java调用http接口的几种方式总结

本文参考： https://blog.csdn.net/fightingXia/article/details/71775516

　　　　　https://www.cnblogs.com/jeffen/p/6937788.html

随着网络上java应用越来越多，场景越来越复杂，所以应用之间经常通过HTTP接口来访问资源

首先了解了URL的最常用的两种请求方式：第一种GET，第二种POST

GET：get请求可以获取页面，也可以把参数放到URL后面以?分割传递数据，参数之间以&关联，例如 http://110.32.44.11:8086/sp-test/usertest/1.0/query?mobile=15334567890&name=zhansan

POST：post请求的参数是放在HTTP请求的正文里，请求的参数被封装起来通过流的方式传递

1.HttpURLConnection 

　　1.1简介：

　　　　在java.net包中，已经提供访问HTTP协议的基本功能类：HttpURLConnection，可以向其他系统发送GET，POST访问请求

　　1.2 GET方式调用

　　　　

 1     private void httpURLGETCase() {
 2         String methodUrl = "http://110.32.44.11:8086/sp-test/usertest/1.0/query";
 3         HttpURLConnection connection = null;
 4         BufferedReader reader = null;
 5         String line = null;
 6         try {
 7             URL url = new URL(methodUrl + "?mobile=15334567890&name=zhansan");
 8             connection = (HttpURLConnection) url.openConnection();// 根据URL生成HttpURLConnection
 9             connection.setRequestMethod("GET");// 默认GET请求
10             connection.connect();// 建立TCP连接
11             if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
12                 reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));// 发送http请求
13                 StringBuilder result = new StringBuilder();
14                 // 循环读取流
15                 while ((line = reader.readLine()) != null) {
16                     result.append(line).append(System.getProperty("line.separator"));// "\n"
17                 }
18                 System.out.println(result.toString());
19             }
20         } catch (IOException e) {
21             e.printStackTrace();
22         } finally {
23             try {
24                 reader.close();
25             } catch (IOException e) {
26                 e.printStackTrace();
27             }
28             connection.disconnect();
29         }
30     }

　　1.3 POST方式调用

　　　　1.3.1 带授权的传递json格式参数调用

 1     private static void httpURLPOSTCase() {
 2         String methodUrl = "http://xxx.xxx.xx.xx:8280/xx/adviserxx/1.0 ";
 3         HttpURLConnection connection = null;
 4         OutputStream dataout = null;
 5         BufferedReader reader = null;
 6         String line = null;
 7         try {
 8             URL url = new URL(methodUrl);
 9             connection = (HttpURLConnection) url.openConnection();// 根据URL生成HttpURLConnection
10             connection.setDoOutput(true);// 设置是否向connection输出，因为这个是post请求，参数要放在http正文内，因此需要设为true,默认情况下是false
11             connection.setDoInput(true); // 设置是否从connection读入，默认情况下是true;
12             connection.setRequestMethod("POST");// 设置请求方式为post,默认GET请求
13             connection.setUseCaches(false);// post请求不能使用缓存设为false
14             connection.setConnectTimeout(3000);// 连接主机的超时时间
15             connection.setReadTimeout(3000);// 从主机读取数据的超时时间
16             connection.setInstanceFollowRedirects(true);// 设置该HttpURLConnection实例是否自动执行重定向
17             connection.setRequestProperty("connection", "Keep-Alive");// 连接复用
18             connection.setRequestProperty("charset", "utf-8");
19             
20             connection.setRequestProperty("Content-Type", "application/json");
21             connection.setRequestProperty("Authorization", "Bearer 66cb225f1c3ff0ddfdae31rae2b57488aadfb8b5e7");
22             connection.connect();// 建立TCP连接,getOutputStream会隐含的进行connect,所以此处可以不要
23 
24             dataout = new DataOutputStream(connection.getOutputStream());// 创建输入输出流,用于往连接里面输出携带的参数
25             String body = "[{\"orderNo\":\"44921902\",\"adviser\":\"张怡筠\"}]";
26             dataout.write(body.getBytes());
27             dataout.flush();
28             dataout.close();
29 
30             if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
31                 reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));// 发送http请求
32                 StringBuilder result = new StringBuilder();
33                 // 循环读取流
34                 while ((line = reader.readLine()) != null) {
35                     result.append(line).append(System.getProperty("line.separator"));//
36                 }
37                 System.out.println(result.toString());
38             }
39         } catch (IOException e) {
40             e.printStackTrace();
41         } finally {
42             try {
43                 reader.close();
44             } catch (IOException e) {
45                 e.printStackTrace();
46             }
47             connection.disconnect();
48         }
49     }

　　　　1.3.2 传递键值对的参数

            URL url = new URL(getUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST"); 
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setUseCaches(false);
            connection.connect();

            String body = "userName=zhangsan&password=123456";
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(connection.getOutputStream(), "UTF-8"));
            writer.write(body);
            writer.close();

