當前位置：首頁 > 运维知识 > 数据库 >内容正文

数据库

MyBatis-16MyBatis动态SQL之【支持多种数据库】

發布時間：2025/3/21 数据库 50 豆豆

生活随笔收集整理的這篇文章主要介紹了 MyBatis-16MyBatis动态SQL之【支持多种数据库】小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

概述
配置
- 1.MyBatis全局配置文件增加
- 2.映射文件中的標簽調整包含databaseId屬性
示例
- 增加個查詢當前時間的接口
- 編寫映射文件
- 單元測試
注意事項

概述

MyBatis-15MyBatis動態SQL之【bind】 bind標簽并不能解決更換數據庫帶來的所有問題。那么還有沒其他的方式來支持不同的數據庫呢？

答案是 使用if標簽以及由MyBatis提供的databaseIdProvider數據庫廠商標識配置

MyBatis可以根據不同的數據庫廠商執行不同的SQL,這種多廠商的支持是基于映射語句中的databaseId屬性。 MyBatis會加載不帶databaseId屬性和帶有匹配當前數據庫databaseId屬性的所有語句。如果同時找到了帶有databaseId和不帶databaseId的相同語句，則不帶databaseId的將被舍棄。

配置

1.MyBatis全局配置文件增加

為了支持多廠商數據庫，需要在MyBatis全局配置文件中加入databaseIdProvider配置 <databaseIdProvider type="DB_VENDOR"/>

也可以通過實現接口 org.apache.ibatis.mapping.DatabaseIdProvider 并在 mybatis-config.xml 中注冊來構建自己的 DatabaseIdProvider

DB_VENDOR會通過DatabaseMetaData#getDatabaseProductName()返回的字符串進行設置，通常情況下這個字符串比較長而且相同產品的不同版本會返回不同的值，通常會設置屬性別名使其變短。

<databaseIdProvider type="DB_VENDOR"><property name ="SQL Server" value="sqlserver"/><property name ="DB2" value ="db2"/><property name ="Oracle" value ="oracle"/><property name ="MySQL" value ="mysql"/><property name ="PostgreSQL" value ="postgresql"/><property name ="Derby" value ="derby"/><property name ="HSQL" value ="hsqldb"/><property name ="H2" value ="h2"/></databaseIdProvider>

上述列舉了常見的數據庫產品名稱，在有property配置時，databaseId將被設置為第一個能匹配數據庫產品名稱的屬性鍵對應的值，如果沒有匹配則置為null .

DB_VENDOR的匹配策略為DatabaseMetaData#getDatabaseProductName()返回的字符串包含property中name部分的值即可匹配。

數據庫產品名一般由選擇的當前數據庫的JDBC驅動所決定，只要找到對應數據庫DatabaseMetaData的實現類，一般在getDatabaseProductName()方法中就可以直接找到該值。
任何情況下都可以通過調用DatabaseMetaData#getDatabaseProductName()來獲取具體的值

完整的mybatis-config.xml如下

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration><properties resource="db.properties"/><settings><setting name="logImpl" value="LOG4J" /></settings><typeAliases><package name="com.artisan.mybatis.simple.model" /></typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC"/><dataSource type="UNPOOLED"><property name="driver" value="${jdbc.driver}" /><property name="url" value="${jdbc.url}" /><property name="username" value="${jdbc.username}" /><property name="password" value="${jdbc.password}" /></dataSource></environment></environments><databaseIdProvider type="DB_VENDOR" ><property name ="SQL Server" value="sqlserver"/><property name ="DB2" value ="db2"/><property name ="Oracle" value ="oracle"/><property name ="MySQL" value ="mysql"/><property name ="PostgreSQL" value ="postgresql"/><property name ="Derby" value ="derby"/><property name ="HSQL" value ="hsqldb"/><property name ="H2" value ="h2"/></databaseIdProvider><mappers><mapper resource="com/artisan/mybatis/simple/mapper/CountryMapper.xml" /><package name="com.artisan.mybatis.xml.mapper"/></mappers> </configuration>

注意databaseIdProvider節點的位置。

2.映射文件中的標簽調整包含databaseId屬性

除了增加上述配置之外，映射文件也需要調整，關鍵在于下面幾個映射文件的標簽中含有的databaseId屬性

select
insert
update
delete
selectKey
sql

示例

舉個簡單的例子，查詢當前時間

我們知道 mysql中的語句為

select now() from dual

oracle中為

select sysdate from dual

增加個查詢當前時間的接口

結合mybatis全局配置文件中的 mappers-package節點，在com.artisan.mybatis.xml.mapper包中增加接口

MultiDBMapper.java

package com.artisan.mybatis.xml.mapper;public interface MultiDBMapper {String getSysTime();}

