关于
有时候，随着业务的发展，项目关联的数据来源会变得越来越复杂，使用的数据库会比较分散，这个时候就会采用多数据源的方式来获取数据。另外，多数据源也有其他好处，例如分布式数据库的读写分离，集成多种数据库等等。
下面分享我在实际项目中配置多数据源的案例。话不多说了，来一起看看详细的介绍吧
步骤
1.application.yml文件中，配置数据库源。这里primary是主库，secondary是从库。
server: port: 8089# 多数据源配置#primaryspring: primary: datasource: url: jdbc:mysql://127.0.0.1:3306/database1?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&useSSL=false&useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai username: root password: ****** driver-class-name: com.mysql.jdbc.Driver #secondary secondary: datasource: url: jdbc:mysql://127.0.0.1:3306/database1?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&useSSL=false&useLegacyDatetimeCode=false&serverTimezone=Asia/Shanghai username: root password: ****** driver-class-name: com.mysql.jdbc.Driver jpa: hibernate: primary-dialect: org.hibernate.dialect.MySQL5Dialect secondary-dialect: org.hibernate.dialect.MySQL5Dialect open-in-view: true show-sql: true
2.创建一个Spring配置类，其中spring.primary.datasource的路径参考yml文件的配置。
@Configurationpublic class DataSourceConfig { @Bean(name = "primaryDataSource") @Qualifier("primaryDataSource") @ConfigurationProperties(prefix="spring.primary.datasource") public DataSource primaryDataSource() { return DataSourceBuilder.create().build(); } @Bean(name = "secondaryDataSource") @Qualifier("secondaryDataSource") @Primary @ConfigurationProperties(prefix="spring.secondary.datasource") public DataSource secondaryDataSource() { return DataSourceBuilder.create().build(); }}3.分别创建主库、从库的配置类。
注意：entity包和dao包的配置，以及@Primary注解指定主库。
主库配置类：
@Configuration@EnableTransactionManagement@EnableJpaRepositories( entityManagerFactoryRef = "entityManagerFactoryPrimary", transactionManagerRef = "transactionManagerPrimary", basePackages = {"com.infinitus.yunxiao_data.dao.primary"}) //设置Repository所在位置public class PrimaryConfig { @Autowired private JpaProperties jpaProperties; @Autowired @Qualifier("primaryDataSource") private DataSource primaryDataSource; @Primary @Bean(name = "entityManagerPrimary") public EntityManager entityManager(EntityManagerFactoryBuilder builder) { return entityManagerFactoryPrimary(builder).getObject().createEntityManager(); } @Primary @Bean(name = "entityManagerFactoryPrimary") public LocalContainerEntityManagerFactoryBean entityManagerFactoryPrimary(EntityManagerFactoryBuilder builder) { return builder .dataSource(primaryDataSource) .properties(getVendorProperties(primaryDataSource)) .packages("com.infinitus.yunxiao_data.entity.primary") //设置实体类所在位置 .persistenceUnit("primaryPersistenceUnit") .build(); } private Map getVendorProperties(DataSource dataSource) { return jpaProperties.getHibernateProperties(dataSource); } @Primary @Bean(name = "transactionManagerPrimary") public PlatformTransactionManager transactionManagerPrimary(EntityManagerFactoryBuilder builder) { return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject()); }}从库的配置类：
@Configuration@EnableTransactionManagement@EnableJpaRepositories( entityManagerFactoryRef = "entityManagerFactorySecondary", transactionManagerRef = "transactionManagerSecondary", basePackages = {"com.infinitus.yunxiao_data.dao.secondary"}) //设置Repository所在位置public class SecondaryConfig { @Autowired private JpaProperties jpaProperties; @Autowired @Qualifier("secondaryDataSource") private DataSource secondaryDataSource; @Bean(name = "entityManagerSecondary") public EntityManager entityManager(EntityManagerFactoryBuilder builder) { return entityManagerFactorySecondary(builder).getObject().createEntityManager(); } @Bean(name = "entityManagerFactorySecondary") public LocalContainerEntityManagerFactoryBean entityManagerFactorySecondary(EntityManagerFactoryBuilder builder) { return builder .dataSource(secondaryDataSource) .properties(getVendorProperties(secondaryDataSource)) .packages("com.infinitus.yunxiao_data.entity.secondary") //设置实体类所在位置 .persistenceUnit("primaryPersistenceUnit") .build(); } private Map getVendorProperties(DataSource dataSource) { return jpaProperties.getHibernateProperties(dataSource); } @Bean(name = "transactionManagerSecondary") PlatformTransactionManager transactionManagerSecondary(EntityManagerFactoryBuilder builder) { return new JpaTransactionManager(entityManagerFactorySecondary(builder).getObject()); }}4.分别创建主、从库dao类。
