一、概述
spring框架提供的RestTemplate類可用于在應(yīng)用中調(diào)用rest服務(wù)，它簡(jiǎn)化了與http服務(wù)的通信方式，統(tǒng)一了RESTful的標(biāo)準(zhǔn)，封裝了http鏈接， 我們只需要傳入url及返回值類型即可。相較于之前常用的HttpClient，RestTemplate是一種更優(yōu)雅的調(diào)用RESTful服務(wù)的方式。
在Spring應(yīng)用程序中訪問第三方REST服務(wù)與使用Spring RestTemplate類有關(guān)。RestTemplate類的設(shè)計(jì)原則與許多其他Spring *模板類(例如JdbcTemplate、JmsTemplate)相同，為執(zhí)行復(fù)雜任務(wù)提供了一種具有默認(rèn)行為的簡(jiǎn)化方法。
RestTemplate默認(rèn)依賴JDK提供http連接的能力（HttpURLConnection），如果有需要的話也可以通過setRequestFactory方法替換為例如 Apache HttpComponents、Netty或OkHttp等其它HTTP library。
考慮到RestTemplate類是為調(diào)用REST服務(wù)而設(shè)計(jì)的，因此它的主要方法與REST的基礎(chǔ)緊密相連就不足為奇了，后者是HTTP協(xié)議的方法:HEAD、GET、POST、PUT、DELETE和OPTIONS。例如，RestTemplate類具有headForHeaders()、getForObject()、postForObject()、put()和delete()等方法。
二、實(shí)現(xiàn)
最新api地址：https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html
RestTemplate包含以下幾個(gè)部分：
- HttpMessageConverter 對(duì)象轉(zhuǎn)換器
- ClientHttpRequestFactory 默認(rèn)是JDK的HttpURLConnection
- ResponseErrorHandler 異常處理
- ClientHttpRequestInterceptor 請(qǐng)求攔截器
常規(guī)配置
public MyRestClientService(RestTemplateBuilder restTemplateBuilder) { this.restTemplate = restTemplateBuilder .basicAuthorization("username", "password") .setConnectTimeout(3000) .setReadTimeout(5000) .rootUri("http://api.example.com/") .build(); } |
ClientHttpRequestInterceptor
學(xué)習(xí)使用帶有Spring RestTemplate的ClientHttpRequestInterceptor，以Spring AOP風(fēng)格記錄請(qǐng)求和響應(yīng)頭和主體。
攔截器記錄請(qǐng)求和響應(yīng)
import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.http.HttpRequest;import org.springframework.http.client.ClientHttpRequestExecution;import org.springframework.http.client.ClientHttpRequestInterceptor;import org.springframework.http.client.ClientHttpResponse;import org.springframework.util.StreamUtils; import java.io.IOException;import java.nio.charset.Charset; public class RequestResponseLoggingInterceptor implements ClientHttpRequestInterceptor { private final Logger log = LoggerFactory.getLogger(this.getClass()); @Override public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException { logRequest(request, body); ClientHttpResponse response = execution.execute(request, body); logResponse(response); //Add optional additional headers response.getHeaders().add("headerName", "VALUE"); return response; } private void logRequest(HttpRequest request, byte[] body) throws IOException { if (log.isDebugEnabled()) { log.debug("===========================request begin================================================"); log.debug("URI : {}", request.getURI()); log.debug("Method : {}", request.getMethod()); log.debug("Headers : {}", request.getHeaders()); log.debug("Request body: {}", new String(body, "UTF-8")); log.debug("==========================request end================================================"); } } private void logResponse(ClientHttpResponse response) throws IOException { if (log.isDebugEnabled()) { log.debug("============================response begin=========================================="); log.debug("Status code : {}", response.getStatusCode()); log.debug("Status text : {}", response.getStatusText()); log.debug("Headers : {}", response.getHeaders()); log.debug("Response body: {}", StreamUtils.copyToString(response.getBody(), Charset.defaultCharset())); log.debug("=======================response end================================================="); } }} |
注冊(cè)ClientHttpRequestInterceptor
@Beanpublic RestTemplate restTemplate(){ RestTemplate restTemplate = new RestTemplate(); restTemplate.setRequestFactory(newBufferingClientHttpRequestFactory(clientHttpRequestFactory())); restTemplate.setMessageConverters(Collections.singletonList(mappingJacksonHttpMessageConverter())); restTemplate.setInterceptors( Collections.singletonList(newRequestResponseLoggingInterceptor()) ); return restTemplate;} |
三、請(qǐng)求示例
