帮我写一份使用DS注解同时操作两个数据库的完整Java代码

好的，以下是一份使用@DS注解同时操作两个数据库的Java代码：

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    @Autowired
    private OrderMapper orderMapper;

    @DS("db1")
    public List<User> getUsers() {
        return userMapper.getUsers();
    }

    @DS("db2")
    public List<Order> getOrders() {
        return orderMapper.getOrders();
    }

    @DS("db1")
    public void addUser(User user) {
        userMapper.addUser(user);
    }

    @DS("db2")
    public void addOrder(Order order) {
        orderMapper.addOrder(order);
    }
}

@Mapper
public interface UserMapper {
    @Select("SELECT * FROM user")
    List<User> getUsers();
    @Insert("INSERT INTO user(name, age) VALUES(#{name}, #{age})")
    void addUser(User user);
}

@Mapper
public interface OrderMapper {
    @Select("SELECT * FROM order")
    List<Order> getOrders();
    @Insert("INSERT INTO order(name, price) VALUES(#{name}, #{price})")
    void addOrder(Order order);
}

@Configuration
public class DataSourceConfig {

    @Primary
    @Bean(name = "db1DataSource")
    @ConfigurationProperties(prefix = "spring.datasource.db1")
    public DataSource db1DataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "db2DataSource")
    @ConfigurationProperties(prefix = "spring.datasource.db2")
    public DataSource db2DataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "dynamicDataSource")
    public DataSource dynamicDataSource() {
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        Map<Object, Object> dataSourceMap = new HashMap<>();
        dataSourceMap.put("db1", db1DataSource());
        dataSourceMap.put("db2", db2DataSource());
        dynamicDataSource.setTargetDataSources(dataSourceMap);
        dynamicDataSource.setDefaultTargetDataSource(db1DataSource());
        return dynamicDataSource;
    }

    @Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(dynamicDataSource());
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/**/*.xml"));
        return sessionFactory.getObject();
    }

    @Bean
    public SqlSessionTemplate sqlSessionTemplate() throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory());
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource {

    @Override
    protected Object determineCurrentLookupKey() {
        return DbContextHolder.getDbType();
    }
}

public class DbContextHolder {
    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

    public static void setDbType(String dbType) {
        contextHolder.set(dbType);
    }

    public static String getDbType() {
        return contextHolder.get();
    }

    public static void clearDbType() {
        contextHolder.remove();
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.TYPE})
public @interface DS {
    String value() default "db1";
}

在这份代码中，我们使用了@DS注解来标记不同的方法需要使用哪个数据库。同时，我们也实现了动态数据源的功能，使得我们可以同时操作两个不同的数据库。

需要注意的是，在使用@DS注解时，我们需要保证注解的值与DataSourceConfig中配置的dataSourceMap的Key值相同，否则将会出现数据源找不到的问题。

另外，我们还需要在每个请求结束后手动清空DbContextHolder中的DbType，以免影响下一次请求。