结论：

resttemplate有默认的ErrorHandler，resttemplate发起http请求，一旦server抛异常，默认的只能打印status，无法打印message，自定义ErrorHandler，能打印status和message

server

@RestController
public class HelloController {@GetMapping("/hello")public String hello() {int i = 1 / 0;return "hello world";}
}

client

postman

用postman请求，返回如下，能解析异常信息，"message": "/ by zero",

restTemplate

但为啥restTemplate请求只能看到状态码，看不到详细信息呢，光看到500肯定是不够的，原因是resttemplate没有自定义ErrorHandler

2019-12-14 12:42:07.207 ERROR [hyg,,,] 10144 --- [           main] c.h.d.r.ResponseErrorHandlerTest         : 请求失败，url http://localhost:8000/helloorg.springframework.web.client.HttpServerErrorException$InternalServerError: 500 nullat org.springframework.web.client.HttpServerErrorException.create(HttpServerErrorException.java:79) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]

restTemplate code

@SpringBootTest
@RunWith(SpringRunner.class)
@Slf4j
public class ResponseErrorHandlerTest {@Autowiredprivate RestTemplate restTemplate;@Testpublic void responseErrorHandlerTest() {String url = "http://localhost:8000/hello";try {String hello = restTemplate.getForObject(url, String.class);assertThat(hello).contains(hello);} catch (Exception e) {log.error("请求失败，url {}", url, e);}}
}

自定义ErrorHandler能打印出来

自定义ErrorHandler，是不是能看到了

2019-12-14 12:50:20.302 ERROR [hyg,,,] 8044 --- [           main] c.h.d.r.ResponseErrorHandlerTest         : 请求HelloException失败，异常信息 {"timestamp":"2019-12-14 12:50:20","status":500,"error":"Internal Server Error","message":"/ by zero","path":"/hello"}
2019-12-14 12:50:20.318 ERROR [hyg,,,] 8044 --- [           main] c.h.d.r.ResponseErrorHandlerTest         : 请求失败，url http://localhost:8000/hellocom.hyg.demo.spring.resttemplate.HelloException: {"timestamp":"2019-12-14 12:50:20","status":500,"error":"Internal Server Error","message":"/ by zero","path":"/hello"}at com.hyg.demo.resttemplate.ResponseErrorHandlerTest.responseErrorHandlerTest(ResponseErrorHandlerTest.java:37) ~[test-classes/:na]

如何自定义resttemplate的ErrorHandler

@SpringBootTest
@RunWith(SpringRunner.class)
@Slf4j
public class ResponseErrorHandlerTest {@Autowiredprivate RestTemplate restTemplate;@Testpublic void responseErrorHandlerTest() {this.restTemplate = new RestTemplate();restTemplate.setErrorHandler(responseErrorHandler(new HelloException()));String url = "http://localhost:8000/hello";try {String hello = restTemplate.getForObject(url, String.class);assertThat(hello).contains(hello);} catch (Exception e) {log.error("请求失败，url {}", url, e);}}private ResponseErrorHandler responseErrorHandler(HelloException helloException) {return new ResponseErrorHandler() {@Overridepublic boolean hasError(ClientHttpResponse response) throws IOException {return (response.getStatusCode().series() == HttpStatus.Series.CLIENT_ERROR ||response.getStatusCode().series() == HttpStatus.Series.SERVER_ERROR);}@Overridepublic void handleError(ClientHttpResponse response) throws IOException {String body = org.apache.commons.io.IOUtils.toString(response.getBody(), StandardCharsets.UTF_8);log.error("请求{}失败，异常信息 {}", helloException.getClass().getSimpleName(), body);try {helloException.setStatus(response.getStatusCode().value());helloException.setMessage(body);helloException.setServerSide(response.getStatusCode().series() == HttpStatus.Series.SERVER_ERROR);helloException.setRetryAble(response.getStatusCode().series() != HttpStatus.Series.CLIENT_ERROR);throw helloException;} catch (Exception e) {helloException.setStatus(response.getStatusCode().value());helloException.setMessage(body);throw helloException;}}};}
}

服务端异常：一般以服务端名称+Exception命名

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@ToString(callSuper = true)
@Builder
public class HelloException extends RuntimeException{private int status; //http状态码private boolean isServerSide; //是不是server异常private boolean retryAble; // 是否重试，如果不是client_error就会重试private String code;private String message; //异常信息的bodyprivate Map<String,String> detail;
}

DefaultResponseErrorHandler

resttemplate的私有成员变量
private ResponseErrorHandler errorHandler = new DefaultResponseErrorHandler();

DefaultResponseErrorHandlerd的handleError方法

 protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {String statusText = response.getStatusText();HttpHeaders headers = response.getHeaders();byte[] body = getResponseBody(response);Charset charset = getCharset(response);switch (statusCode.series()) {case CLIENT_ERROR:  throw HttpClientErrorException.create(statusCode, statusText, headers, body, charset);case SERVER_ERROR:  //body是详细信息，但没把body赋值给messagethrow HttpServerErrorException.create(statusCode, statusText, headers, body, charset);default:throw new UnknownHttpStatusCodeException(statusCode.value(), statusText, headers, body, charset);}}// 把statusCode.value() + " " + statusText当做maeeage，传给RestClientResponseExceptionorg.springframework.web.client.RestClientResponseException#RestClientResponseException
super(statusCode.value() + " " + statusText, statusCode.value(), statusText,responseHeaders, responseBody, responseCharset);public RestClientResponseException(String message, int statusCode, String statusText,@Nullable HttpHeaders responseHeaders, @Nullable byte[] responseBody, @Nullable Charset responseCharset) {super(message);this.rawStatusCode = statusCode;this.statusText = statusText;this.responseHeaders = responseHeaders;this.responseBody = (responseBody != null ? responseBody : new byte[0]);this.responseCharset = (responseCharset != null ? responseCharset.name() : null);}

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自定义resttemplate的ErrorHandler

结论：