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| |
| <h1 id="_1">异常处理</h1> |
| <h2 id="_2">异常分类及客户端如何判断异常类型</h2> |
| <ul> |
| <li>业务异常：这类异常由业务接口定义。用户在获取到服务swagger定义的时候，就能够从定义中看到这类异常对 |
| 应的错误码，以及返回值类型。 下面的例子展现了业务定义异常。<pre><code>@Path("/errorCode") |
| @POST |
| @ApiResponses({ |
| @ApiResponse(code = 200, response = MultiResponse200.class, message = ""), |
| @ApiResponse(code = 400, response = MultiResponse400.class, message = ""), |
| @ApiResponse(code = 500, response = MultiResponse500.class, message = "")}) |
| public MultiResponse200 errorCode(MultiRequest request) { |
| if (request.getCode() == 400) { |
| MultiResponse400 r = new MultiResponse400(); |
| r.setCode(400); |
| r.setMessage("bad request"); |
| throw new InvocationException(javax.ws.rs.core.Response.Status.BAD_REQUEST, r); |
| } else if (request.getCode() == 500) { |
| MultiResponse500 r = new MultiResponse500(); |
| r.setCode(500); |
| r.setMessage("internal error"); |
| throw new InvocationException(javax.ws.rs.core.Response.Status.INTERNAL_SERVER_ERROR, r); |
| } else { |
| MultiResponse200 r = new MultiResponse200(); |
| r.setCode(200); |
| r.setMessage("success result"); |
| return r; |
| } |
| } |
| </code></pre> |
| </li> |
| </ul> |
| <p><strong><em>注意</em></strong>： 对于 2xx 错误码，可以返回具体的业务 model， 对于其他的错误码， |
| 必须抛出 InvocationException。 </p> |
| <p>客户端代码可以按照如下方式处理异常。异常的类型是确定的，可以通过cast获取到异常类型。</p> |
| <pre><code> MultiRequest request = new MultiRequest(); |
| |
| request.setCode(200); |
| ResponseEntity<MultiResponse200> result = template |
| .postForEntity(SERVER + "/MultiErrorCodeService/errorCode", request, MultiResponse200.class); |
| TestMgr.check(result.getStatusCode(), 200); |
| TestMgr.check(result.getBody().getMessage(), "success result"); |
| |
| request.setCode(400); |
| MultiResponse400 t400 = null; |
| try { |
| template.postForEntity(SERVER + "/MultiErrorCodeService/errorCode", request, MultiResponse400.class); |
| } catch (InvocationException e) { |
| t400 = (MultiResponse400) e.getErrorData(); |
| } |
| TestMgr.check(t400.getCode(), 400); |
| TestMgr.check(t400.getMessage(), "bad request"); |
| |
| request.setCode(500); |
| MultiResponse500 t500 = null; |
| try { |
| template.postForEntity(SERVER + "/MultiErrorCodeService/errorCode", request, MultiResponse400.class); |
| } catch (InvocationException e) { |
| t500 = (MultiResponse500) e.getErrorData(); |
| } |
| TestMgr.check(t500.getCode(), 500); |
| TestMgr.check(t500.getMessage(), "internal error"); |
| </code></pre> |
| <ul> |
| <li>控制异常：这类异常通常是框架处理流程上的异常。比如流控Handler抛出TOO_MANY_REQUESTS_STATUS异常。<pre><code>public class ConsumerQpsFlowControlHandler implements Handler { |
| ... ... |
| if (qpsController.isLimitNewRequest()) { |
| // return http status 429 |
| CommonExceptionData errorData = new CommonExceptionData("rejected by qps flowcontrol"); |
| asyncResp.consumerFail( |
| new InvocationException(QpsConst.TOO_MANY_REQUESTS_STATUS, errorData)); |
| return; |
| } |
| |
| invocation.next(asyncResp); |
| } |
| } |
| </code></pre> |
| </li> |
| </ul> |
| <p>控制异常在接口定义里面没有声明。客户端在做异常处理的时候，不知道异常类型。可以采用弱类型的方式处理异常：</p> |
| <pre><code> JsonObject requestJson = new JsonObject(); |
| requestJson.put("code", 400); |
| requestJson.put("message", "test message"); |
| |
| try { |
| template |
| .postForEntity(SERVER + "/MultiErrorCodeService/noClientErrorCode", requestJson, Object.class); |
| } catch (InvocationException e) { |
| TestMgr.check(e.getStatusCode(), 400); |
| mapResult = RestObjectMapperFactory.getRestObjectMapper().convertValue(e.getErrorData(), Map.class); |
| TestMgr.check(mapResult.get("message"), "test message"); |
| TestMgr.check(mapResult.get("code"), 400); |
| TestMgr.check(mapResult.get("t400"), 400); |
| } |
| </code></pre> |
| <p>上面的代码假设不知道异常类型，通过API将异常类型转换为Map类型，然后从Map里面读取异常类型。 |
| ServiceComb自己抛出的异常类型中，一般控制异常的类型也是固定的，为CommonExceptionData。</p> |
| <ul> |
| <li>未知异常：这类异常发生的情况不确定。比如业务代码实现的时候，抛出NullPointerException等未捕获异常、底层 |
| 的网络连接超时异常等。这类异常会由ServiceComb封装成590或者490错误返回。比如：<pre><code>CommonExceptionData errorData = new CommonExceptionData(cause.getMessage()); |
