概述

本人最近接到一个任务，将一个系统改成同时兼容Oracle和PostgreSQL(原来是仅支持Oracle)。虽然大部分的sql语句通用，但是还有许多语法存在差异，所以我们可以通过mybatis自身提供的databaseIdProvider解决这个问题，这里记录一下过程。

databaseId属性： 如果配置了 databaseIdProvider，MyBatis 会加载所有的不带 databaseId 或匹配当前 databaseId 的语句；如果带或者不带的语句都有，则不带的会被忽略。新增，修改和删除都有这个属性。

配置

pom依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--oracle-->
<dependency>
    <groupId>com.oracle</groupId>
    <artifactId>ojdbc6</artifactId>
    <version>11.2.0.3</version>
</dependency>
<!--postgresql-->
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>9.4.1212</version>
</dependency>
<!-- 集成mybatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.1</version>
</dependency>
<!--fastjson-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.16</version>
</dependency>
<!-- druid数据库连接池组件 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.1.10</version>
</dependency>

配置文件

通过配置文件开启mysql支持或者postgresql支持

application.yml

# 切换对应的环境 postgresql mysql
spring:
  profiles:
    active: postgresql

# mybatis配置
mybatis:
  mapper-locations: classpath:mapper/**/*.xml
  type-aliases-package: com.valten.**.model

# showSql 控制台打印sql日志
logging:
  level:
    com:
      valten:
        dao: debug

application-mysql.yml

# 端口
server:
  port: 8001

# 数据源配置
spring:
  datasource:
    hikari:
      jdbc-url: jdbc:mysql://127.0.0.1:3306/test?&useSSL=false
      driver-class-name: com.mysql.jdbc.Driver
      username: root
      password: 123456

application-postgresql.yml

# 端口
server:
  port: 8002

# 数据源配置
spring:
  datasource:
    hikari:
      jdbc-url: jdbc:postgresql://127.0.0.1:5432/test
      driver-class-name: org.postgresql.Driver
      username: root
      password: 123456

注意 SpringBoot1和2的数据原配置写法区别

数据源配置类

@Configuration
public class DataSourceConfig {
    @Value("${mybatis.mapper-locations}")
    private String mapperLocations;

    @Primary
    @Bean(name = "dataSource")
    @ConfigurationProperties("spring.datasource.hikari")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    public JdbcTemplate jdbcTemplate() {
        return new JdbcTemplate(dataSource());
    }

    @Bean
    public DatabaseIdProvider databaseIdProvider() {
        DatabaseIdProvider databaseIdProvider = new VendorDatabaseIdProvider();
        Properties p = new Properties();
        p.setProperty("Oracle", "oracle");
        p.setProperty("MySQL", "mysql");
        p.setProperty("PostgreSQL", "postgresql");
        p.setProperty("DB2", "db2");
        p.setProperty("SQL Server", "sqlserver");
        databaseIdProvider.setProperties(p);
        return databaseIdProvider;
    }

    @Primary
    @Bean
    public SqlSessionFactoryBean sqlSessionFactoryBean(@Qualifier("dataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        factoryBean.setDatabaseIdProvider(databaseIdProvider());
        factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));
        return factoryBean;
    }
}

UserMapper.xml

  <select id="selectByPrimaryKey" parameterType="java.lang.String" resultMap="BaseResultMap">
        select
        <if test="_databaseId == 'oracle'">
          account
        </if>
        <if test="_databaseId == 'postgresql'">
          dep_code
        </if>
        from SYS_USER
        where ID = #{id,jdbcType=CHAR}
  </select>