一些 API 的報錯信息通過 Response 的 body返回。
使用 HttpClient 能正常獲取到 StatusCode 和 body 中的錯誤提示。然而使用 RestTemplate ,會直接拋出下面的異常。
如果想獲取原始的信息並進一步處理會比較麻煩。
類似下面這種404、403響應碼直接拋出異常並不是我們想要的
org.springframework.web.client.HttpClientErrorException: 404 null
at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:94)
at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:79)
at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63)
at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:777)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:730)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:704)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:621)
RestTemplate 異常處理流程
下面看一下原因, RestTemplate 中的 getForObject, getForEntity 和 exchange 等常用方法最終都是調用 doExecute 方法。下面是 doExecute 方法源碼:
public class RestTemplate extends InterceptingHttpAccessor implements RestOperations {
private ResponseErrorHandler errorHandler;
......
@Nullable
protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback, @Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
Assert.notNull(url, "'url' must not be null");
Assert.notNull(method, "'method' must not be null");
ClientHttpResponse response = null;
String resource;
try {
ClientHttpRequest request = this.createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
// 處理 Response
this.handleResponse(url, method, response);
if (responseExtractor != null) {
Object var14 = responseExtractor.extractData(response);
return var14;
}
resource = null;
} catch (IOException var12) {
resource = url.toString();
String query = url.getRawQuery();
resource = query != null ? resource.substring(0, resource.indexOf(63)) : resource;
throw new ResourceAccessException("I/O error on " + method.name() + " request for \"" + resource + "\": " + var12.getMessage(), var12);
} finally {
if (response != null) {
response.close();
}
}
return resource;
}
protected void handleResponse(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
ResponseErrorHandler errorHandler = this.getErrorHandler();
boolean hasError = errorHandler.hasError(response);
if (this.logger.isDebugEnabled()) {
try {
this.logger.debug(method.name() + " request for \"" + url + "\" resulted in " + response.getRawStatusCode() + " (" + response.getStatusText() + ")" + (hasError ? "; invoking error handler" : ""));
} catch (IOException var7) {
;
}
}
// 異常處理
if (hasError) {
errorHandler.handleError(url, method, response);
}
}
}
從下面的代碼可以看出,DefaultResponseErrorHandler 捕獲並拋出了異常。
public class DefaultResponseErrorHandler implements ResponseErrorHandler {
...
protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
switch(statusCode.series()) {
case CLIENT_ERROR:
throw new HttpClientErrorException(statusCode, response.getStatusText(), response.getHeaders(), this.getResponseBody(response), this.getCharset(response));
case SERVER_ERROR:
throw new HttpServerErrorException(statusCode, response.getStatusText(), response.getHeaders(), this.getResponseBody(response), this.getCharset(response));
default:
throw new UnknownHttpStatusCodeException(statusCode.value(), response.getStatusText(), response.getHeaders(), this.getResponseBody(response), this.getCharset(response));
}
}
}
如果想自己捕獲異常信息,自己處理異常的話可以通過實現 ResponseErrorHandler 類來實現。其源碼如下:
public interface ResponseErrorHandler {
// 標示 Response 是否存在任何錯誤。實現類通常會檢查 Response 的 HttpStatus。
boolean hasError(ClientHttpResponse var1) throws IOException;
// 處理 Response 中的錯誤, 當 HasError 返回 true 時才調用此方法。
void handleError(ClientHttpResponse var1) throws IOException;
// handleError 的替代方案,提供訪問請求URL和HTTP方法的額外信息。
default void handleError(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
this.handleError(response);
}
}
自定義 RestTemplate 異常處理
如果想像 HttpClient 一樣直接從 Response 獲取 HttpStatus 和 body 中的報錯信息 而不拋出異常,可以通過下面的代碼實現:
public class CustomErrorHandler implements ResponseErrorHandler {
@Override
public boolean hasError(ClientHttpResponse response) throws IOException {
return true;
}
@Override
public void handleError(ClientHttpResponse response) throws IOException {
}
}
設置 RestTemplate 的異常處理類
restTemplate.setErrorHandler(new CustomErrorHandler());
ResponseEntity<String> response = restTemplate.exchange(uri, HttpMethod.GET, null, String.class);
System.out.println(response.getBody());
輸出結果
{"code":404,"result":null,"message":"Resources not found"}