/**@class java.net.HttpURLConnection
@extends java.net.URLConnection
A URLConnection with support for HTTP-specific features. See
<A HREF="http://www.w3.org/pub/WWW/Protocols/"> the spec </A> for
details.
<p>
<p>Uses of this class follow a pattern:
<ol>
<li>Obtain a new {@code HttpURLConnection} by calling {@link java.net.URL#openConnection() java.net.URL.openConnection()} and casting the result to
{@code HttpURLConnection}.
<li>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.
<li>Optionally upload a request body. Instances must be configured with
{@link #setDoOutput(boolean) setDoOutput(true)} if they include a
request body. Transmit data by writing to the stream returned by {@link #getOutputStream}().
<li>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 {@link #getInputStream}(). If the response has no body, that method returns an
empty stream.
<li>Disconnect. Once the response body has been read, the {@code
HttpURLConnection} should be closed by calling {@link #disconnect}().
Disconnecting releases the resources held by a connection so they may
be closed or reused.
</ol>
<p>For example, to retrieve the webpage at {@code http://www.android.com/}:
<pre> {@code
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();
}
}</pre>
<h3>Secure Communication with HTTPS</h3>
Calling {@link java.net.URL#openConnection()} on a URL with the "https"
scheme will return an {@code HttpsURLConnection}, which allows for
overriding the default {@link javax.net.ssl.HostnameVerifier
HostnameVerifier} and {@link javax.net.ssl.SSLSocketFactory
SSLSocketFactory}. An application-supplied {@code SSLSocketFactory}
created from an {@link javax.net.ssl.SSLContext SSLContext} can
provide a custom {@link javax.net.ssl.X509TrustManager
X509TrustManager} for verifying certificate chains and a custom
{@link javax.net.ssl.X509KeyManager X509KeyManager} for supplying
client certificates. See {@link javax.net.ssl.HttpsURLConnection
HttpsURLConnection} for more details.
<h3>Response Handling</h3>
{@code 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.
<p>If the HTTP response indicates that an error occurred, {@link #getInputStream}() will throw an {@link IOException}. Use {@link #getErrorStream}() to read the error response. The headers can be read in
the normal way using {@link #getHeaderFields}(),
<h3>Posting Content</h3>
To upload data to a web server, configure the connection for output using
{@link #setDoOutput(boolean) setDoOutput(true)}.
<p>For best performance, you should call either {@link #setFixedLengthStreamingMode}(int) when the body length is known in advance,
or {@link #setChunkedStreamingMode}(int) when it is not. Otherwise {@code
HttpURLConnection} will be forced to buffer the complete request body in
memory before it is transmitted, wasting (and possibly exhausting) heap and
increasing latency.
<p>For example, to perform an upload: <pre> {@code
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();
}
}</pre>
<h3>Performance</h3>
The input and output streams returned by this class are <strong>not
buffered</strong>. Most callers should wrap the returned streams with {@link java.io.BufferedInputStream BufferedInputStream} or {@link java.io.BufferedOutputStream BufferedOutputStream}. Callers that do only bulk
reads or writes may omit buffering.
<p>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).
<p>To reduce latency, this class may reuse the same underlying {@code Socket}
for multiple request/response pairs. As a result, HTTP connections may be
held open longer than necessary. Calls to {@link #disconnect}() may return
the socket to a pool of connected sockets.
<p>By default, this implementation of {@code HttpURLConnection} requests that
servers use gzip compression and it automatically decompresses the data for
callers of {@link #getInputStream}(). The Content-Encoding and Content-Length
response headers are cleared in this case. Gzip compression can be disabled by
setting the acceptable encodings in the request header: <pre> {@code
urlConnection.setRequestProperty("Accept-Encoding", "identity");
}</pre>
<p>Setting the Accept-Encoding request header explicitly disables automatic
decompression and leaves the response headers intact; callers must handle
decompression as needed, according to the Content-Encoding header of the
response.
<p>{@link #getContentLength}() returns the number of bytes transmitted and
cannot be used to predict how many bytes can be read from
{@link #getInputStream}() for compressed streams. Instead, read that stream
until it is exhausted, i.e. when {@link InputStream#read} returns -1.
