1 restTemplate — spring 提供
特点：
1、RestOperations 提供了各种封装办法，十分不便间接将返回转成实体类。
2、默认应用 JDK 的 HttpURLConnection 进行通信，然而能够通过 RestTemplate.setRequestFactory 切换到不同的 HTTP 源：如 Apache HttpComponents、Netty、OkHttp。
3、反对同步、异步申请；
4、反对更多的定制，比方拦截器等。
ps：反对 get 申请，参数是 body 的模式。
参考：https://www.huaweicloud.com/a…
国外出名博客 Baeldung 的博客 The Guide to RestTemplate: https://www.baeldung.com/rest…
1.1 底层是 java 的 HttpURLConnection(默认应用，能够定制)
所有的申请都须要执行 doExecute() 办法
@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;
Object var14;
try {
// 创立申请
ClientHttpRequest request = this.createRequest(url, method);
if (requestCallback != null) {requestCallback.doWithRequest(request);
}
response = request.execute();
this.handleResponse(url, method, response);
var14 = responseExtractor != null ? responseExtractor.extractData(response) : null;
} catch (IOException var12) {String resource = url.toString();
String query = url.getRawQuery();
resource = query != null ? resource.substring(0, resource.indexOf(63)) : resource;
throw new ResourceAccessException("I/O error on" + method.name() + "request for \"" + resource + "\": " + var12.getMessage(), var12);
} finally {if (response != null) {response.close();
}
}
return var14;
}HttpAccessor 创立申请
public abstract class HttpAccessor {
... // 省略代码有数
protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
// 应用 ClientHttpRequestFactory 创立申请
ClientHttpRequest request = this.getRequestFactory().createRequest(url, method);
if (this.logger.isDebugEnabled()) {this.logger.debug("HTTP" + method.name() + " " + url);
}
return request;
}
}ClientHttpRequestFactory 接口的具体实现，如：SimpleClientHttpRequestFactory 创立申请
public ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod) throws IOException {
// 应用 HttpURLConnection 创立申请
HttpURLConnection connection = this.openConnection(uri.toURL(), this.proxy);
this.prepareConnection(connection, httpMethod.name());
return (ClientHttpRequest)(this.bufferRequestBody ? new SimpleBufferingClientHttpRequest(connection, this.outputStreaming) : new SimpleStreamingClientHttpRequest(connection, this.chunkSize, this.outputStreaming));
}1.2 post 申请，返回间接封装为实体
RestTemplate restTemplate = new RestTemplate();
HttpEntity<Foo> request = new HttpEntity<>(new Foo("bar"));
Foo foo = restTemplate.postForObject(fooResourceUrl, request, Foo.class);
assertThat(foo, notNullValue());
assertThat(foo.getName(), is("bar"));1.3 get 申请，然而参数是 body 模式
个别 get 申请，不反对 body 传参。
参考：https://stackoverflow.com/que…
HTTP GET with a body is a somewhat unconventional construct that falls in a gray area of the HTTP specification – the end result is that many older pieces of software either cannot handle such a request at all, or will explicitly reject it because they believe it to be malformed.
