refactor some Mapper code

- removed AbstractSULMapper, since #pre and #post are now default methods in the interface
- added Mappers class for composing arbitrary mappers
- split up SULMapperComposition for re-use

Author: mtf90

drivers/basic/src/main/java/de/learnlib/drivers/reflect/SimplePOJODataMapper.java

@@ -21,16 +21,14 @@
 import java.util.Map;
 
 import de.learnlib.api.exception.SULException;
-import de.learnlib.mapper.AbstractSULMapper;
 import de.learnlib.mapper.api.SULMapper;
 
 /**
  * Basic stateless data mapper for objects.
  *
  * @author falkhowar
  */
-public class SimplePOJODataMapper
-        extends AbstractSULMapper<MethodInput, AbstractMethodOutput, ConcreteMethodInput, Object> {
+public class SimplePOJODataMapper implements SULMapper<MethodInput, AbstractMethodOutput, ConcreteMethodInput, Object> {
 
     private final Constructor<?> initMethod;
     private final Object[] initParams;

drivers/mapper/src/main/java/de/learnlib/mapper/AbstractSULMapper.java

@@ -0,0 +1,82 @@
+/* Copyright (C) 2013-2017 TU Dortmund
+ * This file is part of LearnLib, http://www.learnlib.de/.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package de.learnlib.mapper;
+
+import de.learnlib.api.Mapper;
+import de.learnlib.api.Mapper.AsynchronousMapper;
+import de.learnlib.api.Mapper.SynchronousMapper;
+
+/**
+ * Utility class for the nested the application of two {@link Mapper mappers}.
+ * <p>
+ * This class implements both {@link SynchronousMapper} and {@link AsynchronousMapper} since for the nesting semantics
+ * is the same for both processing contracts.
+ *
+ * @param <AI>
+ *         abstract (outer) input type
+ * @param <AO>
+ *         abstract (outer) output type
+ * @param <ACI>
+ *         intermediate input type
+ * @param <CAO>
+ *         intermediate output type
+ * @param <CI>
+ *         concrete (inner) input type
+ * @param <CO>
+ *         concrete (inner) output output
+ * @param <OUTER>
+ *         type of the outer mapper
+ * @param <INNER>
+ *         type of the inner mapper
+ *
+ * @author frohme
+ */
+class MapperComposition<AI, AO, ACI, CAO, CI, CO, OUTER extends Mapper<? super AI, ? extends AO, ACI, CAO>, INNER extends Mapper<? super ACI, ? extends CAO, ? extends CI, ? super CO>>
+        implements SynchronousMapper<AI, AO, CI, CO>, AsynchronousMapper<AI, AO, CI, CO> {
+
+    protected final OUTER mapper1;
+    protected final INNER mapper2;
+
+    MapperComposition(OUTER outerMapper, INNER innerMapper) {
+        this.mapper1 = outerMapper;
+        this.mapper2 = innerMapper;
+    }
+
+    @Override
+    public void pre() {
+        mapper1.pre();
+        mapper2.pre();
+    }
+
+    @Override
+    public void post() {
+        mapper2.post();
+        mapper1.post();
+    }
+
+    @Override
+    public CI mapInput(AI abstractInput) {
+        ACI aci = mapper1.mapInput(abstractInput);
+        return mapper2.mapInput(aci);
+    }
+
+    @Override
+    public AO mapOutput(CO concreteOutput) {
+        CAO cao = mapper2.mapOutput(concreteOutput);
+        return mapper1.mapOutput(cao);
+    }
+
+}