<h3>Handling Network Sign-On</h3>
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 {@link #getURL}() to test if your connection has been
unexpectedly redirected. This check is not valid until <strong>after</strong>
the response headers have been received, which you can trigger by calling
{@link #getHeaderFields}() or {@link #getInputStream}(). For example, to
check that a response was not redirected to an unexpected host:
<pre> {@code
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();
}
}</pre>
<h3>HTTP Authentication</h3>
{@code HttpURLConnection} supports <a
href="http://www.ietf.org/rfc/rfc2617">HTTP basic authentication</a>. Use
{@link java.net.Authenticator} to set the VM-wide authentication handler:
<pre> {@code
Authenticator.setDefault(new Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password.toCharArray());
}
});
}</pre>
Unless paired with HTTPS, this is <strong>not</strong> a secure mechanism for
user authentication. In particular, the username, password, request and
response are all transmitted over the network without encryption.
<h3>Sessions with Cookies</h3>
To establish and maintain a potentially long-lived session between client
and server, {@code HttpURLConnection} includes an extensible cookie manager.
Enable VM-wide cookie management using {@link java.net.CookieHandler} and {@link java.net.CookieManager}: <pre> {@code
CookieManager cookieManager = new CookieManager();
CookieHandler.setDefault(cookieManager);
}</pre>
By default, {@code CookieManager} accepts cookies from the <a
href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec1.html">origin
server</a> only. Two other policies are included: {@link java.net.CookiePolicy#ACCEPT_ALL} and {@link java.net.CookiePolicy#ACCEPT_NONE}. Implement
{@link java.net.CookiePolicy} to define a custom policy.
<p>The default {@code CookieManager} keeps all accepted cookies in memory. It
will forget these cookies when the VM exits. Implement {@link java.net.CookieStore} to
define a custom cookie store.
<p>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.
<p>By default, new instances of {@code HttpCookie} work only with servers
that support <a href="http://www.ietf.org/rfc/rfc2965.txt">RFC 2965</a>
cookies. Many web servers support only the older specification, <a
href="http://www.ietf.org/rfc/rfc2109.txt">RFC 2109</a>. For compatibility
with the most web servers, set the cookie version to 0.
<p>For example, to receive {@code www.twitter.com} in French: <pre> {@code
HttpCookie cookie = new HttpCookie("lang", "fr");
cookie.setDomain("twitter.com");
cookie.setPath("/");
cookie.setVersion(0);
cookieManager.getCookieStore().add(new URI("http://twitter.com/"), cookie);
}</pre>
<h3>HTTP Methods</h3>
<p>{@code HttpURLConnection} uses the {@code GET} method by default. It will
use {@code POST} if {@link #setDoOutput setDoOutput(true)} has been called.
Other HTTP methods ({@code OPTIONS}, {@code HEAD}, {@code PUT}, {@code
DELETE} and {@code TRACE}) can be used with {@link #setRequestMethod}.
<h3>Proxies</h3>
By default, this class will connect directly to the <a
href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec1.html">origin
server</a>. It can also connect via an {@link java.net.Proxy.Type#HTTP HTTP} or {@link java.net.Proxy.Type#SOCKS SOCKS} proxy. To use a proxy, use {@link java.net.URL#openConnection(Proxy) java.net.URL.openConnection(Proxy)} when creating the
connection.
<h3>IPv6 Support</h3>
<p>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.
<h3>Response Caching</h3>
Android 4.0 (Ice Cream Sandwich, API level 15) includes a response cache. See
{@code android.net.http.HttpResponseCache} for instructions on enabling HTTP
caching in your application.
<h3>Avoiding Bugs In Earlier Releases</h3>
Prior to Android 2.2 (Froyo), this class had some frustrating bugs. In
particular, calling {@code close()} on a readable {@code InputStream} could
<a href="http://code.google.com/p/android/issues/detail?id=2939">poison the
connection pool</a>. Work around this by disabling connection pooling:
<pre> {@code
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");
}
}}</pre>
<p>Each instance of {@code HttpURLConnection} may be used for one
request/response pair. Instances of this class are not thread safe.
