Java 调用http接口（基于OkHttp的Http工具类方法示例）

现在的互联网项目中，自己单撸所有功能的时代已经过去了，有些功能往往有第三方或者公司其他团队提供服务，你要做得仅仅就是和它们进行对接。对接一些大公司提供的服务时，它们往往会提供对应语言的SDK和说明文档；而团队与团队之间的项目对接往往通过接口进行数据交互，往往都是HTTP JSON交互的形式。

本文介绍如何使用这些API，然后给出博主自己写的一个工具列demo，需要的可以在此基础上修改。

OkHttp3

一般来说，Java 直接调用HTTP接口常见的有三种方式，第一种是JDK原生的方式，第二种是apache 提供的HTTP工具，还有一种是本文着重介绍的OkHttp3工具

OkHttp3官方文档介绍了它的4点优势：

• HTTP/2支持允许对同一主机的所有请求共享一个socket。
• 连接池减少了请求延迟(如果HTTP/2不可用)。
• 透明GZIP压缩下载大小。
• 响应缓存完全避免了网络重复请求。

使用OkHttp很容易。它的请求/响应API设计为流畅的构建器和不变性。它同时支持同步阻塞调用和带回调的异步调用。

下面介绍一下常见的GET方法和POST方法官方示例，首先添加依赖：

MAVEN依赖

<!--okhttp依赖-->
<dependency><groupId>com.squareup.okhttp3</groupId><artifactId>okhttp</artifactId><version>4.0.0</version>
</dependency>

Http get操作示例

OkHttpClient client = new OkHttpClient();String run(String url) throws IOException {Request request = new Request.Builder().url(url).build();try (Response response = client.newCall(request).execute()) {return response.body().string();}
}

Http Post操作示例

public static final MediaType JSON= MediaType.get("application/json; charset=utf-8");OkHttpClient client = new OkHttpClient();String post(String url, String json) throws IOException {RequestBody body = RequestBody.create(JSON, json);Request request = new Request.Builder().url(url).post(body).build();try (Response response = client.newCall(request).execute()) {return response.body().string();}
}

Http 超时控制

当调用的对等方不可用时，超时使调用失败。网络可能是由于客户机连接问题、服务器可用性问题或两者之间的任何问题造成的。OkHttp支持连接、读取和写入超时。

private final OkHttpClient client;public ConfigureTimeouts() throws Exception {client = new OkHttpClient.Builder().connectTimeout(10, TimeUnit.SECONDS).writeTimeout(10, TimeUnit.SECONDS).readTimeout(30, TimeUnit.SECONDS).build();}public void run() throws Exception {Request request = new Request.Builder().url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay..build();try (Response response = client.newCall(request).execute()) {System.out.println("Response completed: " + response);}
}

