Support java.util.Optional as return type of mapper method

src/main/java/org/apache/ibatis/binding/MapperMethod.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2017 the original author or authors.
+ *    Copyright 2009-2018 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -21,7 +21,9 @@
 import org.apache.ibatis.mapping.MappedStatement;
 import org.apache.ibatis.mapping.SqlCommandType;
 import org.apache.ibatis.mapping.StatementType;
+import org.apache.ibatis.reflection.Jdk;
 import org.apache.ibatis.reflection.MetaObject;
+import org.apache.ibatis.reflection.OptionalUtil;
 import org.apache.ibatis.reflection.ParamNameResolver;
 import org.apache.ibatis.reflection.TypeParameterResolver;
 import org.apache.ibatis.session.Configuration;
@@ -39,6 +41,7 @@
  * @author Clinton Begin
  * @author Eduardo Macarron
  * @author Lasse Voss
+ * @author Kazuki Shimizu
  */
 public class MapperMethod {
 
@@ -54,7 +57,7 @@ public Object execute(SqlSession sqlSession, Object[] args) {
     Object result;
     switch (command.getType()) {
       case INSERT: {
-      Object param = method.convertArgsToSqlCommandParam(args);
+    	Object param = method.convertArgsToSqlCommandParam(args);
         result = rowCountResult(sqlSession.insert(command.getName(), param));
         break;
       }
@@ -81,6 +84,10 @@ public Object execute(SqlSession sqlSession, Object[] args) {
         } else {
           Object param = method.convertArgsToSqlCommandParam(args);
           result = sqlSession.selectOne(command.getName(), param);
+          if (method.returnsOptional() &&
+              (result == null || !method.getReturnType().equals(result.getClass()))) {
+            result = OptionalUtil.ofNullable(result);
+          }
         }
         break;
       case FLUSH:
@@ -116,8 +123,8 @@ private void executeWithResultHandler(SqlSession sqlSession, Object[] args) {
     MappedStatement ms = sqlSession.getConfiguration().getMappedStatement(command.getName());
     if (!StatementType.CALLABLE.equals(ms.getStatementType())
         && void.class.equals(ms.getResultMaps().get(0).getType())) {
-      throw new BindingException("method " + command.getName()
-          + " needs either a @ResultMap annotation, a @ResultType annotation,"
+      throw new BindingException("method " + command.getName() 
+          + " needs either a @ResultMap annotation, a @ResultType annotation," 
           + " or a resultType attribute in XML so a ResultHandler can be used as a parameter.");
     }
     Object param = method.convertArgsToSqlCommandParam(args);
@@ -176,7 +183,7 @@ private <E> Object convertToArray(List<E> list) {
       for (int i = 0; i < list.size(); i++) {
         Array.set(array, i, list.get(i));
       }
-      return array;
+    return array;
     } else {
       return list.toArray((E[])array);
     }
@@ -219,7 +226,7 @@ public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method
       MappedStatement ms = resolveMappedStatement(mapperInterface, methodName, declaringClass,
           configuration);
       if (ms == null) {
-        if (method.getAnnotation(Flush.class) != null) {
+        if(method.getAnnotation(Flush.class) != null){
           name = null;
           type = SqlCommandType.FLUSH;
         } else {
@@ -270,6 +277,7 @@ public static class MethodSignature {
     private final boolean returnsMap;
     private final boolean returnsVoid;
     private final boolean returnsCursor;
+    private final boolean returnsOptional;
     private final Class<?> returnType;
     private final String mapKey;
     private final Integer resultHandlerIndex;
@@ -288,6 +296,7 @@ public MethodSignature(Configuration configuration, Class<?> mapperInterface, Me
       this.returnsVoid = void.class.equals(this.returnType);
       this.returnsMany = configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray();
       this.returnsCursor = Cursor.class.equals(this.returnType);
+      this.returnsOptional = Jdk.optionalExists && Optional.class.equals(this.returnType);
       this.mapKey = getMapKey(method);
       this.returnsMap = this.mapKey != null;
       this.rowBoundsIndex = getUniqueParamIndex(method, RowBounds.class);
@@ -339,6 +348,15 @@ public boolean returnsCursor() {
       return returnsCursor;
     }
 
