Android APIs
public abstract class

HttpURLConnection

extends URLConnection
java.lang.Object
   ↳ java.net.URLConnection
     ↳ java.net.HttpURLConnection
Known Direct Subclasses

Class Overview

An URLConnection for HTTP (RFC 2616) used to send and receive data over the web. Data may be of any type and length. This class may be used to send and receive streaming data whose length is not known in advance.

Uses of this class follow a pattern:

  1. Obtain a new HttpURLConnection by calling URL.openConnection() and casting the result to HttpURLConnection.
  2. Prepare the request. The primary property of a request is its URI. Request headers may also include metadata such as credentials, preferred content types, and session cookies.
  3. Optionally upload a request body. Instances must be configured with setDoOutput(true) if they include a request body. Transmit data by writing to the stream returned by getOutputStream().
  4. Read the response. Response headers typically include metadata such as the response body's content type and length, modified dates and session cookies. The response body may be read from the stream returned by getInputStream(). If the response has no body, that method returns an empty stream.
  5. Disconnect. Once the response body has been read, the HttpURLConnection should be closed by calling disconnect(). Disconnecting releases the resources held by a connection so they may be closed or reused.

For example, to retrieve the webpage at http://www.android.com/:

   URL url = new URL("http://www.android.com/");
   HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
   try {
     InputStream in = new BufferedInputStream(urlConnection.getInputStream());
     readStream(in);
    finally {
     urlConnection.disconnect();
   }
 }

Secure Communication with HTTPS

Calling openConnection() on a URL with the "https" scheme will return an HttpsURLConnection, which allows for overriding the default HostnameVerifier and SSLSocketFactory. An application-supplied SSLSocketFactory created from an SSLContext can provide a custom X509TrustManager for verifying certificate chains and a custom X509KeyManager for supplying client certificates. See HttpsURLConnection for more details.

Response Handling

HttpURLConnection will follow up to five HTTP redirects. It will follow redirects from one origin server to another. This implementation doesn't follow redirects from HTTPS to HTTP or vice versa.

If the HTTP response indicates that an error occurred, getInputStream() will throw an IOException. Use getErrorStream() to read the error response. The headers can be read in the normal way using getHeaderFields(),

Posting Content

To upload data to a web server, configure the connection for output using setDoOutput(true).

For best performance, you should call either setFixedLengthStreamingMode(int) when the body length is known in advance, or setChunkedStreamingMode(int) when it is not. Otherwise HttpURLConnection will be forced to buffer the complete request body in memory before it is transmitted, wasting (and possibly exhausting) heap and increasing latency.

For example, to perform an upload:

   HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
   try {
     urlConnection.setDoOutput(true);
     urlConnection.setChunkedStreamingMode(0);

     OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
     writeStream(out);

     InputStream in = new BufferedInputStream(urlConnection.getInputStream());
     readStream(in);
    finally {
     urlConnection.disconnect();
   }
 }

Performance

The input and output streams returned by this class are not buffered. Most callers should wrap the returned streams with BufferedInputStream or BufferedOutputStream. Callers that do only bulk reads or writes may omit buffering.

When transferring large amounts of data to or from a server, use streams to limit how much data is in memory at once. Unless you need the entire body to be in memory at once, process it as a stream (rather than storing the complete body as a single byte array or string).

To reduce latency, this class may reuse the same underlying Socket for multiple request/response pairs. As a result, HTTP connections may be held open longer than necessary. Calls to disconnect() may return the socket to a pool of connected sockets. This behavior can be disabled by setting the http.keepAlive system property to false before issuing any HTTP requests. The http.maxConnections property may be used to control how many idle connections to each server will be held.

By default, this implementation of HttpURLConnection requests that servers use gzip compression. Since getContentLength() returns the number of bytes transmitted, you cannot use that method to predict how many bytes can be read from getInputStream(). Instead, read that stream until it is exhausted: when read() returns -1. Gzip compression can be disabled by setting the acceptable encodings in the request header:

   urlConnection.setRequestProperty("Accept-Encoding", "identity");
 

Handling Network Sign-On

Some Wi-Fi networks block Internet access until the user clicks through a sign-on page. Such sign-on pages are typically presented by using HTTP redirects. You can use getURL() to test if your connection has been unexpectedly redirected. This check is not valid until after the response headers have been received, which you can trigger by calling getHeaderFields() or getInputStream(). For example, to check that a response was not redirected to an unexpected host:
   HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
   try {
     InputStream in = new BufferedInputStream(urlConnection.getInputStream());
     if (!url.getHost().equals(urlConnection.getURL().getHost())) {
       // we were redirected! Kick the user out to the browser to sign on?
     
