i'm stuck on this process from two days, before posting i've searched a lot of topic and looks like it's a so simple issue. But i didn't get the problem.
Scenario is basic: i want to parse an XML from a remote computer through http connection:
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
try {
URL url = new URL("http://host:port/file.xml");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setRequestProperty("Accept","application/xml");
InputStream is = connection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
PrintWriter pw = new PrintWriter("localfile_pw.xml");
FileOutputStream fos = new FileOutputStream("localfile_os.xml");
Then i tried three different ways to read the XML
Reading byte stream
byte[] buffer = new byte[4 * 1024];
int byteRead;
while((byteRead= is.read(buffer)) != -1){
fos.write(buffer, 0, byteRead);
}
Reading charachter per character
char c;
while((c = (char)br.read()) != -1){
pw.print(c);
System.out.print(c);
}
Reading line per line
String line = null;
while((line = br.readLine()) != null){
pw.println(line);
System.out.println(line);
}
In all cases my xml reading stops at the same point, after the same exact nuumber of bytes. And gets stuck without reading and without giving any exception.
Thanks in advance.
How about this (see IOUtils from Apache):
URL url = new URL("http://host:port/file.xml");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setRequestProperty("Accept","application/xml");
InputStream is = connection.getInputStream();
FileOutputStream fos = new FileOutputStream("localfile_os.xml");
IOUtils.copy(is, fos);
is.close();
fos.close();
The class supports persistent HTTP connections by default. If the size of the response is know at the time of the response, after it sends your data, the server will wait for another request. There are 2 ways of handling this:
Read the content-length:
InputStream is = connection.getInputStream();
String contLen = connection.getHeaderField("Content-length");
int numBytes = Integer.parse(contLen);
Read numBytes bytes from the input stream. Note: contLen may be null, in this case you should read until EOF.
Disable connection keep alive:
connection.setRequestProperty("Connection","close");
InputStream is = connection.getInputStream();
After sending the last byte of data the server will close the connection.
Related
For my project i need to download a pdf file from google drive using java
I get my httpresponse code 200 and by using following method i store it in abc.pdf file
String url = "https://docs.google.com/uc?id="+fileid+"&export=download";
URL obj = new URL(url);
HttpURLConnection conn = (HttpURLConnection) obj.openConnection();
// optional default is GET
conn.setRequestMethod("GET");
//add request header
conn.setRequestProperty("User-Agent", USER_AGENT);
int responseCode = conn.getResponseCode();
System.out.println("\nSending 'GET' request to URL : " + url);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String inputLine;
OutputStream f0 = new FileOutputStream("C:\\Users\\Darshil\\Desktop\\abc.pdf",true);
while ((inputLine = in.readLine()) != null) {
//System.out.println(inputLine);
byte b[]=inputLine.getBytes();
//System.out.println(b);
f0.write(b);
}
in.close();
f0.close();
But when i try to open abc.pdf in my adobe reader x i get following error:
There was an error opening this document.The file is damaged and could not be repaired
You seem to be directly accessing the Google drive using Raw HTTP requests.
You may be better of using the Google Drive SDK. This link contains good examples to address the use cases you state in your question.
However if you do want to stick to your technique then you should not be using a BufferedReader.readLine(). This is because the PDF file is a binary finally that would depend upon the correct byte sequences to be preserved in order to be read correctly by the PDF reader software. Hopefully the below technique should help you:
//read in chunks of 2KB
byte[] buffer = new byte[2048];
int bytesRead = 0;
try(InputStream is = conn.getInputStream())
{
try(DataOutputStream os = new DataOutputStream(new FileOutputStream("file.pdf"))
{
while((bytesRead = is.read(buffer)) != -1)
{
os.write(buffer, 0, bytesRead);
}
}
}
catch(Exception ex)
{
//handle exception
}
Note that I am using the try-with-resources statement in Java 7
Hope this helps.
I am using HttpURLConnection to upload an image and get its response.
It works on emulator and my XiaoMi device.
However, it always get a SocketTimeoutException on my Sony device on the line connection.getInputStream().
I've tried to set timeouts to large value like 1 minute but not work.
public String uploadFile(File file, String requestURL) {
if (file != null) {
long fileSize = file.length();
HttpURLConnection.setFollowRedirects(false);
HttpURLConnection connection = null;
try {
//config of connection
connection = (HttpURLConnection) new URL(requestURL).openConnection();
connection.setConnectTimeout(10000);
connection.setReadTimeout(10000);
connection.setRequestMethod("PUT");
connection.setRequestProperty("Content-Type", "image/jpeg");
connection.setDoOutput(true);
connection.setRequestProperty("Content-length", "" + fileSize);
connection.connect();
//upload file
DataOutputStream out = new DataOutputStream(connection.getOutputStream());
int bytesRead;
byte buf[] = new byte[1024];
BufferedInputStream bufInput = new BufferedInputStream(new FileInputStream(file));
while ((bytesRead = bufInput.read(buf)) != -1) {
out.write(buf, 0, bytesRead);
out.flush();
}
out.flush();
out.close();
//get response message, but SocketTimeoutException occurs here
BufferedReader br = new BufferedReader(new InputStreamReader((connection.getInputStream())));
StringBuilder sb = new StringBuilder();
String output;
while ((output = br.readLine()) != null) {
sb.append(output);
}
//return response message
return output;
} catch (Exception e) {
// Exception
e.printStackTrace();
} finally {
if (connection != null) connection.disconnect();
}
}
return null;
}
What causes this problem happen?And how to fix it?