@see java.net.HttpURLConnection#disconnect()
@since JDK1.1
*/
var HttpURLConnection = {
/** HTTP Status-Code 200: OK.
*/
HTTP_OK : "200",
/** HTTP Status-Code 201: Created.
*/
HTTP_CREATED : "201",
/** HTTP Status-Code 202: Accepted.
*/
HTTP_ACCEPTED : "202",
/** HTTP Status-Code 203: Non-Authoritative Information.
*/
HTTP_NOT_AUTHORITATIVE : "203",
/** HTTP Status-Code 204: No Content.
*/
HTTP_NO_CONTENT : "204",
/** HTTP Status-Code 205: Reset Content.
*/
HTTP_RESET : "205",
/** HTTP Status-Code 206: Partial Content.
*/
HTTP_PARTIAL : "206",
/** HTTP Status-Code 300: Multiple Choices.
*/
HTTP_MULT_CHOICE : "300",
/** HTTP Status-Code 301: Moved Permanently.
*/
HTTP_MOVED_PERM : "301",
/** HTTP Status-Code 302: Temporary Redirect.
*/
HTTP_MOVED_TEMP : "302",
/** HTTP Status-Code 303: See Other.
*/
HTTP_SEE_OTHER : "303",
/** HTTP Status-Code 304: Not Modified.
*/
HTTP_NOT_MODIFIED : "304",
/** HTTP Status-Code 305: Use Proxy.
*/
HTTP_USE_PROXY : "305",
/** HTTP Status-Code 400: Bad Request.
*/
HTTP_BAD_REQUEST : "400",
/** HTTP Status-Code 401: Unauthorized.
*/
HTTP_UNAUTHORIZED : "401",
/** HTTP Status-Code 402: Payment Required.
*/
HTTP_PAYMENT_REQUIRED : "402",
/** HTTP Status-Code 403: Forbidden.
*/
HTTP_FORBIDDEN : "403",
/** HTTP Status-Code 404: Not Found.
*/
HTTP_NOT_FOUND : "404",
/** HTTP Status-Code 405: Method Not Allowed.
*/
HTTP_BAD_METHOD : "405",
/** HTTP Status-Code 406: Not Acceptable.
*/
HTTP_NOT_ACCEPTABLE : "406",
/** HTTP Status-Code 407: Proxy Authentication Required.
*/
HTTP_PROXY_AUTH : "407",
/** HTTP Status-Code 408: Request Time-Out.
*/
HTTP_CLIENT_TIMEOUT : "408",
/** HTTP Status-Code 409: Conflict.
*/
HTTP_CONFLICT : "409",
/** HTTP Status-Code 410: Gone.
*/
HTTP_GONE : "410",
/** HTTP Status-Code 411: Length Required.
*/
HTTP_LENGTH_REQUIRED : "411",
/** HTTP Status-Code 412: Precondition Failed.
*/
HTTP_PRECON_FAILED : "412",
/** HTTP Status-Code 413: Request Entity Too Large.
*/
HTTP_ENTITY_TOO_LARGE : "413",
/** HTTP Status-Code 414: Request-URI Too Large.
*/
HTTP_REQ_TOO_LONG : "414",
/** HTTP Status-Code 415: Unsupported Media Type.
*/
HTTP_UNSUPPORTED_TYPE : "415",
/** HTTP Status-Code 500: Internal Server Error.
@deprecated it is misplaced and shouldn't have existed.
*/
HTTP_SERVER_ERROR : "500",
/** HTTP Status-Code 500: Internal Server Error.
*/
HTTP_INTERNAL_ERROR : "500",
/** HTTP Status-Code 501: Not Implemented.
*/
HTTP_NOT_IMPLEMENTED : "501",
/** HTTP Status-Code 502: Bad Gateway.
*/
HTTP_BAD_GATEWAY : "502",
/** HTTP Status-Code 503: Service Unavailable.
*/
HTTP_UNAVAILABLE : "503",
/** HTTP Status-Code 504: Gateway Timeout.
*/
HTTP_GATEWAY_TIMEOUT : "504",
/** HTTP Status-Code 505: HTTP Version Not Supported.