drivers/mapper/src/main/java/de/learnlib/mapper/MapperComposition.java

@@ -0,0 +1,47 @@
+/* Copyright (C) 2013-2017 TU Dortmund
+ * This file is part of LearnLib, http://www.learnlib.de/.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package de.learnlib.mapper;
+
+import de.learnlib.api.Mapper;
+import de.learnlib.api.Mapper.AsynchronousMapper;
+import de.learnlib.api.Mapper.SynchronousMapper;
+
+/**
+ * Utility methods for manipulating mappers.
+ *
+ * @author frohme
+ */
+public final class Mappers {
+
+    private Mappers() {
+        // prevent instantiation
+    }
+
+    public static <AI, AO, ACI, CAO, CI, CO> Mapper<AI, AO, CI, CO> compose(Mapper<? super AI, ? extends AO, ACI, CAO> outerMapper,
+                                                                            Mapper<? super ACI, ? extends CAO, ? extends CI, ? super CO> innerMapper) {
+        return new MapperComposition<>(outerMapper, innerMapper);
+    }
+
+    public static <AI, AO, ACI, CAO, CI, CO> AsynchronousMapper<AI, AO, CI, CO> compose(AsynchronousMapper<? super AI, ? extends AO, ACI, CAO> outerMapper,
+                                                                                        AsynchronousMapper<? super ACI, ? extends CAO, ? extends CI, ? super CO> innerMapper) {
+        return new MapperComposition<>(outerMapper, innerMapper);
+    }
+
+    public static <AI, AO, ACI, CAO, CI, CO> SynchronousMapper<AI, AO, CI, CO> compose(SynchronousMapper<? super AI, ? extends AO, ACI, CAO> outerMapper,
+                                                                                       SynchronousMapper<? super ACI, ? extends CAO, ? extends CI, ? super CO> innerMapper) {
+        return new MapperComposition<>(outerMapper, innerMapper);
+    }
+}

drivers/mapper/src/main/java/de/learnlib/mapper/Mappers.java

@@ -20,39 +20,13 @@
 import de.learnlib.api.exception.SULException;
 import de.learnlib.mapper.api.SULMapper;
 
-final class SULMapperComposition<AI, AO, ACI, CAO, CI, CO> implements SULMapper<AI, AO, CI, CO> {
-
-    private final SULMapper<? super AI, ? extends AO, ACI, CAO> mapper1;
-    private final SULMapper<? super ACI, ? extends CAO, ? extends CI, ? super CO> mapper2;
+final class SULMapperComposition<AI, AO, ACI, CAO, CI, CO>
+        extends MapperComposition<AI, AO, ACI, CAO, CI, CO, SULMapper<? super AI, ? extends AO, ACI, CAO>, SULMapper<? super ACI, ? extends CAO, ? extends CI, ? super CO>>
+        implements SULMapper<AI, AO, CI, CO> {
 
     SULMapperComposition(SULMapper<? super AI, ? extends AO, ACI, CAO> outerMapper,
                          SULMapper<? super ACI, ? extends CAO, ? extends CI, ? super CO> innerMapper) {
-        this.mapper1 = outerMapper;
-        this.mapper2 = innerMapper;
-    }
-
-    @Override
-    public void pre() {
-        mapper1.pre();
-        mapper2.pre();
-    }
-
-    @Override
-    public void post() {
-        mapper2.post();
-        mapper1.post();
-    }
-
-    @Override
-    public CI mapInput(AI abstractInput) {
-        ACI aci = mapper1.mapInput(abstractInput);
-        return mapper2.mapInput(aci);
-    }
-
-    @Override
-    public AO mapOutput(CO concreteOutput) {
-        CAO cao = mapper2.mapOutput(concreteOutput);
-        return mapper1.mapOutput(cao);
+        super(outerMapper, innerMapper);
     }
 
     @Override

drivers/mapper/src/main/java/de/learnlib/mapper/SULMapperComposition.java

@@ -18,10 +18,11 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import de.learnlib.mapper.api.SULMapper;
 import net.automatalib.words.Alphabet;
 import net.automatalib.words.impl.SimpleAlphabet;
 
-public class StringMapper<CI> extends AbstractSULMapper<String, String, CI, Object> {
+public class StringMapper<CI> implements SULMapper<String, String, CI, Object> {
 
     private final Map<String, CI> inputs = new HashMap<>();
     private final Alphabet<String> mappedInputs = new SimpleAlphabet<>();