使用策略模式解决代码中If elseIf与Switch Case问题

策略模式+工厂方法 实现多分支操作(代替多个if else)或是Switch Case情况。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;



/**
 *  
 *
 */
@Service
public class CommonSyncService implements ICommonSyncService{
	/** 日志打印 */
	private static final Logger LOGGER = LoggerFactory.getLogger(CommonSyncService.class);
	
	/** 对应base_bdm表的service处理层 */
	@Autowired
	private IBaseBdmService baseBdmService;
	/** 对应base_dad表的service处理层 */
	@Autowired
	private IBaseDadService baseDadService;
	/** 对应base_net表的service处理层 */
	@Autowired
	private IBaseNetService baseNetService;
	/** 对应base_sys表的service处理层 */
	@Autowired
	private IBaseSysService baseSysService;
	/** 对应product表的service处理层 */
	@Autowired
	private IProductService productService;
	/** 对应wms表的service处理层 */
	@Autowired
	private IWmsService wmsService;
	/** 对应user表的service处理层 */
	@Autowired
	private IUserSysEmployeeService userSysEmployeeService;
	/** 对应route表的service处理层  */
	@Autowired
	private IRouteService routeService;
	
	/**
	 * 数据同步-移动端
	 * 公共的服务层处理方法
	 * @param tableName 表名
	 * @param lastTime 最后修改时间
	 * @param startIndex 页数
	 * @param pageSize 当前页显示的条数
	 * @param cdstatus 查询条件comp_code(公司编码,默认值为all)
	 * @return
	 */
	public SyncServerResult commonCallSyncService(String tableName ,String lastTime,
										int startIndex, int pageSize,String cdstatus){
		SyncServerResult result = null;
		
		//通过表名调用service层
		switch (tableName) {
		  case Constants.TableConstants.BASE_NET_DEPT_BASE_INFO:
			/**
			 * hanyg
			 * 部门网点信息base_net_dept_base_info
			 */
			 result = baseNetService.getDeptBaseInfoSyncServerData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;

		  case Constants.TableConstants.BASE_BDM_QC_TYPE:
			/**
			 * hanyg
			 * 问题件异常类型base_bdm_qc_type
			 */
			result = baseBdmService.getQcTypeSyncServerData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.BASE_SYS_COMPANY:
			/** 
			 * 账号base_sys_company
			 */
			result = baseSysService.getSyncSysCompanyServerData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
			
		  case Constants.TableConstants.BASE_NET_DISTRICT:
			/** 
			 * 行政区域base_net_district
			 */
			result = baseNetService.getSyncNetDistrictServerData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
			
		  case Constants.TableConstants.BASE_BDM_FORWARD_ZONE:
			/** 
			 * 查询 转寄地base_bdm_forward_zone表
			 */
			result = baseBdmService.getForwardZoneSyncData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.BASE_DAD_DICTIONARY_VALUE:
			/** 
			 * 查询 数据字典base_dad_dictionary_value表
			 */
			result = baseDadService.getDictionarySyncData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
			
		  case Constants.TableConstants.BASE_BDM_PRODUCT_TYPE:
			/** 
			 * 查询 货物品类维护base_bdm_product_type表
			 */
			result = baseBdmService.getProductTypeSyncData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
			
		  case Constants.TableConstants.BASE_BDM_PRODUCT_TYPE_APPLY:
			/** 
			 * 查询 货物品类管理base_bdm_product_type_apply表
			 */
			result = baseBdmService.getProductTypeApplySyncData(tableName,lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.BASE_BDM_PRINT_CONFIG:
			/** 
			 * 查询 (打印配置)base_bdm_print_config表数据
			 */
			result = baseBdmService.getPrintConfigSyncServerData(tableName ,lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.BASE_BDM_WEIGHT_VOLUMN_RATIO:
			/** 
			 * 查询 (重量体积比率)base_bdm_weight_volumn_ratio表数据
			 */
			result = baseBdmService.getWeightVolumnRatioSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			
			break;
			
		  case Constants.TableConstants.BASE_DAD_DICTIONARY_CONFIG_VALUE:
			/** 
			 * 查询 (数据字典适用)base_dad_dictionary_config_value表数据
			 */
			result = baseBdmService.getDictConfValSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			
			break;
			
		  case Constants.TableConstants.BASE_EACH_COMPANY:
			/** 
			 * 查询 (经营属性配置)base_each_company表数据
			 */
			result = baseBdmService.getEachCompanySyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			
			break;
			
