Develop Reference

Posting JSON to REST API from Java Servlet

I'm having issues trying to send over a JSON string to a REST API. Long story short, I'm taking user input in a form, sending it over to a java servlet to validate and work with it a bit, and then trying to send it to an endpoint.
I have the following method being called on in my doPost method in my servlet, I am using printwriter pw to be able to read back data being returned in my response in the browser console at this point.
String jsonData = //JSON STRING HERE\\
String username = //USERNAME\\
String password = //PASSWORD\\
String endpointURL = //ENDPOINT URL HERE\\
pw.println(sendJson(jsonData, username, password));
private String sendJSON(String jsonData, String usrname, String usrpass) {
try {
String auth = usrname + ":" + usrpass;
byte[] encodedAuth = Base64.encodeBase64(auth.getBytes(StandardCharsets.UTF_8));
String authHeaderValue = "Basic " + new String(encodedAuth);
URL url = new URL(endpointURL);
HttpURLConnection http = (HttpURLConnection)url.openConnection();
http.setConnectTimeout(5000);
http.setReadTimeout(5000);
http.setRequestMethod("POST");
http.setRequestProperty("Content-Type", "application/json; utf-8");
http.setRequestProperty("Authorization", authHeaderValue);
http.setDoOutput(true);
//POST Json to URL using HttpURLConnection
//try(OutputStream os = http.getOutputStream()) {
OutputStream os = http.getOutputStream();
byte[] input = jsonData.getBytes("utf-8");
os.write(input, 0, input.length);
//}
/*String responseBody;
try(BufferedReader br = new BufferedReader(
new InputStreamReader(http.getInputStream(), "utf-8"))) {
StringBuilder response = new StringBuilder();
String responseLine = null;
while ((responseLine = br.readLine()) != null) {
response.append(responseLine.trim());
}
//System.out.println(response.toString());
responseBody = response.toString();
return responseBody;
}
return responseBody;*/
BufferedReader in = new BufferedReader(
new InputStreamReader(http.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
return response.toString();
} catch (IOException e) {
return e.toString();
}
}
}
I was having issues with the try's so I rewrote it to try and just get functionality right away first. Right now I'm receiving "java.io.IOException: Server Returned HTTP response code: 500 for URL: //URL HERE\"
Would anybody have any tips to point me in the right direction? I feel like I'm just missing like a small piece of the puzzle at this point, and I'm having a hard time finding any tutorials showing what it is that I'm trying to do. Thank you so much to anyone for any tips/pointers!
Made sure I was able to authenticate and that wasn't the issue by just connecting and returning:
int statusCode = http.getResponseCode();
String statusCodeString = Integer.toString(statusCode);
return statusCodeString;
This worked fine, received 403 response when setting wrong password/username and 400 response when I change to correct.
I attempted using HttpClient as well instead, but was having issues trying to get that to work at all. I also had an error earlier with week trying to do this with a certificate error, but after reimporting the cert to my cacerts file this was resolved (unrelated to this issue I believe).

How to get correct data from HTTP Request

I'm trying to get my user information from stackoverflow api using a simple HTTP request with GET method in Java.
This code I had used before to get another HTTP data using GET method without problems:
URL obj;
StringBuffer response = new StringBuffer();
String url = "http://api.stackexchange.com/2.2/users?inname=HCarrasko&site=stackoverflow";
try {
obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("GET");
int responseCode = con.getResponseCode();
System.out.println("\nSending 'GET' request to URL : " + url);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
System.out.println(response.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
But in this case I'm getting just stranger symbols when I print the response var, like this:
�mRM��0�+�N!���FZq�\�pD�z�:V���JX���M��̛yO^���뾽�g�5J&� �9�YW�%c`do���Y'��nKC38<A�&It�3��6a�,�,]���`/{�D����>6�Ɠ��{��7tF ��E��/����K���#_&�yI�a�v��uw}/�g�5����TkBTķ���U݊c���Q�y$���$�=ۈ��ñ���8f�<*�Amw�W�ـŻ��X$�>'*QN�?�<v�ݠ FH*��Ҏ5����ؔA�z��R��vK���"���#�1��ƭ5��0��R���z�ϗ/�������^?r��&�f��-�OO7���������Gy�B���Rxu�#:0�xͺ}�\�����
thanks in advance.

