Java character set and encoding/decoding

Convert character set

1. Encoding : java uni code to byte array
   • String to bytes : Encoded array
   • ex) byte[] bytes = str.getBytes(“UTF-8”);
2. Decoding : byte array to uni code string
   • bytes to String : Decoded string
   • ex) String str = new String(bytes, “UTF-8”);

EUC-KR <—> java.lang.String <—-> UTF-8

// Check default charset
String charset = Charset.defaultCharset().toString();
System.out.println(String.format("Default charset: [%s]", charset));

Convert between UTF-8 and EUC-KR

String tmp = "TEST";
String euckr = new String(tmp.getBytes("EUC-KR"), "EUC-KR");
String utf9 = new String(tmp.getBytes("UTF-8"), "UTF-8");

Apache HttpClient

addHeader(String name, String value

Adds a header to this message. The header will be appended to the end of the list. setHeader method override headers if header’s names are same. But addHeader method doesn’t. It adds headers even header’s name are same

setHeader(String name, String value

Overwrites the first header with the same name. The new header will be appended to the end of the list, if no header with the given name can be found.

    httpPost.setEntity(new StringEntity(json, "UTF-8"));​
    httpPost.addRequestHeader("Content-Type", "text/plain;charset=UTF-8");​

    httpPost.addHeader("AuthenticationKey",authenticationKey);
    httpPost.addHeader("Content-Type","application/json");

    httpPost.setHeader("Cache-Control", "no-cache"); // HTTP 1.1
    httpPost.setHeader("Pragma", "no-cache"); // HTTP 1.0
    httpPost.setHeader("X-Requested-With", "XMLHttpRequest");

Usage

URI urlObject = new URI(url,"UTF-8");
HttpClient httpclient = new DefaultHttpClient();

List<NameValuePair> formparams = URLEncodedUtils.parse(urlObject,"UTF-8");
UrlEncodedFormEntity entity;
entity = new UrlEncodedFormEntity(formparams);

HttpPost httppost = new HttpPost(urlObject.getPath());
httppost.setEntity(entity);
httppost.addHeader("Content-Type","application/x-www-form-urlencoded");

HttpResponse response = httpclient.execute(httppost);

HttpEntity entity2 = response.getEntity();

Java URLConnection

// Iterate over query params from urlObject.getQuery() like
while(en.hasMoreElements()){
    String paramName  = (String)en.nextElement(); // Iterator over yourListOfKeys
    String paramValue = yourMapOfValues.get(paramName); // replace yourMapOfNameValues
    str = str + "&" + paramName + "=" + URLEncoder.encode(paramValue);
}
try{
    URL u = new URL(urlObject.getPath()); //here's the url path from your urlObject
    URLConnection uc = u.openConnection();
    uc.setDoOutput(true);
    uc.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
    PrintWriter pw = new PrintWriter(uc.getOutputStream());
    pw.println(str);
    pw.close();

    BufferedReader in = new BufferedReader(new 
            InputStreamReader(uc.getInputStream()));
    String res = in.readLine();
    in.close();
    // ...
}