i'm trying to look for an example on how to retry whenever we get a exception out of dynamoDBMapper.transactionWrite. Thanks in Advance.
TransactionWriteRequest transactionWriteRequest = new TransactionWriteRequest();
transactionWriteRequest.withIdempotencyToken(generateNewToken());
transactionWriteRequest.addUpdate(idMapping);
executeTransactionWrite(transactionWriteRequest);
return idMapping;
}
public void executeTransactionWrite(TransactionWriteRequest transactionWriteRequest) {
try {
dynamoDBMapper.transactionWrite(transactionWriteRequest);
} catch (DynamoDBMappingException ddbme) {
System.err.println("Client side error in Mapper, fix before retrying. Error: " + ddbme.getMessage());
} catch (ResourceNotFoundException rnfe) {
System.err.println("One of the tables was not found, verify table exists before retrying. Error: " + rnfe.getMessage());
} catch (InternalServerErrorException ise) {
System.err.println("Internal Server Error, generally safe to retry with back-off. Error: " + ise.getMessage());
} catch (TransactionCanceledException tce) {
System.err.println("Transaction Canceled, implies a client issue, fix before retrying. Error: " + tce.getMessage());
} catch (Exception ex) {
System.err.println("An exception occurred, investigate and configure retry strategy. Error: " + ex.getMessage());
}
}
I am doing an app in which i am calling a web api. I am getting task cancel exception when i call the api in iPad/iPhone.But the response is fine in simulator and android devices.Can anyone please help me in resolving the issue.I am not able to fine where it is going wrong.
Thanks in advance.
Try using Native Http Handler to see it improves.
Declare an interface.
public interface IHttpHandler
{
HttpClient ReturnHandler();
}
Implement it this way.
public class HttpHandler : IHttpHandler
{
public HttpClient ReturnHandler()
{
try
{
var client = new HttpClient(new NSUrlSessionHandler()
{
});
client.Timeout = TimeSpan.FromSeconds(120);
return client;
}
catch (TaskCanceledException ex)
{
Console.WriteLine("TaskCanceledException ReturnHandler-->" + ex.Message);
if (ex.InnerException != null)
{
Console.WriteLine("TaskCanceledException ReturnHandler-->" + ex.InnerException.Message);
}
return null;
}
catch (Exception ex)
{
Console.WriteLine("ReturnHandler Exception-->" + ex.Message);
if (ex.InnerException != null)
{
Console.WriteLine("ReturnHandler Exception-->" + ex.InnerException.Message);
}
return null;
}
}
}
Use Xamarin forms inbuilt Dependency injection to utilise the interface I gave you to have HTTPClient with native handler.
If you don't know how to read Here
REQUEST :
URL: http://localhost:8080/RESTfulExample/rest/file/upload
METHOD : POST
HEADER: Content-Type : multipart/form-data
RESPONSE :
HTTP Status 400 - Bad Request
The same code is working with html forms but in postman it's throwing 400 BAD REQUEST, I looked up on google for solution and found that boundary is missing, How to resolve it ? As I have to recieve files from multiple clients like mobile application and web clients via Jquery and rest client.
#Path("/file")
public class UploadFileService {
#POST
#Path("/upload")
#Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadFile(#FormDataParam("file") InputStream uploadedInputStream,
#FormDataParam("file") FormDataContentDisposition fileDetail) {
try {
String uploadedFileLocation = "/home/nash/" + fileDetail.getFileName();
// save it
writeToFile(uploadedInputStream, uploadedFileLocation);
String output = "File uploaded to : " + uploadedFileLocation;
System.out.println("File uploaded..........");
return Response.status(200).entity(output).build();
} catch (Exception e) {
e.printStackTrace();
System.out.println("Exception " + e);
return null;
}
}
// save uploaded file to new location
private void writeToFile(InputStream uploadedInputStream, String uploadedFileLocation) {
try {
OutputStream out = new FileOutputStream(new File(uploadedFileLocation));
int read = 0;
byte[] bytes = new byte[1024];
out = new FileOutputStream(new File(uploadedFileLocation));
while ((read = uploadedInputStream.read(bytes)) != -1) {
out.write(bytes, 0, read);
}
out.flush();
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Please follow these steps:
Add jersey-multipart dependency.
In Your Application Class (or in web.xml) enable MultipartFeature.class.
