juneau-core/juneau-marshall/src/main/java/org/apache/juneau/transform/SurrogateSwap.java

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package org.apache.juneau.transform;

import java.lang.reflect.*;
import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.annotation.*;
import org.apache.juneau.parser.*;
import org.apache.juneau.reflect.*;
import org.apache.juneau.serializer.*;

/**
 * Specialized {@link PojoSwap} for {@link Surrogate} classes.
 *
 * @param <T> The class type that this transform applies to.
 * @param <F> The transformed class type.
 */
public class SurrogateSwap<T,F> extends PojoSwap<T,F> {

	private Constructor<F> constructor;   // public F(T t);
	private Method unswapMethod;        // public T build();

	/**
	 * Constructor.
	 *
	 * @param forClass The normal class.
	 * @param constructor The constructor on the surrogate class that takes the normal class as a parameter.
	 * @param unswapMethod The static method that converts surrogate objects into normal objects.
	 */
	protected SurrogateSwap(Class<T> forClass, Constructor<F> constructor, Method unswapMethod) {
		super(forClass, constructor.getDeclaringClass());
		this.constructor = constructor;
		this.unswapMethod = unswapMethod;
	}

	/**
	 * Given the specified surrogate class, return the list of POJO swaps.
	 *
	 * <p>
	 * A transform is returned for each public 1-arg constructor found.
	 * Returns an empty list if no public 1-arg constructors are found.
	 *
	 * @param c The surrogate class.
	 * @param bc The bean context to use for looking up annotations.
	 * @return The list of POJO swaps that apply to this class.
	 */
	@SuppressWarnings({"unchecked", "rawtypes"})
	public static List<SurrogateSwap<?,?>> findPojoSwaps(Class<?> c, BeanContext bc) {
		List<SurrogateSwap<?,?>> l = new LinkedList<>();
		ClassInfo ci = ClassInfo.of(c);
		for (ConstructorInfo cc : ci.getPublicConstructors()) {
			if (! bc.hasAnnotation(BeanIgnore.class, cc) && cc.hasNumParams(1) && cc.isPublic()) {
				Class<?> pt = cc.getRawParamType(0);
				if (! pt.equals(c.getDeclaringClass())) {
					// Find the unswap method if there is one.
					Method unswapMethod = null;
					for (MethodInfo m : ci.getPublicMethods()) {
						if (m.getReturnType().is(pt) && m.isPublic())
						unswapMethod = m.inner();
					}

					l.add(new SurrogateSwap(pt, cc.inner(), unswapMethod));
				}
			}
		}
		return l;
	}

	@Override /* PojoSwap */
	public F swap(BeanSession session, T o) throws SerializeException {
		try {
			return constructor.newInstance(o);
		} catch (Exception e) {
			throw new SerializeException(e);
		}
	}

	@Override /* PojoSwap */
	@SuppressWarnings("unchecked")
	public T unswap(BeanSession session, F f, ClassMeta<?> hint) throws ParseException {
		if (unswapMethod == null)
			throw new ParseException("unswap() method not implement on surrogate class ''{1}''",
				f.getClass().getName(), getNormalClass().getFullName());
		try {
			return (T)unswapMethod.invoke(f);
		} catch (Exception e) {
			throw new ParseException(e);
		}
	}
}