SpringBoot | RestTemplate异常处理器ErrorHandler使用详解

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引言

  在代码开发过程中，发现很多地方通过RestTemplate调用了第三方接口，而第三方接口需要根据某些状态码或者异常进行重试调用，此时，要么在每个调用的地方进行异常捕获，然后重试；要么在封装的RestTemplate工具类中进行统一异常捕获和封装。当然，本文不走寻常路，将会通过RestTemplate的异常处理器进行操作。

RestTemplate异常处理器介绍

分类

RestTemplate异常处理器源码

ResponseErrorHandler

public interface ResponseErrorHandler {
	/**
	 * 判断请求是否异常
	 * false: 请求返回无错误
	 * true: 请求返回有错误
	 * 可定制化根据某一些status的值进行返回，如根据2xx返回false，非2xx返回true
	 * 同时，可根据ClientHttpResponse的返回结果来定制化判断
	 */
    boolean hasError(ClientHttpResponse var1) throws IOException;
	/**
	 * 处理错误
	 */
    void handleError(ClientHttpResponse var1) throws IOException;
	/**
	 * 默认的异常处理方法
	 */
    default void handleError(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
    	//默认调用handleError(response)方法，也可以重写该方法
        this.handleError(response);
    }
}

DefaultResponseErrorHandler

package org.springframework.web.client;

import java.io.IOException;
import java.nio.charset.Charset;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.HttpStatus.Series;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;

public class DefaultResponseErrorHandler implements ResponseErrorHandler {
    public DefaultResponseErrorHandler() {
    }
	/**
	 * 判断请求是否异常
	 */
    public boolean hasError(ClientHttpResponse response) throws IOException {
        HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
        //statusCode不为空并调用受保护的方法hasError()方法
        return statusCode != null && this.hasError(statusCode);
    }

    protected boolean hasError(HttpStatus statusCode) {
    	//遇到客户端错误4xx或服务端错误5xx，就返回true表示有错误
        return statusCode.series() == Series.CLIENT_ERROR || statusCode.series() == Series.SERVER_ERROR;
    }
	/**
	 * 处理错误
	 */
    public void handleError(ClientHttpResponse response) throws IOException {
    	//获取状态码
        HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
        if (statusCode == null) {
            throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(), response.getHeaders(), this.getResponseBody(response), this.getCharset(response));
        } else {
        	//状态码不为空，则处理错误（主要是4xx和5xx错误）
            this.handleError(response, statusCode);
        }
    }
	/**
	 * 处理错误
	 */
    protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
        String statusText = response.getStatusText();
        HttpHeaders headers = response.getHeaders();
        byte[] body = this.getResponseBody(response);
        Charset charset = this.getCharset(response);
        switch(statusCode.series()) {
        case CLIENT_ERROR:
        	//http客户端错误
            throw HttpClientErrorException.create(statusCode, statusText, headers, body, charset);
        case SERVER_ERROR:
        	//http服务端错误
            throw HttpServerErrorException.create(statusCode, statusText, headers, body, charset);
        default:
            throw new UnknownHttpStatusCodeException(statusCode.value(), statusText, headers, body, charset);
        }
    }

    /** @deprecated */
    @Deprecated
    protected HttpStatus getHttpStatusCode(ClientHttpResponse response) throws IOException {
        HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
        if (statusCode == null) {
            throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(), response.getHeaders(), this.getResponseBody(response), this.getCharset(response));
        } else {
            return statusCode;
        }
    }

    protected byte[] getResponseBody(ClientHttpResponse response) {
        try {
            return FileCopyUtils.copyToByteArray(response.getBody());
        } catch (IOException var3) {
            return new byte[0];
        }
    }

    @Nullable
    protected Charset getCharset(ClientHttpResponse response) {
        HttpHeaders headers = response.getHeaders();
        MediaType contentType = headers.getContentType();
        return contentType != null ? contentType.getCharset() : null;
    }
}

ExtractingResponseErrorHandler

package org.springframework.web.client;

import java.io.IOException;

import java.util.Collections;

import java.util.LinkedHashMap;

import java.util.List;

import java.util.Map;

import org.springframework.http.HttpStatus;

import org.springframework.http.HttpStatus.Series;

import org.springframework.http.client.ClientHttpResponse;

import org.springframework.http.converter.HttpMessageConverter;

import org.springframework.lang.Nullable;

import org.springframework.util.CollectionUtils;
public class ExtractingResponseErrorHandler extends DefaultResponseErrorHandler {

	//定义HttpMessageConverter对象列表

    private List