DO NOT Add Content-Type header in your postman request.
For me the above steps worked. Do let me know if that helped you or not.
I am calling a web service from BlackBerry using J2ME code. When I try to open a connection using HttpConnection, it is checking only the GPRS connection. Now, I want to check the Wi-Fi connection and call a webservice through Wi-Fi.
The following code is my connection section. How to change the code for a Wi-Fi connection?
public boolean HttpUrl()
{
HttpConnection conn = null;
OutputStream out = null;
String url = "http://www.google.com";
try
{
conn = (HttpConnection) new ConnectionFactory().getConnection(url).getConnection();
if (conn != null)
{
conn.setRequestMethod(HttpConnection.POST);
conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("User-Agent", "Profile/MIDP-2.0 Configuration/CLDC-1.0");
}
}
catch (Exception e)
{
return false;
}
finally
{
try
{
out.close();
}
catch (Exception e2)
{
}
}
//Only if exception occurs, we close the connection.
//Otherwise the caller should close the connection himself.
try
{
conn.close();
}
catch (Exception e1)
{
}
return true;
}
Check this way:
HttpConnection conn = null;
String URL = "http://www.myServer.com/myContent;deviceside=true;interface=wifi";
conn = (HttpConnection)Connector.open(URL);
source
Making Connections
Rafael's answer will certainly work if you know you'll only be using Wi-Fi.
However, if you only need to support BlackBerry OS 5.0 - 7.1, I would recommend that you do use the ConnectionFactory. Normally, you will not limit your code to only using one transport. You'll normally support (almost) any transport the device has, but you may want to code your app to choose certain transports first.
For example,
class ConnectionThread extends Thread
{
public void run()
{
ConnectionFactory connFact = new ConnectionFactory();
connFact.setPreferredTransportTypes(new int[] {
TransportInfo.TRANSPORT_TCP_WIFI,
TransportInfo.TRANSPORT_BIS_B,
TransportInfo.TRANSPORT_MDS,
TransportInfo.TRANSPORT_TCP_CELLULAR
});
ConnectionDescriptor connDesc;
connDesc = connFact.getConnection("http://www.google.com");
if (connDesc != null)
{
HttpConnection httpConn;
httpConn = (HttpConnection)connDesc.getConnection();
try
{
// TODO: set httpConn request method and properties here!
final int iResponseCode = httpConn.getResponseCode();
UiApplication.getUiApplication().invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("Response code: " +
Integer.toString(iResponseCode));
}
});
}
catch (IOException e)
{
System.err.println("Caught IOException: "
+ e.getMessage());
}
}
}
}
will choose the Wi-Fi transport if Wi-Fi is available, but use the GPRS connection if it isn't. I think this is generally considered best practice for the 5.0+ devices.
Request Properties
This code
conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");
is not right. Content-Length should be the size, in bytes, of your HTTP POST parameters. See an example here.
Threading
Remember that making network connections is slow. Do not block the user interface by running this code on the main/UI thread. Put your code into a background thread to keep the UI responsive while you request remote content.
Any ideas why on some links that I try to access using HttpWebRequest I am getting "The remote server returned an error: (304) Not Modified." in the code?
The code I'm using is from Jeff's post here (the page seems to have disappeared, see an archive copy at the Wayback Machine).
Note the concept of the code is a simple proxy server, so I'm pointing my browser at this locally running piece of code, which gets my browsers request, and then proxies it on by creating a new HttpWebRequest, as you'll see in the code. It works great for most sites/links, but for some this error comes up. You will see one key bit in the code is where it seems to copy the http header settings from the browser request to it's request out to the site, and it copies in the header attributes. Not sure if the issue is something to do with how it mimics this aspect of the request and then what happens as the result comes back?
case "If-Modified-Since":
request.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]);
break;
I get the issue for example from http://en.wikipedia.org/wiki/Main_Page
PS. UPDATE HERE
Still can't work this out. Basically I can identify 1 link which has an issue, and it seems to work fine, 2nd time it gets the error, 3rd time OK, 4th time gets the error, 5th time OK etc. As if there is some state not getting cleared or something in the code. I've tried to clean up the code a bit using "using" type statements etc.
