springboot-mybatis多數據源配置

在平時開發中接觸了多數據源的配置，但是接觸的是分包方式實現的（可能後續也會記錄動態數據源配置）
1.在application.yml中添加配置：

 spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    master:
      url: jdbc:mysql://localhost:3306/multipledatasource1?characterEncoding=utf-8&useSSL=false
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver
    cluster:
      url: jdbc:mysql://localhost:3306/multipledatasource2?characterEncoding=utf-8&useSSL=false
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver

2.建立兩個數據源的配置文件：

import com.alibaba.druid.pool.DruidDataSource;
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.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
// 掃描 Mapper 接口並容器管理
@MapperScan(basePackages = MasterDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "masterSqlSessionFactory")
public class MasterDataSourceConfig {

    // 精確到 master 目錄，以便跟其他數據源隔離
    static final String PACKAGE = "com.dao.master";
    static final String MAPPER_LOCATION = "classpath:mapper/master/*.xml";

    @Value("${spring.datasource.master.url}")
    private String url;

    @Value("${spring.datasource.master.username}")
    private String user;

    @Value("${spring.datasource.master.password}")
    private String password;

    @Value("${spring.datasource.master.driver-class-name}")
    private String driverClass;

    @Bean(name = "masterDataSource")
    @Primary
    public DataSource masterDataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(driverClass);
        dataSource.setUrl(url);
        dataSource.setUsername(user);
        dataSource.setPassword(password);
        return dataSource;
    }

    @Bean(name = "masterTransactionManager")
    @Primary
    public DataSourceTransactionManager masterTransactionManager() {
        return new DataSourceTransactionManager(masterDataSource());
    }

    @Bean(name = "masterSqlSessionFactory")
    @Primary
    public SqlSessionFactory masterSqlSessionFactory(@Qualifier("masterDataSource") DataSource masterDataSource)
            throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(masterDataSource);
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources(MasterDataSourceConfig.MAPPER_LOCATION));
        return sessionFactory.getObject();
    }
}

第二個配置文件：

import com.alibaba.druid.pool.DruidDataSource;
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.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;

import javax.sql.DataSource;

@Configuration
// 掃描 Mapper 接口並容器管理
@MapperScan(basePackages = ClusterDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "clusterSqlSessionFactory")
public class ClusterDataSourceConfig {

    // 精確到 cluster 目錄，以便跟其他數據源隔離
    static final String PACKAGE = "com.dao.cluster";
    static final String MAPPER_LOCATION = "classpath:mapper/cluster/*.xml";

    @Value("${spring.datasource.cluster.url}")
    private String url;

    @Value("${spring.datasource.cluster.username}")
    private String user;

    @Value("${spring.datasource.cluster.password}")
    private String password;

    @Value("${spring.datasource.cluster.driver-class-name}")
    private String driverClass;

    @Bean(name = "clusterDataSource")
    public DataSource clusterDataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(driverClass);
        dataSource.setUrl(url);
        dataSource.setUsername(user);
        dataSource.setPassword(password);
        return dataSource;
    }

    @Bean(name = "clusterTransactionManager")
    public DataSourceTransactionManager clusterTransactionManager() {
        return new DataSourceTransactionManager(clusterDataSource());
    }

    @Bean(name = "clusterSqlSessionFactory")
    public SqlSessionFactory clusterSqlSessionFactory(@Qualifier("clusterDataSource") DataSource clusterDataSource)
            throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(clusterDataSource);
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources(ClusterDataSourceConfig.MAPPER_LOCATION));
        return sessionFactory.getObject();
    }
}

注意：

1、@Primary這個註解必須要加，因爲不加的話spring將分不清楚那個爲主數據源（默認數據源）

2、mapper的接口、xml形式以及dao層都需要兩個分開，目錄如圖：


3、bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(“XXXX”));mapper的xml形式文件位置必須要配置，不然將報錯：no statement （這種錯誤也可能是mapper的xml中，namespace與項目的路徑不一致導致的，具體看情況吧，注意一下就行，問題不大的）

4、在service層中根據不同的業務注入不同的dao層。

5、如果是主從複製- -讀寫分離：比如test01中負責增刪改，test02中負責查詢。但是需要注意的是負責增刪改的數據庫必須是主庫（master）

6、如果是分佈式結構的話，不同模塊操作各自的數據庫就好，test01包下全是test01業務，test02全是test02業務，但是如果test01中摻雜着test02的編輯操作，這時候將會產生事務問題：即test01中的事務是沒法控制test02的事務的。