如何用java实现post请求外部接口（字符串+文件参数）

最近在写证照识别业务（分析上传图片类型->调用该类型对应识别接口），其中第一步分析类型用的是TensorFlow训练出来的模型，接着用java调用其生成的pb文件进行识别类型；接着进行证照识别的接口是在调研后选择了face++的，因为可支持自定义模板。等我有空的时候，会把全部业务流程整理出来，这里先把调用外部接口的方法写了出来。

示例代码：

JSONObject jsonObject = InterfaceUtil.doPost(TEMPLATE_OCR_URL,
				buildTextMap(), buildFileMap(file));
				
   // 传入api_key、api_secret这两个参数，类型为字符串。
	private Map<String, String> buildTextMap() {
		Map<String, String> textMap = new HashMap<String, String>();
		textMap.put("api_key", API_KEY);
		textMap.put("api_secret", API_SECRET);
		return textMap;
	}

    // 传一个叫image_file的MultipartFile格式参数。
	private Map<String, MultipartFile> buildFileMap(MultipartFile file) {
		Map<String, MultipartFile> fileMap = new HashMap<String, MultipartFile>();
		fileMap.put("image_file", file);
		return fileMap;
	}

原工具类（返回状态码非200时会报错，优化后代码在下面）：



import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Iterator;
import java.util.Map;

import org.springframework.web.multipart.MultipartFile;

import com.alibaba.rocketmq.shade.com.alibaba.fastjson.JSONObject;

public class InterfaceUtil {
	/**
	 * 表单形式上传数据
	 * 
	 * @param urlStr  接口地址
	 * @param textMap 字符串参数
	 * @param fileMap 文件参数
	 * @param contentType 没有传入文件类型默认采用application/octet-stream
	 *                    contentType非空采用filename匹配默认的图片类型
	 * @return 返回response数据
	 */
	@SuppressWarnings("rawtypes")
	public static JSONObject doPost(String urlStr, Map<String, String> textMap,
			Map<String, MultipartFile> fileMap) {
		JSONObject jsonObject = null;
		HttpURLConnection conn = null;
		// boundary就是request头和上传文件内容的分隔符
		String BOUNDARY = "---------------------------123821742118716";
		try {
			URL url = new URL(urlStr);
			conn = (HttpURLConnection) url.openConnection();
			conn.setConnectTimeout(5000);
			conn.setReadTimeout(30000);
			conn.setDoOutput(true);
			conn.setDoInput(true);
			conn.setUseCaches(false);
			conn.setRequestMethod("POST");
			conn.setRequestProperty("Connection", "Keep-Alive");
			conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.6)");
			conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
			OutputStream out = new DataOutputStream(conn.getOutputStream());
			// text
			if (textMap != null) {
				StringBuffer strBuf = new StringBuffer();
				Iterator iter = textMap.entrySet().iterator();
				while (iter.hasNext()) {
					Map.Entry entry = (Map.Entry) iter.next();
					String inputName = (String) entry.getKey();
					String inputValue = (String) entry.getValue();
					if (inputValue == null) {
						continue;
					}
					strBuf.append("\r\n").append("--").append(BOUNDARY).append("\r\n");
					strBuf.append("Content-Disposition:form-data;name=\"" + inputName + "\"\r\n\r\n");
					strBuf.append(inputValue);
				}
				out.write(strBuf.toString().getBytes());
			}
			// file
			if (fileMap != null) {
				Iterator iter = fileMap.entrySet().iterator();
				while (iter.hasNext()) {
					Map.Entry entry = (Map.Entry) iter.next();
					String inputName = (String) entry.getKey();
					MultipartFile inputValue = (MultipartFile) entry.getValue();
					if (inputValue == null) {
						continue;
					}
					String filename = inputValue.getOriginalFilename();

					// 没有传入文件类型，同时根据文件获取不到类型，默认采用application/octet-stream
					String contentType = inputValue.getContentType();

					StringBuffer strBuf = new StringBuffer();
					strBuf.append("\r\n").append("--").append(BOUNDARY).append("\r\n");
					strBuf.append("Content-Disposition:form-data;name=\"" + inputName + "\";filename=\"" + filename
							+ "\"\r\n");
					strBuf.append("Content-Type:" + contentType + "\r\n\r\n");
					out.write(strBuf.toString().getBytes());
					InputStream in = inputValue.getInputStream();
					int bytes = 0;
					byte[] bufferOut = new byte[1024];
					while ((bytes = in.read(bufferOut)) != -1) {
						out.write(bufferOut, 0, bytes);
					}
					in.close();
				}
			}
			byte[] endData = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();
			out.write(endData);
			out.flush();
			out.close();
			// 读取返回数据

