无法使用Java发送帖子表单

Question

The objective of the code is to insert the parameters into the form then submits the form which in turn enters the data into a MySQL database. The problem is that the method doesn't post the data. I'm not sure what I'm doing wrong, I've looked at so many questions regarding this but nothing seems to work.

Here is the form.

<form action="http://localhost/Documents/dataadded.php" method="post">

<b>Add a New Data</b>

<p>Email Address:
<input type="text" name="email_address" size="30" value="" />
</p>

<p>Email Pass:
<input type="text" name="email_pass" size="30" value="" />
</p>

<p>
<input type="submit" name="submit" value="Send" />
</p>

</form>

Here is the Java code.

public static void main(String[] args) {


    String key1 = "email_address";
    String key2 = "email_pass";
    String key3 = "submit";

    String param1 = "testemail@gmail.com";
    String param2 = "password123";
    String param3 = "Send";
    try {
        URL website = new URL("http://localhost/Documents/added.php");

        Map<String,String> arguments = new LinkedHashMap<>();
        arguments.put(key1, param1);
        arguments.put(key2, param2);
        arguments.put(key3, param3);

        StringJoiner sj = new StringJoiner("&");
        for(Map.Entry<String,String> entry : arguments.entrySet())
            sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" 
                 + URLEncoder.encode(entry.getValue(), "UTF-8"));
        byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
        int length = out.length;

        HttpURLConnection connection =  (HttpURLConnection) website.openConnection(); 
        connection.setRequestMethod("POST");
        connection.setFixedLengthStreamingMode(length);
        connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
        connection.setDoOutput(true);
        connection.getOutputStream().write(out);


        System.out.println(sj.toString());

        InputStream response = connection.getInputStream();

        @SuppressWarnings("resource")
        Scanner scan = new Scanner(response);
        String responsebody = scan.useDelimiter("\\A").next();
        System.out.println(responsebody);



    } catch (IOException e) {

        e.printStackTrace();
    }

}

If anyone could shed some light on what's wrong with the code, it will be greatly appreciated.

Answer 1

You have to flush the OutputStream before you can open the InputStream. Below is the method I created to do POST requests.

private String doPost(String urlString, LinkedHashMap<String, String> params) throws Exception {
    //...make the content
    StringBuilder content = new StringBuilder();
    //...append params
    boolean first = true;
    for (Map.Entry<String, String> entry : params.entrySet()) {
        if (!first) {
            content.append("&");
        } else {
            first = false;
        }
        content.append(entry.getKey()).append("=").append(URLEncoder.encode(entry.getValue(), charset));
    }
    //... send POST request
    URL url = new URL(urlString);
    HttpURLConnection con;
    con = (HttpURLConnection) url.openConnection();
    con.setDoInput(true);
    con.setDoOutput(true);
    con.setUseCaches(false);
    try (OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), charset)) {
        writer.write(content.toString());
        writer.flush();
    }
    //...get response
    try (Scanner s = new Scanner(con.getInputStream(), charset)) {
        String resp = s.useDelimiter("\\A").hasNext() ? s.next() : "";
        return resp;
    }
}