public abstract class HttpURLConnection extends URLConnection
Uses of this class follow a pattern:
HttpURLConnection
by calling URL.openConnection()
and casting the result to
HttpURLConnection
.
setDoOutput(true)
if they include a
request body. Transmit data by writing to the stream returned by URLConnection.getOutputStream()
.
URLConnection.getInputStream()
. If the response has no body, that method returns an
empty stream.
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();
}
URL.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.
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, URLConnection.getInputStream()
will throw an IOException
. Use getErrorStream()
to read the error response. The headers can be read in
the normal way using URLConnection.getHeaderFields()
,
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();
}
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 and it automatically decompresses the data for
callers of URLConnection.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:
urlConnection.setRequestProperty("Accept-Encoding", "identity");
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.
URLConnection.getContentLength()
returns the number of bytes transmitted and
cannot be used to predict how many bytes can be read from
URLConnection.getInputStream()
for compressed streams. Instead, read that stream
until it is exhausted, i.e. when InputStream.read()
returns -1.
URLConnection.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
URLConnection.getHeaderFields()
or URLConnection.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();
}
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.
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: CookiePolicy.ACCEPT_ALL
and CookiePolicy.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);
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(java.lang.String)
.
HTTP
or SOCKS
proxy. To use a proxy, use URL.openConnection(Proxy)
when creating the
connection.
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.
android.net.http.HttpResponseCache
for instructions on enabling HTTP
caching in your application.
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.
Modifier and Type | Field and Description |
---|---|
protected int |
chunkLength
The chunk-length when using chunked encoding streaming mode for output.
|
protected int |
fixedContentLength
The fixed content-length when using fixed-length streaming mode.
|
protected long |
fixedContentLengthLong
The fixed content-length when using fixed-length streaming mode.
|
static int |
HTTP_ACCEPTED
HTTP Status-Code 202: Accepted.
|
static int |
HTTP_BAD_GATEWAY
HTTP Status-Code 502: Bad Gateway.
|
static int |
HTTP_BAD_METHOD
HTTP Status-Code 405: Method Not Allowed.
|
static int |
HTTP_BAD_REQUEST
HTTP Status-Code 400: Bad Request.
|
static int |
HTTP_CLIENT_TIMEOUT
HTTP Status-Code 408: Request Time-Out.
|
static int |
HTTP_CONFLICT
HTTP Status-Code 409: Conflict.
|
static int |
HTTP_CREATED
HTTP Status-Code 201: Created.
|
static int |
HTTP_ENTITY_TOO_LARGE
HTTP Status-Code 413: Request Entity Too Large.
|
static int |
HTTP_FORBIDDEN
HTTP Status-Code 403: Forbidden.
|
static int |
HTTP_GATEWAY_TIMEOUT
HTTP Status-Code 504: Gateway Timeout.
|
static int |
HTTP_GONE
HTTP Status-Code 410: Gone.
|
static int |
HTTP_INTERNAL_ERROR
HTTP Status-Code 500: Internal Server Error.
|
static int |
HTTP_LENGTH_REQUIRED
HTTP Status-Code 411: Length Required.
|
static int |
HTTP_MOVED_PERM
HTTP Status-Code 301: Moved Permanently.
|
static int |
HTTP_MOVED_TEMP
HTTP Status-Code 302: Temporary Redirect.
|
static int |
HTTP_MULT_CHOICE
HTTP Status-Code 300: Multiple Choices.
|
static int |
HTTP_NO_CONTENT
HTTP Status-Code 204: No Content.
|
static int |
HTTP_NOT_ACCEPTABLE
HTTP Status-Code 406: Not Acceptable.
|
static int |
HTTP_NOT_AUTHORITATIVE
HTTP Status-Code 203: Non-Authoritative Information.
|
static int |
HTTP_NOT_FOUND
HTTP Status-Code 404: Not Found.
|
static int |
HTTP_NOT_IMPLEMENTED
HTTP Status-Code 501: Not Implemented.
|
static int |
HTTP_NOT_MODIFIED
HTTP Status-Code 304: Not Modified.
|
static int |
HTTP_OK
HTTP Status-Code 200: OK.
|
static int |
HTTP_PARTIAL
HTTP Status-Code 206: Partial Content.
|
static int |
HTTP_PAYMENT_REQUIRED
HTTP Status-Code 402: Payment Required.
|
static int |
HTTP_PRECON_FAILED
HTTP Status-Code 412: Precondition Failed.
|
static int |
HTTP_PROXY_AUTH
HTTP Status-Code 407: Proxy Authentication Required.
|
static int |
HTTP_REQ_TOO_LONG
HTTP Status-Code 414: Request-URI Too Large.
|
static int |
HTTP_RESET
HTTP Status-Code 205: Reset Content.
|
static int |
HTTP_SEE_OTHER
HTTP Status-Code 303: See Other.
|
static int |
HTTP_SERVER_ERROR
Deprecated.
it is misplaced and shouldn't have existed.
|
static int |
HTTP_UNAUTHORIZED
HTTP Status-Code 401: Unauthorized.
|
static int |
HTTP_UNAVAILABLE
HTTP Status-Code 503: Service Unavailable.
|
static int |
HTTP_UNSUPPORTED_TYPE
HTTP Status-Code 415: Unsupported Media Type.
|
static int |
HTTP_USE_PROXY
HTTP Status-Code 305: Use Proxy.