*/
HTTP_VERSION : "505",
Some implementations may treat the {@code 0}<sup>th</sup>
header field as special, i.e. as the status line returned by the HTTP
server. In this case, {@link #getHeaderField(int) getHeaderField(0)} returns the status
line, but {@code getHeaderFieldKey(0)} returns null.
@param {Number} n an index, where {@code n >=0}.
@return {String} the key for the {@code n}<sup>th</sup> header field,
or {@code null} if the key does not exist.
*/
getHeaderFieldKey : function( ) {},
/**This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is known in
advance.
<p>
An exception will be thrown if the application
attempts to write more data than the indicated
content-length, or if the application closes the OutputStream
before writing the indicated amount.
<p>
When output streaming is enabled, authentication
and redirection cannot be handled automatically.
A HttpRetryException will be thrown when reading
the response if authentication or redirection are required.
This exception can be queried for the details of the error.
<p>
This method must be called before the URLConnection is connected.
<p>
<B>NOTE:</B> {@link #setFixedLengthStreamingMode}(long) is recommended
instead of this method as it allows larger content lengths to be set.
@param {Number} contentLength The number of bytes which will be written
to the OutputStream.
@throws IllegalStateException if URLConnection is already connected
or if a different streaming mode is already enabled.
@throws IllegalArgumentException if a content length less than
zero is specified.
@see #setChunkedStreamingMode(int)
@since 1.5
*/
setFixedLengthStreamingMode : function( ) {},
/**This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is known in
advance.
<P> An exception will be thrown if the application attempts to write
more data than the indicated content-length, or if the application
closes the OutputStream before writing the indicated amount.
<P> When output streaming is enabled, authentication and redirection
cannot be handled automatically. A {@linkplain java.net.HttpRetryException} will
be thrown when reading the response if authentication or redirection
are required. This exception can be queried for the details of the
error.
<P> This method must be called before the URLConnection is connected.
<P> The content length set by invoking this method takes precedence
over any value set by {@link #setFixedLengthStreamingMode}(int).
@param {Number} contentLength
The number of bytes which will be written to the OutputStream.
@throws IllegalStateException
if URLConnection is already connected or if a different
streaming mode is already enabled.
@throws IllegalArgumentException
if a content length less than zero is specified.
@since 1.7
*/
setFixedLengthStreamingMode : function( ) {},
/**This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is <b>not</b>
known in advance. In this mode, chunked transfer encoding
is used to send the request body. Note, not all HTTP servers
support this mode.
<p>
When output streaming is enabled, authentication
and redirection cannot be handled automatically.
A HttpRetryException will be thrown when reading
the response if authentication or redirection are required.
This exception can be queried for the details of the error.
<p>
This method must be called before the URLConnection is connected.
@param {Number} chunklen The number of bytes to write in each chunk.
If chunklen is less than or equal to zero, a default
value will be used.
@throws IllegalStateException if URLConnection is already connected
or if a different streaming mode is already enabled.
@see #setFixedLengthStreamingMode(int)
@since 1.5
*/
setChunkedStreamingMode : function( ) {},
Some implementations may treat the {@code 0}<sup>th</sup>
header field as special, i.e. as the status line returned by the HTTP
server.
<p>
This method can be used in conjunction with the
{@link #getHeaderFieldKey getHeaderFieldKey} method to iterate through all
the headers in the message.
@param {Number} n an index, where {@code n>=0}.
@return {String} the value of the {@code n}<sup>th</sup> header field,
or {@code null} if the value does not exist.
@see java.net.HttpURLConnection#getHeaderFieldKey(int)
*/
getHeaderField : function( ) {},
/**Sets whether HTTP redirects (requests with response code 3xx) should
be automatically followed by this class. True by default. Applets
cannot change this variable.
<p>
If there is a security manager, this method first calls
the security manager's {@code checkSetFactory} method
to ensure the operation is allowed.
This could result in a SecurityException.
@param {Boolean} set a {@code boolean} indicating whether or not
to follow HTTP redirects.
@exception SecurityException if a security manager exists and its
{@code checkSetFactory} method doesn't
allow the operation.
@see SecurityManager#checkSetFactory
@see #getFollowRedirects()
*/
setFollowRedirects : function( ) {},
/**Returns a {@code boolean} indicating
whether or not HTTP redirects (3xx) should
be automatically followed.