     ...
   } finally {
     urlConnection.disconnect();
   }
 }

HTTP Authentication

HttpURLConnection supports HTTP basic authentication. Use Authenticator to set the VM-wide authentication handler:
   Authenticator.setDefault(new Authenticator() {
     protected PasswordAuthentication getPasswordAuthentication() {
       return new PasswordAuthentication(username, password.toCharArray());
     
   });
 }
Unless paired with HTTPS, this is not a secure mechanism for user authentication. In particular, the username, password, request and response are all transmitted over the network without encryption.

Sessions with Cookies

To establish and maintain a potentially long-lived session between client and server, HttpURLConnection includes an extensible cookie manager. Enable VM-wide cookie management using CookieHandler and CookieManager:
   CookieManager cookieManager = new CookieManager();
   CookieHandler.setDefault(cookieManager);
 
By default, CookieManager accepts cookies from the origin server only. Two other policies are included: ACCEPT_ALL and ACCEPT_NONE. Implement CookiePolicy to define a custom policy.

The default CookieManager keeps all accepted cookies in memory. It will forget these cookies when the VM exits. Implement CookieStore to define a custom cookie store.

In addition to the cookies set by HTTP responses, you may set cookies programmatically. To be included in HTTP request headers, cookies must have the domain and path properties set.

By default, new instances of HttpCookie work only with servers that support RFC 2965 cookies. Many web servers support only the older specification, RFC 2109. For compatibility with the most web servers, set the cookie version to 0.

For example, to receive www.twitter.com in French:

   HttpCookie cookie = new HttpCookie("lang", "fr");
   cookie.setDomain("twitter.com");
   cookie.setPath("/");
   cookie.setVersion(0);
   cookieManager.getCookieStore().add(new URI("http://twitter.com/"), cookie);
 

HTTP Methods

HttpURLConnection uses the GET method by default. It will use POST if setDoOutput(true) has been called. Other HTTP methods (OPTIONS, HEAD, PUT, DELETE and TRACE) can be used with setRequestMethod(String).

Proxies

By default, this class will connect directly to the origin server. It can also connect via an HTTP or SOCKS proxy. To use a proxy, use URL.openConnection(Proxy) when creating the connection.

IPv6 Support

This class includes transparent support for IPv6. For hosts with both IPv4 and IPv6 addresses, it will attempt to connect to each of a host's addresses until a connection is established.

Response Caching

Android 4.0 (Ice Cream Sandwich, API level 15) includes a response cache. See android.net.http.HttpResponseCache for instructions on enabling HTTP caching in your application.

Avoiding Bugs In Earlier Releases

Prior to Android 2.2 (Froyo), this class had some frustrating bugs. In particular, calling close() on a readable InputStream could poison the connection pool. Work around this by disabling connection pooling:
   private void disableConnectionReuseIfNecessary() {
   // Work around pre-Froyo bugs in HTTP connection reuse.
   if (Integer.parseInt(Build.VERSION.SDK) < Build.VERSION_CODES.FROYO) {
     System.setProperty("http.keepAlive", "false");
   
 }}

Each instance of HttpURLConnection may be used for one request/response pair. Instances of this class are not thread safe.

