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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.
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package org.scijava.util;
import java.lang.reflect.Type;
import org.scijava.convert.ConversionRequest;
import org.scijava.convert.ConvertService;
import org.scijava.convert.Converter;
import org.scijava.convert.DefaultConverter;
/**
* Useful methods for converting and casting between classes and types.
*
* For extensible type conversion, use {@link ConvertService}.
*
*
* @author Curtis Rueden
* @author Mark Hiner
*/
public class ConversionUtils {
private static ConvertService convertService;
private static Converter converterNoContext;
private static double servicePriority = 0.0;
private ConversionUtils() {
// prevent instantiation of utility class
}
// -- Type casting --
/**
* Converts the given string value to an enumeration constant of the specified
* type.
*
* @param src The value to convert.
* @param dest The type of the enumeration constant.
* @return The converted enumeration constant, or null if the type is not an
* enumeration type or has no such constant.
*/
public static T convertToEnum(final String src, final Class dest) {
if (src == null || !dest.isEnum()) return null;
try {
@SuppressWarnings({ "rawtypes", "unchecked" })
final Enum result = Enum.valueOf((Class) dest, src);
@SuppressWarnings("unchecked")
final T typedResult = (T) result;
return typedResult;
}
catch (final IllegalArgumentException exc) {
// no such enum constant
return null;
}
}
/**
* Casts the given object to the specified type, or null if the types are
* incompatible.
*/
public static T cast(final Object src, final Class dest) {
if (!canCast(src, dest)) return null;
@SuppressWarnings("unchecked")
final T result = (T) src;
return result;
}
/**
* Checks whether objects of the given class can be assigned to the specified
* type. Unlike {@link Class#isAssignableFrom(Class)}, this method considers
* auto-unboxing.
*
* @return true If the destination class is assignable from the source one, or
* if the source class is null and destination class is non-null.
*/
public static boolean canAssign(final Class src, final Class dest) {
return canCast(src, dest);
}
/**
* Checks whether the given object can be assigned to the specified type.
* Unlike {@link Class#isAssignableFrom(Class)}, this method considers
* auto-unboxing.
*
* @return true If the destination class is assignable from the source
* object's class, or if the source object is null and destionation
* class is non-null.
*/
public static boolean canAssign(final Object src, final Class dest) {
return canCast(src, dest);
}
/**
* @deprecated use {@link #canAssign(Class, Class)} instead
*/
@Deprecated
public static boolean canCast(final Class src, final Class dest) {
if (dest == null) return false;
if (src == null) return true;
final Class saneSrc = getNonprimitiveType(src);
final Class saneDest = getNonprimitiveType(dest);
return saneDest.isAssignableFrom(saneSrc);
}
/**
* @deprecated use {@link #canAssign(Object, Class)} instead
*/
@Deprecated
public static boolean canCast(final Object src, final Class dest) {
if (dest == null) return false;
return src == null || canCast(src.getClass(), dest);
}
/**
* Returns the primitive {@link Class} closest to the given type.
*
* Specifically, the following type conversions are done:
*
*
* - Boolean.class becomes boolean.class
* - Byte.class becomes byte.class
* - Character.class becomes char.class
* - Double.class becomes double.class
* - Float.class becomes float.class
* - Integer.class becomes int.class
* - Long.class becomes long.class
* - Short.class becomes short.class
* - Void.class becomes void.class
*
*
* All other types are unchanged.
*
*/
public static Class getPrimitiveType(final Class type) {
final Class destType;
if (type == Boolean.class) destType = boolean.class;
else if (type == Byte.class) destType = byte.class;
else if (type == Character.class) destType = char.class;
else if (type == Double.class) destType = double.class;
else if (type == Float.class) destType = float.class;
else if (type == Integer.class) destType = int.class;
else if (type == Long.class) destType = long.class;
else if (type == Short.class) destType = short.class;
else if (type == Void.class) destType = void.class;
else destType = type;
@SuppressWarnings("unchecked")
final Class result = (Class) destType;
return result;
}
/**
* Returns the non-primitive {@link Class} closest to the given type.
