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）
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；
一、通过SpringBoot-RestTemplate方式（其余几种的集大成者）
目前可以采用的调用第三方接口有：
- delete() ： 在特定的URL上对资源执行HTTP DELETE操作
- exchange() ： 在URL上执行特定的HTTP方法，返回包含对象的ResponseEntity，这个对象是从响应体中映射得到的
- execute() ： 在URL上执行特定的HTTP方法，返回一个从响应体映射得到的对象
- getForEntity() ：发送一个HTTP GET请求，返回的ResponseEntity包含了响应体所映射成的对象
- getForObject() ：发送一个HTTP GET请求，返回的请求体将映射为一个对象
- postForEntity() ：POST 数据到一个URL，返回包含一个对象的ResponseEntity，这个对象是从响应体中映射得到的
- postForObject()： POST 数据到一个URL，返回根据响应体匹配形成的对象
- headForHeaders() ：发送HTTP HEAD请求，返回包含特定资源URL的HTTP头
- optionsForAllow() ：发送HTTP OPTIONS请求，返回对特定URL的Allow头信息
- postForLocation() ：POST 数据到一个URL，返回新创建资源的URL
- put() ：PUT 资源到特定的URL
1.1、RestTemplateConfig.java类
import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.client.ClientHttpRequestFactory;import org.springframework.http.client.SimpleClientHttpRequestFactory;import org.springframework.web.client.RestTemplate; @Configurationpublic class RestTemplateConfig { @Beanpublic RestTemplate restTemplate(ClientHttpRequestFactory factory){return new RestTemplate(factory);} @Beanpublic ClientHttpRequestFactory simpleClientHttpRequestFactory(){SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();factory.setConnectTimeout(15000);factory.setReadTimeout(5000);return factory;}}1.2、然后在Service类（RestTemplateToInterface ）中注入使用
import com.alibaba.fastjson.JSONObject;import com.swordfall.model.User;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.http.*;import org.springframework.stereotype.Service;import org.springframework.web.client.RestTemplate; @Servicepublic class RestTemplateToInterface { @Autowiredprivate RestTemplate restTemplate; /** * 以get方式请求第三方http接口 getForEntity * @param url * @return */public User doGetWith1(String url){ResponseEntity<User> responseEntity = restTemplate.getForEntity(url, User.class);User user = responseEntity.getBody();return user;} /** * 以get方式请求第三方http接口 getForObject * 返回值返回的是响应体，省去了我们再去getBody() * @param url * @return */public User doGetWith2(String url){User user= restTemplate.getForObject(url, User.class);return user;} /** * 以post方式请求第三方http接口 postForEntity * @param url * @return */public String doPostWith1(String url){User user = new User("小白", 20);ResponseEntity<String> responseEntity = restTemplate.postForEntity(url, user, String.class);String body = responseEntity.getBody();return body;} /** * 以post方式请求第三方http接口 postForEntity * @param url * @return */public String doPostWith2(String url){User user = new User("小白", 20);String body = restTemplate.postForObject(url, user, String.class);return body;} /** * exchange * @return */public String doExchange(String url, Integer age, String name){//header参数HttpHeaders headers = new HttpHeaders();String token = "asdfaf2322";headers.add("authorization", token);headers.setContentType(MediaType.APPLICATION_JSON); //放入body中的json参数JSONObject obj = new JSONObject();obj.put("age", age);obj.put("name", name); //组装HttpEntity<JSONObject> request = new HttpEntity<>(obj, headers);ResponseEntity<String> responseEntity = restTemplate.exchange(url, HttpMethod.POST, request, String.class);String body = responseEntity.getBody();return body;}}二、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
import java.io.*;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;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", "");}}三、 通过apache common封装好的HttpClient
（1）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。
（2）导入如下jar包
<dependency><groupId>commons-httpclient</groupId><artifactId>commons-httpclient</artifactId><version>3.1</version></dependency>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;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HeaderpostMethod.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"); JSONObject jsonObject = new JSONObject();jsonObject.put("commentId", "13026194071");doPost("http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", jsonObject);}}四、 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
（1）maven
<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>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; 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contentTypes.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contentTypes.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jsonObjectJSONObject 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tokentokenString = 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 list = JSONObject.parseArray(response, Result.class); System.out.println(response); } catch (Exception e) {e.printStackTrace();}} public static void main(String[] args) {test("12345678910");} }/** * 执行一个HTTP POST请求，返回请求响应的HTML * @param url *请求的URL地址 * @param params *请求的查询参数,可以为null * @return 返回请求响应的HTML */public static void doPost(String url, String name, String pwd, String phone, String content) {// 创建默认的httpClient实例.CloseableHttpClient httpclient = HttpClients.createDefault();// 创建httppostHttpPost httppost = new HttpPost(url);// 创建参数队列List<NameValuePair> formparams = new ArrayList<NameValuePair>();formparams.add(new BasicNameValuePair("account", name));formparams.add(new BasicNameValuePair("passwd", pwd));formparams.add(new BasicNameValuePair("phone", phone));formparams.add(new BasicNameValuePair("content", content));UrlEncodedFormEntity uefEntity;try {uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");httppost.setEntity(uefEntity);System.out.println("executing request " + httppost.getURI());CloseableHttpResponse response = httpclient.execute(httppost);try {HttpEntity entity = response.getEntity();if (entity != null) {System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8"));}} finally {response.close();}} catch (Exception e) {e.printStackTrace();} finally {// 关闭连接,释放资源try {httpclient.close();} catch (IOException e) {e.printStackTrace();}}}