mysql做读写分离实操示例

在Java项目中实现MySQL读写分离需要进行一系列配置和代码编写。以下是一般的实施步骤，以Spring框架为例：

1. 添加依赖：

<dependencies>
    
    <dependency>
        <groupId>mysqlgroupId>
        <artifactId>mysql-connector-javaartifactId>
        <version>8.0.23version> 
    dependency>

    
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-data-jpaartifactId>
    dependency>
dependencies>

2. 配置数据源和事务：

// DataSourceConfig.java
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
    basePackages = "com.example.repository",
    entityManagerFactoryRef = "entityManagerFactory",
    transactionManagerRef = "transactionManager"
)
public class DataSourceConfig {

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

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

    @Primary
    @Bean(name = "entityManagerFactory")
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(
            EntityManagerFactoryBuilder builder,
            @Qualifier("masterDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages("com.example.domain")
                .persistenceUnit("master")
                .build();
    }

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

3. 创建实体类和DAO：

// User.java
@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String username;

    private String email;

    // Getters and setters...
}

// UserRepository.java
@Repository
public interface UserRepository extends JpaRepository<User, Long> {

    // 读操作
    @Query(value = "SELECT * FROM user WHERE id = :id", nativeQuery = true)
    User findUserById(@Param("id") Long id);

    // 写操作
    @Modifying
    @Query(value = "INSERT INTO user (username, email) VALUES (:username, :email)", nativeQuery = true)
    void saveUser(@Param("username") String username, @Param("email") String email);
}

4. Service层使用DAO进行读写操作：

// UserService.java
@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    @Transactional(readOnly = true)
    public User getUserById(Long id) {
        // 读操作，使用从数据库
        return userRepository.findUserById(id);
    }

    @Transactional
    public void saveUser(String username, String email) {
        // 写操作，使用主数据库
        userRepository.saveUser(username, email);
    }
}

在这个例子中，UserRepository中的findUserById方法使用从数据库进行读操作，而saveUser方法使用主数据库进行写操作。

这样，通过配置数据源和事务管理，以及在DAO层实施读写分离策略，你就能在Java项目中成功实现MySQL读写分离。确保在实际项目中根据具体情况进行适当的调整和优化。