@return {Boolean} {@code true} if HTTP redirects should
be automatically followed, {@code false} if not.
@see #setFollowRedirects(boolean)
*/
getFollowRedirects : function( ) {},
/**Sets whether HTTP redirects (requests with response code 3xx) should
be automatically followed by this {@code HttpURLConnection}
instance.
<p>
The default value comes from followRedirects, which defaults to
true.
@param {Boolean} followRedirects a {@code boolean} indicating
whether or not to follow HTTP redirects.
@see java.net.HttpURLConnection#instanceFollowRedirects
@see #getInstanceFollowRedirects
@since 1.3
*/
setInstanceFollowRedirects : function( ) {},
/**Returns the value of this {@code HttpURLConnection}'s
{@code instanceFollowRedirects} field.
@return {Boolean} the value of this {@code HttpURLConnection}'s
{@code instanceFollowRedirects} field.
@see java.net.HttpURLConnection#instanceFollowRedirects
@see #setInstanceFollowRedirects(boolean)
@since 1.3
*/
getInstanceFollowRedirects : function( ) {},
/**Set the method for the URL request, one of:
<UL>
<LI>GET
<LI>POST
<LI>HEAD
<LI>OPTIONS
<LI>PUT
<LI>DELETE
<LI>TRACE
</UL> are legal, subject to protocol restrictions. The default
method is GET.
@param {String} method the HTTP method
@exception ProtocolException if the method cannot be reset or if
the requested method isn't valid for HTTP.
@exception SecurityException if a security manager is set and the
method is "TRACE", but the "allowHttpTrace"
NetPermission is not granted.
@see #getRequestMethod()
*/
setRequestMethod : function( ) {},
/**Get the request method.
@return {String} the HTTP request method
@see #setRequestMethod(java.lang.String)
*/
getRequestMethod : function( ) {},
/**Gets the status code from an HTTP response message.
For example, in the case of the following status lines:
<PRE>
HTTP/1.0 200 OK
HTTP/1.0 401 Unauthorized
</PRE>
It will return 200 and 401 respectively.
Returns -1 if no code can be discerned
from the response (i.e., the response is not valid HTTP).
@throws IOException if an error occurred connecting to the server.
@return {Number} the HTTP Status-Code, or -1
*/
getResponseCode : function( ) {},
/**Gets the HTTP response message, if any, returned along with the
response code from a server. From responses like:
<PRE>
HTTP/1.0 200 OK
HTTP/1.0 404 Not Found
</PRE>
Extracts the Strings "OK" and "Not Found" respectively.
Returns null if none could be discerned from the responses
(the result was not valid HTTP).
@throws IOException if an error occurred connecting to the server.
@return {String} the HTTP response message, or {@code null}
*/
getResponseMessage : function( ) {},
*/
getHeaderFieldDate : function( ) {},
/**Indicates that other requests to the server
are unlikely in the near future. Calling disconnect()
should not imply that this HttpURLConnection
instance can be reused for other requests.
*/
disconnect : function( ) {},
/**Indicates if the connection is going through a proxy.
@return {Boolean} a boolean indicating if the connection is
using a proxy.
*/
usingProxy : function( ) {},
/**Returns a {@link java.net.SocketPermission} object representing the
permission necessary to connect to the destination host and port.
@exception IOException if an error occurs while computing
the permission.
@return {Object {java.security.Permission}} a {@code SocketPermission} object representing the
permission necessary to connect to the destination
host and port.
*/
getPermission : function( ) {},
/**Returns the error stream if the connection failed
but the server sent useful data nonetheless. The
typical example is when an HTTP server responds
with a 404, which will cause a FileNotFoundException
to be thrown in connect, but the server sent an HTML
help page with suggestions as to what to do.
<p>This method will not cause a connection to be initiated. If
the connection was not connected, or if the server did not have
an error while connecting or if the server had an error but
no error data was sent, this method will return null. This is
the default.
@return {Object {java.io.InputStream}} an error stream if any, null if there have been no
errors, the connection is not connected or the server sent no
useful data.
*/
getErrorStream : function( ) {},
};