GET
private static void getEmployees(){ final String uri = "http://localhost:8080/springrestexample/employees"; RestTemplate restTemplate = new RestTemplate(); String result = restTemplate.getForObject(uri, String.class); System.out.println(result);} |
使用RestTemplate定制HTTP頭文件
private static void getEmployees(){ final String uri = "http://localhost:8080/springrestexample/employees"; RestTemplate restTemplate = new RestTemplate(); HttpHeaders headers = new HttpHeaders(); headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON)); HttpEntity<String> entity = new HttpEntity<String>("parameters", headers); ResponseEntity<String> result = restTemplate.exchange(uri, HttpMethod.GET, entity, String.class); System.out.println(result);} |
Get請(qǐng)求獲取響應(yīng)為一個(gè)對(duì)象
private static void getEmployees(){ final String uri = "http://localhost:8080/springrestexample/employees"; RestTemplate restTemplate = new RestTemplate(); EmployeeListVO result = restTemplate.getForObject(uri, EmployeeListVO.class); System.out.println(result);} |
URL 參數(shù)
private static void getEmployeeById(){ final String uri = "http://localhost:8080/springrestexample/employees/{id}"; Map<String, String> params = new HashMap<String, String>(); params.put("id", "1"); RestTemplate restTemplate = new RestTemplate(); EmployeeVO result = restTemplate.getForObject(uri, EmployeeVO.class, params); System.out.println(result);} |
POST
private static void createEmployee(){ final String uri = "http://localhost:8080/springrestexample/employees"; EmployeeVO newEmployee = new EmployeeVO(-1, "Adam", "Gilly", "test@email.com"); RestTemplate restTemplate = new RestTemplate(); EmployeeVO result = restTemplate.postForObject( uri, newEmployee, EmployeeVO.class); System.out.println(result);} |
Submit Form Data
HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED); MultiValueMap<String, String> map= new LinkedMultiValueMap<>();map.add("id", "1"); HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers); RestTemplate restTemplate = new RestTemplate();EmployeeVO result = restTemplate.postForObject( uri, request, EmployeeVO.class);System.out.println(result); |
PUT
private static void updateEmployee(){ final String uri = "http://localhost:8080/springrestexample/employees/{id}"; Map<String, String> params = new HashMap<String, String>(); params.put("id", "2"); EmployeeVO updatedEmployee = new EmployeeVO(2, "New Name", "Gilly", "test@email.com"); RestTemplate restTemplate = new RestTemplate(); restTemplate.put ( uri, updatedEmployee, params);} |
Simple PUT
Foo updatedInstance = new Foo("newName");updatedInstance.setId(createResponse.getBody().getId());String resourceUrl = fooResourceUrl + '/' + createResponse.getBody().getId();HttpEntity<Foo> requestUpdate = new HttpEntity<>(updatedInstance, headers);template.exchange(resourceUrl, HttpMethod.PUT, requestUpdate, Void.class); |
使用.exchange和請(qǐng)求回調(diào)
RequestCallback requestCallback(final Foo updatedInstance) { return clientHttpRequest -> { ObjectMapper mapper = new ObjectMapper(); mapper.writeValue(clientHttpRequest.getBody(), updatedInstance); clientHttpRequest.getHeaders().add( HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE); clientHttpRequest.getHeaders().add( HttpHeaders.AUTHORIZATION, "Basic " + getBase64EncodedLogPass()); };} |
DELETE
private static void deleteEmployee(){ final String uri = "http://localhost:8080/springrestexample/employees/{id}"; Map<String, String> params = new HashMap<String, String>(); params.put("id", "2"); RestTemplate restTemplate = new RestTemplate(); restTemplate.delete ( uri, params );} |
參考資料：
https://howtodoinjava.com/spring-restful/spring-restful-client-resttemplate-example/
https://www.xncoding.com/2017/07/06/spring/sb-restclient.html
https://www.baeldung.com/rest-template
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