a compatible conversion.

convert

@Nullable
public static Object convert(@Nullable
                                        String value,
                                        Class<?> targetType)
                                 throws ValueConverter.IncompatibleTypeException

Attempts to convert a String to the target datatype.

Conversions are as follows:

1. String: value
2. Enum type: convertEnum(value) (convertEnum(String, Class))
3. with source string length == 1
   1. Character: value.charAt(0)
   2. Otherwise: convert(value.charAt(0)) (convert(Character, Class))
4. with source string length > 1
   1. Number (or primitive number): convertNumber(value) (convertNumber(String, Class))
   2. Boolean (or primitive boolean): value.equalsIgnoreCase("true") ? true : value.equalsIgnoreCase("false") ? false : nothing (IncompatibleTypeException)

Parameters:

value - The string to convert.

targetType - The target datatype the string should be converted into.

Returns:

The converted string.

Throws:

ValueConverter.IncompatibleTypeException - Thrown when unable to find a compatible conversion.

convertEnum

@Nullable
public static Object convertEnum(@Nullable
                                            String value,
                                            Class<? extends Enum<?>> targetType)

Attempts to convert a String to an Enum instance, by mapping to the enum's name using Enum.valueOf(Class, String).

Parameters:

value - The value, which should be the name of one instance of the given enum.

targetType - The enum type to which which we'll try to convert.

Returns:

An enum of the given type, or null otherwise.

convertNumber

@Nullable
public static Object convertNumber(@Nullable
                                              String value,
                                              Class<? extends Number> numberType)

Attempts to convert a String to the specified Number type.

Conversions are as follows:

1. Integer (or primitive int): Integer.parseInt(value)
2. Byte (or primitive byte): Byte.parseByte(value)
3. Short (or primitive short): Short.parseShort(value)
4. Long (or primitive long): Long.parseLong(value)
5. Float (or primitive float): Float.parseFloat(value)
6. Double (or primitive double): Double.parseDouble(value)
7. BigInteger: BigInteger.valueOf(Long.parseLong(value))
8. BigDecimal: BigDecimal.valueOf(Long.parseLong(value))

Parameters:

value - The string value which should be a number.

numberType - The Class type that should be one of Number.

Returns:

A Number subtype value converted from value (or null if value is null).

isPrimitiveNumber

public static boolean isPrimitiveNumber(Class<?> targetType)

Returns whether a Class is a primitive number.

Parameters:

targetType - The class to check whether it's a number.

Returns:

Whether specified class is a primitive number.