Spring AbstractRoutingDatasource 动态数据源的实例讲解

public enum ClientDatabase {
    CLIENT_A, CLIENT_B
}

public class ClientDatabaseContextHolder {
    private static ThreadLocal<ClientDatabase> CONTEXT  = new ThreadLocal<>();
    public static void set(ClientDatabase clientDatabase) {
        Assert.notNull(clientDatabase, "clientDatabase cannot be null");
        CONTEXT.set(clientDatabase);
    }
    public static ClientDatabase getClientDatabase() {
        return CONTEXT.get();
    }
    public static void clear() {
        CONTEXT.remove();
    }
}

public class ClientDataSourceRouter extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return ClientDatabaseContextHolder.getClientDatabase();
    }
}

@Configuration
public class RoutingTestConfiguration {
    @Bean
    public ClientService clientService() {
        return new ClientService(new ClientDao(clientDatasource()));
    }
 
    @Bean
    public DataSource clientDatasource() {
        Map<Object, Object> targetDataSources = new HashMap<>();
        DataSource clientADatasource = clientADatasource();
        DataSource clientBDatasource = clientBDatasource();
        targetDataSources.put(ClientDatabase.CLIENT_A, clientADatasource);
        targetDataSources.put(ClientDatabase.CLIENT_B, clientBDatasource);
        ClientDataSourceRouter clientRoutingDatasource  = new ClientDataSourceRouter();
        clientRoutingDatasource.setTargetDataSources(targetDataSources);
        clientRoutingDatasource.setDefaultTargetDataSource(clientADatasource);        
        return clientRoutingDatasource;
    }
    // ...
}

public class ClientDao {
    private static final String SQL_GET_CLIENT_NAME = "select name from client";
    private final JdbcTemplate jdbcTemplate;
    public ClientDao(DataSource datasource) {
        this.jdbcTemplate = new JdbcTemplate(datasource);
    }
    public String getClientName() {
        return this.jdbcTemplate.query(SQL_GET_CLIENT_NAME, rowMapper).get(0);
    }
    private static RowMapper<String> rowMapper = (rs, rowNum) -> {
        return rs.getString("name");
    };
}

public class ClientService {
    private final ClientDao clientDao;
    public ClientService(ClientDao clientDao) {
        this.clientDao = clientDao;
    }
    public String getClientName(ClientDatabase clientDb) {
        ClientDatabaseContextHolder.set(clientDb);
        String clientName = this.clientDao.getClientName();
        ClientDatabaseContextHolder.clear();
        return clientName;
    }
}