Add possibility for Tuples as return types to dbus method calls

In dbus it is possible for a method to have multiple return types. To
map this into the java world, the dbus-java library wraps the return
types into a class, that contains all desired values as fields. This
class extends the Tuple class and is normally generated by the
InterfaceCodeGenerator.
There was a piece missing in the library, that could deal with such
Tuples as a return type to a dbus method call.
This commit adds the missing piece and a little test case.

dbus-java/src/main/java/org/freedesktop/dbus/Marshalling.java

@@ -628,6 +628,21 @@ public static Object[] deSerializeParameters(Object[] _parameters, Type[] _types
             _types = ((ParameterizedType) _types[0]).getActualTypeArguments();
         }
 
+        if (_types.length == 1 && Tuple.class.isAssignableFrom((Class<?>) _types[0])) {
+            String typeName = _types[0].getTypeName();
+            Constructor<?>[] constructors = Class.forName(typeName).getDeclaredConstructors();
+            if (constructors.length != 1) {
+                throw new DBusException("Error deserializing message: We had a Tuple type but wrong number of constructors for this Tuple. There should be exactly one.");
+            }
+
+            if (constructors[0].getParameterCount() != _parameters.length) {
+                throw new DBusException("Error deserializing message: We had a Tuple type but it had wrong number of constructor arguments. The number of constructor arguments should match the number of parameters to deserialize.");
+            }
+
+            Object o = constructors[0].newInstance(_parameters);
+            return new Object[] {o};
+        }
+
         for (int i = 0; i < _parameters.length; i++) {
             // CHECK IF ARRAYS HAVE THE SAME LENGTH <-- has to happen after expanding parameters
             if (i >= _types.length) {

dbus-java/src/test/java/org/freedesktop/dbus/test/MarshallingTest.java

@@ -1,34 +1,30 @@
 package org.freedesktop.dbus.test;
 
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 import java.io.File;
 import java.io.IOException;
-import java.lang.reflect.Constructor;
-import java.lang.reflect.GenericDeclaration;
-import java.lang.reflect.Type;
-import java.lang.reflect.TypeVariable;
+import java.lang.reflect.*;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
-import org.freedesktop.dbus.DBusPath;
-import org.freedesktop.dbus.Marshalling;
-import org.freedesktop.dbus.ObjectPath;
-import org.freedesktop.dbus.Struct;
+import jnr.ffi.annotations.In;
+import org.freedesktop.dbus.*;
 import org.freedesktop.dbus.annotations.DBusInterfaceName;
 import org.freedesktop.dbus.annotations.Position;
 import org.freedesktop.dbus.exceptions.DBusException;
 import org.freedesktop.dbus.interfaces.DBusInterface;
 import org.freedesktop.dbus.messages.DBusSignal;
 import org.freedesktop.dbus.messages.Message;
 import org.freedesktop.dbus.messages.MessageFactory;
+import org.freedesktop.dbus.test.helper.structs.MarkTuple;
 import org.freedesktop.dbus.types.DBusListType;
 import org.freedesktop.dbus.types.Variant;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.*;
+
 public class MarshallingTest {
 
 	@Test
@@ -86,7 +82,20 @@ public void testMarshalling() throws Exception {
         assertTrue(params[1] instanceof List, "Second param is not a List");
 
     }
-
+
+    @Test
+    public void testDeserializeParametersWithTuple() throws Exception {
+        Object[] ob = { new String("rootfs.1"), new String("marked slot rootfs.1 as good")};
+        Method m = Installer.class.getDeclaredMethod("Mark", String.class, String.class);
+        Type[] ts = new Type[] { m.getGenericReturnType() };
+
+        Object[] params = Marshalling.deSerializeParameters(ob, ts, null);
+
+        assertTrue(params[0] instanceof MarkTuple, "First param is not a MarkTuple");
+        MarkTuple mt = (MarkTuple) params[0];
+        assertEquals(mt.getSlotName(), "rootfs.1", "Slot name does not match after deSerialization");
+        assertEquals(mt.getMessage(), "marked slot rootfs.1 as good", "Message does not match after deSerialization");
+    }
 
     /*
      ****************************************** 
@@ -158,4 +167,8 @@ void setProperties(Map<String, Variant<?>> _properties) {
 
 
     }
+
+    public interface Installer extends DBusInterface {
+        public MarkTuple Mark(String state, String slotIdentifier);
+    }
 }

dbus-java/src/test/java/org/freedesktop/dbus/test/helper/structs/MarkTuple.java

@@ -0,0 +1,33 @@
+package org.freedesktop.dbus.test.helper.structs;
+
+import org.freedesktop.dbus.Tuple;
+import org.freedesktop.dbus.annotations.Position;
+
+public class MarkTuple extends Tuple {
+    @Position(0)
+    private String slotName;
+    @Position(1)
+    private String message;
+
+    public MarkTuple(String slotName, String message) {
+        this.slotName = slotName;
+        this.message = message;
+    }
+
+    public void setSlotName(String arg) {
+        slotName = arg;
+    }
+
+    public String getSlotName() {
+        return slotName;
+    }
+    public void setMessage(String arg) {
+        message = arg;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+
+}