1. 概述

在实际开发过程中，我们经常需要调用对方提供的接口或测试自己写的接口是否合适。很多项目都会封装规定好本身项目的接口规范，所以大多数需要去调用对方提供的接口或第三方接口（短信、天气等）。

在Java项目中调用第三方接口的方式有：

①通过JDK网络类Java.net.HttpURLConnection；

②通过common封装好的HttpClient；

③通过Apache封装好的CloseableHttpClient；

④通过SpringBoot-RestTemplate；

2. Java调用第三方http接口的方式

2.1 通过JDK网络类Java.net.HttpURLConnection

 比较原始的一种调用做法，这里把get请求和post请求都统一放在一个方法里面，直接上代码：

import java.io.*; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; /** * @Author: Yang JianQiu * @Date: 2019/4/26 11:34 * jdk类HttpURLConnection调用第三方http接口 * * 通常分get和post两种方式 * * 参考资料： * http://www.cnblogs.com/angusbao/p/7727649.html */ public class HttpUrlConnectionToInterface { /** * 以post或get方式调用对方接口方法， * @param pathUrl */ public static void doPostOrGet(String pathUrl, String data){ OutputStreamWriter out = null; BufferedReader br = null; String result = ""; try { URL url = new URL(pathUrl); //打开和url之间的连接 HttpURLConnection conn = (HttpURLConnection) url.openConnection(); //请求方式 conn.setRequestMethod("POST"); //conn.setRequestMethod("GET"); //设置通用的请求属性 conn.setRequestProperty("accept", "*/*"); conn.setRequestProperty("connection", "Keep-Alive"); conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); conn.setRequestProperty("Content-Type", "application/json;charset=utf-8"); //DoOutput设置是否向httpUrlConnection输出，DoInput设置是否从httpUrlConnection读入，此外发送post请求必须设置这两个 conn.setDoOutput(true); conn.setDoInput(true); /** * 下面的三句代码，就是调用第三方http接口 */ //获取URLConnection对象对应的输出流 out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8"); //发送请求参数即数据 out.write(data); //flush输出流的缓冲 out.flush(); /** * 下面的代码相当于，获取调用第三方http接口后返回的结果 */ //获取URLConnection对象对应的输入流 InputStream is = conn.getInputStream(); //构造一个字符流缓存 br = new BufferedReader(new InputStreamReader(is)); String str = ""; while ((str = br.readLine()) != null){ result += str; } System.out.println(result); //关闭流 is.close(); //断开连接，disconnect是在底层tcp socket链接空闲时才切断，如果正在被其他线程使用就不切断。 conn.disconnect(); } catch (Exception e) { e.printStackTrace(); }finally { try { if (out != null){ out.close(); } if (br != null){ br.close(); } } catch (IOException e) { e.printStackTrace(); } } } public static void main(String[] args) { /** *手机信息查询接口：http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=手机号 　　　　 *　　　　　　http://api.showji.com/Locating/www.showji.com.aspx?m=手机号&output=json&callback=querycallback */ doPostOrGet("https://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", ""); } }

2.2 通过apache common封装好的HttpClient

httpClient的get或post请求方式步骤：

生成一个HttpClient对象并设置相应的参数；生成一个GetMethod对象或PostMethod并设置响应的参数；用HttpClient生成的对象来执行GetMethod生成的Get方法；处理响应状态码；若响应正常，处理HTTP响应内容；释放连接。

导入如下jar包：

<!--HttpClient--> <dependency> <groupId>commons-httpclient</groupId> <artifactId>commons-httpclient</artifactId> <version>3.1</version> </dependency>

代码如下：

import com.alibaba.fastjson.JSONObject; import org.apache.commons.httpclient.*; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.httpclient.methods.PostMethod; import org.apache.commons.httpclient.params.HttpMethodParams; import java.io.IOException; import java.io.InputStream; /** * @Author: Yang JianQiu * @Date: 2019/4/28 11:07 * * HttpClient模拟get、post请求并发送请求参数（json等） * 【参考资料】 * https://javasam.iteye.com/blog/2117845 * https://blog.csdn.net/qq_28379809/article/details/82898792 */ public class HttpClientToInterface { /** * httpClient的get请求方式 * 使用GetMethod来访问一个URL对应的网页实现步骤： * 1.生成一个HttpClient对象并设置相应的参数； * 2.生成一个GetMethod对象并设置响应的参数； * 3.用HttpClient生成的对象来执行GetMethod生成的Get方法； * 4.处理响应状态码； * 5.若响应正常，处理HTTP响应内容； * 6.释放连接。 * @param url * @param charset * @return */ public static String doGet(String url, String charset){ /** * 1.生成HttpClient对象并设置参数 */ HttpClient httpClient = new HttpClient(); //设置Http连接超时为5秒 httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(5000); /** * 2.生成GetMethod对象并设置参数 */ GetMethod getMethod = new GetMethod(url); //设置get请求超时为5秒 getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 5000); //设置请求重试处理，用的是默认的重试处理：请求三次 getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler()); String response = ""; /** * 3.执行HTTP GET 请求 */ try { int statusCode = httpClient.executeMethod(getMethod); /** * 4.判断访问的状态码 */ if (statusCode != HttpStatus.SC_OK){ System.err.println("请求出错：" + getMethod.getStatusLine()); } /** * 5.处理HTTP响应内容 */ //HTTP响应头部信息，这里简单打印 Header[] headers = getMethod.getResponseHeaders(); for (Header h: headers){ System.out.println(h.getName() + "---------------" + h.getValue()); } //读取HTTP响应内容，这里简单打印网页内容 //读取为字节数组 byte[] responseBody = getMethod.getResponseBody(); response = new String(responseBody, charset); System.out.println("-----------response:" + response); //读取为InputStream，在网页内容数据量大时候推荐使用 //InputStream response = getMethod.getResponseBodyAsStream(); } catch (HttpException e) { //发生致命的异常，可能是协议不对或者返回的内容有问题 System.out.println("请检查输入的URL!"); e.printStackTrace(); } catch (IOException e){ //发生网络异常 System.out.println("发生网络异常!"); }finally { /** * 6.释放连接 */ getMethod.releaseConnection(); } return response; } /** * post请求 * @param url * @param json * @return */ public static String doPost(String url, JSONObject json){ HttpClient httpClient = new HttpClient(); PostMethod postMethod = new PostMethod(url); postMethod.addRequestHeader("accept", "*/*"); postMethod.addRequestHeader("connection", "Keep-Alive"); //设置json格式传送 postMethod.addRequestHeader("Content-Type", "application/json;charset=utf-8"); //必须设置下面这个Header postMethod.addRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36"); //添加请求参数 postMethod.addParameter("commentId", json.getString("commentId")); String res = ""; try { int code = httpClient.executeMethod(postMethod); if (code == 200){ res = postMethod.getResponseBodyAsString(); System.out.println(res); } } catch (IOException e) { e.printStackTrace(); } return res; } public static void main(String[] args) { doGet("http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", "UTF-8"); System.out.println("-----------分割线------------"); System.out.println("-----------分割线------------"); System.out.println("-----------分割线------------"); JSONObject jsonObject = new JSONObject(); jsonObject.put("commentId", "13026194071"); doPost("http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", jsonObject); } }

