Spring Data与多数据源配置

Spring Data与多数据源配置

大家好，我是免费搭建查券返利机器人省钱赚佣金就用微赚淘客系统3.0的小编，也是冬天不穿秋裤，天冷也要风度的程序猿！今天我们来探讨如何在Spring Data中配置和使用多个数据源。

在现代应用程序中，处理多个数据源变得越来越常见。可能因为不同的数据存储需求，例如读写分离、跨系统数据访问，或者集成多个数据库系统。本文将详细讲解如何在Spring Boot中使用Spring Data配置多个数据源，并提供具体的Java代码示例。

一、项目依赖

首先，我们需要在pom.xml中添加Spring Boot、Spring Data JPA以及数据库驱动的依赖。

<dependencies>
    <!-- Spring Boot Starter Data JPA -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <!-- H2 Database -->
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
    </dependency>
    <!-- MySQL Database -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
</dependencies>

二、配置多数据源

我们将配置两个数据源：一个用于H2数据库，另一个用于MySQL数据库。

1. 配置文件

在application.yml中配置数据源信息。

spring:
  datasource:
    h2:
      url: jdbc:h2:mem:testdb
      driver-class-name: org.h2.Driver
      username: sa
      password: password
    mysql:
      url: jdbc:mysql://localhost:3306/testdb
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: root
      password: password
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.dialect.H2Dialect
        format_sql: true

2. 数据源配置类

我们需要为每个数据源创建单独的配置类。

package cn.juwatech.config;

import org.springframework.beans.factory.annotation.Qualifier;
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 org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;

@Configuration
@EnableTransactionManagement
public class DataSourceConfig {

    @Primary
    @Bean(name = "h2DataSource")
    @ConfigurationProperties(prefix = "spring.datasource.h2")
    public DataSource h2DataSource() {
        return DataSourceBuilder.create().build();
    }

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

    @Primary
    @Bean(name = "h2EntityManagerFactory")
    public LocalContainerEntityManagerFactoryBean h2EntityManagerFactory(@Qualifier("h2DataSource") DataSource dataSource) {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource);
        em.setPackagesToScan("cn.juwatech.model.h2");
        em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        em.setPersistenceUnitName("h2PU");
        return em;
    }

    @Bean(name = "mysqlEntityManagerFactory")
    public LocalContainerEntityManagerFactoryBean mysqlEntityManagerFactory(@Qualifier("mysqlDataSource") DataSource dataSource) {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource);
        em.setPackagesToScan("cn.juwatech.model.mysql");
        em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        em.setPersistenceUnitName("mysqlPU");
        return em;
    }

    @Primary
    @Bean(name = "h2TransactionManager")
    public PlatformTransactionManager h2TransactionManager(@Qualifier("h2EntityManagerFactory") EntityManagerFactory entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory);
    }

    @Bean(name = "mysqlTransactionManager")
    public PlatformTransactionManager mysqlTransactionManager(@Qualifier("mysqlEntityManagerFactory") EntityManagerFactory entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory);
    }
}

3. 启用JPA仓库

为每个数据源分别配置JPA仓库。

package cn.juwatech.config;

import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@Configuration
@EnableJpaRepositories(
        basePackages = "cn.juwatech.repository.h2",
        entityManagerFactoryRef = "h2EntityManagerFactory",
        transactionManagerRef = "h2TransactionManager"
)
@EntityScan(basePackages = "cn.juwatech.model.h2")
public class H2DataSourceConfig {
}

@Configuration
@EnableJpaRepositories(
        basePackages = "cn.juwatech.repository.mysql",
        entityManagerFactoryRef = "mysqlEntityManagerFactory",
        transactionManagerRef = "mysqlTransactionManager"
)
@EntityScan(basePackages = "cn.juwatech.model.mysql")
public class MysqlDataSourceConfig {
}

三、定义实体类

在不同的包中定义不同数据源的实体类。

package cn.juwatech.model.h2;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class H2Entity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    // getters and setters
}

package cn.juwatech.model.mysql;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class MysqlEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    // getters and setters
}

四、定义仓库接口

为每个数据源定义对应的仓库接口。

package cn.juwatech.repository.h2;

import cn.juwatech.model.h2.H2Entity;
import org.springframework.data.jpa.repository.JpaRepository;

public interface H2EntityRepository extends JpaRepository<H2Entity, Long> {
}

package cn.juwatech.repository.mysql;

import cn.juwatech.model.mysql.MysqlEntity;
import org.springframework.data.jpa.repository.JpaRepository;

public interface MysqlEntityRepository extends JpaRepository<MysqlEntity, Long> {
}

五、测试多数据源配置

最后，我们编写一个测试类，验证多数据源配置是否成功。

package cn.juwatech;

import cn.juwatech.model.h2.H2Entity;
import cn.juwatech.model.mysql.MysqlEntity;
import cn.juwatech.repository.h2.H2EntityRepository;
import cn.juwatech.repository.mysql.MysqlEntityRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MultiDataSourceApplication implements CommandLineRunner {

    @Autowired
    private H2EntityRepository h2EntityRepository;

    @Autowired
    private MysqlEntityRepository mysqlEntityRepository;

    public static void main(String[] args) {
        SpringApplication.run(MultiDataSourceApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        H2Entity h2Entity = new H2Entity();
        h2Entity.setName("H2 Entity");
        h2EntityRepository.save(h2Entity);

        MysqlEntity mysqlEntity = new MysqlEntity();
        mysqlEntity.setName("MySQL Entity");
        mysqlEntityRepository.save(mysqlEntity);

        System.out.println("H2 Entities: " + h2EntityRepository.findAll());
        System.out.println("MySQL Entities: " + mysqlEntityRepository.findAll());
    }
}