（1）starter-web

		<!-- web -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

（2）jackson-databind

		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.11.3</version>
		</dependency>

（3）mybatis

		<!-- mybatis -->
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>2.1.3</version>
		</dependency>

（4）alibaba 数据连接池

		<!-- alibaba 数据连接池 -->
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid</artifactId>
			<version>1.1.13</version>
		</dependency>

（5）mysql 驱动

		<!-- mysql 驱动 -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>

（6）sqlserver 驱动

		<!-- sqlserver 驱动 -->
		<dependency>
			<groupId>com.microsoft.sqlserver</groupId>
			<artifactId>mssql-jdbc</artifactId>
			<version>7.4.1.jre8</version>
			<scope>runtime</scope>
		</dependency>

（7）Oracle数据库驱动

		<!-- Oracle数据库驱动 -->
		<dependency>
			<groupId>com.oracle</groupId>
			<artifactId>ojdbc14</artifactId>
			<version>10.2.0.4.0</version>
		</dependency>

（8）lombok主要用来记录日志

		<!-- lombok -->
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>

（9）tomcat

		<!-- tomcat -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
			<scope>provided</scope>
		</dependency>

二、配置

2.1 application.properties配置文件

server.port= 9000
server.servlet.context-path= /multiDatabase

#mybatis
mybatis.mapper-locations=classpath:mapper/\*/\*.xml
#将扫描到的mapper.xml显示在控制台
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

#MaBatis在控制台打印执行的SQL语句 注意其中dump.xxx.xxxx.dao是Dao层的包名，注意不是XML文件的包名=日志等级
logging.level.dump.xxx.xxxx.dao=debug

#spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
#spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#spring.datasource.url=jdbc:mysql://localhost:3306/MySQL数据库名?useUnicode=true&characterEncoding=utf8&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8
#spring.datasource.username=root
#spring.datasource.password=root


################################# 多数据源配置 #########################################
#参考：https://www.cnblogs.com/viwofer/p/13149863.html （Oracle数据源的配置使用默认的即可）
#如果同时配置了MySQL和SqlServer的数据源，并同时启动MySQL和SqlServer的数据源配置，注意是两个数据源的都同时启动，可能会出现如下错误并给出提示信息：
#错误：Field transactionManager in dump.pspaceTodb.base.aspect.TransactionAdviceConfig required a single bean, but 2 were found:
#提示信息：Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

#问题的原因：MySQL和SqlServer数据库的配置类没有分主次，所以导致启动失败；
#解决方法：在MySQL或SqlServer配置类的每个方法上都加上@Primary，注意只能在其中一个数据源上添加@Primary注解，在加了@Primary注解的配置类上，
# 执行的sql也会优先使用加了@Primary注解的配置类，所以数据只会优先出现在有@Primary注解对应的数据库中；

#MySQL数据库连接配置
spring.datasource.mysql.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.mysql.driver-class-name=com.mysql.cj.jdbc.Driver
#注意是jdbc-url不是url,否则报jdbcUrl is required with driverClassName错误
spring.datasource.mysql.jdbc-url=jdbc:mysql://localhost:3306/mysql数据库名?useUnicode=true&characterEncoding=utf8&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8
spring.datasource.mysql.username=root
spring.datasource.mysql.password=root

#SqlServer数据库连接配置
spring.datasource.mssql.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.mssql.driver-class-name=com.microsoft.sqlserver.jdbc.SQLServerDriver
#注意是jdbc-url不是url,否则报jdbcUrl is required with driverClassName错误
spring.datasource.mssql.jdbc-url=jdbc:sqlserver://localhost:1433;databasename=SqlServer数据库名
spring.datasource.mssql.username=sa
spring.datasource.mssql.password=admin123

#Oracle数据库连接配置
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=oracle.jdbc.driver.OracleDriver
spring.datasource.url=jdbc:oracle:thin:@192.168.18.200:1521:orcl
spring.datasource.username=root
spring.datasource.password=admin123

通过application.properties里的配置可以看出，项目默认的数据库配置是Oracle连接，所以在连接使用Oracle数据库时，需要把MySQL和SqlServer的 配置类 暂时注释掉，MySQL和SqlServer在application.properties里的配置信息不用注释。

2.2 dao、Mapper配置 省略

需要注意的是因为连接Oracle数据库是使用的SpringBoot默认的配置，所以需要在启动类上加上
@MapperScan扫描dao层接口

@MapperScan({"com.demo.test1.dao","com.demo.test2.dao"})

2.3 MySQL和SqlServer的数据源配置类

2.3.1 MySql数据源配置类

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 org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

/\*\*
 \* MySql数据源配置类
 \* @author chenlc
 \* @created 2020-11-06 15:03
 \*/
@Configuration(value="mysql")
@MapperScan(basePackages = "com.demo.test1.dao", sqlSessionFactoryRef = "MysqlSqlSessionFactory")//此处@MapperScan扫的是dao层接口
public class MySqlDataSourceConfig {

    @Primary
    @Bean(name = "MysqlDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.mysql")
    public DataSource getDateSource() {
        return DataSourceBuilder.create().build();
    }

    /\*\*
 \* 配置事务管理
 \*/
    @Primary
    @Bean(name = "MysqlTransactionManager")
    public DataSourceTransactionManager mysqlTransactionManager(@Qualifier("MysqlDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    /\*\*
 \* 配置工厂
 \* @param datasource
 \* @return
 \* @throws Exception
 \*/
    @Primary
    @Bean(name = "MysqlSqlSessionFactory")
    public SqlSessionFactory mysqlSqlSessionFactory(@Qualifier("MysqlDataSource") DataSource datasource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(datasource);
        //此处 classpath:mapper/\*/\*.xml 对应的是Mapper文件
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/\*/\*.xml"));
        return bean.getObject();
    }

    /\*\*
 \* 配置会话
 \* @param sessionFactory
 \* @return
 \*/
    @Primary
    @Bean("MysqlSqlSessionTemplate")
    public SqlSessionTemplate mysqlSessionTemplate(@Qualifier("MysqlSqlSessionFactory") SqlSessionFactory sessionFactory) {
        return new SqlSessionTemplate(sessionFactory);
    }
}

2.3.2 SqlServer数据源配置类

配置同MySQL数据源配置类的差不多一致，区别如下：
（1）MySQL数据源配置类里每个方法上都加了@Primary

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.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

/\*\*
 \* SqlServer数据源配置类