ConversionRequest: track Types, not Classes

A converter may need to verify type compatibility not just at the
Class level, but potentially for any generic type. Generic types are
not available at runtime from object instances, but they are
available in other scenarios; e.g., the ImageJ OPS framework uses the
converter framework to decide type compatibility (i.e., assignability
or convertibility) based on generic types. This is possible (rather
than generics being erased at runtime) because OPS parameters are
declared as instance fields, which can be introspected at runtime.

Author: ctrueden

src/main/java/org/scijava/convert/ConversionRequest.java

@@ -33,6 +33,8 @@
 
 import java.lang.reflect.Type;
 
+import org.scijava.util.GenericUtils;
+
 /**
  * Currency for use in {@link Converter} and {@link ConvertService}
  * methods.
@@ -57,45 +59,49 @@
  * </p>
  *
  * @author Mark Hiner
+ * @author Curtis Rueden
  */
 public class ConversionRequest {
 
 	// -- Fields --
 
-	private final Class<?> srcClass;
+	private final Type srcType;
+	private final Type destType;
+
 	private Object src;
-	private Class<?> destClass;
-	private Type destType;
 
 	// -- Constructors --
 
-	public ConversionRequest(final Object s, final Class<?> d) {
-		this(s == null ? null : s.getClass(), d);
-		src = s;
+	public ConversionRequest(final Object src, final Type destType) {
+		this(src, src == null ? null : src.getClass(), destType);
 	}
 
-	public ConversionRequest(final Class<?> s, final Class<?> d) {
-		srcClass = s;
-		destClass = d;
+	public ConversionRequest(final Type srcType, final Type destType) {
+		this(null, srcType, destType);
 	}
 
-	public ConversionRequest(final Object s, final Type d) {
-		this(s == null ? null : s.getClass(), d);
-		src = s;
-	}
-
-	public ConversionRequest(final Class<?> s, final Type d) {
-		srcClass = s;
-		destType = d;
+	public ConversionRequest(final Object src, final Type srcType,
+		final Type destType)
+	{
+		this.src = src;
+		this.srcType = srcType;
+		this.destType = destType;
 	}
 
 	// -- Accessors --
 
+	/**
+	 * @return Source type for conversion or lookup.
+	 */
+	public Type sourceType() {
+		return srcType;
+	}
+
 	/**
 	 * @return Source class for conversion or lookup.
 	 */
 	public Class<?> sourceClass() {
-		return srcClass;
+		return GenericUtils.getClass(srcType);
 	}
 
 	/**
@@ -116,7 +122,7 @@ public Type destType() {
 	 * @return Destination class for conversion.
 	 */
 	public Class<?> destClass() {
-		return destClass;
+		return GenericUtils.getClass(destType);
 	}
 
 	// -- Setters --
@@ -128,11 +134,13 @@ public Class<?> destClass() {
 	 *           not match {@link #sourceClass()}.
 	 */
 	public void setSourceObject(final Object o) {
-		if (!srcClass.isAssignableFrom(o.getClass())) {
+		// TODO: More careful check against srcType itself.
+		if (!sourceClass().isInstance(o)) {
 			throw new IllegalArgumentException("Object of type: " + o.getClass() +
-				" provided. Expected: " + srcClass);
+				" provided. Expected: " + srcType);
 		}
 
 		src = o;
 	}
+
 }