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Posted to commits@servicecomb.apache.org by li...@apache.org on 2020/05/08 07:44:11 UTC
[servicecomb-docs] branch master updated: [SCB-1875]add docs: how
to handle exceptions
This is an automated email from the ASF dual-hosted git repository.
liubao pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/servicecomb-docs.git
The following commit(s) were added to refs/heads/master by this push:
new 15910d5 [SCB-1875]add docs: how to handle exceptions
15910d5 is described below
commit 15910d5baf0bf239fce73c361d9f4722c86562f3
Author: liubao <bi...@qq.com>
AuthorDate: Fri May 8 15:29:59 2020 +0800
[SCB-1875]add docs: how to handle exceptions
---
.../docs/general-development/error-handling.md | 355 +++++++++++----------
1 file changed, 192 insertions(+), 163 deletions(-)
diff --git a/java-chassis-reference/zh_CN/docs/general-development/error-handling.md b/java-chassis-reference/zh_CN/docs/general-development/error-handling.md
index 6bb2a74..52b2938 100644
--- a/java-chassis-reference/zh_CN/docs/general-development/error-handling.md
+++ b/java-chassis-reference/zh_CN/docs/general-development/error-handling.md
@@ -1,171 +1,200 @@
# 异常处理
-ServiceComb异常情况可以分为三类:
-* 业务定义异常:这类异常由业务接口定义。用户在获取到服务swagger定义到时候,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。
+## 异常分类及客户端如何判断异常类型
+
+* 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。
+
+ @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;
+ }
+ }
+
+ 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。
+
+ 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");
+
+
+* 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。
+
+ 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);
+ }
+ }
+
+ 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:
+
+ 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);
+ }
+
+ 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。
+
+* 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:
+
+ CommonExceptionData errorData = new CommonExceptionData(cause.getMessage());
+ asyncResp.producerFail(new InvocationException(590, errorData)
-* 处理控制异常: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。
-
- ```java
- CommonExceptionData errorData = new CommonExceptionData("rejected by qps flowcontrol");
- asyncResp.producerFail(new InvocationException(QpsConst.TOO_MANY_REQUESTS_STATUS, errorData));
- ```
-
-* 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:
-
- ```java
- CommonExceptionData errorData = new CommonExceptionData(cause.getMessage());
- asyncResp.producerFail(new InvocationException(590, errorData)
- ```
或者
- ```java
- asyncResp.consumerFail(new InvocationException(490, errorData)
- ```
-
-
-## 业务定义异常
-
-通常业务在开发服务代码的时候,只有一个返回值,但有些情况,也需要视具体情况返回不同的消息。可以通过@ApiResonse来定义不同错误码对应的返回消息。业务异常具备确定的数据类型,并且会在swagger里面体现,客户端代码在处理异常的时候,能够直接获取到错误类型。比如下面的代码:
-
-```java
- @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;
- }
- }
-```
-
-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。
-
-```java
- 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");
-```
-
-## 控制异常
-
-控制异常一般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:
-
-```java
- 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);
- }
-```
-
-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。在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。
-
-## 未知异常
-
-未知异常统一被封装为490, 590错误码,异常消息的类型固定为CommonExceptionData类型。
-
-## 异常转换和定制
-
-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。
+
+ asyncResp.consumerFail(new InvocationException(490, errorData)
+
+ 未知异常消息的类型固定为CommonExceptionData类型。
+
+
+## 异常拦截器
+
+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。
+
+* 通过 `ExceptionToProducerResponseConverter` 拦截异常
+
+ `ExceptionToProducerResponseConverter`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 `ProducerOperationHandler` 捕获的异常都会被
+ `ExceptionToProducerResponseConverter` 处理。 `ExceptionToProducerResponseConverter` 包含如下
+ 几个接口:
+
+ - `getExceptionClass()` 实现类所处理的异常类型。如果该方法返回`null`,则说明此实现类为默认converter。
+ - `Response convert(SwaggerInvocation swaggerInvocation, T e)` 处理异常逻辑,该方法返回的`Response`决定了ServiceComb将会返回何种状态码、何种response body的应答。
+ - `getOrder()` 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`0`。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。
+
+ 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`Throwable`仍未找到converter时,将使用默认converter处理异常。
+
+ 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);
+ }
+ }
+
+ ***说明*** : 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。
+
+* 通过 Handler 拦截异常
+
+ 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[2.0.1 新特性介绍: 在日志中记录trace id](../featured-topics/features/trace-id.md)
+
+ 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);
+ });
+ }
+ }
* 控制消息消息体序列化
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制定序列化类型:
- ```java
- 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;
- }
- ```
-
-* 异常转换
-
- 如果业务不对异常进行转换,ServiceComb会将InvocationException中的data直接序列化到响应消息中。如果不是InvocationException,则转换为490, 590,序列化的消息为CommonExceptionData。业务可以通过SPI实现`org.apache.servicecomb.swagger.invocation.exception.ExceptionToProducerResponseConverter`对异常进行转换。`ExceptionToProducerResponseConverter`的说明如下:
- - `getExceptionClass()`方法会返回converter实现类所处理的异常类型。如果该方法返回`null`,则说明此实现类为默认converter。
- - `Response convert(SwaggerInvocation swaggerInvocation, T e)`方法中实现处理异常的逻辑,该方法返回的`Response`决定了ServiceComb将会返回何种状态码、何种response body的应答。
- - `getOrder()`方法用以确定converter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`0`。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。
- - 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`Throwable`仍未找到converter时,将使用默认converter处理异常。
-
- ```java
- 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);
- }
- }
- ```
+ 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:
+
+ 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;
+ }