Summary

Constants
int HTTP_ACCEPTED Numeric status code, 202: Accepted
int HTTP_BAD_GATEWAY Numeric status code, 502: Bad Gateway
int HTTP_BAD_METHOD Numeric status code, 405: Bad Method
int HTTP_BAD_REQUEST Numeric status code, 400: Bad Request
int HTTP_CLIENT_TIMEOUT Numeric status code, 408: Client Timeout
int HTTP_CONFLICT Numeric status code, 409: Conflict
int HTTP_CREATED Numeric status code, 201: Created
int HTTP_ENTITY_TOO_LARGE Numeric status code, 413: Entity too large
int HTTP_FORBIDDEN Numeric status code, 403: Forbidden
int HTTP_GATEWAY_TIMEOUT Numeric status code, 504: Gateway timeout
int HTTP_GONE Numeric status code, 410: Gone
int HTTP_INTERNAL_ERROR Numeric status code, 500: Internal error
int HTTP_LENGTH_REQUIRED Numeric status code, 411: Length required
int HTTP_MOVED_PERM Numeric status code, 301 Moved permanently
int HTTP_MOVED_TEMP Numeric status code, 302: Moved temporarily
int HTTP_MULT_CHOICE Numeric status code, 300: Multiple choices
int HTTP_NOT_ACCEPTABLE Numeric status code, 406: Not acceptable
int HTTP_NOT_AUTHORITATIVE Numeric status code, 203: Not authoritative
int HTTP_NOT_FOUND Numeric status code, 404: Not found
int HTTP_NOT_IMPLEMENTED Numeric status code, 501: Not implemented
int HTTP_NOT_MODIFIED Numeric status code, 304: Not modified
int HTTP_NO_CONTENT Numeric status code, 204: No content
int HTTP_OK Numeric status code, 200: OK
int HTTP_PARTIAL Numeric status code, 206: Partial
int HTTP_PAYMENT_REQUIRED Numeric status code, 402: Payment required
int HTTP_PRECON_FAILED Numeric status code, 412: Precondition failed
int HTTP_PROXY_AUTH Numeric status code, 407: Proxy authentication required
int HTTP_REQ_TOO_LONG Numeric status code, 414: Request too long
int HTTP_RESET Numeric status code, 205: Reset
int HTTP_SEE_OTHER Numeric status code, 303: See other
int HTTP_SERVER_ERROR This constant was deprecated in API level 1. Use HTTP_INTERNAL_ERROR instead.
int HTTP_UNAUTHORIZED Numeric status code, 401: Unauthorized
int HTTP_UNAVAILABLE Numeric status code, 503: Unavailable
int HTTP_UNSUPPORTED_TYPE Numeric status code, 415: Unsupported type
int HTTP_USE_PROXY Numeric status code, 305: Use proxy.
int HTTP_VERSION Numeric status code, 505: Version not supported
Fields
protected int chunkLength If the HTTP chunked encoding is enabled this parameter defines the chunk-length.
protected int fixedContentLength The byte count in the request body if it is both known and streamed; and -1 otherwise.
protected long fixedContentLengthLong The byte count in the request body if it is both known and streamed; and -1 otherwise.
protected boolean instanceFollowRedirects Flag to define whether the protocol will automatically follow redirects or not.
protected String method The HTTP request method of this HttpURLConnection.
protected int responseCode The status code of the response obtained from the HTTP request.
protected String responseMessage The HTTP response message which corresponds to the response code.
[Expand]
Inherited Fields
From class java.net.URLConnection
Protected Constructors
HttpURLConnection(URL url)
Constructs a new HttpURLConnection instance pointing to the resource specified by the url.
Public Methods
abstract void disconnect()
Releases this connection so that its resources may be either reused or closed.
String getContentEncoding()
Returns the encoding used to transmit the response body over the network.
InputStream getErrorStream()
Returns an input stream from the server in the case of an error such as the requested file has not been found on the remote server.
static boolean getFollowRedirects()
Returns the value of followRedirects which indicates if this connection follows a different URL redirected by the server.
long getHeaderFieldDate(String field, long defaultValue)
Returns the date value in milliseconds since 01.01.1970, 00:00h corresponding to the header field field.
boolean getInstanceFollowRedirects()
Returns whether this connection follows redirects.
Permission getPermission()
Returns the permission object (in this case SocketPermission) with the host and the port number as the target name and "resolve, connect" as the action list.
String getRequestMethod()
Returns the request method which will be used to make the request to the remote HTTP server.
int getResponseCode()
Returns the response code returned by the remote HTTP server.
String getResponseMessage()
Returns the response message returned by the remote HTTP server.
void setChunkedStreamingMode(int chunkLength)
Stream a request body whose length is not known in advance.
void setFixedLengthStreamingMode(int contentLength)
Equivalent to setFixedLengthStreamingMode((long) contentLength), but available on earlier versions of Android and limited to 2 GiB.
void setFixedLengthStreamingMode(long contentLength)
Configures this connection to stream the request body with the known fixed byte count of contentLength.
static void setFollowRedirects(boolean auto)
Sets the flag of whether this connection will follow redirects returned by the remote server.
void setInstanceFollowRedirects(boolean followRedirects)
Sets whether this connection follows redirects.
void setRequestMethod(String method)
Sets the request command which will be sent to the remote HTTP server.
abstract boolean usingProxy()
Returns whether this connection uses a proxy server or not.
[Expand]
Inherited Methods
From class java.net.URLConnection
From class java.lang.Object

