!54 Bug：使用 join 联表查询一个对象数据丢失

Merge pull request !54 from 王帅/main

docs/zh/base/field-query.md

@@ -188,16 +188,3 @@ UserVO{userId='1', userName='admin', roleList=[Role{roleId=1, roleKey='admin', r
 UserVO{userId='2', userName='ry', roleList=[Role{roleId=2, roleKey='common', roleName='普通角色'}]}
 UserVO{userId='3', userName='test', roleList=[Role{roleId=1, roleKey='admin', roleName='超级管理员'}, Role{roleId=2, roleKey='common', roleName='普通角色'}]}
 ```
-
-## 特别注意！！！
-
-使用 `join` 联表查询的时候，只能使用 `selectListXxx` 方法查询 List 数据，不能使用 `selectOneXxx` 方法查询单个数据。
-
-```java
-default <R> R selectOneByQueryAs(QueryWrapper queryWrapper, Class<R> asType) {
-    List<R> entities = selectListByQueryAs(queryWrapper.limit(1), asType);
-    return (entities == null || entities.isEmpty()) ? null : entities.get(0);
-}
-```
-
-因为这个 `selectOneXxx` 方法都是调用的对应的 `selectListXxx` 方法，其中添加了 `queryWrapper.limit(1)` 约束，将数据限制在了一条，而联表查询数据有可能是多条的，这样自动映射就会出现数据丢失。

mybatis-flex-core/src/main/java/com/mybatisflex/core/BaseMapper.java

@@ -1,17 +1,17 @@
-/**
+/*
- * Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
+ *  Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
- * <p>
+ *  <p>
- * Licensed under the Apache License, Version 2.0 (the "License");
+ *  Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
+ *  you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
+ *  You may obtain a copy of the License at
- * <p>
+ *  <p>
- * http://www.apache.org/licenses/LICENSE-2.0
+ *  http://www.apache.org/licenses/LICENSE-2.0
- * <p>
+ *  <p>
- * Unless required by applicable law or agreed to in writing, software
+ *  Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
+ *  distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
+ *  See the License for the specific language governing permissions and
- * limitations under the License.
+ *  limitations under the License.
  */
 package com.mybatisflex.core;
 
@@ -346,8 +346,7 @@ public interface BaseMapper<T> {
      * @return entity 数据
      */
     default T selectOneByQuery(QueryWrapper queryWrapper) {
-        List<T> entities = selectListByQuery(queryWrapper.limit(1));
+        return SqlUtil.getSelectOneResult(selectListByQuery(queryWrapper));
-        return (entities == null || entities.isEmpty()) ? null : entities.get(0);
     }
 
 
@@ -359,8 +358,7 @@ public interface BaseMapper<T> {
      * @return 数据内容
      */
     default <R> R selectOneByQueryAs(QueryWrapper queryWrapper, Class<R> asType) {
-        List<R> entities = selectListByQueryAs(queryWrapper.limit(1), asType);
+        return SqlUtil.getSelectOneResult(selectListByQueryAs(queryWrapper, asType));
-        return (entities == null || entities.isEmpty()) ? null : entities.get(0);
     }
 
     /**
@@ -507,8 +505,7 @@ public interface BaseMapper<T> {
      * @return 数据量
      */
     default Object selectObjectByQuery(QueryWrapper queryWrapper) {
-        List<Object> objects = selectObjectListByQuery(queryWrapper.limit(1));
+        return SqlUtil.getSelectOneResult(selectObjectListByQuery(queryWrapper));
-        return objects == null || objects.isEmpty() ? null : objects.get(0);
     }
 
 

mybatis-flex-core/src/main/java/com/mybatisflex/core/util/SqlUtil.java

@@ -15,13 +15,18 @@
  */
 package com.mybatisflex.core.util;
 
+import org.apache.ibatis.exceptions.TooManyResultsException;
+import org.apache.ibatis.session.defaults.DefaultSqlSession;
+
 import java.time.LocalDateTime;
 import java.util.Date;
+import java.util.List;
 import java.util.regex.Matcher;
 
 public class SqlUtil {
 
-    private SqlUtil() {}
+    private SqlUtil() {
+    }
 
     public static void keepColumnSafely(String column) {
         if (StringUtil.isBlank(column)) {
@@ -78,7 +83,7 @@ public class SqlUtil {
     }
 
 
-    public static String replaceSqlParams(String sql, Object[] params){
+    public static String replaceSqlParams(String sql, Object[] params) {
         if (params != null && params.length > 0) {
             for (Object value : params) {
                 // null
@@ -108,4 +113,19 @@ public class SqlUtil {
         return sql;
     }
 
+    /**
+     * 搬运加改造 {@link DefaultSqlSession#selectOne(String, Object)}
+     */
+    public static <T> T getSelectOneResult(List<T> list) {
+        if (list == null || list.isEmpty()) {
+            return null;
+        }
+        int size = list.size();
+        if (size == 1) {
+            return list.get(0);
+        }
+        throw new TooManyResultsException(
+                "Expected one result (or null) to be returned by selectOne(), but found: " + size);
+    }
+
 }

mybatis-flex-test/mybatis-flex-spring-boot-test/src/test/java/com/mybatisflex/test/mapper/UserMapperTest.java

@@ -18,7 +18,7 @@ package com.mybatisflex.test.mapper;
 
 import com.mybatisflex.core.query.QueryWrapper;
 import com.mybatisflex.test.model.UserInfo;
-import com.mybatisflex.test.model.UserVO1;
+import com.mybatisflex.test.model.UserVO;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
@@ -52,10 +52,10 @@ class UserMapperTest {
                 .leftJoin(ROLE).as("r").on(USER_ROLE.ROLE_ID.eq(ROLE.ROLE_ID))
                 .where(USER.USER_ID.eq(3));
         System.out.println(queryWrapper.toSQL());
-//        UserVO userVO = userMapper.selectListByQueryAs(queryWrapper, UserVO.class);
+        UserVO userVO = userMapper.selectOneByQueryAs(queryWrapper, UserVO.class);
-        UserVO1 userVO = userMapper.selectOneByQueryAs(queryWrapper, UserVO1.class);
+//        UserVO1 userVO = userMapper.selectOneByQueryAs(queryWrapper, UserVO1.class);
-//        UserVO2 userVO = userMapper.selectListByQueryAs(queryWrapper, UserVO2.class);
+//        UserVO2 userVO = userMapper.selectOneByQueryAs(queryWrapper, UserVO2.class);
-//        UserVO3 userVO = userMapper.selectListByQueryAs(queryWrapper, UserVO3.class);
+//        UserVO3 userVO = userMapper.selectOneByQueryAs(queryWrapper, UserVO3.class);
         System.err.println(userVO);
     }
 
@@ -68,8 +68,8 @@ class UserMapperTest {
                 .leftJoin(ROLE).as("r").on(USER_ROLE.ROLE_ID.eq(ROLE.ROLE_ID))
                 .where(USER.USER_ID.ge(2));
         System.out.println(queryWrapper.toSQL());
-//        List<UserVO> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO.class);
+        List<UserVO> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO.class);
-        List<UserVO1> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO1.class);
+//        List<UserVO1> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO1.class);
 //        List<UserVO2> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO2.class);
 //        List<UserVO3> userVOS = userMapper.selectListByQueryAs(queryWrapper, UserVO3.class);
         userVOS.forEach(System.err::println);