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1   /*
2    *    Copyright 2009-2023 the original author or authors.
3    *
4    *    Licensed under the Apache License, Version 2.0 (the "License");
5    *    you may not use this file except in compliance with the License.
6    *    You may obtain a copy of the License at
7    *
8    *       https://www.apache.org/licenses/LICENSE-2.0
9    *
10   *    Unless required by applicable law or agreed to in writing, software
11   *    distributed under the License is distributed on an "AS IS" BASIS,
12   *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *    See the License for the specific language governing permissions and
14   *    limitations under the License.
15   */
16  package org.apache.ibatis.submitted.cursor_cache_oom;
17  
18  import java.io.IOException;
19  import java.io.Reader;
20  import java.lang.reflect.Field;
21  import java.util.List;
22  import java.util.Map;
23  
24  import org.apache.ibatis.BaseDataTest;
25  import org.apache.ibatis.cache.CacheKey;
26  import org.apache.ibatis.cursor.Cursor;
27  import org.apache.ibatis.cursor.defaults.DefaultCursor;
28  import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
29  import org.apache.ibatis.io.Resources;
30  import org.apache.ibatis.session.SqlSession;
31  import org.apache.ibatis.session.SqlSessionFactory;
32  import org.apache.ibatis.session.SqlSessionFactoryBuilder;
33  import org.apache.ibatis.session.defaults.DefaultSqlSession;
34  import org.junit.jupiter.api.Assertions;
35  import org.junit.jupiter.api.BeforeAll;
36  import org.junit.jupiter.api.Test;
37  
38  @SuppressWarnings("ALL")
39  class CursorOomTest {
40  
41    private static SqlSessionFactory sqlSessionFactory;
42  
43    @BeforeAll
44    static void setUp() throws Exception {
45      // create an SqlSessionFactory
46      try (Reader reader = Resources
47          .getResourceAsReader("org/apache/ibatis/submitted/cursor_cache_oom/mybatis-config.xml")) {
48        sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
49      }
50  
51      // populate in-memory database
52      BaseDataTest.runScript(sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(),
53          "org/apache/ibatis/submitted/cursor_cache_oom/CreateDB.sql");
54    }
55  
56    private static Map<CacheKey, Object> getNestedResultObjects(Cursor<User> users)
57        throws IllegalAccessException, NoSuchFieldException {
58      DefaultCursor<User> defaultCursor = (DefaultCursor<User>) users;
59      Field resultSetHandlerField = DefaultCursor.class.getDeclaredField("resultSetHandler");
60      resultSetHandlerField.setAccessible(true);
61      DefaultResultSetHandler defaultResultSetHandler = (DefaultResultSetHandler) resultSetHandlerField
62          .get(defaultCursor);
63      Field nestedResultObjectsField = DefaultResultSetHandler.class.getDeclaredField("nestedResultObjects");
64      nestedResultObjectsField.setAccessible(true);
65      return (Map<CacheKey, Object>) nestedResultObjectsField.get(defaultResultSetHandler);
66    }
67  
68    private static List<Cursor<?>> getCursors(SqlSession sqlSession) throws NoSuchFieldException, IllegalAccessException {
69      DefaultSqlSession session = (DefaultSqlSession) sqlSession;
70      Field cursorListField = DefaultSqlSession.class.getDeclaredField("cursorList");
71      cursorListField.setAccessible(true);
72      List<Cursor<?>> cursorList = (List<Cursor<?>>) cursorListField.get(session);
73      return cursorList;
74    }
75  
76    @Test
77    void shouldNotCacheAllDataForWholeSessionWhileUsingCursor()
78        throws IOException, NoSuchFieldException, IllegalAccessException {
79      try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
80        Mapper mapper = sqlSession.getMapper(Mapper.class);
81        try (Cursor<User> users = mapper.fetchUsers()) {
82          for (User user : users) {
83            consumeUser(user);
84          }
85          Map nestedResultObjects = getNestedResultObjects(users);
86  
87          Assertions.assertFalse(nestedResultObjects.isEmpty());
88  
89          // does not pass now
90          // will be great, if cursor will use constant memory instead of linear one
91          // Assertions.assertTrue(nestedResultObjects.size() <= 2);
92        }
93  
94        List<Cursor<?>> cursorList = getCursors(sqlSession);
95  
96        // expect that either reference to the cursor itselfis gone or cursor does not contains all the fetched data
97        // the most preferrable way will be not to cache data, when the row is already processed (see commented
98        // line above)
99        Assertions
100           .assertTrue(cursorList.isEmpty() || getNestedResultObjects((Cursor<User>) cursorList.get(0)).size() <= 2);
101     }
102   }
103 
104   private void consumeUser(User user) {
105     // do nothing
106   }
107 }