編寫映射文件

MultiDBMapper.xml

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >  <mapper namespace="com.artisan.mybatis.xml.mapper.MultiDBMapper"><select id="getSysTime" resultType="String" databaseId="mysql">select now() from dual</select><select id="getSysTime" resultType="String" databaseId="oracle">select 'oralce-'||to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual </select></mapper>

單元測試

package com.artisan.mybatis.xml.mapper;import java.io.InputStream; import java.sql.Connection; import java.sql.DatabaseMetaData; import java.sql.DriverManager; import java.util.Properties;import org.apache.ibatis.session.SqlSession; import org.junit.Test;public class MultiDBMapperTest extends BaseMapperTest {public String getDatabaseProductName() {String productName = null;try {String dbfile = "db.properties";InputStream in = ClassLoader.getSystemResourceAsStream(dbfile);Properties p = new Properties();p.load(in);Class.forName(p.getProperty("jdbc.driver"));String url = p.getProperty("jdbc.url");String user = p.getProperty("jdbc.username");String pass = p.getProperty("jdbc.password");Connection con = DriverManager.getConnection(url, user, pass);DatabaseMetaData dbmd = con.getMetaData();productName = dbmd.getDatabaseProductName();System.out.println("數據庫名稱是：" + productName);} catch (Exception e) {e.printStackTrace();}return productName;}@Testpublic void getSysTimeTest() {// 獲取數據庫名稱getDatabaseProductName();// 獲取SqlSessionSqlSession sqlSession = getSqlSession();// 獲取MultiDBMapperMultiDBMapper multiDBMapper = sqlSession.getMapper(MultiDBMapper.class);// 調用接口方法String sysTime = multiDBMapper.getSysTime();System.out.println("當前時間:" + sysTime);sqlSession.close();}}

日志

2018-04-27 16:05:57,730 INFO [main] (BaseMapperTest.java:26) - sessionFactory bulit successfully 2018-04-27 16:05:57,730 INFO [main] (BaseMapperTest.java:29) - reader close successfully 數據庫名稱是：MySQL 2018-04-27 16:05:57,819 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: select now() from dual 2018-04-27 16:05:57,929 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: 2018-04-27 16:05:57,959 TRACE [main] (BaseJdbcLogger.java:151) - <== Columns: now() 2018-04-27 16:05:57,959 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 2018-04-27 16:05:57.0 2018-04-27 16:05:57,969 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 1 當前時間:2018-04-27 16:05:57.0

當基于不同的數據庫運行時，MyBatis會根據配置找到合適的SQL去執行。

注意事項

我們在上面演示了基于databaseId的基本用法，實際在工作中，大部分的SQL還是相同的，沒有必要寫成2個。這樣會導致大量重復的SQL。

數據庫的更換可能只會引起某個SQL語句的部分不同，可以使用if標簽配合默認的上下文中的_databaseId參數去實現。

我們用前幾篇博文的例子來演示下

改造前

<select id="selectSysUsersAdvancedWithWhere" resultType="com.artisan.mybatis.xml.domain.SysUser">SELECTa.id,a.user_name userName,a.user_password userPassword,a.user_email userEmail,a.user_info userInfo,a.head_img headImg,a.create_time createTimeFROMsys_user a<where><if test="userName != null and userName != '' ">and user_name like concat('%',#{userName},'%')</if><if test="userEmail != null and userEmail != '' ">and user_email = #{userEmail}</if></where></select>

改造后

<select id="selectSysUsersAdvancedMulitDB" resultType="com.artisan.mybatis.xml.domain.SysUser">SELECTa.id,a.user_name userName,a.user_password userPassword,a.user_email userEmail,a.user_info userInfo,a.head_img headImg,a.create_time createTimeFROMsys_user a<where><if test="userName != null and userName != '' "><if test="_databaseId == 'mysql' ">and user_name like concat('%',#{userName},'%')</if><if test="_databaseId == 'oracle' ">and user_name like '%'||#{username}||'%'</if></if><if test="userEmail != null and userEmail != '' ">and user_email = #{userEmail}</if></where></select>

增加個接口方法，方便區分測試

/*** * * @Title: selectSysUsersAdvancedMulitDB* * @Description: selectSysUsersAdvancedMulitDB* * @param sysUser* @return* * @return: List<SysUser>*/List<SysUser> selectSysUsersAdvancedMulitDB(SysUser sysUser);