工具类示例

提供同步的GET和POST调用工具方法示例，提供了异步调用HTTP接口的demo

import okhttp3.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpMethod;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.util.CollectionUtils;import java.io.IOException;
import java.util.Map;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;/*** @author axin* @since 2019-08-14*/
public class OkHttpUtils {private static final Logger log = LoggerFactory.getLogger(OkHttpUtils.class);private static final String HTTP_JSON = "application/json; charset=utf-8";private static final String HTTP_FORM = "application/x-www-form-urlencoded; charset=utf-8";private static final OkHttpClient okHttpClient = new OkHttpClient.Builder().connectTimeout(120, TimeUnit.SECONDS).readTimeout(120, TimeUnit.SECONDS).writeTimeout(120, TimeUnit.SECONDS).build();/*** get请求* 对于小文档，响应体上的string()方法非常方便和高效。* 但是，如果响应主体很大(大于1 MB)，则应避免string()，* 因为它会将整个文档加载到内存中。在这种情况下，将主体处理为流。** @param url* @return*/public static String httpGet(String url) {if (url == null || "".equals(url)) {log.error("url为null!");return "";}Request.Builder builder = new Request.Builder();Request request = builder.get().url(url).build();try {Response response = okHttpClient.newCall(request).execute();if (response.code() == 200) {log.info("http GET 请求成功; [url={}]", url);return response.body().string();} else {log.warn("Http GET 请求失败; [errorCode = {} , url={}]", response.code(), url);}} catch (IOException e) {throw new RuntimeException("同步http GET 请求失败,url:" + url, e);}return null;}public static String httpGet(String url, Map<String, String> headers) {if (CollectionUtils.isEmpty(headers)) {return httpGet(url);}Request.Builder builder = new Request.Builder();headers.forEach((String key, String value) -> builder.header(key, value));Request request = builder.get().url(url).build();try {Response response = okHttpClient.newCall(request).execute();if (response.code() == 200) {log.info("http GET 请求成功; [url={}]", url);return response.body().string();} else {log.warn("Http GET 请求失败; [errorxxCode = {} , url={}]", response.code(), url);}} catch (IOException e) {throw new RuntimeException("同步http GET 请求失败,url:" + url, e);}return null;}/*** 同步 POST调用 无Header** @param url* @param json* @return*/public static String httpPostJson(String url, String json) {if (url == null || "".equals(url)) {log.error("url为null!");return "";}MediaType JSON = MediaType.parse(HTTP_JSON);RequestBody body = RequestBody.create(JSON, json);Request.Builder requestBuilder = new Request.Builder().url(url);Request request = requestBuilder.post(body).build();try {Response response = okHttpClient.newCall(request).execute();if (response.code() == 200) {log.info("http Post 请求成功; [url={}, requestContent={}]", url, json);return response.body().string();} else {log.warn("Http POST 请求失败; [ errorCode = {}, url={}, param={}]", response.code(), url, json);}} catch (IOException e) {throw new RuntimeException("同步http请求失败,url:" + url, e);}return null;}/*** 同步 POST调用 有Header** @param url* @param headers* @param json* @return*/public static String httpPostJson(String url, Map<String, String> headers, String json) {if (CollectionUtils.isEmpty(headers)) {httpPostJson(url, json);}MediaType JSON = MediaType.parse(HTTP_JSON);RequestBody body = RequestBody.create(JSON, json);Request.Builder requestBuilder = new Request.Builder().url(url);headers.forEach((k, v) -> requestBuilder.addHeader(k, v));Request request = requestBuilder.post(body).build();try {Response response = okHttpClient.newCall(request).execute();if (response.code() == 200) {log.info("http Post 请求成功; [url={}, requestContent={}]", url, json);return response.body().string();} else {log.warn("Http POST 请求失败; [ errorCode = {}, url={}, param={}]", response.code(), url, json);}} catch (IOException e) {throw new RuntimeException("同步http请求失败,url:" + url, e);}return null;}/*** 提交表单* @param url* @param content* @param headers* @return*/public static String postDataByForm(String url, String content, Map<String, String> headers) {MediaType JSON = MediaType.parse(HTTP_FORM);RequestBody body = RequestBody.create(JSON, content);Request.Builder requestBuilder = new Request.Builder().url(url);if (headers != null && headers.size() > 0) {headers.forEach((k, v) -> requestBuilder.addHeader(k, v));}Request request = requestBuilder.post(body).build();Response response = null;try {response = okHttpClient.newCall(request).execute();if (response.code() == 200) {log.info("postDataByForm; [postUrl={}, requestContent={}, responseCode={}]", url, content, response.code());return response.body().string();} else {log.warn("Http Post Form请求失败,[url={}, param={}]", url, content);}} catch (IOException e) {log.error("Http Post Form请求失败,[url={}, param={}]", url, content, e);throw new RuntimeException("Http Post Form请求失败,url:" + url);}return null;}/*** 异步Http调用参考模板：Get、Post、Put* 需要异步调用的接口一般情况下你需要定制一个专门的Http方法** @param httpMethod* @param url* @param content* @return*/@Deprecatedpublic static Future<Boolean> asyncHttpByJson(HttpMethod httpMethod, String url, Map<String, String> headers, String content) {MediaType JSON = MediaType.parse(HTTP_JSON);RequestBody body = RequestBody.create(JSON, content);Request.Builder requestBuilder = new Request.Builder().url(url);if (!CollectionUtils.isEmpty(headers)) {headers.forEach((key, value) -> requestBuilder.header(key, value));}switch (httpMethod) {case GET:requestBuilder.get();break;case POST:requestBuilder.post(body);break;default:}Request request = requestBuilder.build();Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {log.error("异步http {} 请求失败,[url={}, param={}]", httpMethod.name(), url, content);throw new RuntimeException("异步http请求失败,url:" + url);}@Overridepublic void onResponse(Call call, final Response response) throws IOException {if (response.code() == 200) {System.out.println("需要加入异步回调操作");} else {log.error("异步http {} 请求失败,错误码为{},请求参数为[url={}, param={}]", httpMethod.name(), response.code(), url, content);}}});return new AsyncResult(true);}/*** lambda表达式异步调用http模板,不建议使用** @param request* @param failure* @param respConsumer*/public static void asyncCall(Request request, Consumer<Exception> failure, Consumer<Response> respConsumer) {okHttpClient.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {failure.accept(e);}@Overridepublic void onResponse(Call call, Response response) throws IOException {respConsumer.accept(response);}});}//testpublic static void main(String[] args) {String url = "http://www.baidu.com";System.out.println(httpGet(url));}}

综上，本文介绍了Okhttp3的使用，并给出了工具类的demo，要注意的是，对于异步调用http方法需要根据你们项目的具体业务进行改造，增加回调失败与成功的业务逻辑。

文档链接：OkHttp官网