The content is likely GZIP encoded/compressed. The following is a general snippet that I use in all of my Java-based client applications that utilize HTTP, which is intended to deal with this exact problem:
// Read in the response
// Set up an initial input stream:
InputStream inputStream = fetchAddr.getInputStream(); // fetchAddr is the HttpURLConnection
// Check if inputStream is GZipped
if("gzip".equalsIgnoreCase(fetchAddr.getContentEncoding())){
// Format is GZIP
// Replace inputSteam with a GZIP wrapped stream
inputStream = new GZIPInputStream(inputStream);
}else if("deflate".equalsIgnoreCase(fetchAddr.getContentEncoding())){
inputStream = new InflaterInputStream(inputStream, new Inflater(true));
} // Else, we assume it to just be plain text
BufferedReader sr = new BufferedReader(new InputStreamReader(inputStream));
String inputLine;
StringBuilder response = new StringBuilder();
// ... and from here forward just read the response...
This relies on the following imports: java.util.zip.GZIPInputStream; java.util.zip.Inflater; and java.util.zip.InflaterInputStream.

Reading rest service of content type application/vnd.oracle.adf.resourceitem+json

I have a webservice whose content type is application/vnd.oracle.adf.resourceitem+json.
The HttpEntity of the reponse obtained by hitting this service is looks like this
ResponseEntityProxy{[Content-Type: application/vnd.oracle.adf.resourceitem+json,Content-Length: 3,Chunked: false]}
When I try to convert this HttpEntity into String it gives me a blank String {}.
Below are the ways I tried to convert the HttpEntity to String
1.
String strResponse = EntityUtils.toString(response.getEntity());
2.
String strResponse = "";
String inputLine;
BufferedReader br = new BufferedReader(new InputStreamReader(entity.getContent()));
try {
while ((inputLine = br.readLine()) != null) {
System.out.println(inputLine);
strResponse += inputLine;
}
br.close();
} catch (IOException e) {
e.printStackTrace();
}
3.
response.getEntity().writeTo(new FileOutputStream(new File("C:\\Users\\harshita.sethi\\Documents\\Chabot\\post.txt")));
All returns String -> {}.
Can anyone tell me what am I doing wrong?
Is this because of the content type?

The above code is still giving the same response with empty JSON object. So I modified and wrote the below code. This one seems to run perfectly fine.
URL url = new URL(urlString);
HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
con.setDoOutput(true);
con.setRequestMethod("POST");
con.addRequestProperty("Authorization", getAuthToken());
con.addRequestProperty("Content-Type", "application/vnd.oracle.adf.resourceitem+json;charset=utf-8");
String input = String.format("{\"%s\":\"%s\",\"%s\":\"%s\"}", field, value, field2, value2);
System.out.println(input);
OutputStream outputStream = con.getOutputStream();
outputStream.write(input.getBytes());
outputStream.flush();
con.connect();
System.out.println(con.getResponseCode());
// Uncompressing gzip content encoding
GZIPInputStream gzip = new GZIPInputStream(con.getInputStream());
StringBuffer szBuffer = new StringBuffer();
byte tByte[] = new byte[1024];
while (true) {
int iLength = gzip.read(tByte, 0, 1024);
if (iLength < 0) {
break;
}
szBuffer.append(new String(tByte, 0, iLength));
}
con.disconnect();
returnString = szBuffer.toString();
Authentication method
private String getAuthToken() {
String name = user;
String pwd = this.password;
String authString = name + ":" + pwd;
byte[] authEncBytes = Base64.getEncoder().encode(authString.getBytes());
System.out.println(new String(authEncBytes));
return "Basic " + new String(authEncBytes);
}
In case anybody faces the same issue. Let me share the challenged I faced and how I rectified those.
The above code works for all content-types/methods. Can be used for any type (GET, POST, PUT,DELETE).
For my requirement I had a POST webservice with
Content-Encoding →gzip
Content-Type →application/vnd.oracle.adf.resourceitem+json
Challenges : I was able to get the correct response code but I was getting junk characters as my response string.
Solution : This was because the output was compressed in gzip format which needed to be uncompressed.
The code of uncompressing the gzip content encoding is also mentioned above.
Hope it helps future users.

