SpringBoot项目多数据源配置（亲测有效）

1、开发环境准备

开发工具：IDEA
开发工具：Maven+JDK8
所用技术：SpringBoot+Mybatis
数据库：MySQL
SpringBoot版本：2.1.0

2、创建SpringBoot项目，项目结构如下

3、数据库信息

创建两个数据库和 user 表、money表。
我们一共创建的两个数据库 test1 和 test2，然后分别在这两个数据库中创建了 user 用户表、money工资详情表（字段随便设置）。

4、pom文件依赖

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

5、配置application.yml

注意事项：
	在1.0 配置数据源的过程中主要是写成：spring.datasource.url 和spring.datasource.driverClassName。
而在2.0升级之后需要变更成：spring.datasource.jdbc-url和spring.datasource.driver-class-name！不然在连接数据库时可能会报下面的错误：另外在在2.0.2+版本后需要在datasource后面加上hikari，如果你没有加的话，同样可能会报错。

Error querying database. Cause: java.lang.IllegalArgumentException: jdbcUrl is required with driverClassName.

Spring:
  datasource:
    hikari:
      db1:
        jdbc-url: jdbc:mysql://localhost:3306/test1?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=GMT%2B8
        username: root
        password: root
      db2:
        jdbc-url: jdbc:mysql://localhost:3306/test2?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=GMT%2B8
        username: root
        password: root
      driver-class-name: com.mysql.cj.jdbc.Driver

6、实现

①：创建实体类bean
②：数据源配置

package com.test.demo.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.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.test.demo.db1.dao", sqlSessionTemplateRef = "db1SqlSessionTemplate")
public class DataSource1Config {

    /**
     * 生成数据源.  @Primary 注解声明为默认数据源
     */
    @Bean(name = "db1DataSource")
    @ConfigurationProperties(prefix = "spring.datasource.hikari.db1")
    @Primary
    public DataSource testDataSource() {
        return DataSourceBuilder.create().build();
    }

    /**
     * 创建 SqlSessionFactory
     */
    @Bean(name = "db1SqlSessionFactory")
    @Primary
    public SqlSessionFactory testSqlSessionFactory(@Qualifier("db1DataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        //  bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/db1/*.xml"));
        return bean.getObject();
    }

    /**
     * 配置事务管理
     */
    @Bean(name = "db1TransactionManager")
    @Primary
    public DataSourceTransactionManager testTransactionManager(@Qualifier("db1DataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "db1SqlSessionTemplate")
    @Primary
    public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("db1SqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

package com.test.demo.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.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.test.demo.db2.dao", sqlSessionTemplateRef = "db2SqlSessionTemplate")
public class DataSource2Config {

    @Bean(name = "db2DataSource")
    @ConfigurationProperties(prefix = "spring.datasource.hikari.db2")
    public DataSource testDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "db2SqlSessionFactory")
    public SqlSessionFactory testSqlSessionFactory(@Qualifier("db2DataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        //bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/db2/*.xml"));
        return bean.getObject();
    }

    @Bean(name = "db2TransactionManager")
    public DataSourceTransactionManager testTransactionManager(@Qualifier("db2DataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "db2SqlSessionTemplate")
    public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("db2SqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

}

关于上面的配置类这里主要提一下下面这几点：
1、@MapperScan 注解中我们声明了使用数据库1的dao类所在的位置,还声明了 SqlSessionTemplate 。SqlSessionTemplate是MyBatis-Spring的核心。这个类负责管理MyBatis的SqlSession,调用MyBatis的SQL方法，翻译异常。SqlSessionTemplate是线程安全的，可以被多个DAO所共享使用。
2、由于使用的是全注解的方式开发,所以下面这条找并且解析 mapper.xml 配置语句被注释掉了
bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(“classpath:mybatis/mapper/db2/*.xml”));
3、比如我们要声明使用数据1，直接在 dao 层的类上加上这样一个注释即可：@Qualifier(“db1SqlSessionTemplate”)
4、我们在数据库1配置类的每个方法前加上了 @Primary 注解来声明这个数据库时默认数据库，不然可能会报错。

③dao层和service层

package com.test.demo.db1.dao;

import com.test.demo.bean.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.springframework.beans.factory.annotation.Qualifier;

@Mapper
@Qualifier("db1SqlSessionTemplate")
public interface UserDao {
    /**
     * 通过名字查询用户信息
     */
    @Select("SELECT * FROM user WHERE name = #{name}")
    User findUserByName(String name);
}

package com.test.demo.db1.service.impl;

import com.test.demo.bean.User;
import com.test.demo.db1.dao.UserDao;
import com.test.demo.db1.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;

    @Override
    public User selectUserByName(String name) {
        return userDao.findUserByName(name);
    }
}

package com.test.demo.db2.dao;

import com.test.demo.bean.Money;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.beans.factory.annotation.Qualifier;

@Mapper
@Qualifier("db2SqlSessionTemplate")
public interface MoneyDao {
    /**
     * 通过id 查看工资详情
     */
    @Select("SELECT * FROM money WHERE id = #{id}")
    Money findMoneyById(@Param("id") int id);
}

package com.test.demo.db2.service.impl;

import com.test.demo.bean.Money;
import com.test.demo.db2.dao.MoneyDao;
import com.test.demo.db2.service.MoneyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class MoneyServiceImpl implements MoneyService {
    @Autowired
    private MoneyDao moneyDao;

    @Override
    public Money selectMoneyById(int id) {
        return moneyDao.findMoneyById(id);
    }
}

④controller层实现

package com.test.demo.controller;

import com.test.demo.bean.User;
import com.test.demo.db1.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired(required = false)
    private UserService userService;

    @RequestMapping("/query")
    public User testQuery() {
        return userService.selectUserByName("Daisy");
    }
}

package com.test.demo.controller;

import com.test.demo.bean.Money;
import com.test.demo.db2.service.MoneyService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/money")
public class MoneyController {
    @Autowired(required = false)
    private MoneyService moneyService;

    @RequestMapping("/query")
    public Money testQuery() {
        return moneyService.selectMoneyById(1);
    }
}

7、之后访问接口就可以了。

在这里边有个问题，我的是在其他 module 中调用 基础 module 类，在Base里边，要用application.yml，而在Ping中，则需要使用application.properties，如果后缀不同的话会报以下错误：

There was an unexpected error (type=Internal Server Error, status=500)

nested exception is org.apache.ibatis.exceptions.PersistenceException: ### Error querying database. Cause: java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required. ### The error may exist in com/test/demo/db2/dao/MoneyDao.java (best guess) ### The error may involve com.test.demo.db2.dao.MoneyDao.findMoneyById ### The error occurred while executing a query ### Cause: java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required.

参考：http://bbs.itheima.com/thread-452900-1-1.html