RestTemplate详解

拼搏现实的明天。 2022-05-22 09:05 346阅读 0赞

概述

  1.     RestTemplate与httpClient类似，都是java中可以模拟http请求的封装。httpClient的使用，已经在另一篇文章中有所论述，但是RestTemplate比httpClient更优雅，它是spring中的一个封装功能。
  3.     RestTemplate也是java中的模板类。采用的设计模式中的模板模式。

源码解析

  1.     RestTemplate继承InterceptingHttpAccessor抽象类，实现RestOperation接口
  3. public class RestTemplate extends InterceptingHttpAccessor implements RestOperations
  5.     在RestOperations定义了基本的Rest操作集合。RestTemplate实现了这个接口
  7. public interface RestOperations {
  9.     // GET
  11.     <T> T getForObject(String url, Class<T> responseType, Object... uriVariables) throws RestClientException;
  13.     <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException;
  15.     <T> T getForObject(URI url, Class<T> responseType) throws RestClientException;
  17.     <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables) throws RestClientException;
  19.     <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException;
  21.     <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType) throws RestClientException;
  24.     // HEAD
  26.     HttpHeaders headForHeaders(String url, Object... uriVariables) throws RestClientException;
  28.     HttpHeaders headForHeaders(String url, Map<String, ?> uriVariables) throws RestClientException;
  30.     HttpHeaders headForHeaders(URI url) throws RestClientException;
  33.     // POST
  35.     URI postForLocation(String url, Object request, Object... uriVariables) throws RestClientException;
  37.     URI postForLocation(String url, Object request, Map<String, ?> uriVariables) throws RestClientException;
  39.     URI postForLocation(URI url, Object request) throws RestClientException;
  41.     <T> T postForObject(String url, Object request, Class<T> responseType, Object... uriVariables)
  42.             throws RestClientException;
  44.     <T> T postForObject(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
  45.             throws RestClientException;
  47.     <T> T postForObject(URI url, Object request, Class<T> responseType) throws RestClientException;
  49.     <T> ResponseEntity<T> postForEntity(String url, Object request, Class<T> responseType, Object... uriVariables)
  50.             throws RestClientException;
  52.     <T> ResponseEntity<T> postForEntity(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
  53.             throws RestClientException;
  55.     <T> ResponseEntity<T> postForEntity(URI url, Object request, Class<T> responseType) throws RestClientException;
  58.     // PUT
  60.     void put(String url, Object request, Object... uriVariables) throws RestClientException;
  62.     void put(String url, Object request, Map<String, ?> uriVariables) throws RestClientException;
  64.     void put(URI url, Object request) throws RestClientException;
  67.     // PATCH
  69.     <T> T patchForObject(String url, Object request, Class<T> responseType, Object... uriVariables)
  70.             throws RestClientException;
  72.     <T> T patchForObject(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
  73.             throws RestClientException;
  75.     <T> T patchForObject(URI url, Object request, Class<T> responseType) throws RestClientException;
  79.     // DELETE
  81.     void delete(String url, Object... uriVariables) throws RestClientException;
  83.     void delete(String url, Map<String, ?> uriVariables) throws RestClientException;
  85.     void delete(URI url) throws RestClientException;
  88.     // OPTIONS
  90.     Set<HttpMethod> optionsForAllow(String url, Object... uriVariables) throws RestClientException;
  92.     Set<HttpMethod> optionsForAllow(String url, Map<String, ?> uriVariables) throws RestClientException;
  94.     Set<HttpMethod> optionsForAllow(URI url) throws RestClientException;
  97.     // exchange
  99.     <T> ResponseEntity<T> exchange(String url, HttpMethod method, HttpEntity<?> requestEntity,
  100.             Class<T> responseType, Object... uriVariables) throws RestClientException;