單元測試

@Testpublic void selectSysUsersAdvancedMulitDBTest() {logger.info("selectSysUsersAdvancedMulitDBTest");// 獲取SqlSessionSqlSession sqlSession = getSqlSession();List<SysUser> userList = null;try {// 獲取UserMapper接口UserMapper userMapper = sqlSession.getMapper(UserMapper.class);logger.info("===========1.當用戶只輸入用戶名時，需要根據用戶名模糊查詢===========");// 模擬前臺傳參 1.當用戶只輸入用戶名時，需要根據用戶名模糊查詢SysUser sysUser = new SysUser();sysUser.setUserName("ad");// 調用selectSysUserByAdvancedCondition,根據查詢條件查詢用戶userList = userMapper.selectSysUsersAdvancedMulitDB(sysUser);// 根據數據庫sys_user表中的記錄,可以匹配到admin, 期望userList不為空Assert.assertNotNull(userList);// 根據查詢條件，期望只有1條數據Assert.assertTrue(userList.size() == 1);logger.info("userList:" + userList);// 為了測試匹配多條記錄的情況，我們將id=1001這條數據的userName 由test 改為artisansysUser.setUserName("i");// 調用selectSysUserByAdvancedCondition,根據查詢條件查詢用戶userList = userMapper.selectSysUsersAdvancedMulitDB(sysUser);// 根據數據庫sys_user表中的記錄,可以匹配到admin和artisan, 期望userList不為空Assert.assertNotNull(userList);// 根據查詢條件，期望只有2條數據Assert.assertTrue(userList.size() == 2);logger.info("userList:" + userList);logger.info("===========2.當用戶只輸入郵箱使，根據郵箱進行完全匹配===========");// 模擬前臺傳參 2.當用戶只輸入郵箱使，根據郵箱進行完全匹配sysUser.setUserEmail("admin@artisan.com");userList = userMapper.selectSysUsersAdvanced(sysUser);Assert.assertNotNull(userList);Assert.assertTrue(userList.size() == 1);logger.info(userList);sysUser.setUserEmail("1admin@artisan.com");userList = userMapper.selectSysUsersAdvancedMulitDB(sysUser);Assert.assertTrue(userList.size() == 0);logger.info("===========3.當用戶同時輸入用戶名和密碼時，用這兩個條件查詢匹配的用戶===========");// 模擬組合查詢條件,存在記錄的情況sysUser.setUserName("i");sysUser.setUserEmail("admin@artisan.com");userList = userMapper.selectSysUsersAdvancedMulitDB(sysUser);Assert.assertNotNull(userList);Assert.assertEquals("admin@artisan.com", sysUser.getUserEmail());Assert.assertTrue(userList.size() == 1);logger.info(userList);logger.info("===========4.當用戶同時輸入無法匹配的用戶名和密碼===========");// 模擬組合查詢條件,不存在記錄的情況sysUser.setUserName("x");sysUser.setUserEmail("admin@artisan.com");userList = userMapper.selectSysUsersAdvancedMulitDB(sysUser);Assert.assertTrue(userList.size() == 0);logger.info(userList);} catch (Exception e) {e.printStackTrace();} finally {sqlSession.close();logger.info("sqlSession close successfully ");}}