+    /**
+     * return whether return type is {@code java.util.Optional}
+     * @return return {@code true}, if return type is {@code java.util.Optional}
+     * @since 3.4.2
+     */
+    public boolean returnsOptional() {
+      return returnsOptional;
+    }
+
     private Integer getUniqueParamIndex(Method method, Class<?> paramType) {
       Integer index = null;
       final Class<?>[] argTypes = method.getParameterTypes();

src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2017 the original author or authors.
+ *    Copyright 2009-2018 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.Set;
 
@@ -80,6 +81,7 @@
 import org.apache.ibatis.mapping.SqlSource;
 import org.apache.ibatis.mapping.StatementType;
 import org.apache.ibatis.parsing.PropertyParser;
+import org.apache.ibatis.reflection.Jdk;
 import org.apache.ibatis.reflection.TypeParameterResolver;
 import org.apache.ibatis.scripting.LanguageDriver;
 import org.apache.ibatis.session.Configuration;
@@ -91,6 +93,7 @@
 
 /**
  * @author Clinton Begin
+ * @author Kazuki Shimizu
  */
 public class MapperAnnotationBuilder {
 
@@ -446,6 +449,12 @@ private Class<?> getReturnType(Method method) {
               returnType = (Class<?>) ((ParameterizedType) returnTypeParameter).getRawType();
             }
           }
+      } else if (Jdk.optionalExists && Optional.class.equals(rawType)) {
+        Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
+        Type returnTypeParameter = actualTypeArguments[0];
+        if (returnTypeParameter instanceof Class<?>) {
+          returnType = (Class<?>) returnTypeParameter;
+        }
       }
     }
 

src/main/java/org/apache/ibatis/reflection/Jdk.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2017 the original author or authors.
+ *    Copyright 2009-2018 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -13,7 +13,6 @@
  *    See the License for the specific language governing permissions and
  *    limitations under the License.
  */
-
 package org.apache.ibatis.reflection;
 
 import org.apache.ibatis.io.Resources;
@@ -52,6 +51,19 @@ public class Jdk {
     dateAndTimeApiExists = available;
   }
 
+  public static final boolean optionalExists;
+
+  static {
+    boolean available = false;
+    try {
+      Resources.classForName("java.util.Optional");
+      available = true;
+    } catch (ClassNotFoundException e) {
+      // ignore
+    }
+    optionalExists = available;
+  }
+
   private Jdk() {
     super();
   }

src/main/java/org/apache/ibatis/reflection/OptionalUtil.java

@@ -0,0 +1,33 @@
+/**
+ *    Copyright 2009-2018 the original author or authors.
+ *
+ *    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 org.apache.ibatis.reflection;
+
+import java.util.Optional;
+
+import org.apache.ibatis.lang.UsesJava8;
+
+public abstract class OptionalUtil {
+
+  @UsesJava8
+  public static Object ofNullable(Object value) {
+    return Optional.ofNullable(value);
+  }
+
+  private OptionalUtil() {
+    super();
+  }
+}

src/test/java/org/apache/ibatis/submitted/usesjava8/optional_on_mapper_method/CreateDB.sql

@@ -0,0 +1,25 @@
+--
+--    Copyright 2009-2016 the original author or authors.
+--
+--    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.
+--
+
+drop table users if exists;
+
+create table users (
+  id int,
+  name varchar(20)
+);
+
+insert into users (id, name) values
+(1, 'User1'), (2, 'User2');

src/test/java/org/apache/ibatis/submitted/usesjava8/optional_on_mapper_method/Mapper.java

@@ -0,0 +1,30 @@
+/**
+ *    Copyright 2009-2016 the original author or authors.
+ *
+ *    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 org.apache.ibatis.submitted.usesjava8.optional_on_mapper_method;
+
+import org.apache.ibatis.annotations.Select;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface Mapper {
+
+  @Select("select * from users where id = #{id}")
+  Optional<User> getUserUsingAnnotation(Integer id);
+
+  Optional<User> getUserUsingXml(Integer id);
+
+}

src/test/java/org/apache/ibatis/submitted/usesjava8/optional_on_mapper_method/Mapper.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+       Copyright 2009-2016 the original author or authors.
+
+       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.
+
+-->
+<!DOCTYPE mapper
+    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
+    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
+
+<mapper namespace="org.apache.ibatis.submitted.usesjava8.optional_on_mapper_method.Mapper">
+
+  <select id="getUserUsingXml" resultType="org.apache.ibatis.submitted.usesjava8.optional_on_mapper_method.User">
+    select * from users where id = #{id}
+  </select>
+
+</mapper>