注：来自 https://blog.csdn.net/qq_16504067/article/details/121114404
推荐：SpringBoot-RestTemplate和okhttp

一、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；

二、 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。
实现过程：

GET:1、创建远程连接2、设置连接方式（get、post、put。。。）3、设置连接超时时间4、设置响应读取时间5、发起请求6、获取请求数据7、关闭连接 POST:1、创建远程连接2、设置连接方式（get、post、put。。。）3、设置连接超时时间4、设置响应读取时间5、当向远程服务器传送数据/写数据时，需要设置为true（setDoOutput）6、当前向远程服务读取数据时，设置为true，该参数可有可无（setDoInput）7、设置传入参数的格式:（setRequestProperty）8、设置鉴权信息：Authorization:（setRequestProperty）9、设置参数10、发起请求11、获取请求数据12、关闭连接

直接上代码：

package com.riemann.springbootdemo.util.common.httpConnectionUtil; import org.springframework.lang.Nullable; import java.io.*;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection; /** * @author riemann * @date 2019/05/24 23:42 */public class HttpURLConnectionUtil {     /**     * Http get请求     * @param httpUrl 连接     * @return 响应数据     */    public static String doGet(String httpUrl){        //链接        HttpURLConnection connection = null;        InputStream is = null;        BufferedReader br = null;        StringBuffer result = new StringBuffer();        try {            //创建连接            URL url = new URL(httpUrl);            connection = (HttpURLConnection) url.openConnection();            //设置请求方式            connection.setRequestMethod("GET");            //设置连接超时时间            connection.setReadTimeout(15000);            //开始连接            connection.connect();            //获取响应数据            if (connection.getResponseCode() == 200) {                //获取返回的数据                is = connection.getInputStream();                if (null != is) {                    br = new BufferedReader(new InputStreamReader(is, "UTF-8"));                    String temp = null;                    while (null != (temp = br.readLine())) {                        result.append(temp);                    }                }            }        } catch (IOException e) {            e.printStackTrace();        } finally {            if (null != br) {                try {                    br.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (null != is) {                try {                    is.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            //关闭远程连接            connection.disconnect();        }        return result.toString();    }     /**     * Http post请求     * @param httpUrl 连接     * @param param 参数     * @return     */    public static String doPost(String httpUrl, @Nullable String param) {        StringBuffer result = new StringBuffer();        //连接        HttpURLConnection connection = null;        OutputStream os = null;        InputStream is = null;        BufferedReader br = null;        try {            //创建连接对象            URL url = new URL(httpUrl);            //创建连接            connection = (HttpURLConnection) url.openConnection();            //设置请求方法            connection.setRequestMethod("POST");            //设置连接超时时间            connection.setConnectTimeout(15000);            //设置读取超时时间            connection.setReadTimeout(15000);            //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            //设置是否可读取            connection.setDoOutput(true);            connection.setDoInput(true);            //设置通用的请求属性            connection.setRequestProperty("accept", "*/*");            connection.setRequestProperty("connection", "Keep-Alive");            connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");            connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");             //拼装参数            if (null != param && param.equals("")) {                //设置参数                os = connection.getOutputStream();                //拼装参数                os.write(param.getBytes("UTF-8"));            }            //设置权限            //设置请求头等            //开启连接            //connection.connect();            //读取响应            if (connection.getResponseCode() == 200) {                is = connection.getInputStream();                if (null != is) {                    br = new BufferedReader(new InputStreamReader(is, "GBK"));                    String temp = null;                    while (null != (temp = br.readLine())) {                        result.append(temp);                        result.append("\r\n");                    }                }            }         } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        } finally {            //关闭连接            if(br!=null){                try {                    br.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if(os!=null){                try {                    os.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if(is!=null){                try {                    is.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            //关闭连接            connection.disconnect();        }        return result.toString();    }     public static void main(String[] args) {        String message = doPost("https://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", "");        System.out.println(message);    }}

运行结果：

2.2 通过apache common封装好的HttpClient

httpClient的get或post请求方式步骤：

1.生成一个HttpClient对象并设置相应的参数；2.生成一个GetMethod对象或PostMethod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。

