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restTemplate使用和踩坑总结

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}
	 */
	@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;
		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 {

	@Override
	public 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);
		}
		}
	}

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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)

@Bean
	public 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。

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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原文  https://juejin.im/post/5cb96e84e51d456e5d3dac38
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