2.3 通过Apache封装好的CloseableHttpClient

 CloseableHttpClient是在HttpClient的基础上修改更新而来的，这里还涉及到请求头token的设置（请求验证），利用fastjson转换请求或返回结果字符串为json格式，当然上面两种方式也是可以设置请求头token、json的，这里只在下面说明。

导入如下jar包：

<!--CloseableHttpClient--> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.2</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.28</version> </dependency>

代码如下：

import com.alibaba.fastjson.JSONObject; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClientBuilder; import org.apache.http.util.EntityUtils; import java.io.IOException; /** * @Author: Yang JianQiu * @Date: 2019/4/26 11:41 * Apache封装好的CloseableHttpClient * 【参考资料】 * https://www.cnblogs.com/siv8/p/6222709.html * https://blog.csdn.net/qq_35860138/article/details/82967727 */ public class CloseableHttpClientToInterface { private static String tokenString = ""; private static String AUTH_TOKEN_EXPIRED = "AUTH_TOKEN_EXPIRED"; private static CloseableHttpClient httpClient = null; /** * 以get方式调用第三方接口 * @param url * @return */ public static String doGet(String url, String token){ //创建HttpClient对象 CloseableHttpClient httpClient = HttpClientBuilder.create().build(); HttpGet get = new HttpGet(url); try { if (tokenString != null && !tokenString.equals("")){ tokenString = getToken(); } //api_gateway_auth_token自定义header头，用于token验证使用 get.addHeader("api_gateway_auth_token", tokenString); get.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36"); HttpResponse response = httpClient.execute(get); if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){ //返回json格式 String res = EntityUtils.toString(response.getEntity()); return res; } } catch (IOException e) { e.printStackTrace(); } return null; } /** * 以post方式调用第三方接口 * @param url * @param json * @return */ public static String doPost(String url, JSONObject json){ try { if (httpClient == null){ httpClient = HttpClientBuilder.create().build(); } HttpPost post = new HttpPost(url); if (tokenString != null && !tokenString.equals("")){ tokenString = getToken(); } //api_gateway_auth_token自定义header头，用于token验证使用 post.addHeader("api_gateway_auth_token", tokenString); post.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36"); StringEntity s = new StringEntity(json.toString()); s.setContentEncoding("UTF-8"); //发送json数据需要设置contentType s.setContentType("application/x-www-form-urlencoded"); //设置请求参数 post.setEntity(s); HttpResponse response = httpClient.execute(post); if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){ //返回json格式 String res = EntityUtils.toString(response.getEntity()); return res; } } catch (Exception e) { e.printStackTrace(); }finally { if (httpClient != null){ try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } return null; } /** * 获取第三方接口的token */ public static String getToken(){ String token = ""; JSONObject object = new JSONObject(); object.put("appid", "appid"); object.put("secretkey", "secretkey"); try { if (httpClient == null){ httpClient = HttpClientBuilder.create().build(); } HttpPost post = new HttpPost("http://localhost/login"); post.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36"); StringEntity s = new StringEntity(object.toString()); s.setContentEncoding("UTF-8"); //发送json数据需要设置contentType s.setContentType("application/x-www-form-urlencoded"); //设置请求参数 post.setEntity(s); HttpResponse response = httpClient.execute(post); //这里可以把返回的结果按照自定义的返回数据结果，把string转换成自定义类 //ResultTokenBO result = JSONObject.parseObject(response, ResultTokenBO.class); //把response转为jsonObject JSONObject result = JSONObject.parseObject(response); if (result.containsKey("token")){ token = result.getString("token"); } } catch (Exception e) { e.printStackTrace(); } return token; } /** * 测试 */ public static void test(String telephone){ JSONObject object = new JSONObject(); object.put("telephone", telephone); try { //首先获取token tokenString = getToken(); String response = doPost("http://localhost/searchUrl", object); //如果返回的结果是list形式的，需要使用JSONObject.parseArray转换 //List<Result> list = JSONObject.parseArray(response, Result.class); System.out.println(response); } catch (Exception e) { e.printStackTrace(); } } public static void main(String[] args) { test("12345678910"); } }