本文章使用的是持久化框架为JPA，所以数据源也是基于JPA。采用的是SpringBoot2 + SpringDataJPA + MySQL + 双数据源！
一、双数据源的适用场景：
1、主从库分离（数据库读写分离）
2、数据迁移
3、系统版本升级，数据库升级到另外一款
二、application.yml中配置
spring:
jpa:
hibernate:
ddl-auto: create
naming:
physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
implicit-strategy: org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy
open-in-view: true
show-sql: true
generate-ddl: true
datasource: #database
primary: # 3.0 Datasource
jdbc-url: jdbc:mysql://127.0.0.1:3306/gtu?characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai
username: root
password: 123456
secondary: # 2.0 Datasource
jdbc-url: jdbc:mysql://127.0.0.1:3306/gtu-not-completed?characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai
username: root
password: 123456
注：配置文件中需要指定两个数据源，这里在配置的时候是没有自动提示的，因为这是我们自定义的，需要在程序中动态读取。
三、读取application.yml配置的两个数据源，并将其注入到Spring的IOC容器中
@Configuration
public class DataSourceConfig {
@Bean(name = "primaryDataSource")
@Qualifier("primaryDataSource")
@Primary
@ConfigurationProperties(prefix = "spring.datasource.primary")
public DataSource primaryDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "secondaryDataSource")
@Qualifier("secondaryDataSource")
@ConfigurationProperties(prefix = "spring.datasource.secondary")
public DataSource secondaryDataSource() {
return DataSourceBuilder.create().build();
}
}
注解解释：
@Configuration：SpringBoot启动将该类作为配置类，同配置文件一起加载
@Bean：将该实体注入到IOC容器中
@Qualifier：指定数据源名称，与Bean中的name属性原理相同，主要是为了确保注入成功
@Primary：指定主数据源
@ConfigurationProperties：将配置文件中的数据源读取进到方法中，进行build
四、以类的方式配置两个数据源
（1）主数据源（对应DataSourceConfig类中的primaryDataSource）
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactoryPrimary",
transactionManagerRef = "transactionManagerPrimary",
basePackages = {"com.gtcloud.repository"}) // 指定该数据源操作的DAO接口包
public class PrimaryConfig {
@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())
.packages("com.gtcloud.model") //设置实体类所在位置
.persistenceUnit("primaryPersistenceUnit")
.build();
}
private Map getVendorProperties() {
HashMap<String, Object> properties = new HashMap<>();
properties.put("hibernate.dialect",
env.getProperty("hibernate.dialect"));
properties.put("hibernate.ddl-auto",
"create");
properties.put("hibernate.physical_naming_strategy",
"org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy");
properties.put("hibernate.implicit_naming_strategy",
"org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy");
return properties;
}
@Autowired
private Environment env;
@Primary
@Bean(name = "transactionManagerPrimary")
public PlatformTransactionManager transactionManagerPrimary(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject());
}
}
（2）从（次）数据源
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactorySecondary",
transactionManagerRef = "transactionManagerSecondary",
basePackages = {"com.gtmove.repository"}) //设置DAO接口层所在包位置
public class SecondaryConfig {
@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())
.packages("com.gtmove.model") //设置实体类所在包的位置
.persistenceUnit("primaryPersistenceUnit")
.build();
}
private Map getVendorProperties() {
HashMap<String, Object> properties = new HashMap<>();
properties.put("hibernate.hbm2ddl.auto",
env.getProperty("hibernate.hbm2ddl.auto"));
properties.put("hibernate.ddl-auto",
env.getProperty("update"));
properties.put("hibernate.dialect",
env.getProperty("hibernate.dialect"));
properties.put("hibernate.physical_naming_strategy",
"org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy");
properties.put("hibernate.implicit_naming_strategy",
"org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy");
return properties;
}
@Autowired
private Environment env;
@Bean(name = "transactionManagerSecondary")
PlatformTransactionManager transactionManagerSecondary(EntityManagerFactoryBuilder builder) {
return new JpaTransactionManager(entityManagerFactorySecondary(builder).getObject());
}
}
这两个类主要配置每个数据源，包括事务管理器、以及实体管理器等配置。
注：必须要指定DAO接口所在的包以及实体类所在的包。每个数据源主要操作它指定的资源（DAO接口CURD、实体类）
五、注意点：
1、SpringBoot启动类必须关闭 --程序启动加载的仓库（@EnableJpaRepositories），因为在数据源配置类中已经开启了。如果没有去掉，程序会跑不起来！
@SpringBootApplication(scanBasePackages = {""}) // 指定加载程序主包，存在默认值【可选】
//@EntityScan({""})
//@EnableJpaRepositories(basePackages = {""})
public class Gt3datamoverApplication {
public static void main(String[] args) {
SpringApplication.run(Gt3datamoverApplication.class, args);
}
}
2、如果需要对数据源连接的表进行DDL（正向生成表、程序启动动态更新表），需要在PrimaryConfig类中 / SecondaryConfig类中的getVendorProperties()方法中进行手动设置（此教程都已设置好了！）