在代码中使用自定义的异常类,可以对异常进行统一的封装处理。使得整个项目的异常处理更规范、更统一、更优雅。同时,使得日志的记录上更加清晰,便于后续查日志定位问题。
以下为自定义异常类的完整过程:
1、需要自定义一个类,继承自系统的异常类。具体需要什么样类型的异常类,就继承自相应的系统类。
- 如果希望写一个检查性异常类,则需要继承 Exception 类。
如果你想写一个运行时异常类,那么需要继承 RuntimeException 类。
public class InvalidReqException extends Exception { private final String userErrMsg; private final ErrorCode errorCode; public InvalidReqException(ErrorCode errorCode, String sysErrMsg, String userErrMsg) { super(sysErrMsg); this.userErrMsg = userErrMsg; this.errorCode = errorCode; } public InvalidReqException(ErrorCode errorCode, String sysErrMsg, String userErrMsg, Throwable cause) { super(sysErrMsg, cause); this.userErrMsg = userErrMsg; this.errorCode = errorCode; } public InvalidReqException(ErrorCode errorCode, String sysErrMsg) { super(sysErrMsg); this.userErrMsg = null; this.errorCode = errorCode; } public ErrorCode getErrorCode() { return errorCode; } public String getUserErrMsg() { return userErrMsg; } public String getSysErrMsg() { return getMessage(); } }
2、在需要抛出该异常的类或方法中,定义当出现异常时抛出自定义的异常。
static void checkTemplateValid(String content) throws InvalidReqException { if (content.length() > 100 * 1024) { throw new InvalidReqException(ErrorCode.TEMPLATE_INVALID, "template is too large, over 100KB", "模板HTML原文不得超过100KB"); } }
3、在使用到该类或方法的地方捕捉该异常(或继续抛出,交给上级去处理),并对异常进行业务相关的响应与处理。
public void onMessage(Message message) { String tenantId = (String) message.getMessageProperties().getHeaders().get(MQRouting.HEADER_TENANT_ID); String requestId = (String) message.getMessageProperties().getHeaders().get(MQRouting.HEADER_REQ_ID); String body = null; CertApplyMsg msg; try { body = new String(message.getBody(), "utf8"); log.debug("received cert apply message: {}", body); msg = JsonUtil.parse(body, CertApplyMsg.class); } catch (IOException e) { // impossible to happen log.error("message failed due to invalid format:" + body, e); failMsg(MQRouting.EXCH_CERT, MQRouting.RK_CERT_APPLY_FAILED, message, e); return; } LegalEntityCertBo entity = msg.getLegalEntityCert(); try { if (entity.getCert().getStatus() != CertStatus.APPLYING) { reconcileConcurrentUpdate(tenantId, requestId, msg); // due to retry return; } LegalEntityCertBo created = certService.applyCert(entity.getOrganization(), entity.getCert().getCa(), entity.getLegalEntity()); if (!certService.updateCert(created, entity.getCert().getStatus())) { // due to data race reconcileConcurrentUpdate(tenantId, requestId, msg); } else { enqueueCallback(tenantId, requestId, msg, created, null, null); log.info("successfully processed cert application:" + body); } } catch (InvalidReqException e) { log.error("applying cert rejected. body=" + body + ", message=" + message, e); enqueueCallback(tenantId, requestId, msg, entity, e.getErrorCode(), e.getSysErrMsg()); rejectMsg(MQRouting.EXCH_CERT, MQRouting.RK_CERT_APPLY_REJECTED, message, e); } catch (RuntimeException e) { log.error("cert application failed, probably will retry, body=" + body + ", msg=" + e.getMessage(), e); throw e; } }