I'm a client side developer, moving over to server side development.
One common problem I am encountering is the need to make one API call (say to get an authentication token) and then make a follow up API call to get the data I want. Sometimes, I need to make two API calls in succession for data, without an auth token as well.
Is there a common design pattern or Java library to address this issue? Or do I need to manually create the string of calls each time I need to do so?
Edit: I'm hoping for something that looks like this
CustomClassBasedOnJson myStuff = callAPI("url", getResponse("authURL"));
This would make a call to the "url" with data received from the "authURL".
The point here is that I'm stringing multiple url calls, using the result of one call to define the next one.
When doing Server side programming, it is acceptable for HTTP calls to be called synchronously.
Therefore the proper pattern is to simply make the first call, receive the result, and then use that in the next line. There is no need to separate the calls into separate threads, or asynchronous calls, unless there is major processing happening between http calls.
For example:
JsonResponseEntry getJsonReportResponse() throws IOException {
String sReportURL = "https://someurl.com/v2/report/report?" +
"startts=" + getDateYesterday("ts") +
"&endts=" + getDateNow("ts") +
"&auth=" + getAuthCode();
URL reportURL = new URL(sReportURL);
URLConnection conn = reportURL.openConnection();
BufferedReader buf = new BufferedReader(new InputStreamReader(conn.getInputStream()));
ObjectMapper mapper = new ObjectMapper();
JsonNode reportResult = mapper.readTree(buf);
return convertJSonNodeToJsonResponseEntry(reportResult);
}
String getAuthCode() throws IOException {
String sReportURL = "https://someurl.com/auth";
URL reportURL = new URL(sReportURL);
HttpURLConnection conn = (HttpURLConnection) reportURL.openConnection();
conn.setRequestMethod("POST");
conn.setDoOutput(true);
conn.setDoInput(true);
conn.connect();
String urlParameters = "username=myUserName&password=mypassword";
DataOutputStream wr = new DataOutputStream(conn.getOutputStream());
wr.writeBytes(urlParameters);
wr.flush();
wr.close();
BufferedReader buf = new BufferedReader(new InputStreamReader(conn.getInputStream()));
ObjectMapper mapper = new ObjectMapper();
AuthResponse response = mapper.readValue(buf, AuthResponse.class);
return response.toString();
}
The function getAuthCode() is synchronously called within the URL call that requires the response.
Related
I just want to start Nifi processor through REST API java code, i am able to invoke HTTP connection and able to see play button on processors but flow is not happening? and i have multiple processes group in which my first processor is GETSplunk Template which is in cron driven ,manual start is good and fine and when i start through API flow is not working, and changed to Timer schedule it is showing error for SQL template ,can any one bumped with this issue, please suggest me.
sample API code is.
String url = "http://hostname:8080/nifi-api/flow/process-groups/{id};
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
// Setting basic put request
con.setDoOutput(true);
con.setRequestMethod("PUT");
con.setRequestProperty("Content-Type","application/json");
String putJsonData = "{\r\n" +
"\"component\":{\r\n" +
"\"id\":\"<processor-group id>\",\r\n " +"\"state\":\"RUNNING\"\r\n" + "}";
OutputStreamWriter wr = new OutputStreamWriter(con.getOutputStream());
wr.write(putJsonData);
wr.flush();
wr.close();
int responseCode = con.getResponseCode();
System.out.println("nSending 'POST' request to URL : " + url);
System.out.println("Post Data : " + putJsonData);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader( new
InputStreamReader(con.getInputStream())); String output; StringBuffer
response = new StringBuffer();
while ((output = in.readLine()) != null) { response.append(output); }
in.close();
//printing result from response
System.out.println(response.toString());
}
#Sravya99 When I need to trigger flow from outside of Nifi, I often create a NiFi API interface listening on a port via HandleHttpRequest and HandleHttpResponse. This can be very simple request, or very complicated with ssl, access and authorization, etc. It should serve fine for your purpose, leaving your flow always on, and initiating the triggered responses using the HandleHttpRequest.
NOTICE UPDATE!!
The problem got solved and i added my own answer in the thread
In short, I have attempted to add the parameter "scan_id" value but since it is a POST i can't add the value directly in the url path.
using the code i already have, how would i go about modifying or adding so that the url is correct, that is, so that it accepts my POST?.
somehow i have been unable to find any examples that have helped me in figuring out how i would go about doing this..
I know how to do a POST with a payload, a GET with params. but a post with Params is very confusing to me.
