Add abstract delegate converter class

Author: imagejan

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

@@ -0,0 +1,29 @@
+
+package org.scijava.convert;
+
+import org.scijava.plugin.Parameter;
+
+/**
+ * Abstract superclass for {@link Converter} plugins that delegate to other
+ * converters to chain two conversion steps together.
+ * 
+ * @author Jan Eglinger
+ * @param <I> the input type
+ * @param <D> the delegate type
+ * @param <O> the output type
+ */
+public abstract class AbstractDelegateConverter<I, D, O> extends
+	AbstractConverter<I, O>
+{
+
+	@Parameter
+	private ConvertService convertService;
+
+	@Override
+	public <T> T convert(Object src, Class<T> dest) {
+		D delegate = convertService.convert(src, getDelegateType());
+		return convertService.convert(delegate, dest);
+	}
+
+	protected abstract Class<D> getDelegateType();
+}