springboot+mybatis 多数据库支持

1.配置application.yml

mybatis:
  mapper-locations: classpath:/mybatis/mapping/*.xml
  configuration:
    map-underscore-to-camel-case: true #开启驼峰命名
    database-id: ${database.type}
  type-aliases-package: com.mtwl.entity

注意database-id 的配置
2.在springboot中配置DatabaseIdProvider

@Bean
public DatabaseIdProvider getDatabaseIdProvider(){
    DatabaseIdProvider databaseIdProvider = new VendorDatabaseIdProvider();
    Properties properties = new Properties();
    properties.setProperty("Oracle","oracle");
    properties.setProperty("MySQL","mysql");
    properties.setProperty("DB2","db2");
    properties.setProperty("Derby","derby");
    properties.setProperty("H2","h2");
    properties.setProperty("HSQL","hsql");
    properties.setProperty("Informix","informix");
    properties.setProperty("Microsoft SQL Server","sqlserver");
    properties.setProperty("PostgreSQL","postgresql");
    properties.setProperty("Sybase","sybase");
    properties.setProperty("Hana","hana");
    databaseIdProvider.setProperties(properties);
    return databaseIdProvider;
}
注意：数据库版本是否正确
3.在mapper.xml中使用
方法1

<select id="selectTop" resultType="java.util.Map" parameterType="java.lang.Integer" databaseId="sqlserver">
    select top(#{value})*
    from kcjs
  </select>

<select id="selectTop" resultType="java.util.Map" parameterType="java.lang.Integer" databaseId="mysql">
    select *
    from kcjs limit 0,#{value}
</select>


方法2

<select id="selectTop" resultType="java.util.Map" parameterType="java.lang.Integer">
    select
    <if test="_databaseId==sqlserver">
        top(#{value})*
        from kcjs
    </if>
    <if test="_databaseId==mysql">
        *
        from kcjs limit 0,#{value}
    </if>

</select>