Java实现向指定URL用POST方法发送Json格式字符串参数请求的工具类

场景

SpringBoot项目中通过后台Controller向某服务接口发送POST请求。

实现

在项目pom.xml中添加依赖

 
            commons-net
            commons-net
            2.2
            compile
        
        
            com.squareup.okhttp3
            okhttp
            3.6.0
  

在util包下新建HttpRequestUtil.java

public class HttpRequestUtil {
    /**
     * 定义全局OkHttpClient对象
     */
    private static final OkHttpClient httpClient = new OkHttpClient();

/**
     * 向指定 URL 发送POST方法的请求
     *
     * @param url
     *            发送请求的 URL
     * @param param
     *            请求参数，请求参数应该是Json格式字符串的形式。
     * @return 所代表远程资源的响应结果
     */
    public static String sendPost(String url, String jsonData) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection con = realUrl.openConnection();
            HttpURLConnection conn = (HttpURLConnection) con;
            // 设置通用的请求属性
            conn.setRequestMethod("POST"); // 设置Post请求
            conn.setConnectTimeout(5 * 1000);
            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/x-www-form-urlencoded"); // 设置内容类型
            conn.setRequestProperty("Content-Type",
                    "application/json"); // 设置内容类型
            // conn.setRequestProperty("Content-Length",
            // String.valueOf(param.length())); //设置长度
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setUseCaches(false);
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(new OutputStreamWriter(
                    conn.getOutputStream(), "utf-8"));
            // 发送请求参数
            // out.print(param);
            out.write(jsonData);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
            byte[] bresult = result.getBytes();
            result = new String(bresult, "utf-8");
        } catch (Exception e) {
            System.out.println("发送 POST 请求出现异常！" + e);
            e.printStackTrace();
        }
        // 使用finally块来关闭输出流、输入流
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

}

 

注意根据请求的enctype进行相应的设置

conn.setRequestProperty("Content-Type",
                    "application/x-www-form-urlencoded"); // 设置内容类型

或者
 

 conn.setRequestProperty("Content-Type",
                    "application/json"); // 设置内容类型

在后台Controller调用时只需要：

 

String URL="http://IP:7788/PostPrintService/Info";
            Map map=new HashMap();
            map.put("TableName","wms_receive_order_details");
            map.put("PrintID",PrintId);
            String  param= JSON.toJSONString(map);
            String message = HttpRequestUtil.sendPost(URL, param);