【本人禿頂程式設計師】Spring Cloud Gateway的全域性異常處理
阿新 • • 發佈：2018-12-25
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Spring Cloud Gateway中的全域性異常處理不能直接用@ControllerAdvice來處理，通過跟蹤異常資訊的丟擲，找到對應的原始碼，自定義一些處理邏輯來符合業務的需求。
閘道器都是給介面做代理轉發的，後端對應的都是REST API，返回資料格式都是JSON。如果不做處理，當發生異常時，Gateway預設給出的錯誤資訊是頁面，不方便前端進行異常處理。
需要對異常資訊進行處理，返回JSON格式的資料給客戶端。下面先看實現的程式碼，後面再跟大家講下需要注意的地方。
自定義異常處理邏輯：
package com.cxytiandi.gateway.exception; import java.util.HashMap; import java.util.Map; import org.springframework.boot.autoconfigure.web.ErrorProperties; import org.springframework.boot.autoconfigure.web.ResourceProperties; import org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler; import org.springframework.boot.web.reactive.error.ErrorAttributes; import org.springframework.context.ApplicationContext; import org.springframework.http.HttpStatus; import org.springframework.web.reactive.function.server.RequestPredicates; import org.springframework.web.reactive.function.server.RouterFunction; import org.springframework.web.reactive.function.server.RouterFunctions; import org.springframework.web.reactive.function.server.ServerRequest; import org.springframework.web.reactive.function.server.ServerResponse; /** * 自定義異常處理 * * <p>異常時用JSON代替HTML異常資訊<p> * * @author yinjihuan * */ public class JsonExceptionHandler extends DefaultErrorWebExceptionHandler { public JsonExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties, ErrorProperties errorProperties, ApplicationContext applicationContext) { super(errorAttributes, resourceProperties, errorProperties, applicationContext); } /** * 獲取異常屬性 */ @Override protected Map<String, Object> getErrorAttributes(ServerRequest request, boolean includeStackTrace) { int code = 500; Throwable error = super.getError(request); if (error instanceof org.springframework.cloud.gateway.support.NotFoundException) { code = 404; } return response(code, this.buildMessage(request, error)); } /** * 指定響應處理方法為JSON處理的方法 * @param errorAttributes */ @Override protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) { return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse); } /** * 根據code獲取對應的HttpStatus * @param errorAttributes */ @Override protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) { int statusCode = (int) errorAttributes.get("code"); return HttpStatus.valueOf(statusCode); } /** * 構建異常資訊 * @param request * @param ex * @return */ private String buildMessage(ServerRequest request, Throwable ex) { StringBuilder message = new StringBuilder("Failed to handle request ["); message.append(request.methodName()); message.append(" "); message.append(request.uri()); message.append("]"); if (ex != null) { message.append(": "); message.append(ex.getMessage()); } return message.toString(); } /** * 構建返回的JSON資料格式 * @param status 狀態碼 * @param errorMessage 異常資訊 * @return */ public static Map<String, Object> response(int status, String errorMessage) { Map<String, Object> map = new HashMap<>(); map.put("code", status); map.put("message", errorMessage); map.put("data", null); return map; } }
覆蓋預設的配置：
package com.cxytiandi.gateway.exception; import java.util.Collections; import java.util.List; import org.springframework.beans.factory.ObjectProvider; import org.springframework.boot.autoconfigure.web.ResourceProperties; import org.springframework.boot.autoconfigure.web.ServerProperties; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.boot.web.reactive.error.ErrorAttributes; import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.core.Ordered; import org.springframework.core.annotation.Order; import org.springframework.http.codec.ServerCodecConfigurer; import org.springframework.web.reactive.result.view.ViewResolver; /** * 覆蓋預設的異常處理 * * @author yinjihuan * */ @Configuration @EnableConfigurationProperties({ServerProperties.class, ResourceProperties.class}) public class ErrorHandlerConfiguration { private final ServerProperties serverProperties; private final ApplicationContext applicationContext; private final ResourceProperties resourceProperties; private final List<ViewResolver> viewResolvers; private final ServerCodecConfigurer serverCodecConfigurer; public ErrorHandlerConfiguration(ServerProperties serverProperties, ResourceProperties resourceProperties, ObjectProvider<List<ViewResolver>> viewResolversProvider, ServerCodecConfigurer serverCodecConfigurer, ApplicationContext applicationContext) { this.serverProperties = serverProperties; this.applicationContext = applicationContext; this.resourceProperties = resourceProperties; this.viewResolvers = viewResolversProvider.getIfAvailable(Collections::emptyList); this.serverCodecConfigurer = serverCodecConfigurer; } @Bean @Order(Ordered.HIGHEST_PRECEDENCE) public ErrorWebExceptionHandler errorWebExceptionHandler(ErrorAttributes errorAttributes) { JsonExceptionHandler exceptionHandler = new JsonExceptionHandler( errorAttributes, this.resourceProperties, this.serverProperties.getError(), this.applicationContext); exceptionHandler.setViewResolvers(this.viewResolvers); exceptionHandler.setMessageWriters(this.serverCodecConfigurer.getWriters()); exceptionHandler.setMessageReaders(this.serverCodecConfigurer.getReaders()); return exceptionHandler; } }
注意點
- 異常時如何返回JSON而不是HTML?
在org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler中的getRoutingFunction()方法就是控制返回格式的，原始碼如下：
@Override protected RouterFunction<ServerResponse> getRoutingFunction( ErrorAttributes errorAttributes) { return RouterFunctions.route(acceptsTextHtml(), this::renderErrorView) .andRoute(RequestPredicates.all(), this::renderErrorResponse); }
這邊優先是用HTML來顯示的，想用JSON的改下就可以了，如下：
protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse); }
- getHttpStatus需要重寫
原始的方法是通過status來獲取對應的HttpStatus的，程式碼如下：
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
int statusCode = (int) errorAttributes.get("status");
return HttpStatus.valueOf(statusCode);
}
如果我們定義的格式中沒有status欄位的話，這麼就會報錯，找不到對應的響應碼，要麼返回資料格式中增加status子段，要麼重寫，我這邊返回的是code，所以要重寫，程式碼如下：
@Override
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
int statusCode = (int) errorAttributes.get("code");
return HttpStatus.valueOf(statusCode);
}
寫在最後：
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