Appreciate any help. (i'd like to continue using HttpUrlConnection unless an other example is provided that also tells me how to send the request and not only configuring the path.
I've tried adding it to the payload.
I've tried UriBuilder but found it confusing and in contrast with the rest of my code, so wanted to ask for help with HttpUrlConnection.
URL url = new URL("http://localhost/scans/{scan_id}/launch");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("tmp_value_dont_mind_this", "432432");
con.setRequestProperty("X-Cookie", "token=" + "43432");
con.setRequestProperty("X-ApiKeys", "accessKey="+"43234;" + " secretKey="+"43234;");
con.setDoInput(true);
con.setDoOutput(true); //NOT NEEDED FOR GETS
con.setRequestMethod("POST");
con.setRequestProperty("Accept", "application/json");
con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
//First example of writing (works when writing a payload)
OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");
writer.write(payload);
writer.close();
//second attemp at writing, doens't work (wanted to replace {scan_id} in the url)
DataOutputStream writer = new DataOutputStream(con.getOutputStream());
writer.writeChars("scan_id=42324"); //tried writing directly
//writer.write(payload);
writer.close();
Exception:
Exception in thread "main" java.io.IOException: Server returned HTTP response code: 400 for URL: http://localhost/scans/launch
I'd like one of the three response codes because then i know the Url is correct:
200 Returned if the scan was successfully launched.
403 Returned if the scan is disabled.
404 Returned if the scan does not exist.
I've tried several urls
localhost/scans/launch,
localhost/scans//launch,
localhost/scans/?/launch,
localhost/scans/{scan_id}/launch,
So with the help of a friend and everyone here i solved my problem.
The below code is all the code in an entire class explained bit by bit. at the bottom you have the full class with all its syntax etc, that takes parameters and returns a string.
in a HTTP request there are certain sections.
Such sections include in my case, Request headers, parameters in the Url and a Payload.
depending on the API certain variables required by the API need to go into their respective category.
My ORIGINAL URL looked like this: "http://host:port/scans/{scan_id}/export?{history_id}"
I CHANGED to: "https://host:port/scans/" + scan_Id + "/export?history_id=" + ID;
and the API i am calling required an argument in the payload called "format" with a value.
String payload = "{\"format\" : \"csv\"}";
So with my new URL i opened a connection and set the request headers i needed to set.
HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
The setDoOutput should be commented out when making a GET request.
con.setDoInput(true);
con.setDoOutput(true);
con.setRequestMethod("POST");
con.setRequestProperty("Accept", "application/json");
con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
con.setRequestProperty("X-Cookie", "token=" + token);
con.setRequestProperty("X-ApiKeys", "accessKey="+"23243;" +"secretKey="+"45543;");
Here i write to the payload.
//WRITING THE PAYLOAD to the http call
OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");
writer.write(payload);
writer.close();
After i've written the payload i read whatever response i get back (this depends on the call, when i do a file download (GET Request) i don't have a response to read as i've already read the response through another piece of code).
I hope this helps anyone who might encounter this thread.
public String requestScan(int scan_Id, String token, String ID) throws MalformedInputException, ProtocolException, IOException {
try {
String endpoint = "https://host:port/scans/" + scan_Id + "/export?history_id=" ID;
URL url = new URL(endpoint);
String payload= "{\"format\" : \"csv\"}";
HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
con.setDoInput(true);
con.setDoOutput(true);
con.setRequestMethod("POST");
con.setRequestProperty("Accept", "application/json");
con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
con.setRequestProperty("X-Cookie", "token=" + token);
con.setRequestProperty("X-ApiKeys", "accessKey="+"324324;" +
"secretKey="+"43242;");
//WRITING THE PAYLOAD to the http call
OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream(), "UTF-8");
writer.write(payload);
writer.close();
//READING RESPONSE
BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream()));
StringBuffer jsonString = new StringBuffer();
String line;
while ((line = br.readLine()) != null) {
jsonString.append(line);
}
br.close();
con.disconnect();
return jsonString.toString();
} catch (Exception e) {
throw new RuntimeException(e.getMessage());
}
}
As discussed here the solution would be to change the content type to application/x-www-form-urlencoded, but since you are already using application/json; charset=UTF-8 (which I am assuming is a requirement of your project) you have no choise to redesign the whole thing. I suggest you one of the following:
Add another GET service;
Add another POST service with content type application/x-www-form-urlencoded;
Replace this service with one of the above.