　　　　1.3.3 在post请求上传文件

try {
    URL url = new URL(getUrl);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setUseCaches(false);
    connection.setRequestProperty("Content-Type", "file/*");//设置数据类型
    connection.connect();

    OutputStream outputStream = connection.getOutputStream();
    FileInputStream fileInputStream = new FileInputStream("file");//把文件封装成一个流
    int length = -1;
    byte[] bytes = new byte[1024];
    while ((length = fileInputStream.read(bytes)) != -1){
        outputStream.write(bytes,0,length);//写的具体操作
    }
    fileInputStream.close();
    outputStream.close();

    int responseCode = connection.getResponseCode();
    if(responseCode == HttpURLConnection.HTTP_OK){
        InputStream inputStream = connection.getInputStream();
        String result = is2String(inputStream);//将流转换为字符串。
        Log.d("kwwl","result============="+result);
    }

} catch (Exception e) {
    e.printStackTrace();
}

　　　　1.3.4 同时上传参数和文件

在实际应用时，上传文件的同时也常常需要上传键值对参数。比如在微信中发朋友圈时，不仅有图片，还有有文字。此时就需要同时上传参数和文件。

在httpURLconnection中并没有提供直接上传参数和文件的API，需要我们自己去探索。我们知道在Web页面上传参数和文件很简单，只需要在form标签写上contentype=”multipart/form-data”即可，剩余工作便都交给浏览器去完成数据收集并发送Http请求。但是如果没有页面的话要怎么上传文件呢？

由于脱离了浏览器的环境，我们就要自己去完成数据的封装并发送。首先我们来看web页面上传参数和文件是什么样子的？

我们写一个web表单，上传两个键值对参数和一个文件。使用抓包工具抓取的数据结果如下：

经过分析可知，上传到服务器的数据除了键值对数据和文件数据外，还有其他字符串，使用这些这些字符串来拼接一定的格式。

那么我们只要模拟这个数据，并写入到Http请求中便能实现同时传递参数和文件。

代码如下：

try {

    String BOUNDARY = java.util.UUID.randomUUID().toString();
    String TWO_HYPHENS = "--";
    String LINE_END = "\r\n";

    URL url = new URL(URLContant.CHAT_ROOM_SUBJECT_IMAGE);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setUseCaches(false);

    //设置请求头
    connection.setRequestProperty("Connection", "Keep-Alive");
    connection.setRequestProperty("Charset", "UTF-8");
    connection.setRequestProperty("Content-Type","multipart/form-data; BOUNDARY=" + BOUNDARY);
    connection.setRequestProperty("Authorization","Bearer "+UserInfoConfigure.authToken);
    connection.connect();

    DataOutputStream outputStream = new DataOutputStream(connection.getOutputStream());
    StringBuffer strBufparam = new StringBuffer();
    //封装键值对数据一
    strBufparam.append(TWO_HYPHENS);
    strBufparam.append(BOUNDARY);
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Disposition: form-data; name=\"" + "groupId" + "\"");
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Type: " + "text/plain" );
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Lenght: "+(""+groupId).length());
    strBufparam.append(LINE_END);
    strBufparam.append(LINE_END);
    strBufparam.append(""+groupId);
    strBufparam.append(LINE_END);

    //封装键值对数据二
    strBufparam.append(TWO_HYPHENS);
    strBufparam.append(BOUNDARY);
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Disposition: form-data; name=\"" + "title" + "\"");
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Type: " + "text/plain" );
    strBufparam.append(LINE_END);
    strBufparam.append("Content-Lenght: "+"kwwl".length());
    strBufparam.append(LINE_END);
    strBufparam.append(LINE_END);
    strBufparam.append("kwwl");
    strBufparam.append(LINE_END);

    //拼接完成后，一块写入
    outputStream.write(strBufparam.toString().getBytes());


    //拼接文件的参数
    StringBuffer strBufFile = new StringBuffer();
    strBufFile.append(LINE_END);
    strBufFile.append(TWO_HYPHENS);
    strBufFile.append(BOUNDARY);
    strBufFile.append(LINE_END);
    strBufFile.append("Content-Disposition: form-data; name=\"" + "image" + "\"; filename=\"" + file.getName() + "\"");
    strBufFile.append(LINE_END);
    strBufFile.append("Content-Type: " + "image/*" );
    strBufFile.append(LINE_END);
    strBufFile.append("Content-Lenght: "+file.length());
    strBufFile.append(LINE_END);
    strBufFile.append(LINE_END);

    outputStream.write(strBufFile.toString().getBytes());

    //写入文件
    FileInputStream fileInputStream = new FileInputStream(file);
    byte[] buffer = new byte[1024*2];
    int length = -1;
    while ((length = fileInputStream.read(buffer)) != -1){
        outputStream.write(buffer,0,length);
    }
    outputStream.flush();
    fileInputStream.close();

    //写入标记结束位
    byte[] endData = (LINE_END + TWO_HYPHENS + BOUNDARY + TWO_HYPHENS + LINE_END).getBytes();//写结束标记位
    outputStream.write(endData);
    outputStream.flush();