		  case Constants.TableConstants.PRODUCT_PRO_MANAGE:
			/** 
			 * 查询(产品类型)product_pro_manage表数据
			 */
			result = productService.getProManageSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.PRODUCT_LINE_MAINTENANCE:
			/** 
			 * 查询(产品类型时效)product_line_maintenance表数据
			 */
			result = productService.getProLineSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.PRODUCT_SAL_SERVICE_FEE:
			/** 
			 * 查询(增值服务)product_sal_service_fee表数据
			 */
			result = productService.getProSalFeeSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
          case Constants.TableConstants.PRODUCT_SAL_SERVICE_ZONE:
        	/** 
			 * 查询(增值服务适用网点)product_sal_service_zone表数据
			 */
			result = productService.getProSalZoneSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.PRODUCT_SAL_SPECIAL_GOODS:
			/** 
			 * 查询(货物品类价格)product_sal_special_goods表数据
			 */
			result = productService.getProSalGoodsSyncServerData(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.ROUTE_LINE_CODE:
			/** 
			 * 查询(线路编码)route_line_code表数据
			 */
			result = routeService.queryRouteLineCodeByparameter(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.ROUTE_LINE:
			/** 
			 * 查询 线路route_line表数据
			 */
			result = routeService.queryRouteLineByparameter(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.USER_SYS_EMPLOYEE:
			/** 
			 * 查询员工(user_sys_employee)表数据
			 */
			result = userSysEmployeeService.queryUserSysEmployeeByparameter(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.WMS_STORAGE:
			/** 
			 * 查询(库区)wms_storage表数据
			 */
			result = wmsService.queryWmsStorageByparameter(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		  case Constants.TableConstants.WMS_STORAGE_DETAIL:
			/** 
			 * 查询(库区详情)wms_storage_detail表数据
			 */
			result = wmsService.queryWmsStorageDetailByparameter(tableName, lastTime, startIndex, pageSize, cdstatus);
			break;
			
		default:
			LOGGER.error("APP移动端传入的表名{}不存在!",tableName);
			
		}
		return result;
	}
	
}

策略+工厂模式优化：

枚举类：

import org.apache.commons.lang3.StringUtils;

/**
 * 策略枚举(增加新策略时需要添加数据)
 * 保存具体策略类类型
 * 
 * @author 000125
 *
 */
public enum StrategyTypeEnum {
	BASE_NET_DEPT_BASE_INFO("base_net_dept_base_info", "BaseNetDeptBaseInfoStrategy", "部门网点信息"),
	BASE_BDM_QC_TYPE("base_bdm_qc_type", "BaseBdmQcTypeStrategy", "问题件异常类型"),
	BASE_SYS_COMPANY("base_sys_company", "BaseSysCompanyStrategy", "账号"),
	BASE_NET_DISTRICT("base_net_district", "BaseNetDistrictStrategy", "行政区域"),
	BASE_BDM_FORWARD_ZONE("base_bdm_forward_zone", "BaseBdmForwardZoneStrategy", "转寄地"),
	BASE_DAD_DICTIONARY_VALUE("base_dad_dictionary_value", "BaseDadDictionaryValueStrategy", "数据字典"),
	BASE_DAD_DICTIONARY_CONFIG_VALUE("base_dad_dictionary_config_value", "BaseDadDictionaryConfigValueStrategy", "数据字典适用"),
	BASE_BDM_PRODUCT_TYPE("base_bdm_product_type", "BaseBdmProductTypeStrategy","货物品类维护"),
	BASE_BDM_PRODUCT_TYPE_APPLY("base_bdm_product_type_apply", "BaseBdmProductTypeApplyStrategy", "货物品类管理"),
	BASE_BDM_PRINT_CONFIG("base_bdm_print_config", "BaseBdmPrintConfigStrategy", "打印配置"),
	BASE_BDM_WEIGHT_VOLUMN_RATIO("base_bdm_weight_volumn_ratio", "BaseBdmWeightVolumnRatioStrategy", "重量体积比率"),
	BASE_EACH_COMPANY("base_each_company", "BaseEachCompanyStrategy", "经营属性配置"),
	PRODUCT_PRO_MANAGE("product_pro_manage", "ProductProManageStrategy", "产品类型"),
	PRODUCT_LINE_MAINTENANCE("product_line_maintenance", "ProductLineMaintenanceStrategy", "产品类型时效"),
	PRODUCT_SAL_SERVICE_FEE("product_sal_service_fee", "ProductSalServiceFeeStrategy", "增值服务表"),
	PRODUCT_SAL_SERVICE_ZONE("product_sal_service_zone", "ProductSalServiceZoneStrategy", "增值服务适用网点"), 
	PRODUCT_SAL_SPECIAL_GOODS("product_sal_special_good", "ProductSalSpecialGoodStrategy", "货物品类价格"),
	ROUTE_LINE_CODE("route_line_code", "RoutLineCodeStrategy", "线路编码"),
	ROUTE_LINE("route_line", "RouteLineStrategy", "线路"),
	USER_SYS_EMPLOYEE("user_sys_employee", "UserSysEmployeeStrategy", "员工表"),
	WMS_STORAGE("wms_storage", "WmsStorageDetailStrategy", "库区"),
	WMS_STORAGE_DETAIL("wms_storage_detail", "WmsStorageStrategy", "库区详情"), 
	
	NOT_EXITS_ENUM("", "", "");