导入如下jar包：

<!--HttpClient--><dependency>    <groupId>commons-httpclient</groupId>    <artifactId>commons-httpclient</artifactId>    <version>3.1</version></dependency> <!--fastjson--><dependency>    <groupId>com.alibaba</groupId>    <artifactId>fastjson</artifactId>    <version>1.2.32</version></dependency>

代码如下：

package com.riemann.springbootdemo.util.common.httpConnectionUtil; 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; /** * @author riemann * @date 2019/05/25 0:58 */public class HttpClientUtil {    /**     * 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=GBK");        //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) {        System.out.println(doGet("http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", "GBK"));        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");        System.out.println(doPost("http://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=13026194071", jsonObject));    }}

运行结果：

 post请求的jsonObject 的参数也成功写入

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> <!--fastjson--><dependency>    <groupId>com.alibaba</groupId>    <artifactId>fastjson</artifactId>    <version>1.2.32</version></dependency>

代码如下：

package com.riemann.springbootdemo.util.common.httpConnectionUtil; import com.alibaba.fastjson.JSONObject;import org.apache.http.HttpResponse;import org.apache.http.HttpStatus;import org.apache.http.client.methods.CloseableHttpResponse;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;import java.io.UnsupportedEncodingException; /** * @author riemann * @date 2019/05/25 1:35 */public class CloseableHttpClientUtil {     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     * @param token     * @return     */    public static String doGet(String url, String token) {        //创建HttpClient对象        CloseableHttpClient httpClient = HttpClientBuilder.create().build();        HttpGet httpGet = new HttpGet(url);        if (null != tokenString && !tokenString.equals("")) {            tokenString = getToken();        }        //api_gateway_auth_token自定义header头，用于token验证使用        httpGet.addHeader("api_gateway_auth_token",tokenString);        httpGet.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");        try {            HttpResponse response = httpClient.execute(httpGet);            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) {        if (null == httpClient) {            httpClient = HttpClientBuilder.create().build();        }        HttpPost httpPost = new HttpPost(url);        if (null != tokenString && tokenString.equals("")) {            tokenString = getToken();        }        //api_gateway_auth_token自定义header头，用于token验证使用        httpPost.addHeader("api_gateway_auth_token", tokenString);        httpPost.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");        try {            StringEntity se = new StringEntity(json.toString());            se.setContentEncoding("UTF-8");            //发送json数据需要设置contentType            se.setContentType("application/x-www-form-urlencoded");            //设置请求参数            httpPost.setEntity(se);            HttpResponse response = httpClient.execute(httpPost);            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();        } 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");        if (null == httpClient) {            httpClient = HttpClientBuilder.create().build();        }        HttpPost httpPost = new HttpPost("http://localhost/login");        httpPost.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");        try {            StringEntity se = new StringEntity(object.toString());            se.setContentEncoding("UTF-8");            //发送json数据需要设置contentType            se.setContentType("application/x-www-form-urlencoded");            //设置请求参数            httpPost.setEntity(se);            HttpResponse response = httpClient.execute(httpPost);            //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) JSONObject.parseObject(String.valueOf(response));            if (result.containsKey("token")) {                token = result.getString("token");            }        } catch (IOException e) {            e.printStackTrace();        }        return token;    }     /**     * 测试     */    public static void test(String telephone) {         JSONObject object = new JSONObject();        object.put("telephone", telephone);         //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);    }     public static void main(String[] args) {        test("12345678910");    }}

2.4 通过SpringBoot-RestTemplate

springBoot-RestTemple是上面三种方式的集大成者，代码编写更加简单，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URLput() PUT 资源到特定的URL

注意：目前标粗的为常用的

首先导入springboot的web包

<parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>2.0.4.RELEASE</version>    </parent>     <dependencies>        <!--CloseableHttpClient-->        <dependency>            <groupId>org.apache.httpcomponents</groupId>            <artifactId>httpclient</artifactId>            <version>4.5.2</version>        </dependency>         <!--spring restTemplate-->        <!-- @ConfigurationProperties annotation processing (metadata for IDEs)                生成spring-configuration-metadata.json类，需要引入此类-->        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-configuration-processor</artifactId>            <optional>true</optional>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-aop</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>            <exclusions>                <exclusion>                    <groupId>org.springframework.boot</groupId>                    <artifactId>spring-boot-starter-tomcat</artifactId>                </exclusion>            </exclusions>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-jetty</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>    </dependencies>