日志

2018-04-27 16:22:51,822 INFO [main] (BaseMapperTest.java:26) - sessionFactory bulit successfully 2018-04-27 16:22:51,826 INFO [main] (BaseMapperTest.java:29) - reader close successfully 2018-04-27 16:22:51,827 INFO [main] (UserMapperTest.java:934) - selectSysUsersAdvancedMulitDBTest 2018-04-27 16:22:51,857 INFO [main] (UserMapperTest.java:943) - ===========1.當用戶只輸入用戶名時，需要根據用戶名模糊查詢=========== 2018-04-27 16:22:51,987 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE user_name like concat('%',?,'%') 2018-04-27 16:22:52,086 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: ad(String) 2018-04-27 16:22:52,157 TRACE [main] (BaseJdbcLogger.java:151) - <== Columns: id, userName, userPassword, userEmail, userInfo, headImg, createTime 2018-04-27 16:22:52,157 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 1, admin, 123456, admin@artisan.com, <<BLOB>>, <<BLOB>>, 2018-04-13 21:12:47.0 2018-04-27 16:22:52,167 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 1 2018-04-27 16:22:52,167 INFO [main] (UserMapperTest.java:953) - userList:[SysUser [id=1, userName=admin, userPassword=123456, userEmail=admin@artisan.com, userInfo=管理員用戶, headImg=[18, 49, 35, 18, 48], createTime=Fri Apr 13 21:12:47 BOT 2018]] 2018-04-27 16:22:52,177 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE user_name like concat('%',?,'%') 2018-04-27 16:22:52,177 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: i(String) 2018-04-27 16:22:52,177 TRACE [main] (BaseJdbcLogger.java:151) - <== Columns: id, userName, userPassword, userEmail, userInfo, headImg, createTime 2018-04-27 16:22:52,177 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 1, admin, 123456, admin@artisan.com, <<BLOB>>, <<BLOB>>, 2018-04-13 21:12:47.0 2018-04-27 16:22:52,177 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 1001, artisan, 123456, test@artisan.com, <<BLOB>>, <<BLOB>>, 2018-04-13 21:12:47.0 2018-04-27 16:22:52,177 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 2 2018-04-27 16:22:52,187 INFO [main] (UserMapperTest.java:964) - userList:[SysUser [id=1, userName=admin, userPassword=123456, userEmail=admin@artisan.com, userInfo=管理員用戶, headImg=[18, 49, 35, 18, 48], createTime=Fri Apr 13 21:12:47 BOT 2018], SysUser [id=1001, userName=artisan, userPassword=123456, userEmail=test@artisan.com, userInfo=測試用戶, headImg=[18, 49, 35, 18, 48], createTime=Fri Apr 13 21:12:47 BOT 2018]] 2018-04-27 16:22:52,187 INFO [main] (UserMapperTest.java:966) - ===========2.當用戶只輸入郵箱使，根據郵箱進行完全匹配=========== 2018-04-27 16:22:52,187 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE 1=1 and user_name like concat('%',?,'%') and user_email = ? 2018-04-27 16:22:52,187 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: i(String), admin@artisan.com(String) 2018-04-27 16:22:52,187 TRACE [main] (BaseJdbcLogger.java:151) - <== Columns: id, userName, userPassword, userEmail, userInfo, headImg, createTime 2018-04-27 16:22:52,187 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 1, admin, 123456, admin@artisan.com, <<BLOB>>, <<BLOB>>, 2018-04-13 21:12:47.0 2018-04-27 16:22:52,187 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 1 2018-04-27 16:22:52,187 INFO [main] (UserMapperTest.java:972) - [SysUser [id=1, userName=admin, userPassword=123456, userEmail=admin@artisan.com, userInfo=管理員用戶, headImg=[18, 49, 35, 18, 48], createTime=Fri Apr 13 21:12:47 BOT 2018]] 2018-04-27 16:22:52,187 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE user_name like concat('%',?,'%') and user_email = ? 2018-04-27 16:22:52,197 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: i(String), 1admin@artisan.com(String) 2018-04-27 16:22:52,197 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 0 2018-04-27 16:22:52,197 INFO [main] (UserMapperTest.java:978) - ===========3.當用戶同時輸入用戶名和密碼時，用這兩個條件查詢匹配的用戶=========== 2018-04-27 16:22:52,197 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE user_name like concat('%',?,'%') and user_email = ? 2018-04-27 16:22:52,197 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: i(String), admin@artisan.com(String) 2018-04-27 16:22:52,197 TRACE [main] (BaseJdbcLogger.java:151) - <== Columns: id, userName, userPassword, userEmail, userInfo, headImg, createTime 2018-04-27 16:22:52,207 TRACE [main] (BaseJdbcLogger.java:151) - <== Row: 1, admin, 123456, admin@artisan.com, <<BLOB>>, <<BLOB>>, 2018-04-13 21:12:47.0 2018-04-27 16:22:52,207 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 1 2018-04-27 16:22:52,207 INFO [main] (UserMapperTest.java:987) - [SysUser [id=1, userName=admin, userPassword=123456, userEmail=admin@artisan.com, userInfo=管理員用戶, headImg=[18, 49, 35, 18, 48], createTime=Fri Apr 13 21:12:47 BOT 2018]] 2018-04-27 16:22:52,207 INFO [main] (UserMapperTest.java:989) - ===========4.當用戶同時輸入無法匹配的用戶名和密碼=========== 2018-04-27 16:22:52,207 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Preparing: SELECT a.id, a.user_name userName, a.user_password userPassword, a.user_email userEmail, a.user_info userInfo, a.head_img headImg, a.create_time createTime FROM sys_user a WHERE user_name like concat('%',?,'%') and user_email = ? 2018-04-27 16:22:52,207 DEBUG [main] (BaseJdbcLogger.java:145) - ==> Parameters: x(String), admin@artisan.com(String) 2018-04-27 16:22:52,207 DEBUG [main] (BaseJdbcLogger.java:145) - <== Total: 0 2018-04-27 16:22:52,207 INFO [main] (UserMapperTest.java:995) - [] 2018-04-27 16:22:52,217 INFO [main] (UserMapperTest.java:1001) - sqlSession close successfully

總結

以上是生活随笔為你收集整理的MyBatis-16MyBatis动态SQL之【支持多种数据库】的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。

上一篇： MyBatis-15MyBatis动态S
下一篇： MyBatis-17MyBatis代码生