Here's the code. If anyone can spot why every 2nd time I browse to a link like http://newsimg.bbc.co.uk/css/screen/1_0_16/nol/v4/story.css (starting at the 2nd time, not the first) via this proxy code I get the error I'd love to hear.
class Program
{
static void Main(string[] args)
{
Proxy p = new Proxy(8080);
Thread proxythread = new Thread(new ThreadStart(p.Start));
proxythread.Start();
Console.WriteLine("Proxy Started. Press Any Key To Stop...");
Console.ReadKey();
p.Stop();
}
}
public class Proxy
{
private HttpListener _listener;
private int _port;
public Proxy(int port)
{
int defaultport = 8080;
// Setup Thread Pool
System.Threading.ThreadPool.SetMaxThreads(50, 1000);
System.Threading.ThreadPool.SetMinThreads(50, 50);
// Sanitize Port Number
if (port < 1024 || port > 65535)
port = defaultport;
// Create HttpListener Prefix
string prefix = string.Format("http://*:{0}/", port);
_port = port;
// Create HttpListener
_listener = new HttpListener();
_listener.Prefixes.Add(prefix);
}
public void Start()
{
_listener.Start();
while (true)
{
HttpListenerContext request = null;
try
{
request = _listener.GetContext();
// Statistics (by Greg)
int availThreads = -1;
int compPortThreads = -1;
ThreadPool.GetAvailableThreads(out availThreads, out compPortThreads);
log("INFO", request.Request.Url.ToString(), "START - [" + availThreads + "]");
ThreadPool.QueueUserWorkItem(ProcessRequest, request);
}
catch (HttpListenerException ex)
{
log("ERROR", "NA", "INFO: HttpListenerException - " + ex.Message);
break;
}
catch (InvalidOperationException ex)
{
log("ERROR", "NA", "INFO: InvalidOperationException - " + ex.Message);
break;
}
}
}
public void Stop()
{
_listener.Stop();
}
private void log(string sev, string uri, string message)
{
Console.Out.WriteLine(Process.GetCurrentProcess().Id + " - " + sev + " (" + uri + "): " + message);
}
private void ProcessRequest(object _listenerContext)
{
#region local variables
HttpWebRequest psRequest; // Request to send to remote web server
HttpWebResponse psResponse; // Response from remote web server
List<byte> requestBody = new List<byte>(); // Byte array to hold the request's body
List<byte> responseBody = new List<byte>(); // Byte array to hold the response's body
byte[] buffer;
string uri = "";
#endregion
var listenerContext = (HttpListenerContext)_listenerContext;
uri = listenerContext.Request.Url.ToString().Replace(string.Format(":{0}", _port), "");
// Create Interent Request
HttpWebRequest internetRequest = (HttpWebRequest)WebRequest.Create(uri);
#region Build Request Up
internetRequest.Method = listenerContext.Request.HttpMethod;
internetRequest.ProtocolVersion = listenerContext.Request.ProtocolVersion;
internetRequest.UserAgent = listenerContext.Request.UserAgent;
foreach (string key in listenerContext.Request.Headers.AllKeys)
{
try
{
switch (key)
{
case "Proxy-Connection":
case "Connection":
internetRequest.KeepAlive = (listenerContext.Request.Headers[key].ToLower() == "keep-alive") ? true : false;
break;
case "Content-Length":
internetRequest.ContentLength = listenerContext.Request.ContentLength64;
break;
case "Content-Type":
internetRequest.ContentType = listenerContext.Request.ContentType;
break;
case "Accept":
internetRequest.Accept = listenerContext.Request.Headers[key];
break;
case "Host":
break;
case "Referer":
internetRequest.Referer = listenerContext.Request.Headers[key];
break;
case "If-Modified-Since":
internetRequest.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]);
break;
default:
internetRequest.Headers.Add(key, listenerContext.Request.Headers[key]);
break;
}
}
catch (Exception ex)
{
Console.WriteLine("Error settup up psRequest object. Error = " + ex.Message + "\n" + ex.StackTrace);
}
}
#endregion
#region Copy content into request
buffer = new byte[1024];
using (Stream instream = listenerContext.Request.InputStream)
{
int incount = instream.Read(buffer, 0, buffer.Length);
while (incount > 0)
{
internetRequest.GetRequestStream().Write(buffer, 0, incount);
incount = instream.Read(buffer, 0, buffer.Length);
}
}
#endregion
// Get Internet Response
HttpWebResponse internetResponse = null;
try
{
using (internetResponse = (HttpWebResponse)internetRequest.GetResponse())
{
#region Configure Local Response Header Keys
foreach (string key in internetResponse.Headers.Keys)
{
try
{
switch (key)
{