主dao：
@Repositorypublic interface PrimaryRepository extends JpaRepository<PrimaryEntity, Long> { @Query(value = "SELECT p FROM PrimaryEntity p") List<PrimaryEntity> queryList();}从dao：
@Repositorypublic interface SecondaryRepository extends JpaRepository<SecondaryEntity, Long> { @Query(value = "SELECT p FROM SecondaryEntity p") List<SecondaryEntity> queryList();}5.分别创建主、从库entity类。
主entity：
@Entity@Table(name = "holiday_scheme")@EntityListeners(AuditingEntityListener.class)public class PrimaryEntity extends AbstractPersistable<Long> { @Column(name = "date") public String date; @Column(name = "hour") public String hour; @Column(name = "holiday") public String holiday; @Column(name = "holiday_explain") public String holiday_explain; public String getDate() { return date; } public void setDate(String date) { this.date = date; } public String getHour() { return hour; } public void setHour(String hour) { this.hour = hour; } public String getHoliday() { return holiday; } public void setHoliday(String holiday) { this.holiday = holiday; } public String getHoliday_explain() { return holiday_explain; } public void setHoliday_explain(String holiday_explain) { this.holiday_explain = holiday_explain; } @Override public String toString() { return "PrimaryEntity{" + "date='" + date + '/'' + ", hour='" + hour + '/'' + ", holiday='" + holiday + '/'' + ", holiday_explain='" + holiday_explain + '/'' + '}'; }}从entity：
@Entity@Table(name = "active_dashboards")@EntityListeners(AuditingEntityListener.class)public class SecondaryEntity extends AbstractPersistable<Long> { @Column(name = "dashboard_id") public String dashboard_id; @Column(name = "user_id") public String user_id; @Column(name = "order_index") public String order_index; public String getDashboard_id() { return dashboard_id; } public void setDashboard_id(String dashboard_id) { this.dashboard_id = dashboard_id; } public String getUser_id() { return user_id; } public void setUser_id(String user_id) { this.user_id = user_id; } public String getOrder_index() { return order_index; } public void setOrder_index(String order_index) { this.order_index = order_index; } @Override public String toString() { return "SecondaryEntity{" + "dashboard_id='" + dashboard_id + '/'' + ", user_id='" + user_id + '/'' + ", order_index='" + order_index + '/'' + '}'; }}6.controller请求获取不同数据库的数据。
@RestController@RequestMapping("/database")public class MailController { private final Logger logger = LoggerFactory.getLogger(this.getClass()); @Autowired PrimaryRepository primaryRepository; @Autowired SecondaryRepository secondaryRepository; @RequestMapping("/primary") @ResponseBody public String primary() { return primaryRepository.queryList().toString(); } @RequestMapping("/secondary") @ResponseBody public String secondary() { return secondaryRepository.queryList().toString(); }}注意
下面提两个在配置多数据源时遇到的坑点，一不注意就掉坑了。
1.Application类不需要配置@EnableJpaRepositories注解，会报如下错误。
A component required a bean named 'entityManagerFactory' that could not be f
2.注意检查dao类，获取数据的方法上格式是否正确，有没有某个字段是表中不存在的，避免启动异常。如下，SecondaryEntity表中是不存在job_name字段的，所以注释掉才能启动成功等。
//@Query(value = "SELECT p FROM SecondaryEntity p where p.job_name = ?1")//List<SecondaryEntity> queryOdcRecord(String job_name);
总结
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