在启动类同包下创建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; /** * @author riemann * @date 2019/05/25 2:16 */@Configurationpublic class RestTemplateConfig {     @Bean    public RestTemplate restTemplate(ClientHttpRequestFactory factory){        return new RestTemplate(factory);    }     @Bean    public ClientHttpRequestFactory simpleClientHttpRequestFactory(){        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();        factory.setConnectTimeout(15000);        factory.setReadTimeout(5000);        return factory;    }}

然后在Service类（RestTemplateToInterface ）中注入使用

具体代码如下：

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; /** * @author riemann * @date 2019/05/25 2:20 */@Servicepublic class RestTemplateToInterface {     @Autowired    private 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;    }}

2.5 通过okhttp

应大家的响应，okhttp 现在也是蛮流行的，基于手机端很火，这里分享一下OkHttpClient客户端，业务代码get、post请求直接调用就好哈。

pom文件引入依赖包

<dependency>    <groupId>com.squareup.okhttp3</groupId>    <artifactId>okhttp</artifactId>    <version>3.10.0</version></dependency>

@Slf4jpublic class OkHttpClient {    private static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");     private volatile static okhttp3.OkHttpClient client;     private static final int MAX_IDLE_CONNECTION = Integer            .parseInt(ConfigManager.get("httpclient.max_idle_connection"));     private static final long KEEP_ALIVE_DURATION = Long            .parseLong(ConfigManager.get("httpclient.keep_alive_duration"));     private static final long CONNECT_TIMEOUT = Long.parseLong(ConfigManager.get("httpclient.connectTimeout"));     private static final long READ_TIMEOUT = Long.parseLong(ConfigManager.get("httpclient. "));     /**     * 单例模式(双重检查模式) 获取类实例     *     * @return client     */    private static okhttp3.OkHttpClient getInstance() {        if (client == null) {            synchronized (okhttp3.OkHttpClient.class) {                if (client == null) {                    client = new okhttp3.OkHttpClient.Builder()                            .connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)                            .readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)                            .connectionPool(new ConnectionPool(MAX_IDLE_CONNECTION, KEEP_ALIVE_DURATION,                                    TimeUnit.MINUTES))                            .build();                }            }        }        return client;    }     public static String syncPost(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 = OkHttpClient.getInstance().newCall(request).execute();            if (response.isSuccessful()) {                String result = response.body().string();                log.info("syncPost response = {}, responseBody= {}", response, result);                return result;            }            String result = response.body().string();            log.info("syncPost response = {}, responseBody= {}", response, result);            throw new IOException("三方接口返回http状态码为" + response.code());        } catch (Exception e) {            log.error("syncPost() url:{} have a ecxeption {}", url, e);            throw new RuntimeException("syncPost() have a ecxeption {}" + e.getMessage());        }    }     public static String syncGet(String url, Map<String, Object> headParamsMap) throws IOException {        Request request;        final Request.Builder builder = new Request.Builder().url(url);        try {            if (!CollectionUtils.isEmpty(headParamsMap)) {                final Iterator<Map.Entry<String, Object>> iterator = headParamsMap.entrySet()                        .iterator();                while (iterator.hasNext()) {                    final Map.Entry<String, Object> entry = iterator.next();                    builder.addHeader(entry.getKey(), (String) entry.getValue());                }            }            request = builder.build();            Response response = OkHttpClient.getInstance().newCall(request).execute();            String result = response.body().string();            log.info("syncGet response = {},responseBody= {}", response, result);            if (!response.isSuccessful()) {                throw new IOException("三方接口返回http状态码为" + response.code());            }            return result;        } catch (Exception e) {            log.error("remote interface url:{} have a ecxeption {}", url, e);            throw new RuntimeException("三方接口返回异常");        }    } }