case "Transfer-Encoding":
listenerContext.Response.SendChunked = (internetResponse.Headers[key].ToLower() == "chunked") ? true : false;
break;
case "Content-Length":
listenerContext.Response.ContentLength64 = internetResponse.ContentLength;
break;
case "Content-Type":
listenerContext.Response.ContentType = internetResponse.Headers[key];
break;
case "Keep-Alive":
listenerContext.Response.KeepAlive = true;
break;
default:
listenerContext.Response.Headers.Add(key, internetResponse.Headers[key]);
break;
}
}
catch (Exception ex)
{
log("ERROR", uri, "Error settup up listenerContext.Response objects. Error = " + ex.Message + "\n" + ex.StackTrace);
}
}
#endregion
try
{
// Transfer the body data from Internet Response to Internal Response
buffer = new byte[1024];
using (Stream inputStream = internetResponse.GetResponseStream())
{
int outcount = inputStream.Read(buffer, 0, buffer.Length);
while (outcount > 0)
{
listenerContext.Response.OutputStream.Write(buffer, 0, outcount);
outcount = inputStream.Read(buffer, 0, buffer.Length);
}
}
}
catch (Exception ex)
{
log("ERROR", uri, "Could not obtain response from URI: " + ex.Message);
}
finally
{
listenerContext.Response.OutputStream.Close();
}
}
}
catch (Exception ex)
{
//if (ex is InvalidOperationException ||
// ex is ProtocolViolationException ||
// ex is WebException)
//{
// log(uri, "Could not successfully get response: " + ex.GetType() + " - " + ex.Message);
// listenerContext.Response.Close();
// return;
//}
//else { throw; }
log("ERROR", uri, "Could not successfully get response: " + ex.GetType() + " - " + ex.Message);
listenerContext.Response.Close();
}
}
}
And here is an example of what I see - first hit is good, 2nd has error...
Proxy Started. Press Any Key To Stop...
2080 - INFO (http://newsimg.bbc.co.uk:8080/css/screen/1_0_16/nol/v4/story.css): START - [50]
2080 - INFO (http://newsimg.bbc.co.uk:8080/css/screen/1_0_16/nol/v4/story.css): START - [50]
2080 - ERROR (http://newsimg.bbc.co.uk/css/screen/1_0_16/nol/v4/story.css): Could not successfully get response: System.Net.WebException - The remote server returned an error: (304) Not Modified.
First, this is not an error. The 3xx denotes a redirection. The real errors are 4xx (client error) and 5xx (server error).
If a client gets a 304 Not Modified, then it's the client's responsibility to display the resouce in question from its own cache. In general, the proxy shouldn't worry about this. It's just the messenger.
This is intended behavior.
When you make an HTTP request, the server normally returns code 200 OK. If you set If-Modified-Since, the server may return 304 Not modified (and the response will not have the content). This is supposed to be your cue that the page has not been modified.
The authors of the class have foolishly decided that 304 should be treated as an error and throw an exception. Now you have to clean up after them by catching the exception every time you try to use If-Modified-Since.
Just pressing F5 is not always working.
why?
Because your ISP is also caching web data for you.
Solution: Force Refresh.
Force refresh your browser by pressing CTRL + F5 in Firefox or Chrome to clear ISP cache too, instead of just pressing F5
You then can see 200 response instead of 304 in the browser F12 developer tools network tab.
Another trick is to add question mark ? at the end of the URL string of the requested page:
http://localhost:52199/Customers/Create?
The question mark will ensure that the browser refresh the request without caching any previous requests.
Additionally in Visual Studio you can set the default browser to Chrome in Incognito mode to avoid cache issues while developing, by adding Chrome in Incognito mode as default browser, see the steps (self illustrated):
It is not an issue it is because of caching...
To overcome this add a timestamp to your endpoint call, e.g. axios.get('/api/products').
After timestamp it should be axios.get(/api/products?${Date.now()}.
It will resolve your 304 status code.
I think you have not installed these features. see below in picture.
I also suffered from this problem some days ago. After installing this feature then I solved it. If you have not installed this feature then installed it.
Install Process:
go to android studio
Tools
Android
SDK Manager
Appearance & Behavior
Android SDK