	/**
	 * 编码，此处为同步的表名
	 */
	private String code;
	
	/**
	 * 具体的策略实现类的名称，类名
	 */
	private String value;
	
	/**
	 * 描述
	 */
	private String description;
	
	private StrategyTypeEnum(String code, String value, String description) {
		this.code = code;
		this.value = value;
		this.description = description;
	}

	public String getCode(){
        return this.code;
    }

	public String getValue(){
        return this.value;
    }
	
	public String getDescription(){
        return this.description;
    }
	
	public static StrategyTypeEnum getByCode(String code) {

		if (StringUtils.isBlank(code)) {			
			return StrategyTypeEnum.NOT_EXITS_ENUM;
		}
		
        for(StrategyTypeEnum type : StrategyTypeEnum.values()) {
            if(type.getCode().equals(code)) {
                return type;
            }
        }
        return null;
    }
	
	public static StrategyTypeEnum getByValue(String value) {

		if (StringUtils.isBlank(value)) {			
			return StrategyTypeEnum.NOT_EXITS_ENUM;
		}
		
        for(StrategyTypeEnum type : StrategyTypeEnum.values()) {
            if(type.getValue().equals(value)) {
                return type;
            }
        }
        return null;
    }

}

策略接口：

 
/**
 * 策略模式
 *    解决数据同步时需要提供多个类似重复的对外接口，
 *    通过策略模式+工厂模式基本上可以解决多个判断分支情况
 *    
 * 
 * @author 000125
 *
 */
public interface SyncStrategy {
	/**
	 * 策略执行方法，即需要处理的每个业务单元逻辑
	 * 
	 * @param tableName - 需同步数据的表名
	 * @param lastTime - 增量同步时，上一次同步时间
	 * @param startIndex - 页数
	 * @param pageSize - 当前页显示的条数
	 * @param cdstatus - 查询条件comp_code(公司编码,默认值为all)
	 * @return
	 */
	public Object doOperate(String tableName, String lastTime, int startIndex, int pageSize, String cdstatus);

}

策略具体实现类：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 实现策略接口中的方法，实现具体的策略方案（业务逻辑）
 * 
 * @author 000125
 *
 */
public class BaseBdmForwardZoneStrategy implements SyncStrategy { 
	/** 日志打印 */
	private static final Logger LOGGER = LoggerFactory.getLogger(BaseBdmForwardZoneStrategy.class);
	
	/**
	 * 查询 转寄地base_bdm_forward_zone表
	 */
	@Override
	public Object doOperate(String tableName, String lastTime, int startIndex, int pageSize, String cdstatus) {
		// TODO 业务逻辑 此处较简单只需要调用一下具体业务方法
		IBaseBdmService baseBdmService = SpringContextUtil.getBean("baseBdmServiceImpl", BaseBdmServiceImpl.class);
		if (baseBdmService == null){
			LOGGER.error("获取Spring Bean对象失败！");
			return null;
		}
		return baseBdmService.getForwardZoneSyncData(tableName, lastTime, startIndex, pageSize, cdstatus);
	}

}

工厂类：

import org.apache.commons.lang3.StringUtils;


/**
 * 生成具体策略工厂方法
 * 
 * @author 000125
 *
 */
public class StrategyFactory {
	
	private StrategyFactory() {
		
	}
	
	public static SyncStrategy getStrategy(String code){
	    
		String clazzPrefix = "com.appsync.core.gof.strategy.impl.";
        String clazzName = StrategyTypeEnum.getByCode(code).getValue();
        
        SyncStrategy strategy = null;        
        if (StringUtils.isNotBlank(clazzName)) {
        	try {
        		//通过反射获取策略对象
                strategy = (SyncStrategy) Class.forName(clazzPrefix + clazzName).newInstance();
            } catch (Exception e) {
                e.printStackTrace(); 
                System.out.println("生成策略出错");
            } 
		}
		              
        
        return strategy;
    }

}

 

客户端类（单元测试用例）：

public class BaseTest extends SpringTestCase{
		
	@Test
	public void queryPrintConfigSql(){
		
		String tableName="base_bdm_forward_zone",
			   lastTime="2018-01-10 00:00:00",
			   cdstatus="all";
		int startIndex=1; int pageSize=10; 
		
		try {
			HystrixRequestContext.initializeContext();
			//策略模式
		 
			SyncServerResult result = SyncStrategyFacade.sync(tableName, lastTime, startIndex, pageSize, cdstatus);
			
			 
			String jsonResult = JSONObject.toJSONString(result);
			System.out.println("jsonResult="+jsonResult);
			
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		
	}
	
	 

}

上面代码可以看出，策略模式把具体的算法封装到了具体策略角色内部，增强了可扩展性，隐蔽了实现细节；它替代继承来实现，避免了if- else这种不易维护的条件语句。当然我们也可以看到，策略模式由于独立策略实现，使得系统内增加了很多策略类；对客户端来说必须知道兜友哪些具体策略， 而且需要知道选择具体策略的条件