			ByteArrayOutputStream bStream = new ByteArrayOutputStream();
			byte[] buffer = new byte[1024];
			int len = -1;
			while ((len = conn.getInputStream().read(buffer)) != -1) {
				bStream.write(buffer, 0, len);
			}
			jsonObject = JSONObject.parseObject(new String(bStream.toByteArray(), "UTF-8"));
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (conn != null) {
				conn.disconnect();
				conn = null;
			}
		}
		return jsonObject;
	}

}

————–后续补充2020年11月20日 10:07:08————–

调试时发现，当返回的状态码不等于200时，会报错，猜测是获取流的方式有些不一样，又找到一篇文章，果然是这样，解决方案：报错时通过 getErrorStream获取错误信息，文章链接

httpurlconnection post请求获取返回码为400的异常信息

优化后工具类：

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Iterator;
import java.util.Map;

import org.springframework.web.multipart.MultipartFile;

import com.alibaba.rocketmq.shade.com.alibaba.fastjson.JSONObject;

public class InterfaceUtil {
	/**
	 * 表单形式上传数据
	 * 
	 * @param urlStr
	 * @param textMap
	 * @param fileMap
	 * @param contentType 没有传入文件类型默认采用application/octet-stream
	 *                    contentType非空采用filename匹配默认的图片类型
	 * @return 返回response数据
	 */
	@SuppressWarnings("rawtypes")
	public static JSONObject doPost(String urlStr, Map<String, String> textMap, Map<String, MultipartFile> fileMap) {
		JSONObject jsonObject = null;
		HttpURLConnection conn = null;
		// boundary就是request头和上传文件内容的分隔符
		String BOUNDARY = "---------------------------123821742118716";
		try {
			URL url = new URL(urlStr);
			conn = (HttpURLConnection) url.openConnection();
			conn.setConnectTimeout(5000);
			conn.setReadTimeout(30000);
			conn.setDoOutput(true);
			conn.setDoInput(true);
			conn.setUseCaches(false);
			conn.setRequestMethod("POST");
			conn.setRequestProperty("Connection", "Keep-Alive");
			conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.6)");
			conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
			OutputStream out = new DataOutputStream(conn.getOutputStream());
			// text
			if (textMap != null) {
				StringBuffer strBuf = new StringBuffer();
				Iterator iter = textMap.entrySet().iterator();
				while (iter.hasNext()) {
					Map.Entry entry = (Map.Entry) iter.next();
					String inputName = (String) entry.getKey();
					String inputValue = (String) entry.getValue();
					if (inputValue == null) {
						continue;
					}
					strBuf.append("\r\n").append("--").append(BOUNDARY).append("\r\n");
					strBuf.append("Content-Disposition:form-data;name=\"" + inputName + "\"\r\n\r\n");
					strBuf.append(inputValue);
				}
				out.write(strBuf.toString().getBytes());
			}
			// file
			if (fileMap != null) {
				Iterator iter = fileMap.entrySet().iterator();
				while (iter.hasNext()) {
					Map.Entry entry = (Map.Entry) iter.next();
					String inputName = (String) entry.getKey();
					MultipartFile inputValue = (MultipartFile) entry.getValue();
					if (inputValue == null) {
						continue;
					}
					String filename = inputValue.getOriginalFilename();

					// 没有传入文件类型，同时根据文件获取不到类型，默认采用application/octet-stream
					String contentType = inputValue.getContentType();

					StringBuffer strBuf = new StringBuffer();
					strBuf.append("\r\n").append("--").append(BOUNDARY).append("\r\n");
					strBuf.append("Content-Disposition:form-data;name=\"" + inputName + "\";filename=\"" + filename
							+ "\"\r\n");
					strBuf.append("Content-Type:" + contentType + "\r\n\r\n");
					out.write(strBuf.toString().getBytes());
					InputStream in = inputValue.getInputStream();
					int bytes = 0;
					byte[] bufferOut = new byte[1024];
					while ((bytes = in.read(bufferOut)) != -1) {
						out.write(bufferOut, 0, bytes);
					}
					in.close();
				}
			}
			byte[] endData = ("\r\n--" + BOUNDARY + "--\r\n").getBytes();
			out.write(endData);
			out.flush();
			out.close();

			InputStream inputStream = null;
			if (conn.getResponseCode() != HttpURLConnection.HTTP_OK ) {
				inputStream = conn.getErrorStream();//主要就是这里
			} else {
				inputStream = conn.getInputStream();//主要就是这里
			}
			BufferedReader br = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
			StringBuffer buffer = new StringBuffer();
			String line = "";
			while ((line = br.readLine()) != null) {
				buffer.append(line);
			}
			String result = new String(buffer);
			jsonObject = JSONObject.parseObject(result);
			inputStream.close();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (conn != null) {
				conn.disconnect();
				conn = null;
			}
		}
		return jsonObject;
	}

}

原文链接：https://blog.csdn.net/qq_39380155/article/details/109767990

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