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

异常处理器	功能描述
ResponseErrorHandler	异常处理器接口，是restTemplate所有异常处理器的实现接口
DefaultResponseErrorHandler	默认的异常处理器，处理客户端和服务端异常
ExtractingResponseErrorHandler	将HTTP错误响应转换RestClientException
NoOpResponseErrorHandler	不处理异常

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<HttpMessageConverter<?>> messageConverters = Collections.emptyList();
    private final Map<HttpStatus, Class<? extends RestClientException>> statusMapping = new LinkedHashMap();
    private final Map<Series, Class<? extends RestClientException>> seriesMapping = new LinkedHashMap();

    public ExtractingResponseErrorHandler() {
    }

    public ExtractingResponseErrorHandler(List<HttpMessageConverter<?>> messageConverters) {
        this.messageConverters = messageConverters;
    }

    public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
        this.messageConverters = messageConverters;
    }

    public void setStatusMapping(Map<HttpStatus, Class<? extends RestClientException>> statusMapping) {
        if (!CollectionUtils.isEmpty(statusMapping)) {
            this.statusMapping.putAll(statusMapping);
        }

    }

    public void setSeriesMapping(Map<Series, Class<? extends RestClientException>> seriesMapping) {
        if (!CollectionUtils.isEmpty(seriesMapping)) {
            this.seriesMapping.putAll(seriesMapping);
        }

    }

    protected boolean hasError(HttpStatus statusCode) {
        if (this.statusMapping.containsKey(statusCode)) {
            return this.statusMapping.get(statusCode) != null;
        } else if (this.seriesMapping.containsKey(statusCode.series())) {
            return this.seriesMapping.get(statusCode.series()) != null;
        } else {
            return super.hasError(statusCode);
        }
    }

    public void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
        if (this.statusMapping.containsKey(statusCode)) {
            this.extract((Class)this.statusMapping.get(statusCode), response);
        } else if (this.seriesMapping.containsKey(statusCode.series())) {
            this.extract((Class)this.seriesMapping.get(statusCode.series()), response);
        } else {
            super.handleError(response, statusCode);
        }

    }
	//转换抽取为RestClientException异常
    private void extract(@Nullable Class<? extends RestClientException> exceptionClass, ClientHttpResponse response) throws IOException {
        if (exceptionClass != null) {
            HttpMessageConverterExtractor<? extends RestClientException> extractor = new HttpMessageConverterExtractor(exceptionClass, this.messageConverters);
            RestClientException exception = (RestClientException)extractor.extractData(response);
            if (exception != null) {
                throw exception;
            }
        }
    }
}

NoOpResponseErrorHandler

	//在TestRestTemplate类中
    private static class NoOpResponseErrorHandler extends DefaultResponseErrorHandler {
        private NoOpResponseErrorHandler() {
        }
		//不做错误处理
        public void handleError(ClientHttpResponse response) throws IOException {
        }
    }

RestTemplate异常处理器被触发源码

1. 初始化errorHandler变量
   
2. 执行doExecute()方法

    @Nullable
    protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback, @Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
        Assert.notNull(url, "URI is required");
        Assert.notNull(method, "HttpMethod is required");
        ClientHttpResponse response = null;

        Object var14;
        try {
            ClientHttpRequest request = this.createRequest(url, method);
            if (requestCallback != null) {
                requestCallback.doWithRequest(request);
            }

            response = request.execute();
            //处理响应
            this.handleResponse(url, method, response);
            var14 = responseExtractor != null ? responseExtractor.extractData(response) : null;
        } catch (IOException var12) {
            String resource = url.toString();
            String query = url.getRawQuery();
            resource = query != null ? resource.substring(0, resource.indexOf(63)) : resource;
            throw new ResourceAccessException("I/O error on " + method.name() + " request for \"" + resource + "\": " + var12.getMessage(), var12);
        } finally {
            if (response != null) {
                response.close();
            }

        }

        return var14;
    }

3. 处理响应，调用handleResponse()方法

    protected void handleResponse(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
    	//获取异常处理器
        ResponseErrorHandler errorHandler = this.getErrorHandler();
        boolean hasError = errorHandler.hasError(response);
        if (this.logger.isDebugEnabled()) {
            try {
                int code = response.getRawStatusCode();
                HttpStatus status = HttpStatus.resolve(code);
                this.logger.debug("Response " + (status != null ? status : code));
            } catch (IOException var8) {
            }
        }

        if (hasError) {
            errorHandler.handleError(url, method, response);
        }

    }

4. 获取异常处理器，调用getErrorHandler()方法

    public ResponseErrorHandler getErrorHandler() {
    	//返回的就是RestTemplate中的成员变量errorHandler
        return this.errorHandler;
    }

RestTemplate异常处理器实践模板

定义一个自定义的errorHandler实现ResponseErrorHandler接口

1. errorHandler

/**
 * 继承默认错误处理器DefaultResponseErrorHandler，无需关注hasError和handlerError方法
 */
@Component
public class MyResponseErrorHandler implements ResponseErrorHandler {

    private static final Logger LOGGER = LoggerFactory.getLogger(MyResponseErrorHandler.class);

