restTemplate 支持GET请求，并支持传递Request body参数

╰+攻爆jí腚メ 2021-10-24 01:24 355阅读 0赞

### 核心思路： ###

`RestTemplate`支持通过`setRequestFactory`设置HTTP请求客户端工具，支持jdk、httpclient、okHttp等，默认使用的是`SimpleClientHttpRequestFactory`，该工程使用的JDK实现，底层使用`OutputStream`来传递body数据，不支持GET传递body。

我们可以修改为httpclient，只需要使用`HttpComponentsClientHttpRequestFactory`，但是默认的httpclient的GET请求也是不支持传递body的。有两个用于定义Http请求的基础抽象类：`HttpRequestBase`、`HttpEntityEnclosingRequestBase`，前者扩展的不能传递body，而后者可以。

private String getRemote(String url, HttpMethod httpMethod, Map<String, String> body) {
        val restTemplate = RestTemplateConfig.getOAuth2RestTemplate();
         //核心代码
        restTemplate.setRequestFactory(new HttpComponentsClientRestfulHttpRequestFactory());
        val headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        val entity = new HttpEntity<String>(JsonConverter.serializeObject(body), headers);
        val result = restTemplate.exchange(url, httpMethod, entity, String.class);
        log.info("[ServiceTask] Remote {}:{}->{} updated:{} row changed.", url, httpMethod,
                entity.toString(), result);
        if (result == null || result.getStatusCodeValue() != 200 || !result.hasBody()) {
          return null;
        } else {
          return result.getBody();
        }
      }
         //核心代码
      private static final class HttpComponentsClientRestfulHttpRequestFactory extends HttpComponentsClientHttpRequestFactory {
        @Override
        protected HttpUriRequest createHttpUriRequest(HttpMethod httpMethod, URI uri) {
          if (httpMethod == HttpMethod.GET) {
            return new HttpGetRequestWithEntity(uri);
          }
          return super.createHttpUriRequest(httpMethod, uri);
        }
      }
         //核心代码
      private static final class HttpGetRequestWithEntity extends HttpEntityEnclosingRequestBase {
        public HttpGetRequestWithEntity(final URI uri) {
          super.setURI(uri);
        }
    
        @Override
        public String getMethod() {
          return HttpMethod.GET.name();
        }
      }

源码如下：

public abstract class HttpEntityEnclosingRequestBase extends HttpRequestBase implements HttpEntityEnclosingRequest {
        private HttpEntity entity;
    
        public HttpEntityEnclosingRequestBase() {
        }
    
        public HttpEntity getEntity() {
            return this.entity;
        }
    
        public void setEntity(HttpEntity entity) {
            this.entity = entity;
        }
    
        public boolean expectContinue() {
            Header expect = this.getFirstHeader("Expect");
            return expect != null && "100-continue".equalsIgnoreCase(expect.getValue());
        }
    
        public Object clone() throws CloneNotSupportedException {
            HttpEntityEnclosingRequestBase clone = (HttpEntityEnclosingRequestBase)super.clone();
            if (this.entity != null) {
                clone.entity = (HttpEntity)CloneUtils.cloneObject(this.entity);
            }
    
            return clone;
        }
    }