Java模拟FormData表单提交

在敲代码之前，我们需要了解正常的FormData表单提交究竟向服务器提交了哪些内容。
首先使用postman向本地socket服务器发送FormData表单，postman示例如下：

socket服务端收到的内容如下：

127.0.0.1:11787
Data Request : POST / HTTP/1.1
User-Agent: PostmanRuntime/7.19.0
Accept: */*
Cache-Control: no-cache
Postman-Token: 067860f8-4295-493a-a597-184d22b3e247
Host: localhost:8080
Content-Type: multipart/form-data; boundary=--------------------------926274221155642082481101
Accept-Encoding: gzip, deflate
Cookie: JSESSIONID=ED0FA7D018270E8CF75AA978B36EAEDE
Content-Length: 262
Connection: keep-alive

----------------------------926274221155642082481101
Content-Disposition: form-data; name="12"

34
----------------------------926274221155642082481101
Content-Disposition: form-data; name="56"

78
----------------------------926274221155642082481101--

再使用postman发送text数据，示例如下：

socket服务端收到的数据如下：

127.0.0.1:11933
Data Request : POST / HTTP/1.1
User-Agent: PostmanRuntime/7.19.0
Accept: */*
Cache-Control: no-cache
Postman-Token: d3356b13-b5e0-47b8-973a-c8ff7cc39d88
Host: localhost:8080
Accept-Encoding: gzip, deflate
Content-Length: 3
Cookie: JSESSIONID=ED0FA7D018270E8CF75AA978B36EAEDE
Connection: keep-alive

123

通过对比我们可以得出，相比较text、xml及json数据，formdata表单只是在发送信息的格式和头信息中有特定的要求，其余并无任何差异，主要集中在“boundary”参数上。
具体代码如下：

	public String postFormData(String path, HashMap<String, String> Headers, HashMap<String, String> formMap) {
        String result = "";
        HttpURLConnection connection = null;
        String boundary = "--------------------------132183525382215881770481";
        try {
            URL url = new URL(path);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
            connection.setDoOutput(true);
            connection.setDoInput(true);
            connection.setRequestProperty("Connection", "Keep-Alive");
            // 不使用缓存
            connection.setUseCaches(false);
            if (Headers != null) {
                if (Headers.size() > 0) {
                    for (Map.Entry<String, String> entry : Headers.entrySet()) {
                        connection.setRequestProperty(entry.getKey(), entry.getValue());
                    }
                }
            }
            StringBuffer formSB = new StringBuffer();
            if (formMap != null) {
                if (formMap.size() > 0) {
                    for (Map.Entry<String, String> entry : formMap.entrySet()) {
                        String inputName = entry.getKey();
                        String inputValue = entry.getValue();
                        formSB.append("\r\n").append("--").append(boundary).append("\r\n");
                        formSB.append("Content-Disposition: form-data; name=\"" + inputName + "\"\r\n\r\n");
                        formSB.append(inputValue);
                    }
                    formSB.append("\r\n").append("--").append(boundary).append("--");
                }
            }
            connection.connect();
            //OutputStream out = new DataOutputStream(connection.getOutputStream());
            PrintWriter out = new PrintWriter(new OutputStreamWriter(connection.getOutputStream(), "UTF-8"));
            out.print(formSB.toString());
            out.flush();
            //获得响应状态
            int resultCode = connection.getResponseCode();
            if (HttpURLConnection.HTTP_OK == resultCode) {
                formSB = new StringBuffer();
                String readLine;
                BufferedReader responseReader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
                while ((readLine = responseReader.readLine()) != null) {
                    formSB.append(readLine).append("\n");
                }
                responseReader.close();
                result = formSB.toString();
            } else {
                result = "{\"code\":\"" + resultCode + "\"}";
            }
            out.close();
        } catch (Exception e) {
            logger.error(e.toString());
            return "{\"code\":500,\"result\":\"" + "POST表单请求 " + path + " 时出现异常\"}";
        } finally {
            connection.disconnect();
        }
        return result;
    }