*
* Specifically, the following type conversions are done:
*
*
* - boolean.class becomes Boolean.class
* - byte.class becomes Byte.class
* - char.class becomes Character.class
* - double.class becomes Double.class
* - float.class becomes Float.class
* - int.class becomes Integer.class
* - long.class becomes Long.class
* - short.class becomes Short.class
* - void.class becomes Void.class
*
*
* All other types are unchanged.
*
*/
public static Class getNonprimitiveType(final Class type) {
final Class destType;
if (type == boolean.class) destType = Boolean.class;
else if (type == byte.class) destType = Byte.class;
else if (type == char.class) destType = Character.class;
else if (type == double.class) destType = Double.class;
else if (type == float.class) destType = Float.class;
else if (type == int.class) destType = Integer.class;
else if (type == long.class) destType = Long.class;
else if (type == short.class) destType = Short.class;
else if (type == void.class) destType = Void.class;
else destType = type;
@SuppressWarnings("unchecked")
final Class result = (Class) destType;
return result;
}
/**
* Gets the "null" value for the given type. For non-primitives, this will
* actually be null. For primitives, it will be zero for numeric types, false
* for boolean, and the null character for char.
*/
public static T getNullValue(final Class type) {
final Object defaultValue;
if (type == boolean.class) defaultValue = false;
else if (type == byte.class) defaultValue = (byte) 0;
else if (type == char.class) defaultValue = '\0';
else if (type == double.class) defaultValue = 0d;
else if (type == float.class) defaultValue = 0f;
else if (type == int.class) defaultValue = 0;
else if (type == long.class) defaultValue = 0L;
else if (type == short.class) defaultValue = (short) 0;
else defaultValue = null;
@SuppressWarnings("unchecked")
final T result = (T) defaultValue;
return result;
}
// -- ConvertService setter --
/**
* Sets the {@link ConvertService} to use for handling conversion requests.
*/
public static void setDelegateService(final ConvertService convertService,
final double priority)
{
if (ConversionUtils.convertService == null ||
Double.compare(priority, servicePriority) > 0)
{
ConversionUtils.convertService = convertService;
servicePriority = priority;
}
}
// -- Deprecated methods --
/**
* @deprecated
* @see Converter#convert(Object, Type)
*/
@Deprecated
public static Object convert(final Object src, final Type dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? null : handler.convert(src, dest));
}
/**
* @deprecated
* @see Converter#convert(Object, Class)
*/
@Deprecated
public static T convert(final Object src, final Class dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? null : handler.convert(src, dest));
}
/**
* @deprecated
* @see Converter#canConvert(Class, Type)
*/
@Deprecated
public static boolean canConvert(final Class src, final Type dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? false : handler.canConvert(src, dest));
}
/**
* @deprecated
* @see Converter#canConvert(Class, Class)
*/
@Deprecated
public static boolean canConvert(final Class src, final Class dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? false : handler.canConvert(src, dest));
}
/**
* @deprecated
* @see Converter#canConvert(Object, Type)
*/
@Deprecated
public static boolean canConvert(final Object src, final Type dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? false : handler.canConvert(src, dest));
}
/**
* @deprecated
* @see Converter#canConvert(Object, Class)
*/
@Deprecated
public static boolean canConvert(final Object src, final Class dest) {
final Converter handler = handler(new ConversionRequest(src, dest));
return (handler == null ? false : handler.canConvert(src, dest));
}
/** @deprecated use {@link GenericUtils#getClass(Type)} */
@Deprecated
public static Class getClass(final Type type) {
return GenericUtils.getClass(type);
}
/** @deprecated use {@link GenericUtils#getComponentClass(Type)} */
@Deprecated
public static Class getComponentClass(final Type type) {
return GenericUtils.getComponentClass(type);
}
//-- Helper methods --
/**
* Gets the {@link Converter} to use for the given conversion request. If the
* delegate {@link ConvertService} has not been explicitly set, then a
* {@link DefaultConverter} will be used.
*
* @return The {@link Converter} to use for handling the given request.
*/
private static Converter handler(final ConversionRequest data) {
if (convertService != null) return convertService.getHandler(data);
if (converterNoContext == null) converterNoContext = new DefaultConverter();
return converterNoContext;
}
}