Support Stream as mapper method return type

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

@@ -1,5 +1,5 @@
 /*
- *    Copyright 2009-2024 the original author or authors.
+ *    Copyright 2009-2025 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.
@@ -23,6 +23,10 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 import org.apache.ibatis.annotations.Flush;
 import org.apache.ibatis.annotations.MapKey;
@@ -43,6 +47,7 @@
  * @author Eduardo Macarron
  * @author Lasse Voss
  * @author Kazuki Shimizu
+ * @author Yanming Zhou
  */
 public class MapperMethod {
 
@@ -82,6 +87,11 @@ public Object execute(SqlSession sqlSession, Object[] args) {
           result = executeForMap(sqlSession, args);
         } else if (method.returnsCursor()) {
           result = executeForCursor(sqlSession, args);
+        } else if (method.returnsStream()) {
+          Cursor<?> cursor = executeForCursor(sqlSession, args);
+          result = StreamSupport
+              .stream(Spliterators.spliteratorUnknownSize(cursor.iterator(), Spliterator.ORDERED), false)
+              .onClose(cursor::close);
         } else {
           Object param = method.convertArgsToSqlCommandParam(args);
           result = sqlSession.selectOne(command.getName(), param);
@@ -274,6 +284,7 @@ public static class MethodSignature {
     private final boolean returnsMap;
     private final boolean returnsVoid;
     private final boolean returnsCursor;
+    private final boolean returnsStream;
     private final boolean returnsOptional;
     private final Class<?> returnType;
     private final String mapKey;
@@ -293,6 +304,7 @@ 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.returnsStream = Stream.class.equals(this.returnType);
       this.returnsOptional = Optional.class.equals(this.returnType);
       this.mapKey = getMapKey(method);
       this.returnsMap = this.mapKey != null;
@@ -341,6 +353,10 @@ public boolean returnsCursor() {
       return returnsCursor;
     }
 
+    public boolean returnsStream() {
+      return returnsStream;
+    }
+
     /**
      * return whether return type is {@code java.util.Optional}.
      *

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

@@ -93,6 +93,7 @@
 /**
  * @author Clinton Begin
  * @author Kazuki Shimizu
+ * @author Yanming Zhou
  */
 public class MapperAnnotationBuilder {
 
@@ -401,7 +402,8 @@ private static Class<?> getReturnType(Method method, Class<?> type) {
     } else if (resolvedReturnType instanceof ParameterizedType) {
       ParameterizedType parameterizedType = (ParameterizedType) resolvedReturnType;
       Class<?> rawType = (Class<?>) parameterizedType.getRawType();
-      if (Collection.class.isAssignableFrom(rawType) || Cursor.class.isAssignableFrom(rawType)) {
+      if (Collection.class.isAssignableFrom(rawType) || Cursor.class.isAssignableFrom(rawType)
+          || Stream.class.isAssignableFrom(rawType)) {
         Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
         if (actualTypeArguments != null && actualTypeArguments.length == 1) {
           Type returnTypeParameter = actualTypeArguments[0];

src/test/java/org/apache/ibatis/submitted/stream_on_mapper_method/Mapper.java

@@ -0,0 +1,29 @@
+/*
+ *    Copyright 2009-2022 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
+ *
+ *       https://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.stream_on_mapper_method;
+
+import java.util.stream.Stream;
+
+import org.apache.ibatis.annotations.Select;
+
+public interface Mapper {
+
+  @Select("select * from users")
+  Stream<User> findAll();
+
+  Stream<User> findAllUsingXml();
+
+}

src/test/java/org/apache/ibatis/submitted/stream_on_mapper_method/StreamOnMapperMethodTest.java

@@ -0,0 +1,73 @@
+/*
+ *    Copyright 2009-2025 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
+ *
+ *       https://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.stream_on_mapper_method;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.Reader;
+import java.util.stream.Stream;
+
+import org.apache.ibatis.BaseDataTest;
+import org.apache.ibatis.io.Resources;
+import org.apache.ibatis.session.SqlSession;
+import org.apache.ibatis.session.SqlSessionFactory;
+import org.apache.ibatis.session.SqlSessionFactoryBuilder;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests for support the {@code java.util.stream.Stream} as return type of mapper method.
+ *
+ * @author Yanming Zhou
+ */
+class StreamOnMapperMethodTest {
+
+  private static SqlSessionFactory sqlSessionFactory;
+
+  @BeforeAll
+  static void setUp() throws Exception {
+    // create an SqlSessionFactory
+    try (Reader reader = Resources
+        .getResourceAsReader("org/apache/ibatis/submitted/stream_on_mapper_method/mybatis-config.xml")) {
+      sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
+    }
+
+    // populate in-memory database
+    BaseDataTest.runScript(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
+        "org/apache/ibatis/submitted/stream_on_mapper_method/CreateDB.sql");
+  }
+
+  @Test
+  void returnStream() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      try (Stream<User> stream = mapper.findAll()) {
+        assertEquals(2, stream.count());
+      }
+    }
+  }
+
+  @Test
+  void returnStreamUsingXml() {
+    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+      Mapper mapper = sqlSession.getMapper(Mapper.class);
+      try (Stream<User> stream = mapper.findAllUsingXml()) {
+        assertEquals(2, stream.count());
+      }
+    }
+  }
+
+}

src/test/java/org/apache/ibatis/submitted/stream_on_mapper_method/User.java

@@ -0,0 +1,38 @@
+/*
+ *    Copyright 2009-2022 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
+ *
+ *       https://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.stream_on_mapper_method;
+
+public class User {
+
+  private Integer id;
+  private String name;
+
+  public Integer getId() {
+    return id;
+  }
+
+  public void setId(Integer id) {
+    this.id = id;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public void setName(String name) {
+    this.name = name;
+  }
+}

src/test/resources/org/apache/ibatis/submitted/stream_on_mapper_method/CreateDB.sql

@@ -0,0 +1,25 @@
+--
+--    Copyright 2009-2022 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
+--
+--       https://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/resources/org/apache/ibatis/submitted/stream_on_mapper_method/Mapper.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+       Copyright 2009-2022 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
+
+          https://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"
+    "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
+
+<mapper namespace="org.apache.ibatis.submitted.stream_on_mapper_method.Mapper">
+
+  <select id="findAllUsingXml" resultType="org.apache.ibatis.submitted.stream_on_mapper_method.User">
+    select * from users
+  </select>
+
+</mapper>

src/test/resources/org/apache/ibatis/submitted/stream_on_mapper_method/mybatis-config.xml

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+
+       Copyright 2009-2022 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
+
+          https://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 configuration
+    PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
+    "https://mybatis.org/dtd/mybatis-3-config.dtd">
+
+<configuration>
+
+  <environments default="development">
+    <environment id="development">
+      <transactionManager type="JDBC">
+        <property name="" value="" />
+      </transactionManager>
+      <dataSource type="UNPOOLED">
+        <property name="driver" value="org.hsqldb.jdbcDriver" />
+        <property name="url" value="jdbc:hsqldb:mem:useactualparamname" />
+        <property name="username" value="sa" />
+      </dataSource>
+    </environment>
+  </environments>
+
+  <mappers>
+    <mapper class="org.apache.ibatis.submitted.stream_on_mapper_method.Mapper" />
+  </mappers>
+
+</configuration>