SpringBoot | RestTemplate异常处理器ErrorHandler使用详解

喜欢ヅ旅行 2023-10-14 22:33 117阅读 0赞

## 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 ##

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

## RestTemplate异常处理器源码 ##

## ResponseErrorHandler ##

java复制代码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 ##

java复制代码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 ##

java复制代码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 ##

java复制代码	//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

java复制代码 @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;
 }

1.  处理响应，调用handleResponse()方法

java复制代码    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);
            }
    
        }

1.  获取异常处理器，调用getErrorHandler()方法

java复制代码    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

java复制代码/**
     * 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("========================================================");
        }
    }

1.  HttpClientUtils工具类

java复制代码@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;
 }
 
 }

1.  restTemplate调用

java复制代码    /**
         * 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 ##

java复制代码/**
     * 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);
            }
        }
    }