Java使用UTF-8发送http POST

Question

I need to send HTTP POST with Google FCM. With code below, it's OK to send English message but Chinese characters. I did many trials by adding UTF-8 here and there... Need help.

The payload of my message is str2 in the code below. The result shown in Android APP is Hello+%E6%88%91

E68891 is the correct UTF-8 code, but I need it to be shown as a Chinese character.

package tryHttpPost2;
import java.io.DataOutputStream;
import java.net.URL;
import java.net.URLEncoder;
import javax.net.ssl.HttpsURLConnection;

public class TryHttpPost2 
{
    public static void main(String[] args) throws Exception {
        String url = "https://fcm.googleapis.com/fcm/send";
        URL obj = new URL(url);
        HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
        con.setRequestMethod("POST");
        con.setRequestProperty("Content-Type", "application/json;x-www-form-urlencoded;charset=UTF-8");
        con.setRequestProperty("Accept-Charset", "UTF-8");
        con.setRequestProperty("Authorization", "key=...............");

        String str1 = "{\"to\":\"/topics/1\",\"notification\":{\"title\":\"";
        String str2 = URLEncoder.encode("Hello 我", "utf-8");
        String str3 = "\"}}";
        String urlParameters = str1+str2+str3;
        con.setDoOutput(true);
        DataOutputStream wr = new DataOutputStream(con.getOutputStream());

        wr.writeBytes(urlParameters);
        wr.flush();
        wr.close();
        con.getResponseCode();
    }
}

Answer 1

There are two problems:

1. writeBytes : as the Java documentation says:

   For each character, one byte is written, the low-order byte, in exactly the manner of the writeByte method . The high-order eight bits of each character in the string are ignored.

   So this method can not write unicode strings.

2. URLEncoder is intended to be used for GET requests or POST request with the content-type of application/x-www-form-urlencoded . But you transmit data using the content-type application/json . You somehow try to also use url encoding there, but this does not work. (See the relevant RFC for more information)

To fix this, use the right method to transfer the data: As utf-8, without any encoding in the JSON:

con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
con.setRequestProperty("Accept-Charset", "UTF-8");
con.setRequestProperty("Authorization", "key=...............");

String str1 = "{\"to\":\"/topics/1\",\"notification\":\"title\":\"";
String str2 = "Hello 我";
String str3 = "\"}}";
String urlParameters = str1+str2+str3;
con.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(con.getOutputStream(), "UTF-8");

wr.write(urlParameters);
wr.flush();
wr.close();
con.getResponseCode();

Answer 2

Thanks for Kuhn's great help. Here is what I do now and works.

1. Let Content-Type as just "application/json".
2. Let str2 be just the payload string.
3. Replace writeBytes thing by wr.write(urlParameters.getBytes("utf-8"));
   4. The property "Accept-Charset" seems useless here. Works with or without it.