    /**
     * my service进行定制化处理
     */
    @Autowired
    private MyService myService;
    
    @Override
    public boolean hasError(ClientHttpResponse clientHttpResponse) throws IOException {
        return clientHttpResponse.getStatusCode().value() != 200 && clientHttpResponse.getStatusCode().value() != 201 && clientHttpResponse.getStatusCode().value() !=302;
    }

    @Override
    public void handleError(ClientHttpResponse clientHttpResponse) throws IOException {
        //遇到401进行单独处理
        if (HttpStatus.UNAUTHORIZED.value() == response.getStatusCode().value()) {
            myService.doSomething(url.getHost());
        } else {
        	//继续抛异常
            throw new RuntimeException(clientHttpResponse.getStatusText());
        }
    }
    @Override
    public void handleError(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
        LOGGER.error("=======================ERROR HANDLER============================");
        LOGGER.error("DateTime：{}", PoolUtil.currentTime());
        LOGGER.error("HOST:{},URI：{}", url.getHost(), url.getPath());
        LOGGER.error("Method：{}", method.name());
        LOGGER.error("Exception：{}", response.getStatusCode());
        LOGGER.error("StatusText: {}", response.getStatusText());
        LOGGER.error("========================================================");
    }
}

2. HttpClientUtils工具类

@Slf4j
public class HttpClientUtils {
	//http协议
    private static final String HTTP_PROTOCOL = "http";
  	//https协议
    private static final String HTTPS_PROTOCAL = "https";
	//最大连接数
    private static final int MAX_CONNECT = 300;
    //默认连接数
    private static final int DEFAULT_CONNECT = 200;
    public HttpClientUtils(){

    }
	/**
	 * new一个http client
	 */
    public static CloseableHttpClient newHttpClientForHttpsOrHttp()  {
        HttpClientBuilder build = HttpClientBuilder.create();

        try {
             SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, new TrustStrategy() {
                public boolean isTrusted(X509Certificate[] arg0, String arg1){
                    return true;
                }
            }).build();
            build.setSslcontext(sslContext);
            //X509HostnameVerifier校验
            X509HostnameVerifier hostnameVerifier = new X509HostnameVerifier() {
                public boolean verify(String arg0, SSLSession arg1) {
                    return true;
                }
                public void verify(String arg0, SSLSocket arg1){}
                public void verify(String arg0, String[] arg1, String[] arg2){}
                public void verify(String arg0, X509Certificate arg1){}
            };
			//SSL连接socket工厂
            SSLConnectionSocketFactory sslSocketFactory = new SSLConnectionSocketFactory(sslContext, hostnameVerifier);
            //http和https协议register
            Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory> create()
                    .register(HTTP_PROTOCOL, PlainConnectionSocketFactory.getSocketFactory()).register(HTTPS_PROTOCAL, sslSocketFactory)
                    .build();

	        //连接池
            PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
            connMgr.setDefaultMaxPerRoute(DEFAULT_CONNECT_NUM);
            connMgr.setMaxTotal(MAX_CONNECT_NUM);
            build.setConnectionManager(poolingHttpClientConnectionManager);
			//构建CloseableHttpClient
            CloseableHttpClient closeableHttpClient = build.build();
            return closeableHttpClient;
        } catch (Exception e ) {
        	log.error("异常:{}", e.getLocalizedMessage());
        }
        return null;
    }

}

4. restTemplate调用

    /**
     * 获取远程连接template
     *
     * @return
     */
    public static RestTemplate getRestTempte() {
        try {
            HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(HttpClientUtils.newHttpClientForHttpsOrHttp());
            factory.setConnectTimeout(30000);
            //设置handler
            return new RestTemplate(factory).setErrorHandler(new MyResponseErrorHandler());
        } catch (Exception e) {
            return null;
        }
    }

定义一个自定义的errorHandler继承DefaultResponseErrorHandler类

/**
 * 继承默认错误处理器DefaultResponseErrorHandler，无需关注hasError和handlerError方法
 */
@Component
public class MyResponseErrorHandler extends DefaultResponseErrorHandler {

    private static final Logger LOGGER = LoggerFactory.getLogger(MyResponseErrorHandler.class);

    /**
     * my service进行定制化处理
     */
    @Autowired
    private MyService myService;

    @Override
    public void handleError(URI url, HttpMethod method, ClientHttpResponse response) throws IOException {
        LOGGER.error("=======================ERROR HANDLER============================");
        LOGGER.error("DateTime：{}", PoolUtil.currentTime());
        LOGGER.error("HOST:{},URI：{}", url.getHost(), url.getPath());
        LOGGER.error("Method：{}", method.name());
        LOGGER.error("Exception：{}", response.getStatusCode());
        LOGGER.error("StatusText: {}", response.getStatusText());
        LOGGER.error("========================================================");
        //遇到401进行单独处理
        if (HttpStatus.UNAUTHORIZED.value() == response.getStatusCode().value()) {
            myService.doSomething(url.getHost());
        } else {
            this.handleError(response);
        }
    }
}