应用场景: 

        多数据源 小型项目 或者 大项目的临时方案中比较常用.在日常开发中,可能我们需要查询多个数据库,但是数据库实例不同,导致不能通过 指定schema的方式 区分不同的库, 这种情况下就需要我们应用程序配置多数据源

实现方式: 

• 首先自定义实现 datasource数据源

• 为当前数据源添加一些配置信息 例如: mapper 文件扫描地址

• 暴露SqlSessionTemplate 

---

package com.cloud.config;

import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;
import java.io.IOException;

@Configuration
@MapperScan(value = {"com/cloud/dict/mapper"}, sqlSessionFactoryRef = "klinSqlSessionFactory")
public class KlinDataSourceConfig {
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.klin")
    DataSource klin() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    SqlSessionFactory klinSqlSessionFactory(@Qualifier("klin") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource);
        // 指定多数据源 mapper 文件扫描路径,类似yml文件中 mapper-locations: classpath:/mapper/*.xml
        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:/mapper/klin/*.xml"));
        return sqlSessionFactoryBean.getObject();
    }

    @Bean
    SqlSessionTemplate klinSqlSessionTemplate(@Qualifier("klinSqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }


}

为当前系统指定默认数据库 只需要在datasource 的bean上面添加@primary 注解就可以

package com.cloud.config;

import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;


@Configuration
// 扫描接口路径
@MapperScan(value = {"com/cloud/sys/dao", "com/cloud/person/dao", "com/cloud/batch/dao"}, sqlSessionFactoryRef = "firstSqlSessionFactory")
public class FirstDataSourceConfig {

    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.first")
    @Primary
    DataSource first() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    SqlSessionFactory firstSqlSessionFactory(@Qualifier("first") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource);
        // 指定多数据源 mapper 文件扫描路径,类似yml文件中 mapper-locations: classpath:/mapper/*.xml
        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:/mapper/first/*.xml"));
        return sqlSessionFactoryBean.getObject();
    }


    @Bean
    SqlSessionTemplate firstSqlSessionTemplate(@Qualifier("firstSqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }


}