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1.前言
在我们需要进行数据库连接的道路上，必定经历过很多弯路，时至今日，我们明白，必须配置连接池，让连接池来管理连接。另外，数据源真正应该做到的不是切换，而是多数据源同时存在。所以我们可以创建下面的数据源配置。
2.配置类
2.1.主配置类
主要配置类的作用就是为了启动时不报错，比如，我们的主数据源叫苹果数据源，它的配置如下：
import javax.sql.DataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import com.alibaba.druid.pool.DruidDataSource;
@Configuration
@MapperScan(basePackages = AppleDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "appleSqlSessionFactory")
@PropertySource(value = "classpath:databaseConfig.properties", ignoreResourceNotFound = true)
public class AppleDataSourceConfig
{
static final String PACKAGE = "com.hengbao.common.dao.db.mapper.apple";
static final String MAPPER_LOCATION = "classpath:com/hengbao/common/dao/db/map/apple/*.xml";
@Value("${spring.datasource.apple.url}")
private String url;
@Value("${spring.datasource.apple.username}")
private String user;
@Value("${spring.datasource.apple.password}")
private String password;
@Value("${spring.datasource.apple.driver-class-name}")
private String driverClass;
@Bean(name = "appleDataSource")
@Primary
public DataSource appleDataSource() {
DruidDataSource dataSource = new DruidDataSource();
dataSource.setDriverClassName(driverClass);
dataSource.setUrl(url);
dataSource.setUsername(user);
dataSource.setPassword(password);
return dataSource;
}
@Bean(name = "appleTransactionManager")
@Primary
public DataSourceTransactionManager appleTransactionManager() {
return new DataSourceTransactionManager(appleDataSource());
}
@Bean(name = "appleSqlSessionFactory")
@Primary
public SqlSessionFactory appleSqlSessionFactory(@Qualifier("appleDataSource") DataSource appleDataSource)
throws Exception {
final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
sessionFactory.setDataSource(appleDataSource);
sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources(AppleDataSourceConfig.MAPPER_LOCATION));
return sessionFactory.getObject();
}
}
这里需要解释一下：@Primary用来标记“主”，@MapperScan的属性直接配在这里的原因是，这是单独写两个数据源配置的写法，每个数据源要对应自己的包。@PropertySource是用来对应properties文件的，这样写的好处是，你不必将这个配置类放在必须有springboot启动类的项目里了，这样对于对应配置文件也比较方便。
2.2 其它数据源
如果需要香蕉数据源，我们就需要这样配置了：
import javax.sql.DataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import com.alibaba.druid.pool.DruidDataSource;
@Configuration
@MapperScan(basePackages = BananaDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "bananaSqlSessionFactory")
@PropertySource(value = "classpath:databaseConfig.properties", ignoreResourceNotFound = true)
public class BananaDataSourceConfig
{
static final String PACKAGE = "com.hengbao.common.dao.db.mapper.banana";
static final String MAPPER_LOCATION = "classpath:com/hengbao/common/dao/db/map/banana/*.xml";
@Value("${spring.datasource.banana.url}")
private String url;
@Value("${spring.datasource.banana.username}")
private String user;
@Value("${spring.datasource.banana.password}")
private String password;
@Value("${spring.datasource.banana.driver-class-name}")
private String driverClass;
@Bean(name = "bananaDataSource")
public DataSource bananaDataSource() {
DruidDataSource dataSource = new DruidDataSource();
dataSource.setDriverClassName(driverClass);
dataSource.setUrl(url);
dataSource.setUsername(user);
dataSource.setPassword(password);
return dataSource;
}
@Bean(name = "bananaTransactionManager")
public DataSourceTransactionManager bananaTransactionManager() {
return new DataSourceTransactionManager(bananaDataSource());
}
@Bean(name = "bananaSqlSessionFactory")
public SqlSessionFactory bananaSqlSessionFactory(@Qualifier("bananaDataSource") DataSource bananaDataSource)
throws Exception {
final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
sessionFactory.setDataSource(bananaDataSource);
sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources(BananaDataSourceConfig.MAPPER_LOCATION));
return sessionFactory.getObject();
}
}
大家看到区别了吧，就是不写@Primary注解，这样的数据源配置多个是可以的，不过一般的，一个项目里也不会超过5个。需要连的数据源很多就要思考自己的架构和数据库设计了。
3.总结
当我们启动并测试这个配置的时候，假设我们配置了三个数据源，我们将会看到下面的输出：
2019-01-22 10:01:47.129 INFO 21104 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} inited
2019-01-22 10:01:47.316 INFO 21104 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-2} inited
2019-01-22 10:01:47.417 INFO 21104 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-3} inited
2019-01-22 10:01:47.469 INFO 21104 --- [ Thread-2] com.alibaba.druid.pool.DruidDataSource : {dataSource-3} closed
2019-01-22 10:01:47.474 INFO 21104 --- [ Thread-2] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closed
2019-01-22 10:01:47.477 INFO 21104 --- [ Thread-2] com.alibaba.druid.pool.DruidDataSource : {dataSource-2} closed
当然了，如果您并没有使用阿里巴巴的druid数据源，使用了其它的数据源，打印类路径会不同。