| asyncResp.producerFail(new InvocationException(590, errorData) |
| </code></pre> |
| </li> |
| </ul> |
| <p>或者</p> |
| <pre><code> asyncResp.consumerFail(new InvocationException(490, errorData) |
| </code></pre> |
| <p>未知异常消息的类型固定为CommonExceptionData类型。</p> |
| <h2 id="_3">异常拦截器</h2> |
| <p>有时候，业务需要将所有的未知异常、控制异常进行捕获，转换为对用户友好的消息。或者对控制异常进行捕获，将 |
| 消息体转换为自定义的JSON格式。这里面有几个参考点。</p> |
| <ul> |
| <li> |
| <p>通过 <code>ExceptionToProducerResponseConverter</code> 拦截异常</p> |
| <p><code>ExceptionToProducerResponseConverter</code>能够拦截业务异常以及业务实现里面抛出的未知异常。但是不能拦截 |
| Handler，HttpServerFilter 等抛出的异常。更加确切的是 <code>ProducerOperationHandler</code> 捕获的异常都会被 |
| <code>ExceptionToProducerResponseConverter</code> 处理。 <code>ExceptionToProducerResponseConverter</code> 包含如下 |
| 几个接口：</p> |
| <ul> |
| <li><code>getExceptionClass()</code> 实现类所处理的异常类型。如果该方法返回<code>null</code>，则说明此实现类为默认converter。</li> |
| <li><code>Response convert(SwaggerInvocation swaggerInvocation, T e)</code> 处理异常逻辑，该方法返回的<code>Response</code>决定了ServiceComb将会返回何种状态码、何种response body的应答。</li> |
| <li><code>getOrder()</code> 实现类的优先级，该方法返回的值越小，优先级越高，如果不覆写该方法的话，则返回默认优先级<code>0</code>。对于处理同一异常类型的converter（或默认converter），只有优先级最高的生效。</li> |
| </ul> |
| </li> |
| </ul> |
| <p>在为异常选择converter时，会从异常本身的类型开始匹配，如果找不到对应的converter则逐级向上查找父类型的converter。当匹配到<code>Throwable</code>仍未找到converter时，将使用默认converter处理异常。</p> |
| <pre><code> public class CustomExceptionToProducerResponseConverter implements ExceptionToProducerResponseConverter<IllegalStateException> { |
| @Override |
| public Class<IllegalStateException> getExceptionClass() { |
| // 返回IllegalStateException表示该converter处理IllegalStateException类型的异常 |
| return IllegalStateException.class; |
| } |
| |
| @Override |
| public int getOrder() { |
| // 返回的order值越小，优先级越高 |
| return 100; |
| } |
| |
| @Override |
| public Response convert(SwaggerInvocation swaggerInvocation, IllegalStateException e) { |
| // 这里是处理异常的逻辑 |
| IllegalStateErrorData data = new IllegalStateErrorData(); |
| data.setId(500); |
| data.setMessage(e.getMessage()); |
| data.setState(e.getMessage()); |
| InvocationException state = new InvocationException(Status.INTERNAL_SERVER_ERROR, data); |
| return Response.failResp(state); |
| } |
| } |
| </code></pre> |
| <p><strong><em>说明</em></strong> : 2.0.2 之前的版本部分业务异常无法通过 ExceptionToProducerResponseConverter 捕获， |
| 系统做了自动处理，不经过 ExceptionToProducerResponseConverter。 2.0.2 版本规范化了处理流程。 </p> |
| <ul> |
| <li> |
| <p>通过 Handler 拦截异常</p> |
| <p>可以开发一个自定义的 Handler, 并且将其放到其他 Handler 的前面，可以处理绝大多数业务异常、控制异常和 |
| 未知异常。Handler 不仅仅可以帮助和处理异常，还可以记录访问日志，参 |
| 考<a href="../featured-topics/features/trace-id.html">2.0.1 新特性介绍： 在日志中记录trace id</a></p> |
| <pre><code>public class ExceptionConvertHandler implements Handler { |
| @Override |
| public void handle(Invocation invocation, AsyncResponse asyncResp) throws Exception { |
| invocation.next(response -> { |
| if (response.isFailed()) { |
| Throwable e = response.getResult(); |
| if (e instanceof InvocationException && ((InvocationException)e).getStatusCode() == 408) { |
| CustomException customException = new CustomException("change the response", 777); |
| InvocationException stt = new InvocationException(Status.EXPECTATION_FAILED, customException); |
| response.setResult(stt); |
| response.setStatus(stt.getStatus()); |
| } |
| } |
| asyncResp.complete(response); |
| }); |
| } |
| } |
| </code></pre> |
| </li> |
| <li> |
| <p>控制消息消息体序列化</p> |
| </li> |
| </ul> |
| <p>控制消息消息体序列化的目的是简化消费者的异常处理逻辑，不用使用弱类型，而是使用确切类型。可以采用注册全局的错误码类型。 |
| 业务需要通过SPI实现org.apache.servicecomb.swagger.invocation.response.ResponseMetaMapper接口。 |
| 接口的核心内容是为每个错误码指定序列化类型：</p> |
| <pre><code> private final static Map<Integer, ResponseMeta> CODES = new HashMap<>(1); |
| |
| static { |
| ResponseMeta meta = new ResponseMeta(); |
| meta.setJavaType(SimpleType.constructUnsafe(IllegalStateErrorData.class)); |
| CODES.put(500, meta); |
| } |
| |
| @Override |
| public Map<Integer, ResponseMeta> getMapper() { |
| return CODES; |
| } |
| </code></pre> |
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