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一、前言

springboot版本不同对多数据源配置代码有一定影响，部分方法和配置略有不同。
本文采用的springboot版本为2.3.12，数据源为mysql和postgresql

二、配置实战

2.1 基础pom

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter</artifactId>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-test</artifactId>
		<scope>test</scope>
	</dependency>
	<dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>5.1.21</version>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-data-jpa</artifactId>
	</dependency>
	<dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>${ 
   mysql.version}</version>
	</dependency>
</dependencies>

2.2 配置文件

spring.datasource.mysql.jdbc-url=jdbc:mysql://localhost:3306/heilongjiang?characterEncoding=UTF-8&useSSL=false&useTimezone=true&serverTimezone=GMT%2B8
spring.datasource.mysql.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.mysql.username=root
spring.datasource.mysql.password=123456

spring.datasource.pg.jdbc-url=jdbc:postgresql://localhost:5432/hljsyjt?useUnicode=true&characterEncoding=utf8&currentSchema=emergencydev,expert,public
spring.datasource.pg.driver-class-name=org.postgresql.Driver
spring.datasource.pg.username=postgres
spring.datasource.pg.password=postgres

spring.jpa.properties.hibernate.mysql-dialect=org.hibernate.dialect.MySQLDialect
spring.jpa.properties.hibernate.pg-dialect=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults=false

2.3 数据源配置类

package com.gsafety.bg.industrial.config;

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 javax.sql.DataSource;


/** * @author Mr.wanter * @time 2021-8-11 0011 * @description */

@Configuration
public class DataSourceConfig { 
   

    @Bean("dataSourceMysql")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.mysql")
    public DataSource dataSourceMysql() { 
   
        return DataSourceBuilder.create().build();
    }


    @Bean("dataSourcePg")
    @ConfigurationProperties(prefix = "spring.datasource.pg")
    public DataSource dataSourcePg() { 
   
        return DataSourceBuilder.create().build();
    }
}

2.4 数据源指定配置类

mysql指定数据源：

package com.gsafety.bg.industrial.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;
/** * @author Mr.wanter * @time 2021-8-11 0011 * @description */
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactoryMysql",//配置连接工厂 entityManagerFactory
transactionManagerRef = "transactionManagerMysql", //配置 事物管理器 transactionManager
basePackages = { 
"com.gsafety.bg.industrial.dao"}//设置持久层所在位置
)
public class MysqlDataSourceConfig { 

@Autowired
private JpaProperties jpaProperties;
@Autowired
private HibernateProperties hibernateProperties;
// 自动注入配置好的数据源
@Autowired
@Qualifier("dataSourceMysql")
private DataSource mysqlDataSource;
// 获取对应的数据库方言
@Value("${spring.jpa.properties.hibernate.mysql-dialect}")
private String mysqlDialect;
/** * @param builder * @return */
@Bean(name = "entityManagerFactoryMysql")
@Primary
public LocalContainerEntityManagerFactoryBean entityManagerFactoryMysql(EntityManagerFactoryBuilder builder) { 

Map<String, String> map = new HashMap<>();
// 设置对应的数据库方言
map.put("hibernate.dialect", mysqlDialect);
jpaProperties.setProperties(map);
Map<String, Object> properties = hibernateProperties.determineHibernateProperties(
jpaProperties.getProperties(), new HibernateSettings());
return builder
//设置数据源
.dataSource(mysqlDataSource)
//设置数据源属性
.properties(properties)
//设置实体类所在位置.扫描所有带有 @Entity 注解的类
.packages("com.gsafety.bg.industrial.dao.po")
// Spring会将EntityManagerFactory注入到Repository之中.有了 EntityManagerFactory之后,
// Repository就能用它来创建 EntityManager 了,然后 EntityManager 就可以针对数据库执行操作
.persistenceUnit("mysqlPersistenceUnit")
.build();
}
/** * 配置事物管理器 * * @param builder * @return */
@Bean(name = "transactionManagerMysql")
@Primary
PlatformTransactionManager transactionManagerMysql(EntityManagerFactoryBuilder builder) { 

return new JpaTransactionManager(entityManagerFactoryMysql(builder).getObject());
}
}

pg指定数据源：

package com.gsafety.bg.industrial.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;
/** * @author Mr.wanter * @time 2021-8-11 0011 * @description */
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
entityManagerFactoryRef = "entityManagerFactoryPg",//配置连接工厂 entityManagerFactory
transactionManagerRef = "transactionManagerPg", //配置 事物管理器 transactionManager
basePackages = { 
"com.gsafety.bg.data.dao"}//设置持久层所在位置
)
public class PgDataSourceConfig { 