Additional Info:
I tested on devices under same wifi connection. And sure network and file server worked properly. The file size of tested images is about 100~200kbyte.
Because you set a read timeout of ten seconds and no response was received within ten seconds.
Is this a trick question?
NB You don't need to set the content-length header. Java will do that for you.
Just remove connection.setReadTimeout() statement because by default it will set readTiomeout value to 0 i.e it will wait for data until data is available.so,you might not get SocketTimeOut Exception.
I want to download a file from a URL and store it into the file system. However I have memory limitation and I don't want to store it in the memory before. I am not a java expert and I am a bit lost with all the class InputStream, BufferedReader, FileOutputStream, etc. Could you help me please ?
For now I have:
URLConnection ucon = url.openConnection();
ucon.connect();
InputStream is = ucon.getInputStream();
// Create a reader for the input stream.
BufferedReader br = new BufferedReader(isr);
// ?
FileOutputStream fos = context.openFileOutput(FILENAME, Context.MODE_PRIVATE);
// Here the content can be too big for the memory...
fos.write(content.getBytes());
fos.close();
Please, could you give me some clue ? I was thinking also to read it chunk by chunk, but I am not sure what would be the easiest with java...
you can use apache commons
org.apache.commons.io.FileUtils.copyURLToFile(URL, File)
I guess it may not work on android
I use this code
InputStream input = connection.getInputStream();
byte[] buffer = new byte[4096];
int cnt = - 1;
OutputStream output = new FileOutputStream(file);
while ( (cnt = input.read(buffer)) != -1)
{
output.write(buffer, 0, cnt);
}
output.close();
I'm writing a simple client-server system and the question is: how to structure my client code in order to get POST request-response working in a loop?
At the moment it looks something like this (and it's is NOT a loop right now):
open HttpURLConnection
set properties
setDoOutput(true)
writing to output stream
closing output stream
new DataInputStream
reading response
exiting method
I'm not sure which objects do I have to save for the next iterations and which ones I should close.
you need to save the connection object and you should make use of setDoInput(true) for reading data but if you just want to read responseCode and responseMessage you dont need InputStream. check the code below.
HttpURLConnection connection =(HttpURLConnection)new URL("url").openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-type", "text/xml"); // depend on you
connection.setRequestProperty("Accept", "text/xml, application/xml"); // depend on you
connection.setRequestMethod("POST");
OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
writer.write(yaml);
writer.close();
int statusCode = connection.getResponseCode();
String message = connection.getResponseMessage();
for InputStreamReader
connection.setDoInput(true);
InputStreamReader reader = new InputStreamReader(connection.getInputStream());
char[] cbuf = new char[100];
reader.read(cbuf);
// there are 3 read method you can choose as per your convenience
//and put a check for end of line in while loop for reading whole content.
reader.close();
After managing my own 'research' on this subject (thanks to Google and Nokia Developer forums) I've come to the final view of my code. It's a file upload loop:
path = Paths.get(requestString);
in = Files.newInputStream(path);
int i = 0;
while ((bytesRead = in.read(buf)) != -1) {
URL u = new URL(defaultURL);
huc =
(HttpURLConnection) u.openConnection();
huc.setRequestMethod("POST");
huc.setDoOutput(true);
huc.setDoInput(true);
os = huc.getOutputStream();
os.write(buf, 0, bytesRead);
os.flush();
os = null;
// thanks to dku.rajkumar for the following block of code !
InputStreamReader reader =
new InputStreamReader(huc.getInputStream());
char[] cbuf = new char[400];
reader.read(cbuf);
reader.close();
String s = new String(cbuf);
messagebuffer.append(s + "\n\n");
huc.disconnect();
Thread.sleep(16);
}
I want to send an image from a J2ME client to a Servlet.
I am able to get a byte array of the image and send it using HTTP POST.
conn = (HttpConnection) Connector.open(url, Connector.READ_WRITE, true);
conn.setRequestMethod(HttpConnection.POST);
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
os.write(bytes, 0, bytes.length); // bytes = byte array of image
This is the Servlet code:
String line;
BufferedReader r1 = new BufferedReader(new InputStreamReader(in));
while ((line = r1.readLine()) != null) {
System.out.println("line=" + line);
buf.append(line);
}
String s = buf.toString();
byte[] img_byte = s.getBytes();
But the problem I found is, when I send bytes from the J2ME client, some bytes are lost. Their values are 0A and 0D hex. Exactly, the Carriage Return and Line Feed.
Thus, either POST method or readLine() are not able to accept 0A and 0D values.
Any one have any idea how to do this, or how to use any another method?
That's because you're using a BufferedReader to read the binary stream line by line. The readLine() basically splits the content on CRLF. Those individual lines doesn't contain the CRLF anymore.
Don't use the BufferedReader for binary streams, it doesn't make sense. Just write the obtained InputStream to an OutputStream of any flavor, e.g. FileOutputStream, the usual Java IO way.
InputStream input = null;
OutputStream output = null;
try {
input = request.getInputStream();
output = new FileOutputStream("/path/to/file.ext");
byte[] buffer = new byte[10240];
for (int length = 0; (length = input.read(buffer()) > 0;) {
output.write(buffer, 0, length);
}
} finally {
if (output != null) output.close();
if (input != null) input.close();
}
That said, the Content-Type you're using is technically wrong. You aren't sending a WWW-form URL-encoded value in the request body. You are sending a binary stream. It should be application/octet-stream or maybe image. This is not the cause of this problem, but it is just plain wrong.