    //得到响应
    int responseCode = connection.getResponseCode();
    if(responseCode == HttpURLConnection.HTTP_OK){
        InputStream inputStream = connection.getInputStream();
        String result = is2String(inputStream);//将流转换为字符串。
        Log.d("kwwl","result============="+result);
    }

} catch (Exception e) {
    e.printStackTrace();
}

demo2

    private static String imageIdentify(String card,String methodUrl, byte[] fileBytes, String file_id) {
        HttpURLConnection connection = null;
        OutputStream dataout = null;
        BufferedReader bf = null;
        String BOUNDARY = "----WebKitFormBoundary2NYA7hQkjRHg5WJk";
        String END_DATA = ("\r\n--" + BOUNDARY + "--\r\n");
        String BOUNDARY_PREFIX = "--";
        String NEW_LINE = "\r\n";
        try {
            URL url = new URL(methodUrl+"?card="+card);
            connection = (HttpURLConnection) url.openConnection();
            connection.setConnectTimeout(3000);
            connection.setReadTimeout(3000);
            connection.setDoOutput(true);// 设置连接输出流为true,默认false
            connection.setDoInput(true);// 设置连接输入流为true
            connection.setRequestMethod("POST");// 设置请求方式为post
            connection.setUseCaches(false);// post请求缓存设为false
            connection.setInstanceFollowRedirects(true);// 设置该HttpURLConnection实例是否自动执行重定向
            connection.setRequestProperty("connection", "Keep-Alive");// 连接复用
            connection.setRequestProperty("charset", "utf-8");
            connection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + BOUNDARY);
            connection.connect();// 建立连接

            dataout = new DataOutputStream(connection.getOutputStream());// 创建输入输出流,用于往连接里面输出携带的参数
            StringBuilder sb2 = new StringBuilder();
            sb2.append(BOUNDARY_PREFIX);
            sb2.append(BOUNDARY);
            sb2.append(NEW_LINE);
            sb2.append("Content-Disposition:form-data; name=\"type\"");
            // 参数头设置完成后需要2个换行，才是内容
            sb2.append(NEW_LINE);
            sb2.append(NEW_LINE);
            sb2.append("0");
            sb2.append(NEW_LINE);
            dataout.write(sb2.toString().getBytes());

            // 读取文件上传到服务器
            StringBuilder sb1 = new StringBuilder();
            sb1.append(BOUNDARY_PREFIX);
            sb1.append(BOUNDARY);
            sb1.append(NEW_LINE);
            sb1.append("Content-Disposition:form-data; name=\"file\";filename=\"" + file_id + "\"");//文件名必须带后缀
            sb1.append(NEW_LINE);
            sb1.append("Content-Type:application/octet-stream");
            // 参数头设置完成后需要2个换行，才是内容
            sb1.append(NEW_LINE);
            sb1.append(NEW_LINE);
            dataout.write(sb1.toString().getBytes());
            dataout.write(fileBytes);// 写文件字节
            
            dataout.write(NEW_LINE.getBytes());
            dataout.write(END_DATA.getBytes());
            dataout.flush();
            dataout.close();

            bf = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));// 连接发起请求,处理服务器响应
            String line;
            StringBuilder result = new StringBuilder(); // 用来存储响应数据
            // 循环读取流,若不到结尾处
            while ((line = bf.readLine()) != null) {
                result.append(line).append(System.getProperty("line.separator"));
            }
            bf.close();
            connection.disconnect(); // 销毁连接
            return result.toString();
        } catch (Exception e) {
            LOGGER.error(e.getMessage(), e);
        }
        return "";
    }

　　　　1.3.4

从服务器下载文件是比较简单的操作，只要得到输入流，就可以从流中读出数据。使用示例如下：

try {
     String urlPath = "https://www.baidu.com/";
      URL url = new URL(urlPath);
      HttpURLConnection connection = (HttpURLConnection) url.openConnection();
      connection.setRequestMethod("GET");
      connection.connect();
      int responseCode = connection.getResponseCode();
      if(responseCode == HttpURLConnection.HTTP_OK){
          InputStream inputStream = connection.getInputStream();
          File dir = new File("fileDir");
          if (!dir.exists()){
              dir.mkdirs();
          }
          File file = new File(dir, "fileName");//根据目录和文件名得到file对象
          FileOutputStream fos = new FileOutputStream(file);
          byte[] buf = new byte[1024*8];
          int len = -1;
          while ((len = inputStream.read(buf)) != -1){
              fos.write(buf, 0, len);
          }
          fos.flush();
      }

  } catch (Exception e) {
      e.printStackTrace();
  }

2.HttpClient

　　2.1简介：

　　　　 

　　2.2 GET方式调用

　　2.3 POST方式调用

3.Spring RestTemplate

　　3.1简介：

　　　　 

　　3.2 GET方式调用

　　3.3 POST方式调用