如何在Spring Boot中配置Cassandra与MySQL实现按请求参数切换数据源

1. 引入必要依赖 #

在项目的pom.xml中加入两个数据库对应的starter依赖：

<!-- MySQL 相关依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <scope>runtime</scope>
</dependency>

<!-- Cassandra 相关依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-cassandra</artifactId>
</dependency>

2. 编写数据源配置 #

在application.yml中分别配置两个数据库的连接参数，避免前缀冲突：

# MySQL 配置
spring:
  datasource:
    mysql:
      jdbc-url: jdbc:mysql://localhost:3306/你的库名?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8
      username: root
      password: 你的MySQL密码
      driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    mysql:
      hibernate:
        ddl-auto: update
      show-sql: true
      properties:
        hibernate:
          dialect: org.hibernate.dialect.MySQL8Dialect

# Cassandra 配置
  data:
    cassandra:
      contact-points: 127.0.0.1
      port: 9042
      keyspace-name: 你的Cassandra keyspace名称
      username: cassandra
      password: 你的Cassandra密码
      local-datacenter: datacenter1
      schema-action: CREATE_IF_NOT_EXISTS

3. 编写MySQL数据源配置类 #

通过配置类单独扫描MySQL对应的实体和Repository包，添加@Primary注解标记MySQL为默认数据源避免冲突：

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        basePackages = "com.xxx.demo.mysql.repository", // 替换为你的MySQL Repository包路径
        entityManagerFactoryRef = "mysqlEntityManagerFactory",
        transactionManagerRef = "mysqlTransactionManager"
)
public class MysqlDataSourceConfig {

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

    @Bean
    @Primary
    public LocalContainerEntityManagerFactoryBean mysqlEntityManagerFactory(
            EntityManagerFactoryBuilder builder) {
        return builder
                .dataSource(mysqlDataSource())
                .packages("com.xxx.demo.mysql.entity") // 替换为你的MySQL实体类包路径
                .persistenceUnit("mysqlPersistenceUnit")
                .properties(Map.of("hibernate.dialect", "org.hibernate.dialect.MySQL8Dialect",
                        "hibernate.hbm2ddl.auto", "update",
                        "show-sql", true))
                .build();
    }

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

4. 编写Cassandra数据源配置类 #

单独配置Cassandra的连接属性和扫描路径：

@Configuration
@EnableCassandraRepositories(basePackages = "com.xxx.demo.cassandra.repository") // 替换为你的Cassandra Repository包路径
public class CassandraConfig extends AbstractCassandraConfiguration {

    @Value("${spring.data.cassandra.keyspace-name}")
    private String keyspaceName;
    @Value("${spring.data.cassandra.contact-points}")
    private String contactPoints;
    @Value("${spring.data.cassandra.port}")
    private int port;
    @Value("${spring.data.cassandra.local-datacenter}")
    private String localDatacenter;
    @Value("${spring.data.cassandra.username}")
    private String username;
    @Value("${spring.data.cassandra.password}")
    private String password;

    @Override
    protected String getKeyspaceName() {
        return keyspaceName;
    }

    @Override
    protected String getContactPoints() {
        return contactPoints;
    }

    @Override
    protected int getPort() {
        return port;
    }

    @Override
    protected String getLocalDataCenter() {
        return localDatacenter;
    }

    @Override
    protected CqlSessionFactoryBean session() {
        CqlSessionFactoryBean session = super.session();
        session.setUsername(username);
        session.setPassword(password);
        return session;
    }

    @Override
    protected String[] getEntityBasePackages() {
        return new String[]{"com.xxx.demo.cassandra.entity"}; // 替换为你的Cassandra实体类包路径
    }

    @Override
    protected SchemaAction getSchemaAction() {
        return SchemaAction.CREATE_IF_NOT_EXISTS;
    }
}

5. 分层存放代码 #

按包路径区分两个数据库的相关代码，避免扫描冲突：

• MySQL实体类存放在com.xxx.demo.mysql.entity包，Repository接口存放在com.xxx.demo.mysql.repository包，示例如下：

@Repository
public interface MysqlRepository extends JpaRepository<你的MySQL实体类, Integer> {
}

• Cassandra实体类存放在com.xxx.demo.cassandra.entity包，Repository接口存放在com.xxx.demo.cassandra.repository包，示例如下：

@Repository
public interface CassandraRepository extends CassandraRepository<你的Cassandra实体类, Integer> {
}

6. 修正原有接口代码 #

原代码存在路径未加占位符、字符串比较用==、类型不匹配三个问题，修正后如下：

@RestController
public class DataController {
    @Autowired
    private MysqlRepository sqlRepository;
    @Autowired
    private CassandraRepository cassandraRepository;

    @PostMapping(value = "/data/{type}")
    public Object getDataByDB(@PathVariable("type") String type) {
        int id = 123;
        if("Cassandra".equals(type)) {
            return cassandraRepository.findById(id).orElse(null);
        } else if("MySQL".equals(type)) {
            return sqlRepository.findById(id).orElse(null);
        }
        return "不支持的数据库类型";
    }
}

内容的提问来源于stack exchange，提问作者Susmitha