在大型业务系统中, 常常需要从数据库中查询某个实体对象。 在进行处理之前, 必须先检测该实体是否存在,以增强系统的健壮性。 不过, 检测代码充斥在主业务流程中又会大大降低业务逻辑的清晰性, 最好集中起来进行管理。 因此,编写了一个类来做这个事情, 只需要一行调用就可以完成相应实体对象的检测。
美中不足的一点是, 打 log 的位置发生变化了。由于打 log 的主要目标是为了便于调试和定位错误位置, 为了补偿, 一种办法是调用方法时根据具体语境传入自定义的错误消息, 根据错误消息可以定位错误位置; 另一种办法是, 如果不希望每次调用都使用不同的自定义错误消息, 使用 log.error("error", bizEx) 打印异常栈信息, 也可以获取到抛出错误的位置。
NOTE: 为了遵循公司代码的保密性, 隐去导入的包名, 各位读者可以借鉴其思想, 运用到自己的项目中去。
使用方法:
import static util.CheckEntityExistManager.checkEntity;import util.CheckEntityExistManager.EntityChecker;public class EntityExistCheckTester {
private static final Log log = LogFactory.getLog(EntityExistCheckTester.class);
public static void main(String[] args) throws BizException {
demo();
demo2();
}
public static ResultSet demo() {
try { // Not Need type casting
DeviceDO device = checkEntity(EntityChecker.DISK_ID_CHECK, "d-xxx");
System.out.println(device);
VmDO vm = checkEntity(EntityChecker.VM_NAME_CHECK, "vm-name","user-defined msg: vm not exist when creating");
System.out.println(vm); return new ResultSet(IErrorCode.SUCCESSFUL);
} catch (BizException bizEx) {
log.error("error", bizEx); return new ResultSet(bizEx.getErrorCode());
} catch (Exception ex) {
log.error(ex); return new ResultSet(IErrorCode.FAILED);
}
}
public static ResultSet demo2() { try {
ZoneDO zone = checkEntity(EntityChecker.ZONE_ID_CHECK, "z-yy");
System.out.println(zone); return new ResultSet(IErrorCode.SUCCESSFUL);
} catch (BizException bizEx) {
log.error("error", bizEx); return new ResultSet(bizEx.getErrorCode());
} catch (Exception ex) {
log.error(ex); return new ResultSet(IErrorCode.FAILED);
}
}
}
实体存在性集中检测类: CheckEntityExistManager:
public class CheckEntityExistManager {
private static final Log log = LogFactory.getLog(CheckEntityExistManager.class);
private static CheckEntityExistManager checkEntityMgr = getInstance();
private CheckEntityExistManager() {
}
private static CheckEntityExistManager getInstance() { if (checkEntityMgr == null) {
checkEntityMgr = new CheckEntityExistManager();
} return checkEntityMgr;
}
interface ICheckEntityExist<T> {
T checkEntityExist(String entityValue, String msg) throws BizException;
}
private static ICheckEntityExist<DeviceDO> diskIdChecker = checkEntityMgr.new CheckDiskIdExist(); private static ICheckEntityExist<VmDO> vmNameChecker = checkEntityMgr.new CheckVmExist(); private static ICheckEntityExist<ZoneDO> zoneChecker = checkEntityMgr.new CheckZoneExist();
public enum EntityChecker {
DISK_ID_CHECK(diskIdChecker, DeviceErrorCode.DISK_NOT_EXIST),
VM_NAME_CHECK(vmNameChecker, VmErrorCode.ERROR_VM_NOT_EXIST),
ZONE_ID_CHECK(zoneChecker, ZoneErrorCode.ZONE_NOT_EXIST);
EntityChecker(ICheckEntityExist<?> entityChecker, IErrorCode errorCode) { this.entityChecker = entityChecker; this.errorCode = errorCode;
}
private static Map<String, IErrorCode> errorMap = new HashMap<String, IErrorCode>();
static { for (EntityChecker entityChecker: EntityChecker.values()) {
ICheckEntityExist<?> checker = entityChecker.getEntityChecker();
errorMap.put(checker.getClass().getSimpleName(), entityChecker.getErrorCode());
}
}
private static IErrorCode getErrorCode(String checkClassSimpleName) { return errorMap.get(checkClassSimpleName);
}
private ICheckEntityExist<?> entityChecker; private IErrorCode errorCode;
public ICheckEntityExist<?> getEntityChecker() { return entityChecker;
} public void setEntityChecker(ICheckEntityExist<?> entityChecker) { this.entityChecker = entityChecker;
} public IErrorCode getErrorCode() { return errorCode;
} public void setErrorCode(IErrorCode errorCode) { this.errorCode = errorCode;
}
}
@Autowired private DeviceService deviceService;
@Autowired private VmService vmService;
@Autowired private ZoneService zoneService;
class CheckDiskIdExist implements ICheckEntityExist<DeviceDO> {
@Override public DeviceDO checkEntityExist(String diskId, String msg) throws BizException {
IErrorCode errorCode = EntityChecker.getErrorCode(CheckDiskIdExist.class.getSimpleName());
String message = (msg == null ? errorCode.getMessage() : msg); //DeviceDO dev = deviceService.getDevice(diskId);
DeviceDO dev = new DeviceDO(); return CheckEntityExistManager.throwexOrReturn(dev, message, errorCode);
}
}
class CheckVmExist implements ICheckEntityExist<VmDO> {
@Override public VmDO checkEntityExist(String vmName, String msg) throws BizException {
IErrorCode errorCode = EntityChecker.getErrorCode(CheckVmExist.class.getSimpleName());
String message = (msg == null ? errorCode.getMessage() : msg); //VmDO vm = vmService.queryVmByName(vmName);
VmDO vm = null; return CheckEntityExistManager.throwexOrReturn(vm, message, errorCode);
}
}
class CheckZoneExist implements ICheckEntityExist<ZoneDO> {
@Override public ZoneDO checkEntityExist(String zoneId, String msg) throws BizException {
IErrorCode errorCode = EntityChecker.getErrorCode(CheckZoneExist.class.getSimpleName());
String message = (msg == null ? errorCode.getMessage() : msg); //ZoneDO zone = zoneService.queryZoneById(zoneId);
ZoneDO zone = null; return CheckEntityExistManager.throwexOrReturn(zone, message, errorCode);
}
}
public static <T> T throwexOrReturn(T entity, String message, IErrorCode errorCode)
throws BizException { if (entity == null) {
log.error(message); throw new BizException(errorCode);
} return entity;
}
public static <T> T checkEntity(EntityChecker entityChecker, String entityValue, String customMsg) throws BizException {
ICheckEntityExist<T> checker = (ICheckEntityExist<T>) entityChecker.getEntityChecker(); return checker.checkEntityExist(entityValue, customMsg);
}
public static <T> T checkEntity(EntityChecker entityChecker, String entityValue) throws BizException {
ICheckEntityExist<T> checker = (ICheckEntityExist<T>) entityChecker.getEntityChecker(); return checker.checkEntityExist(entityValue, null);
}
}
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