Do not specify the content type at all so the client will accept anything. (Don't know if possible in java)
If there are another solutions I'm not aware of, I don't know how much they would be compliant to HTTP protocol.
(More info)
Hope I helped!
Why you are not using like this. Since you need to do a POST with HttpURLConnection, you need to write the parameters to the connection after you have opened the connection.
String urlParameters = "scan_id=42324";
byte[] postData = urlParameters.getBytes(StandardCharsets.UTF_8);
DataOutputStream dataOutputStream = new DataOutputStream(conn.getOutputStream());
dataOutputStream.write(postData);
Or if you have launch in the end, just change the above code to the following,
String urlParameters = "42324/launch";
byte[] postData = urlParameters.getBytes(StandardCharsets.UTF_8);
DataOutputStream dataOutputStream = new DataOutputStream(conn.getOutputStream());
dataOutputStream.write(postData);
URL url = new URL("http://localhost/scans/{scan_id}/launch");
That line looks odd to me; it seems you are trying to use a URL where you are intending the behavior of a URI Template.
The exact syntax will depend on which template implementation you choose; an implementation using the Spring libraries might look like:
import org.springframework.web.util.UriTemplate;
import java.net.url;
// Warning - UNTESTED code ahead
UriTemplate template = new UriTemplate("http://localhost/scans/{scan_id}/launch");
Map<String,String> uriVariables = Collections.singletonMap("scan_id", "42324");
URI uri = template.expand(uriVariables);
URL url = uri.toURL();
I'm programming android app as my final project. It's connecting to a java web-service on cloud.
My problem is that I want to use complex java objects and share them between my android app and my web service on cloud.
As example I have "Mission" class and i want use methods that get "Mission" type argument as parameter, or returns "Mission" type. I want to use those complex objects just as String, Integer or Boolean.
May I create a library or jar file or something that hold those classes on the client side and the server side?
What should I do to use those classes and complex java objects between the server-side and the client-side just as we use String or other regular java types?
The best method is using JSON. That it can not transfer all the data.
URL url = new URL("Your Web Service URL");
// Send POST data request
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.write( data );
wr.flush();
// Get the server response
reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
// Read Server Response
while((line = reader.readLine()) != null)
{
// Append server response in string
sb.append(line + "");
}
// Append Server Response To Content String
Content = sb.toString();
sample :
http://androidexample.com/Restful_Webservice_Call_And_Get_And_Parse_JSON_Data-_Android_Example/index.php?view=article_discription&aid=101&aaid=123
I'm trying to post a JSON to a web service so that I can get a JSON in response as return, I have searched in Google but most of the response I found is for Android but not for core Java, this question is for a Swing application I'll give the code the code I used below.
Connection class
public class Connection extends Thread {
private String url1;
private JSONObject data;
String line;
//Constuctor to initialize the variables.
public Connection(String url1, JSONObject data) {
this.url1 = url1;
this.data = data;
start();
}
public void run() {
ConnectionReaderWriter();
}
//To fetch the data from the input stream
public String getResult() {
return line;
}
public String ConnectionReaderWriter() {
URL url;
HttpURLConnection connection = null;
ObjectOutputStream out;
try {
/*URL url = new URL(Url.server_url + url1); //Creating the URL.
URLConnection conn = url.openConnection(); //Opening the connection.
conn.setDoOutput(true);
OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
wr.write(data); //Posting the data to the ouput stream.
wr.flush();
BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
line=rd.readLine(); //Reading the data from the input stream.
wr.close();
rd.close();*/
url = new URL(Url.server_url + url1); //Creating the URL.
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/json");
connection.setRequestProperty("Accept", "application/json");
connection.setRequestProperty("api_key", "123456");
connection.setUseCaches(false);
connection.setDoInput(true);
connection.setDoOutput(true);
//Send request
out = new ObjectOutputStream(connection.getOutputStream());
out.writeObject(data);
out.flush();
out.close();
} catch (MalformedURLException ex) {
Logger.getLogger(Connection.class.getName()).log(Level.SEVERE, null, ex);
String nonet = "No Network Connection";
line = nonet;
} catch (IOException ex) {
Logger.getLogger(Connection.class.getName()).log(Level.SEVERE, null, ex);
String nonet = "No Server Connection";
line = nonet;
}
return line; //Return te stream recived from the input stream.