Constants

public static final int HTTP_ACCEPTED

Added in API level 1

Numeric status code, 202: Accepted

Constant Value: 202 (0x000000ca)

public static final int HTTP_BAD_GATEWAY

Added in API level 1

Numeric status code, 502: Bad Gateway

Constant Value: 502 (0x000001f6)

public static final int HTTP_BAD_METHOD

Added in API level 1

Numeric status code, 405: Bad Method

Constant Value: 405 (0x00000195)

public static final int HTTP_BAD_REQUEST

Added in API level 1

Numeric status code, 400: Bad Request

Constant Value: 400 (0x00000190)

public static final int HTTP_CLIENT_TIMEOUT

Added in API level 1

Numeric status code, 408: Client Timeout

Constant Value: 408 (0x00000198)

public static final int HTTP_CONFLICT

Added in API level 1

Numeric status code, 409: Conflict

Constant Value: 409 (0x00000199)

public static final int HTTP_CREATED

Added in API level 1

Numeric status code, 201: Created

Constant Value: 201 (0x000000c9)

public static final int HTTP_ENTITY_TOO_LARGE

Added in API level 1

Numeric status code, 413: Entity too large

Constant Value: 413 (0x0000019d)

public static final int HTTP_FORBIDDEN

Added in API level 1

Numeric status code, 403: Forbidden

Constant Value: 403 (0x00000193)

public static final int HTTP_GATEWAY_TIMEOUT

Added in API level 1

Numeric status code, 504: Gateway timeout

Constant Value: 504 (0x000001f8)

public static final int HTTP_GONE

Added in API level 1

Numeric status code, 410: Gone

Constant Value: 410 (0x0000019a)

public static final int HTTP_INTERNAL_ERROR

Added in API level 1

Numeric status code, 500: Internal error

Constant Value: 500 (0x000001f4)

public static final int HTTP_LENGTH_REQUIRED

Added in API level 1

Numeric status code, 411: Length required

Constant Value: 411 (0x0000019b)

public static final int HTTP_MOVED_PERM

Added in API level 1

Numeric status code, 301 Moved permanently

Constant Value: 301 (0x0000012d)

public static final int HTTP_MOVED_TEMP

Added in API level 1

Numeric status code, 302: Moved temporarily

Constant Value: 302 (0x0000012e)

public static final int HTTP_MULT_CHOICE

Added in API level 1

Numeric status code, 300: Multiple choices

Constant Value: 300 (0x0000012c)

public static final int HTTP_NOT_ACCEPTABLE

Added in API level 1

Numeric status code, 406: Not acceptable

Constant Value: 406 (0x00000196)

public static final int HTTP_NOT_AUTHORITATIVE

Added in API level 1

Numeric status code, 203: Not authoritative

Constant Value: 203 (0x000000cb)

public static final int HTTP_NOT_FOUND

Added in API level 1

Numeric status code, 404: Not found

Constant Value: 404 (0x00000194)

public static final int HTTP_NOT_IMPLEMENTED

Added in API level 1

Numeric status code, 501: Not implemented

Constant Value: 501 (0x000001f5)

public static final int HTTP_NOT_MODIFIED

Added in API level 1

Numeric status code, 304: Not modified

Constant Value: 304 (0x00000130)

public static final int HTTP_NO_CONTENT

Added in API level 1

Numeric status code, 204: No content

Constant Value: 204 (0x000000cc)

public static final int HTTP_OK

Added in API level 1

Numeric status code, 200: OK

Constant Value: 200 (0x000000c8)