POST params empty, what am I doing wrong? HttpURLConnection / Android / Java

The code below shows a method, downloadUrl(), that takes a String, "myurl," its parameter. There are only two possible urls that I ever send to it, and the behavior of the method is different for each.
when myurl = URL1, it uses a GET request and everything works fine.
when myurl = URL2, however, it uses a POST request, and the response from the php page indicates that the post parameters sent with the request were empty. You can see the line where I set the POST params, so I don't understand why it's sending no params?!
Thanks for any help!
-Adam.
private String downloadUrl(String myurl) throws IOException {
InputStream is = null;
String response = "";
try {
URL urlObject = new URL(myurl);
HttpURLConnection conn = (HttpURLConnection) urlObject.openConnection();
// find out if there's a way to incorporate these timeouts into the progress bar
// and what they mean for shitty network situations
conn.setReadTimeout(10000 /* milliseconds */);
conn.setConnectTimeout(15000 /* milliseconds */);
conn.setDoInput(true);
// INSERTED QUICK CHECK TO SEE WHICH URL WE ARE LOADING FROM
// it's important because one is GET, and one is POST
if (myurl.equals(url2)){
Log.i(TAG, "dlurl() in async recognizes we are doing pre-call");
conn.setRequestMethod("POST");
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
String postParams = "?phone=" + phone;
writer.write(postParams);
Log.i(TAG, "we're adding " + postParams + "to " + urlObject);
writer.flush();
writer.close();
os.close();
}
else {
conn.setRequestMethod("GET");
conn.connect();
}
// Starts the query
int responseCode = conn.getResponseCode();
Log.i(TAG, "from " + myurl + ", The response code from SERVER is: " + responseCode);
is = conn.getInputStream();
// Convert the InputStream into a string
// i guess we look up how to do this
if (responseCode == HttpsURLConnection.HTTP_OK) {
String line;
BufferedReader br = new BufferedReader(new InputStreamReader(is));
while ((line = br.readLine()) != null) {
response += line;
}
} else {
response = "from downloadUrl, php page response was not OK: " + responseCode;
}
// it's good to close these things?
is.close();
conn.disconnect();
Log.i(TAG, "response is " + response);
return response;
// Makes sure that the InputStream is closed after the app is
// finished using it.
} finally {
if (is != null) {
is.close();
}
}
}

try with following code block to send parameters of the POST request.
Map<String,String> params = new LinkedHashMap<>();
params.put("phone", "phone");
StringBuilder postPraamString = new StringBuilder();
for (Map.Entry<String,Object> param : params.entrySet()) {
if (postPraamString.length() != 0) postPraamString.append('&');
postPraamString.append(URLEncoder.encode(param.getKey(), "UTF-8"));
postPraamString.append('=');
postPraamString.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
}
byte[] postDataBytes = postData.toString().getBytes("UTF-8");
writer.write(postDataBytes);

So I figured out the root of the problem...
In the line:
String postParams = "?phone=" + phone;
The problem was that leading question mark. The question mark should only be used in GET requests.

Intercepting json in https(not http) with a python cgi script

I am sending json string in an https post request to an apache servert(request sends json data to a cgi-bin script that actually is a python script). Am using a standard cgi call -
f=open("./testfile", "w+")
f.write("usageData json = \n")
<b>form = cgi.FieldStorage()
formList = ['Data']
str = form['Data'].value
str = json.dumps(backupstr)
</b>
print backupstr
to read the json string in the url. Problem is that the script is not reading the json in the url even though the script is getting fired (the basic print statements are executing ...). This is how am sending data from the post side :
HttpsURLConnection connection = null;
try{
connection = (HttpsURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type",
"application/json");
connection.setRequestProperty("Content-Length", "" +
Integer.toString(jsonstring.getBytes().length));
connection.setRequestProperty("Content-Language", "en-US");
connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);
//Send request
DataOutputStream wr = new DataOutputStream (
connection.getOutputStream ());
//wr.writeBytes(jsonstring);
wr.writeUTF(URLEncoder.encode(jsonstring, "UTF-8"));
wr.flush ();
wr.close ();
//Get Response
InputStream is = connection.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
String line;
StringBuffer response = new StringBuffer();
while((line = rd.readLine()) != null) {
response.append(line);
}
rd.close();
//response = httpClient.execute(request);
}
catch (Exception e)
{
System.out.println("Exception " + e.getMessage());
throw e;
}
I suspect am missing one or more of the connection.setRequestProperty() settings on the sending end that's why it's firing the script but not reading the json string in the url ...what am I doing wrong ...?