}
}
The commented code is the one I used before when I was passing as text encoded to the URL. The function call is given below
JSONObject json = new JSONObject();
json.put("username", username);
json.put("password", passwordenc);
Connection conn = new Connection(Url.login, json);
conn.join();
On execution I get the exception shown below
Jan 20, 2014 1:18:32 PM SupportingClass.Connection ConnectionReaderWriter
SEVERE: null
java.io.NotSerializableException: org.json.JSONObject
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at SupportingClass.Connection.ConnectionReaderWriter(Connection.java:74)
at SupportingClass.Connection.run(Connection.java:40)
Please tell me the problem in this code or an alternative to this method.
I'll give the answer:
replace out.writeObject(data); with out.write(data.toString().getBytes());
You were trying to write the JSONObject object, and the writeObject() method will attempt to serialize the object, but it will fail since the JSONObject class does not implement Serializable.
JSon is text, so you cannot use an ObjectOutputStream. The POST method uses the first line of the content as the arguments, so you would need a blank line before the actual content:
OutputStream stream = connection.getOutputStream();
stream.write('\r');
stream.write('\n');
out = new OutputStreamWriter(stream, "UTF-8");
out.write(data.toString());
out.flush();
out.close();
EDIT: actually we need CR LF, so println() may not work.
If you find it awkward to use HttpURLConnection natively, you might use an abstraction library. There are many powerful out there. One of them is DavidWebb. You can find a long list of alternatives at the end of that page.
With this library your code would be shorter and more readable:
JSONObject nameAndPassword = new JSONObject();
// set name and password
Webb webb = Webb.create();
JSONObject result = webb.post("your_serverUrl")
.header("api_key", "123456")
.useCaches(false)
.body(nameAndPassword)
.ensureSuccess()
.asJsonObject()
.getBody();
The code shows only the part that would run in your run() method of the Thread. It is not necessary to set the Content-Type header, because this is done automatically by detecting the type of object you set as the body. The same is true for the Accept header.
I assumed that you receive a JSON Object from your REST service, since you set the "Accept" header to "application/json". For receiving a plain String one could write String result = ... .asString().getBody().
BTW the library has been developed with Android in mind, but it can be used with Swing or server-side as well. Maybe you choose another library (e.g. Jersey Client), because you have no restriction about the size. DavidWebb weighs about 20 kilobytes while most other libraries add several hundred kilobytes to your deployment artifacts.
Another thing: you use JSONObject. For small web services, this is not a problem, but if you have to marshal many and/or big objects, you could think about using JAXB + Jackson or Gson. Less code, less errors, more fun!
I am trying to authenticate to a server's secure URL using java.net.urlconnection - based on the useful tutorial at Using java.net.URLConnection to fire and handle HTTP requests
The response will be as given below--
Return: A session id object: {'session_id': 'username:session_token'}
This session_id will be used for all methods which require authentication.
This response is JSON response, and I am thinking of using the Google GSON library (since my web app is on Google App Engine).
The code I have used so far (based on the tutorial to which I have given link above) is given below--
String url = "https://api.wordstream.com/authentication/login";
String charset = "UTF-8";
String param1 = WORDSTREAM_API_USERNAME;
String param2 = WORDSTREAM_API_PASSWORD;
// ...
String query = String.format("username=%s&password=%s",
URLEncoder.encode(param1, charset),
URLEncoder.encode(param2, charset));
URLConnection connection = new URL(url + "?" + query).openConnection();
connection.setRequestProperty("Accept-Charset", charset);
InputStream response = connection.getInputStream();
InputStream error = ((HttpURLConnection) connection).getErrorStream();
//now checking HTTP Response status
int status = ((HttpURLConnection) connection).getResponseCode();
How do I proceed further to obtain the JSON response and retrieve session ID from that response correctly?
Another question- I want to store the session ID in session data that can be accessed by javascript functions, because I plan to use javascript functions to make calls and obtain further data. Is this possible, and how to implement this?
Step 1- Create a subclass- declare it as static so that it can be utilised by the GSON library. This subclass should mimic the data contained in a single JSON Response- in our case only the session ID is stored in the response- hence this class contains just one string variable...
static class LR {
public String response;
public LR() {
// No args constructor for LR
}
}
Now, use BUfferedReader and readline to read the entire response and store it in a string variable.
InputStream response = connection.getInputStream();
BufferedReader br = new BufferedReader(new
InputStreamReader(response));
String str="", temp;
while (null != ((temp = br.readLine())))
{
System.out.println (str);
str=str + temp;
}
Finally, invoke 'fromJSON(string, class)' to obtain the value-
Gson gson = new Gson();
LR obj2 = gson.fromJson(str, LR.class);
return(" Session ID="+ obj2.response);