public static final int HTTP_PARTIAL

Added in API level 1

Numeric status code, 206: Partial

Constant Value: 206 (0x000000ce)

public static final int HTTP_PAYMENT_REQUIRED

Added in API level 1

Numeric status code, 402: Payment required

Constant Value: 402 (0x00000192)

public static final int HTTP_PRECON_FAILED

Added in API level 1

Numeric status code, 412: Precondition failed

Constant Value: 412 (0x0000019c)

public static final int HTTP_PROXY_AUTH

Added in API level 1

Numeric status code, 407: Proxy authentication required

Constant Value: 407 (0x00000197)

public static final int HTTP_REQ_TOO_LONG

Added in API level 1

Numeric status code, 414: Request too long

Constant Value: 414 (0x0000019e)

public static final int HTTP_RESET

Added in API level 1

Numeric status code, 205: Reset

Constant Value: 205 (0x000000cd)

public static final int HTTP_SEE_OTHER

Added in API level 1

Numeric status code, 303: See other

Constant Value: 303 (0x0000012f)

public static final int HTTP_SERVER_ERROR

Added in API level 1

This constant was deprecated in API level 1.
Use HTTP_INTERNAL_ERROR instead.

Numeric status code, 500: Internal error

Constant Value: 500 (0x000001f4)

public static final int HTTP_UNAUTHORIZED

Added in API level 1

Numeric status code, 401: Unauthorized

Constant Value: 401 (0x00000191)

public static final int HTTP_UNAVAILABLE

Added in API level 1

Numeric status code, 503: Unavailable

Constant Value: 503 (0x000001f7)

public static final int HTTP_UNSUPPORTED_TYPE

Added in API level 1

Numeric status code, 415: Unsupported type

Constant Value: 415 (0x0000019f)

public static final int HTTP_USE_PROXY

Added in API level 1

Numeric status code, 305: Use proxy.

Like Firefox and Chrome, this class doesn't honor this response code. Other implementations respond to this status code by retrying the request using the HTTP proxy named by the response's Location header field.

Constant Value: 305 (0x00000131)

public static final int HTTP_VERSION

Added in API level 1

Numeric status code, 505: Version not supported

Constant Value: 505 (0x000001f9)

Fields

protected int chunkLength

Added in API level 1

If the HTTP chunked encoding is enabled this parameter defines the chunk-length. Default value is -1 that means the chunked encoding mode is disabled.

protected int fixedContentLength

Added in API level 1

The byte count in the request body if it is both known and streamed; and -1 otherwise. If the byte count exceeds MAX_VALUE (2 GiB) then the value of this field will be MAX_VALUE. In that case use fixedContentLengthLong to access the exact byte count.

protected long fixedContentLengthLong

Added in API level 19

The byte count in the request body if it is both known and streamed; and -1 otherwise. Prefer this field over the int-valued fixedContentLength on platforms that support both.

protected boolean instanceFollowRedirects

Added in API level 1

Flag to define whether the protocol will automatically follow redirects or not. The default value is true.

protected String method

Added in API level 1

The HTTP request method of this HttpURLConnection. The default value is "GET".

protected int responseCode

Added in API level 1

The status code of the response obtained from the HTTP request. The default value is -1.

  • 1xx: Informational
  • 2xx: Success
  • 3xx: Relocation/Redirection
  • 4xx: Client Error
  • 5xx: Server Error
  • protected String responseMessage

    Added in API level 1

    The HTTP response message which corresponds to the response code.

    Protected Constructors

    protected HttpURLConnection (URL url)

    Added in API level 1

    Constructs a new HttpURLConnection instance pointing to the resource specified by the url.

    Parameters
    url the URL of this connection.
    See Also

    Public Methods

    public abstract void disconnect ()

    Added in API level 1

    Releases this connection so that its resources may be either reused or closed.

    Unlike other Java implementations, this will not necessarily close socket connections that can be reused. You can disable all connection reuse by setting the http.keepAlive system property to false before issuing any HTTP requests.

    public String getContentEncoding ()

    Added in API level 1

    Returns the encoding used to transmit the response body over the network. This is null or "identity" if the content was not encoded, or "gzip" if the body was gzip compressed. Most callers will be more interested in the content type, which may also include the content's character encoding.