带有 body 参数的 HTTP GET 是一种非传统的结构，属于 HTTP 标准的灰色区域。最终的后果是，许多旧的软件要么基本不能解决这样的申请，要么会明确回绝，因为他们认为它是格局谬误的申请。
/**
* 留神：get 申请，然而参数是 body 模式
*
* @param url
* @param paramBody
* @return
*/
private String getWithBody(String url, Map<String, Object> paramBody) {HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_JSON);
httpHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
HttpEntity requestEntity = new HttpEntity(JsonUtil.of(paramBody), httpHeaders);
RestTemplate template = getTemplate();
ResponseEntity response = template.exchange(url, HttpMethod.GET, requestEntity, String.class);
Object result = response.getBody();
logger.info("/invokeThirdPartyRequest/getWithBody/result/[{}]", result.toString());
return result.toString();}/**
* 获取 RestTemplate
*
* @return
*/
private RestTemplate getTemplate() {RestTemplate restTemplate = new RestTemplate();
// 批改 restTemplate 的 RequestFactory 使其反对 Get 携带 body 参数
restTemplate.setRequestFactory(new HttpComponentsClientRestfulHttpRequestFactory());
return restTemplate;
}
import org.apache.http.client.methods.HttpEntityEnclosingRequestBase;
import org.apache.http.client.methods.HttpUriRequest;
import org.springframework.http.HttpMethod;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import java.net.URI;
public 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);
}
/**
* 定义 HttpGetRequestWithEntity 实现 HttpEntityEnclosingRequestBase 抽象类，以反对 GET 申请携带 body 数据
*/
private static final class HttpGetRequestWithEntity extends HttpEntityEnclosingRequestBase {public HttpGetRequestWithEntity(final URI uri) {super.setURI(uri);
}
@Override
public String getMethod() {return HttpMethod.GET.name();
}
}
}2 HttpUtil — hutool 提供
HttpUtil 其实是 HttpRequest 的封装。
它反对各种封装好的 get、post、put 申请。
2.1 get 申请
public static String get(String urlString, Charset customCharset) {return ((HttpRequest)HttpRequest.get(urlString).charset(customCharset)).execute().body();
}
public static String get(String urlString) {return get(urlString, HttpGlobalConfig.timeout);
}
public static String get(String urlString, int timeout) {return HttpRequest.get(urlString).timeout(timeout).execute().body();
}
// form 表单格局的入参
public static String get(String urlString, Map<String, Object> paramMap) {return HttpRequest.get(urlString).form(paramMap).execute().body();
}
// form 表单格局的入参，并设置超时工夫
public static String get(String urlString, Map<String, Object> paramMap, int timeout) {return HttpRequest.get(urlString).form(paramMap).timeout(timeout).execute().body();
}2.2 post 申请
这些申请最终调用的都是 HttpRequest 的 execute() 办法。
// form 表单格局的入参
public static String post(String urlString, Map<String, Object> paramMap) {return post(urlString, paramMap, HttpGlobalConfig.timeout);
}
// form 表单格局的入参，并设置超时工夫
public static String post(String urlString, Map<String, Object> paramMap, int timeout) {return HttpRequest.post(urlString).form(paramMap).timeout(timeout).execute().body();
}
// body 格局入参
public static String post(String urlString, String body) {return post(urlString, body, HttpGlobalConfig.timeout);
}
// body 格局入参，并设置超时工夫
public static String post(String urlString, String body, int timeout) {return HttpRequest.post(urlString).timeout(timeout).body(body).execute().body();
}2.3 一个例子
Map<String, Object> param = new HashMap<>();
param.put("userId", userId);
String res = HttpUtil.post(url, JsonUtil.of(param));3 HttpRequest — hutool 提供
HttpRequest 提供了十分不便结构申请的构造函数。当参数比拟多、header 比拟多的时候，能够应用这种形式。（这里应用了结构模式）
3.1 底层是 Java 的 HttpURLConnection
HttpRequest 底层又是应用了 java 提供的 HttpURLConnection
上源码：
最终都须要执行这个 execute 办法，这个办法调用了 hutool 封装的 HttpConnection，这个 HttpConnection 又应用了 java 提供的HttpURLConnection。
// hutool 执行办法
public HttpResponse execute(boolean isAsync) {this.urlWithParamIfGet();
this.initConnection();
this.send();
HttpResponse httpResponse = this.sendRedirectIfPossible();
if (null == httpResponse) {httpResponse = new HttpResponse(this.httpConnection, this.charset, isAsync, this.isIgnoreResponseBody());
}
return httpResponse;
}public class HttpConnection {
private final URL url;
private final Proxy proxy;
// 这个连贯 HttpURLConnection，是 java 提供的
private HttpURLConnection conn;
...// 省略有数代码
}3.2 一个例子
private String invoke(String url, String isMock, Map<String, Object> map) {String result = HttpRequest.post(url).body(JSONUtil.toJsonStr(map)).execute().body();
return result;
}