Java网关的统一异常处理

使用网关时，往往会出现一些异常情况，导致没办法请求到真实的URL路径，所以在发生异常时，最好使用一个统一异常处理，返回一些友好的信息。

我使用的是SpringCloud-Gateway网关

统一异常处理步骤：

1. 添加异常配置类

import com.example.itvgetway.exception.CustomWebExceptionHandler;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
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;

import java.util.Collections;
import java.util.List;



@Configuration
public class ExceptionConfig {

    /**
     * 自定义异常处理[@@]注册Bean时依赖的Bean，会从容器中直接获取，所以直接注入即可
     */
    @Primary
    @Bean
    @Order(Ordered.HIGHEST_PRECEDENCE)
    public ErrorWebExceptionHandler errorWebExceptionHandler(ObjectProvider> viewResolversProvider,
                                                             ServerCodecConfigurer serverCodecConfigurer,
                                                             CustomWebExceptionHandler customWebExceptionHandler) {
        customWebExceptionHandler.setViewResolvers(viewResolversProvider.getIfAvailable(Collections::emptyList));
        customWebExceptionHandler.setMessageWriters(serverCodecConfigurer.getWriters());
        customWebExceptionHandler.setMessageReaders(serverCodecConfigurer.getReaders());
        return customWebExceptionHandler;
    }
}

2. 编写异常处理器

import com.example.itvgetway.util.ApiResult;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.util.Assert;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.function.server.RequestPredicates;
import org.springframework.web.reactive.function.server.RouterFunctions;
import org.springframework.web.reactive.function.server.ServerRequest;
import org.springframework.web.reactive.function.server.ServerResponse;
import org.springframework.web.reactive.result.view.ViewResolver;
import org.springframework.web.server.ResponseStatusException;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import java.util.Collections;
import java.util.List;



@Component
public class CustomWebExceptionHandler implements ErrorWebExceptionHandler {

    private static final Logger log = LoggerFactory.getLogger(CustomWebExceptionHandler.class);

    /**
     * MessageReader
     */
    private List> messageReaders = Collections.emptyList();

    /**
     * MessageWriter
     */
    private List> messageWriters = Collections.emptyList();

    /**
     * ViewResolvers
     */
    private List viewResolvers = Collections.emptyList();

    /**
     * 存储处理异常后的信息
     */
    private ThreadLocal exceptionHandlerResult = new ThreadLocal<>();

    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setMessageReaders(List> messageReaders) {
        Assert.notNull(messageReaders, "'messageReaders' must not be null");
        this.messageReaders = messageReaders;
    }

    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setViewResolvers(List viewResolvers) {
        this.viewResolvers = viewResolvers;
    }

    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    public void setMessageWriters(List> messageWriters) {
        Assert.notNull(messageWriters, "'messageWriters' must not be null");
        this.messageWriters = messageWriters;
    }

    @Override
    public Mono handle(ServerWebExchange exchange, Throwable ex) {
        // 按照异常类型进行处理
        HttpStatus httpStatus;
        String body;
        //todo 这里可以自己定义业务需要的异常
        if (ex instanceof ResponseStatusException) {
            ResponseStatusException responseStatusException = (ResponseStatusException) ex;
            httpStatus = responseStatusException.getStatus();
            body = responseStatusException.getMessage();

        }  else {
            httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
            body = httpStatus.name();
        }

        ServerHttpRequest request = exchange.getRequest();
        log.error("[全局异常处理] 异常请求路径:{}, 记录异常信息:{}", request.getPath(), ex.getMessage());
        ex.printStackTrace();

        // 参考AbstractErrorWebExceptionHandler
        if (exchange.getResponse().isCommitted()) {
            return Mono.error(ex);
        }

        exceptionHandlerResult.set(ApiResult.error(httpStatus, body));

        ServerRequest newRequest = ServerRequest.create(exchange, this.messageReaders);
        return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse).route(newRequest)
                .switchIfEmpty(Mono.error(ex))
                .flatMap((handler) -> handler.handle(newRequest))
                .flatMap((response) -> write(exchange, response));

    }

    /**
     * 参考DefaultErrorWebExceptionHandler
     * 在这里定义返回的是Json还是Html
     */
    protected Mono renderErrorResponse(ServerRequest request) {
        ApiResult result = exceptionHandlerResult.get();
        return ServerResponse.status(result.getCode())
                .contentType(MediaType.APPLICATION_JSON)
                .body(BodyInserters.fromValue(result));
    }

    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    private Mono write(ServerWebExchange exchange,
                                       ServerResponse response) {
        exchange.getResponse().getHeaders()
                .setContentType(response.headers().getContentType());
        return response.writeTo(exchange, new ResponseContext());
    }

    /**
     * 参考AbstractErrorWebExceptionHandler
     */
    private class ResponseContext implements ServerResponse.Context {

        @Override
        public List> messageWriters() {
            return CustomWebExceptionHandler.this.messageWriters;
        }

        @Override
        public List viewResolvers() {
            return CustomWebExceptionHandler.this.viewResolvers;
        }
    }
}

3. 定义返回数据格式

import org.springframework.http.HttpStatus;

import java.io.Serializable;


public class ApiResult implements Serializable {

    private static final long serialVersionUID = 1166356696537391753L;

    private Integer code;

    private String msg;

    private T data;

    public ApiResult() {
    }

    public ApiResult(Integer code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }

    public static ApiResult success() {
        return new ApiResult(HttpStatus.OK.value(), "success", null);
    }

    public static ApiResult success(String msg) {
        return new ApiResult(HttpStatus.OK.value(), msg, null);
    }

    public static ApiResult success(String msg, Object data) {
        return new ApiResult(HttpStatus.OK.value(), msg, data);
    }

    public static ApiResult error(HttpStatus status, String msg) {
        return new ApiResult(status.value(), msg, null);
    }

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Result{" +
                "code=" + code +
                ", msg='" + msg + '\'' +
                ", data=" + data +
                '}';
    }
}