    Returns
    • the value of the response header field content-encoding.

    public InputStream getErrorStream ()

    Added in API level 1

    Returns an input stream from the server in the case of an error such as the requested file has not been found on the remote server. This stream can be used to read the data the server will send back.

    Returns
    • the error input stream returned by the server.

    public static boolean getFollowRedirects ()

    Added in API level 1

    Returns the value of followRedirects which indicates if this connection follows a different URL redirected by the server. It is enabled by default.

    Returns
    • the value of the flag.

    public long getHeaderFieldDate (String field, long defaultValue)

    Added in API level 1

    Returns the date value in milliseconds since 01.01.1970, 00:00h corresponding to the header field field. The defaultValue will be returned if no such field can be found in the response header.

    Parameters
    field the header field name.
    defaultValue the default value to use if the specified header field wont be found.
    Returns
    • the header field represented in milliseconds since January 1, 1970 GMT.

    public boolean getInstanceFollowRedirects ()

    Added in API level 1

    Returns whether this connection follows redirects.

    Returns
    • true if this connection follows redirects, false otherwise.

    public Permission getPermission ()

    Added in API level 1

    Returns the permission object (in this case SocketPermission) with the host and the port number as the target name and "resolve, connect" as the action list. If the port number of this URL instance is lower than 0 the port will be set to 80.

    Returns
    • the permission object required for this connection.
    Throws
    IOException if an IO exception occurs during the creation of the permission object.

    public String getRequestMethod ()

    Added in API level 1

    Returns the request method which will be used to make the request to the remote HTTP server. All possible methods of this HTTP implementation is listed in the class definition.

    Returns
    • the request method string.

    public int getResponseCode ()

    Added in API level 1

    Returns the response code returned by the remote HTTP server.

    Returns
    • the response code, -1 if no valid response code.
    Throws
    IOException if there is an IO error during the retrieval.

    public String getResponseMessage ()

    Added in API level 1

    Returns the response message returned by the remote HTTP server.

    Returns
    • the response message. null if no such response exists.
    Throws
    IOException if there is an error during the retrieval.

    public void setChunkedStreamingMode (int chunkLength)

    Added in API level 1

    Stream a request body whose length is not known in advance. Old HTTP/1.0 only servers may not support this mode.

    When HTTP chunked encoding is used, the stream is divided into chunks, each prefixed with a header containing the chunk's size. Setting a large chunk length requires a large internal buffer, potentially wasting memory. Setting a small chunk length increases the number of bytes that must be transmitted because of the header on every chunk. Most caller should use 0 to get the system default.

    Parameters
    chunkLength the length to use, or 0 for the default chunk length.
    Throws
    IllegalStateException if already connected or another mode already set.

    public void setFixedLengthStreamingMode (int contentLength)

    Added in API level 1

    Equivalent to setFixedLengthStreamingMode((long) contentLength), but available on earlier versions of Android and limited to 2 GiB.

    public void setFixedLengthStreamingMode (long contentLength)

    Added in API level 19

    Configures this connection to stream the request body with the known fixed byte count of contentLength.

    Parameters
    contentLength the fixed length of the HTTP request body.
    Throws
    IllegalStateException if already connected or another mode already set.
    IllegalArgumentException if contentLength is less than zero.

    public static void setFollowRedirects (boolean auto)

    Added in API level 1

    Sets the flag of whether this connection will follow redirects returned by the remote server.

    Parameters
    auto the value to enable or disable this option.

    public void setInstanceFollowRedirects (boolean followRedirects)

    Added in API level 1

    Sets whether this connection follows redirects.

    Parameters
    followRedirects true if this connection will follows redirects, false otherwise.

    public void setRequestMethod (String method)

    Added in API level 1

    Sets the request command which will be sent to the remote HTTP server. This method can only be called before the connection is made.

    Parameters
    method the string representing the method to be used.
    Throws
    ProtocolException if this is called after connected, or the method is not supported by this HTTP implementation.

    public abstract boolean usingProxy ()

    Added in API level 1

    Returns whether this connection uses a proxy server or not.

    Returns
    • true if this connection passes a proxy server, false otherwise.