日常工作中肯定会遇到服务之间的调用,尤其是现在都是微服务的架构,所以总结一下restTemplate的最常用的用法以及自己踩过的坑。
restTemplate的使用
restTemplate底层调用的是Execute方法,而Execute底层调用的是doExecute,它是基于http协议的,底层还是httpClient 的使用。
/*** Execute the given method on the provided URI.* <p>The {@link ClientHttpRequest} is processed using the {@link RequestCallback};* the response with the {@link ResponseExtractor}.* @param url the fully-expanded URL to connect to* @param method the HTTP method to execute (GET, POST, etc.)* @param requestCallback object that prepares the request (can be {@code null})* @param responseExtractor object that extracts the return value from the response (can be {@code null})* @return an arbitrary object, as returned by the {@link ResponseExtractor}*/@Nullableprotected <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;try {ClientHttpRequest request = createRequest(url, method);if (requestCallback != null) {requestCallback.doWithRequest(request);}response = request.execute();handleResponse(url, method, response);return (responseExtractor != null ? responseExtractor.extractData(response) : null);}catch (IOException ex) {String resource = url.toString();String query = url.getRawQuery();resource = (query != null ? resource.substring(0, resource.indexOf('?')) : resource);throw new ResourceAccessException("I/O error on " + method.name() +" request for \"" + resource + "\": " + ex.getMessage(), ex);}finally {if (response != null) {response.close();}}}
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我们一般都是用的restTepmlate的exchange方法,这个方法比较灵活,可以接受可变参数,重载方法也有很多。 当然 restTemplate还有其他很多方法,而且遵循restFul风格,像PUT POST GET PATCH DELETE 等都有对应的方法,按需使用。这里就不贴源码了。
然后就贴一个使用案例代码上来:
public YourResponse sampleRestTepmlate (YourRequest request) throws Exception {UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(this.serviceUrl);builder.path("urlpath");log.info("url : {}, request : {}", builder.toUriString(), JsonUtils.toJson(request));HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_JSON);headers.set("headername","headervalue");headers.add("anotherway", "value");HttpEntity<YourRequest> requestEntity = new HttpEntity<>(request, headers);ResponseEntity<YourResponse> responseEntity = null;try {responseEntity = restTemplate.exchange(builder.toUriString(), HttpMethod.POST, requestEntity,YourResponse.class);return responseEntity.getBody();} catch (Exception e) {log.error("exception:{}",e.getMessage());}}
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踩坑大道
这里就要说一下我遇到的坑了。 在使用restTemplate的时候,当你的call没有成功返回200的时候,比如返回400 500之类的,restTemplate里面有一个DefaultResponseErrorHandler,他会自动拦截住这些httpstatus 为400 500的response然后给你抛出一个异常。这就意味着,当你也想拿到带有错误信息的response的时候,他不会给你!它会给你抛出exception并且只是给你返回一个简单的类似500 Internal error! WTF!
贴上这段坑爹的代码:
/*** Handle the error in the given response with the given resolved status code.* <p>This default implementation throws a {@link HttpClientErrorException} if the response status code* is {@link org.springframework.http.HttpStatus.Series#CLIENT_ERROR}, a {@link HttpServerErrorException}* if it is {@link org.springframework.http.HttpStatus.Series#SERVER_ERROR},* and a {@link RestClientException} in other cases.* @since 5.0*/protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {switch (statusCode.series()) {case CLIENT_ERROR:throw new HttpClientErrorException(statusCode, response.getStatusText(),response.getHeaders(), getResponseBody(response), getCharset(response));case SERVER_ERROR:throw new HttpServerErrorException(statusCode, response.getStatusText(),response.getHeaders(), getResponseBody(response), getCharset(response));default:throw new UnknownHttpStatusCodeException(statusCode.value(), response.getStatusText(),response.getHeaders(), getResponseBody(response), getCharset(response));}}
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脱坑之计
遇到了坑就不要害怕,这个问题可以这么解决:
1.不用restTemplate去请求,可以采用httpClient底层去实现
2.重写handleError方法,自定义ErrorHandle继承DefaultResponseErrorHandler
在已经写完实现之后,我选择方式2 : )
@Builder
@Slf4j
public class MyErrorHandle extends DefaultResponseErrorHandler {@Overridepublic void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {int status = statusCode.value();if (status == 200 || status == 400 || status == 500) {//do what u want to do} else {super.handleError(response,statusCode);}}}复制代码
然后在初始化restTemplate的时候调用setErrorHandle方法就可以了。
restTemplate.setErrorHandler(YourErrorHandle).
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至于方式一这里不提了。
导入证书
有的时候当我们调用对方的server时,基于https 的协议是需要导入证书的,那我们该怎么把证书融入到restTemplate中呢?(又一个坑)
@Beanpublic RestTemplate buildRestTemplateWithinSSl(@Value("${service.connectTimeout}") int connectTimeout,@Value("${service.readTimeout}") int readTimeout,@Value("${service.sslFilePath}") String filePath,@Value("${service.sslpassword}") String sslPassword) throws Exception{RestTemplate template = restTemplateBuilder.setConnectTimeout(connectTimeout).setReadTimeout(readTimeout).build();String workingDirectory = BeanUtility.getWorkingDirectory();SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(new File(workingDirectory + "/" + filePath), sslPassword.toCharArray()).build();SSLConnectionSocketFactory socketFactory = new SSLConnectionSocketFactory(sslContext, NoopHostnameVerifier.INSTANCE);CloseableHttpClient httpClient = HttpClients.custom().setSSLSocketFactory(socketFactory).build();HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(httpClient);template.setRequestFactory(factory);return template;}
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相当于重新给RequestFactory值,构造一个已经带有ssl证书的factory给他。
这里注意两个地方:
SSLConnectionSocketFactory socketFactory = new SSLConnectionSocketFactory(sslContext, NoopHostnameVerifier.INSTANCE);
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这里有个参数是NoopHostnameVerifier.INSTANCE, 这里是可以无视ip的,也就是ip或者域名形式都可以。 (适用于对方给我提供证书和 ip地址,试了半天死活不通的情况。。)
第二个就是一个工具类的使用,我相信很多时候new file的时候很容易被路径绕晕。
String workingDirectory = BeanUtility.getWorkingDirectory();
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这个工具类获得的路径不用你去担心,只要你的jks文件和你的jar包同级就行。管他什么环境什么路径,很方便。
贴上地址: github.com/AnsonCong/A…
本地调试证书导入jdk就行。
记录下导入证书的方法:
keytool -import -alias {别名} -file {路径\证书名}.cer -keystore "{jdk路径\jre\lib\security\cacerts}" -storepass {password} -trustcacerts
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删除证书:
keytool -delete -alias {别名} -keystore "C:\Program Files\Java\jdk1.7.0_25\jre\lib\security\cacerts" -storepass {password}
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查看所有安装证书列表
keytool -list -v -keystore "C:\Users\1580977\Downloads\jdk1.8.0_101\jre\lib\security\cacerts" -storepass {password} >> C:\Desktop\abcd.txt
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生成jks文件 (没有默认生存,有就导入)
keytool -import -alias {别名} -file {证书名}.cer -keystore {命名}.jks
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最后
RestTemplate是Spring提供的用于访问Rest服务的客户端,RestTemplate提供了多种便捷访问远程Http服务的方法,能够大大提高客户端的编写效率。
更多restTemplate详细资料,可以参考: juejin.im/post/5b88b1… www.zifangsky.cn/1221.html
或者其他掘金好文。