這次要完成的是從一個數據庫中讀取資料，然後再把資料插入到另一個數據庫中。在同一套專案程式碼中要完成這個操作，就不可避免的涉及到了多資料來源。本文即介紹在mybatis中完成多資料來源的切換相關內容

1. 指定資料來源一

   @Configuration
   // 掃描 Mapper 介面並容器管理
   @MapperScan(basePackages = MasterDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "masterSqlSessionFactory")
   public class MasterDataSourceConfig {
   
       // 精確到 master 目錄，以便跟其他資料來源隔離
       static final String PACKAGE = "com.datareach.kafka.dao.master";
       static final String MAPPER_LOCATION = "classpath:mapper/master/*.xml";
   	//application.yml中的值可以通過@Value註解進行讀取
       @Value("${master.datasource.url}")
       private String url;
       @Value("${master.datasource.username}")
       private String user;
       @Value("${master.datasource.password}")
       private String password;
       @Value("${master.datasource.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();
       }
   }
    
   

   資料來源一的相關配置

   # master 資料來源配置
   master:
     datasource:
       url: jdbc:postgresql://localhost:5432/postgres?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&serverTimezone=GMT%2B8
       driver-class-name: org.postgresql.Driver
       username: product
       password: 
       initial-size: 1
       min-idle: 1
       max-active: 20
       test-on-borrow: true
       max-wait: 60000
       time-between-eviction-runs-millis: 60000
       min-evictable-idle-time-millis: 300000
       validation-query: SELECT 1 FROM DUAL
       test-While-Idle: true
       test-on-return: false
       pool-prepared-statements: false
       max-pool-prepared-statement-per-connection-size: 20
       filters: stat,wall,log4j,config
    
   

2. 指定資料來源二

   @Configuration
   // 掃描 Mapper 介面並容器管理
   @MapperScan(basePackages = SecondDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "secondSqlSessionFactory")
   public class SecondDataSourceConfig {
       // 精確到 cluster 目錄，以便跟其他資料來源隔離
       static final String PACKAGE = "com.datareach.kafka.dao.secondary";
       static final String MAPPER_LOCATION = "classpath:mapper/secondary/*.xml";
       @Value("${second.datasource.url}")
       private String url;
       @Value("${second.datasource.username}")
       private String user;
       @Value("${second.datasource.password}")
       private String password;
       @Value("${second.datasource.driver-class-name}")
       private String driverClass;
   
       @Bean(name = "secondDataSource")
       public DataSource clusterDataSource() {
           DruidDataSource dataSource = new DruidDataSource();
           dataSource.setDriverClassName(driverClass);
           dataSource.setUrl(url);
           dataSource.setUsername(user);
           dataSource.setPassword(password);
           return dataSource;
       }
       @Bean(name = "secondTransactionManager")
       public DataSourceTransactionManager clusterTransactionManager() {
           return new DataSourceTransactionManager(clusterDataSource());
       }
       @Bean(name = "secondSqlSessionFactory")
       public SqlSessionFactory clusterSqlSessionFactory(@Qualifier("secondDataSource") DataSource clusterDataSource)
               throws Exception {
           final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
           sessionFactory.setDataSource(clusterDataSource);
           sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                   .getResources(SecondDataSourceConfig.MAPPER_LOCATION));
           return sessionFactory.getObject();
       }
   }
    
   

   資料來源一的相關配置

   second:
     datasource:
       url: jdbc:mysql://localhost:40000/PG_Data?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&serverTimezone=GMT%2B8
       username: root
       password: 
       driver-class-name: com.mysql.jdbc.Driver
       max-idle: 10
       max-wait: 10000
       min-idle: 5
       initial-size: 5
   

其實就是例項化了兩個SqlSessionFactory——masterSqlSessionFactory和secondSqlSessionFactory，然後通過註解@MapperScan指定掃描指定的mapper介面時用指定的SqlSessionFactory進行連線構建，從而實現了多資料來源。