Spring Cloud Gateway 中的全局异常处理不能直接用 @ControllerAdvice 来处理，通过跟踪异常信息的抛出，找到对应的源码，自定义一些处理逻辑来符合业务的需求。
网关都是给接口做代理转发的，后端对应的都是 REST API，返回数据格式都是 JSON。如果不做处理，当发生异常时，Gateway 默认给出的错误信息是页面，不方便前端进行异常处理。
需要对异常信息进行处理，返回 JSON 格式的数据给客户端。下面先看实现的代码，后面再跟大家讲下需要注意的地方。
自定义异常处理逻辑：
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;
/**
* 自定义异常处理
*
* <p> 异常时用 JSON 代替 HTML 异常信息 <p>
*
* @author yinjihuan
*
*/
public class JsonExceptionHandler extends DefaultErrorWebExceptionHandler {
public JsonExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties,
ErrorProperties errorProperties, ApplicationContext applicationContext) {
super(errorAttributes, resourceProperties, errorProperties, applicationContext);
}
/**
* 获取异常属性
*/
@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));
}
/**
* 指定响应处理方法为 JSON 处理的方法
* @param errorAttributes
*/
@Override
protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse);
}
/**
* 根据 code 获取对应的 HttpStatus
* @param errorAttributes
*/
@Override
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
int statusCode = (int) errorAttributes.get(“code”);
return HttpStatus.valueOf(statusCode);
}
/**
* 构建异常信息
* @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();
}
/**
* 构建返回的 JSON 数据格式
* @param status 状态码
* @param errorMessage 异常信息
* @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;
}
}
覆盖默认的配置：
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;
/**
* 覆盖默认的异常处理
*
* @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;
}
}
注意点
异常时如何返回 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，原代码如下：
@Override
protected RouterFunction<ServerResponse> getRoutingFunction(
ErrorAttributes errorAttributes) {
return RouterFunctions.route(acceptsTextHtml(), this::renderErrorView)
.andRoute(RequestPredicates.all(), this::renderErrorResponse);
}
这边优先是用 HTML 来显示的，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 需要重写
原始的方法是通过 status 来获取对应的 HttpStatus 的，代码如下：
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
int statusCode = (int) errorAttributes.get(“status”);
return HttpStatus.valueOf(statusCode);
}
如果我们定义的格式中没有 status 字段的话，这么就会报错，找不到对应的响应码，要么返回数据格式中增加 status 子段，要么重写，我这边返回的是 code，所以要重写，代码如下：
@Override
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
int statusCode = (int) errorAttributes.get(“code”);
return HttpStatus.valueOf(statusCode);
}
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