Introduction to global exception handling of Spring Cloud Gateway (code example)

This article brings you an introduction to Spring Cloud Gateway's global exception handling (code examples). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Global exception handling in Spring Cloud Gateway cannot be handled directly with @ControllerAdvice. By tracking the exception information thrown, find the corresponding source code and customize some processing logic to meet business needs.

The gateway is a proxy forwarder for the interface, the backend corresponds to the REST API, and the return data format is JSON. If no processing is done, when an exception occurs, the default error message given by Gateway is the page, which is inconvenient for the front-end to handle exceptions.

Need to process exception information and return data in JSON format to the client. Let’s first look at the implemented code, and then I’ll tell you what you need to pay attention to.

Customized exception handling logic:

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;
    }

}

Override the default configuration:

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;
    }
    
}

Notes

• How to return JSON instead of HTML when an exception occurs ?

The getRoutingFunction() method in org.springframework.boot.autoconfigure.web.reactive.error.DefaultErrorWebExceptionHandler controls the return format. The original code is as follows:

@Override
protected RouterFunction<ServerResponse> getRoutingFunction(
            ErrorAttributes errorAttributes) {
       return RouterFunctions.route(acceptsTextHtml(), this::renderErrorView)
                .andRoute(RequestPredicates.all(), this::renderErrorResponse);
}

This Edge priority is displayed in HTML. If you want to use JSON, you can change it, as follows:

protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
       return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse);
}

• getHttpStatus needs to be rewritten

The original method is through status To get the corresponding HttpStatus, the code is as follows:

protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
      int statusCode = (int) errorAttributes.get("status");
      return HttpStatus.valueOf(statusCode);
}

If there is no status field in the format we define, an error will be reported and the corresponding response code cannot be found, or the status subsection will be added to the returned data format. , or rewrite. What I return here is code, so I need to rewrite it. The code is as follows:

@Override
protected HttpStatus getHttpStatus(Map<String, Object> errorAttributes) {
    int statusCode = (int) errorAttributes.get("code");
    return HttpStatus.valueOf(statusCode);
}

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