@Autowired
private JpaProperties jpaProperties;
@Autowired
private HibernateProperties hibernateProperties;
//自动注入配置好的数据源
@Autowired
@Qualifier("dataSourcePg")
private DataSource PgDataSource;
// 获取对应的数据库方言
@Value("${spring.jpa.properties.hibernate.pg-dialect}")
private String pgDialect;
/** * @param builder * @return */
@Bean(name = "entityManagerFactoryPg")
public LocalContainerEntityManagerFactoryBean entityManagerFactoryPg(EntityManagerFactoryBuilder builder) { 

Map<String, String> map = new HashMap<>();
// 设置对应的数据库方言
map.put("hibernate.dialect", pgDialect);
jpaProperties.setProperties(map);
Map<String, Object> properties = hibernateProperties.determineHibernateProperties(
jpaProperties.getProperties(), new HibernateSettings());
return builder
//设置数据源
.dataSource(PgDataSource)
//设置数据源属性
.properties(properties)
//设置实体类所在位置.扫描所有带有 @Entity 注解的类
.packages("com.gsafety.bg.data.dao.po")
// Spring会将EntityManagerFactory注入到Repository之中.有了 EntityManagerFactory之后,
// Repository就能用它来创建 EntityManager 了,然后 EntityManager 就可以针对数据库执行操作
.persistenceUnit("pgPersistenceUnit")
.build();
}
/** * 配置事物管理器 * * @param builder * @return */
@Bean(name = "transactionManagerPg")
PlatformTransactionManager transactionManagerPg(EntityManagerFactoryBuilder builder) { 

return new JpaTransactionManager(entityManagerFactoryPg(builder).getObject());
}
}

2.5 如何应用

数据源配置类中指定了扫描po和dao包的路径
例如entityManagerFactoryPg中的com.gsafety.bg.data.dao.po和com.gsafety.bg.data.dao
那么我们只需要在指定的包下创建po和dao即可，service包层次不受影响，自定义即可。
三数据源同理即可。
左侧为双数据源（与本篇实战内容一致），右侧为三数据源（三数据源目录结构示例）。

其他编码常规开发即可
po：

@Entity
@Builder
@Data
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "jc_repertory")
public class JcRepertoryPO implements Serializable { 

//some fields
}

dao：

public interface JcRepertoryDao extends JpaRepository<JcRepertoryPO, String>, JpaSpecificationExecutor<JcRepertoryPO> { 

}

service：

public interface JcRepertoryService { 

List<JcRepertoryPO> list();
}

@Service
public class JcRepertoryServiceImpl implements JcRepertoryService { 

@Resource
private JcRepertoryDao jcRepertoryDao;
@Override
public List<JcRepertoryPO> list() { 

List<JcRepertoryPO> all = jcRepertoryDao.findAll();
return all;
}
}

controller 略
启动类添加扫描@SpringBootApplication_(_scanBasePackages = _{_"com.gsafety.bg.data", "com.gsafety.bg.industrial"_})_

三、遇到的问题

1. 数据库连接报错 jdbcUrl is required with driverClassName

主要原因是在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

spring.datasource.pg.jdbc-url=jdbc:postgresql://localhost:5432/hljsyjt?useUnicode=true&characterEncoding=utf8&currentSchema=emergencydev,expert,public
spring.datasource.pg.driver-class-name=org.postgresql.Driver

2. Paging query needs to have a Pageable parameter!

原系统中对jap的Repository进行了封装，采用常规方式调用即可。

3. more than one ‘primary’ bean found among candidates

2.4 数据源指定配置类 中只有一个类中的方法添加 @Primary 另外一个不要加这个注解

4. 互联网查询的代码中JpaProperties没有getHibernateProperties

与springboot版本有关，上面代码已修改。