  102.     <T> ResponseEntity<T> exchange(String url, HttpMethod method, HttpEntity<?> requestEntity,
  103.             Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException;
  105.     <T> ResponseEntity<T> exchange(URI url, HttpMethod method, HttpEntity<?> requestEntity,
  106.             Class<T> responseType) throws RestClientException;
  108.     <T> ResponseEntity<T> exchange(String url,HttpMethod method, HttpEntity<?> requestEntity,
  109.             ParameterizedTypeReference<T> responseType, Object... uriVariables) throws RestClientException;
  111.     <T> ResponseEntity<T> exchange(String url, HttpMethod method, HttpEntity<?> requestEntity,
  112.             ParameterizedTypeReference<T> responseType, Map<String, ?> uriVariables) throws RestClientException;
  114.     <T> ResponseEntity<T> exchange(URI url, HttpMethod method, HttpEntity<?> requestEntity,
  115.             ParameterizedTypeReference<T> responseType) throws RestClientException;
  117.     <T> ResponseEntity<T> exchange(RequestEntity<?> requestEntity, Class<T> responseType) throws RestClientException;
  119.     <T> ResponseEntity<T> exchange(RequestEntity<?> requestEntity, ParameterizedTypeReference<T> responseType)
  120.             throws RestClientException;
  123.     // general execution
  125.     <T> T execute(String url, HttpMethod method, RequestCallback requestCallback,
  126.             ResponseExtractor<T> responseExtractor, Object... uriVariables) throws RestClientException;
  128.     <T> T execute(String url, HttpMethod method, RequestCallback requestCallback,
  129.             ResponseExtractor<T> responseExtractor, Map<String, ?> uriVariables) throws RestClientException;
  131.     <T> T execute(URI url, HttpMethod method, RequestCallback requestCallback,
  132.             ResponseExtractor<T> responseExtractor) throws RestClientException;
  134. }
  136.     PostForObject与PostForEntity的区别在于前者请求返回就是响应体，后者返回的是响应行，响应头，响应体。
  138.     这里也有一个基础的http访问类HttpAccessor,里面主要是一个工厂方法，用来构造HttpRequestFactory
  140. public abstract class HttpAccessor {
  142.     protected final Log logger = LogFactory.getLog(getClass());
  144.     private ClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
  146.     public void setRequestFactory(ClientHttpRequestFactory requestFactory) {
  147.         Assert.notNull(requestFactory, "ClientHttpRequestFactory must not be null");
  148.         this.requestFactory = requestFactory;
  149.     }
  151.     public ClientHttpRequestFactory getRequestFactory() {
  152.         return this.requestFactory;
  153.     }
  155.     protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
  156.         ClientHttpRequest request = getRequestFactory().createRequest(url, method);
  157.         if (logger.isDebugEnabled()) {
  158.             logger.debug("Created " + method.name() + " request for \"" + url + "\"");
  159.         }
  160.         return request;
  161.     }
  163. }

springboot对RestTemplate的集成

  1.     首先添加配置;
  3. @Configuration
  4. public class RestTemplateConfig {
  6.     @Bean
  7.     public RestTemplate restTemplate(){
  8.         RestTemplate restTemplate = new RestTemplate();
  9.         restTemplate.getMessageConverters().set(1, new StringHttpMessageConverter(StandardCharsets.UTF_8));
  10.         return restTemplate;
  11.     }
  13. }
  15.     不然在service中的autowired会注入不进去
  17.     再设置请求头
  19. HttpHeaders headers = new HttpHeaders();
  20.         headers.setContentType(MediaType.APPLICATION_JSON);
  22.     请求行，请求头，请求体分装成 一个Entity
  24. HttpEntity<String> entity = new HttpEntity<>(JSONObject.toJSONString(dto),headers );
  26.     接下来就调用出
  28. ResponseEntity<String> r = restTemplate.exchange(ADD_URL, HttpMethod.POST, entity, String.class);
  30.     那就可以请求到结果了。

总结

  1.     整个restTemplate比httpClient使用更加优雅，分装的更好
  3.     restTemplate是org.springframework.web.client包中的类,是spring提供的类。  
  6.     httpclient是org.apache.http.client包中的类，是apache提供的类。

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