|
static int |
HTTP_VERSION
HTTP Status-Code 505: HTTP Version Not Supported.
|
protected boolean |
instanceFollowRedirects
If
true , the protocol will automatically follow redirects. |
protected String |
method
The HTTP method (GET,POST,PUT,etc.).
|
protected int |
responseCode
An
int representing the three digit HTTP Status-Code. |
protected String |
responseMessage
The HTTP response message.
|
allowUserInteraction, connected, doInput, doOutput, ifModifiedSince, url, useCaches
Modifier | Constructor and Description |
---|---|
protected |
HttpURLConnection(URL u)
Constructor for the HttpURLConnection.
|
Modifier and Type | Method and Description |
---|---|
abstract void |
disconnect()
Indicates that other requests to the server
are unlikely in the near future.
|
InputStream |
getErrorStream()
Returns the error stream if the connection failed
but the server sent useful data nonetheless.
|
static boolean |
getFollowRedirects()
Returns a
boolean indicating
whether or not HTTP redirects (3xx) should
be automatically followed. |
String |
getHeaderField(int n)
Returns the value for the
n th header field. |
long |
getHeaderFieldDate(String name,
long Default)
Returns the value of the named field parsed as date.
|
String |
getHeaderFieldKey(int n)
Returns the key for the
n th header field. |
boolean |
getInstanceFollowRedirects()
Returns the value of this
HttpURLConnection 's
instanceFollowRedirects field. |
Permission |
getPermission()
Returns a
SocketPermission object representing the
permission necessary to connect to the destination host and port. |
String |
getRequestMethod()
Get the request method.
|
int |
getResponseCode()
Gets the status code from an HTTP response message.
|
String |
getResponseMessage()
Gets the HTTP response message, if any, returned along with the
response code from a server.
|
void |
setChunkedStreamingMode(int chunklen)
This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is not
known in advance.
|
void |
setFixedLengthStreamingMode(int contentLength)
This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is known in
advance.
|
void |
setFixedLengthStreamingMode(long contentLength)
This method is used to enable streaming of a HTTP request body
without internal buffering, when the content length is known in
advance.
|
static void |
setFollowRedirects(boolean set)
Sets whether HTTP redirects (requests with response code 3xx) should
be automatically followed by this class.
|
void |
setInstanceFollowRedirects(boolean followRedirects)
Sets whether HTTP redirects (requests with response code 3xx) should
be automatically followed by this
HttpURLConnection
instance. |
void |
setRequestMethod(String method)
Set the method for the URL request, one of:
GET
POST
HEAD
OPTIONS
PUT
DELETE
TRACE
are legal, subject to protocol restrictions.
|
abstract boolean |
usingProxy()
Indicates if the connection is going through a proxy.
|
addRequestProperty, connect, getAllowUserInteraction, getConnectTimeout, getContent, getContent, getContentEncoding, getContentLength, getContentLengthLong, getContentType, getDate, getDefaultAllowUserInteraction, getDefaultRequestProperty, getDefaultUseCaches, getDoInput, getDoOutput, getExpiration, getFileNameMap, getHeaderField, getHeaderFieldInt, getHeaderFieldLong, getHeaderFields, getIfModifiedSince, getInputStream, getLastModified, getOutputStream, getReadTimeout, getRequestProperties, getRequestProperty, getURL, getUseCaches, guessContentTypeFromName, guessContentTypeFromStream, setAllowUserInteraction, setConnectTimeout, setContentHandlerFactory, setDefaultAllowUserInteraction, setDefaultRequestProperty, setDefaultUseCaches, setDoInput, setDoOutput, setFileNameMap, setIfModifiedSince, setReadTimeout, setRequestProperty, setUseCaches, toString
protected String method
protected int chunkLength
-1
means chunked encoding is disabled for output.protected int fixedContentLength
-1
means fixed-length streaming mode is disabled
for output.
NOTE: fixedContentLengthLong
is recommended instead
of this field, as it allows larger content lengths to be set.
protected long fixedContentLengthLong
-1
means fixed-length streaming mode is disabled
for output.protected int responseCode
int
representing the three digit HTTP Status-Code.
protected String responseMessage
protected boolean instanceFollowRedirects
true
, the protocol will automatically follow redirects.
If false
, the protocol will not automatically follow
redirects.
This field is set by the setInstanceFollowRedirects
method. Its value is returned by the getInstanceFollowRedirects
method.
Its default value is based on the value of the static followRedirects at HttpURLConnection construction time.
public static final int HTTP_OK
public static final int HTTP_CREATED
public static final int HTTP_ACCEPTED
public static final int HTTP_NOT_AUTHORITATIVE
public static final int HTTP_NO_CONTENT
public static final int HTTP_RESET
public static final int HTTP_PARTIAL
public static final int HTTP_MULT_CHOICE
public static final int HTTP_MOVED_PERM
public static final int HTTP_MOVED_TEMP
public static final int HTTP_SEE_OTHER
public static final int HTTP_NOT_MODIFIED
public static final int HTTP_USE_PROXY
public static final int HTTP_BAD_REQUEST
public static final int HTTP_UNAUTHORIZED
public static final int HTTP_PAYMENT_REQUIRED
public static final int HTTP_FORBIDDEN
public static final int HTTP_NOT_FOUND
public static final int HTTP_BAD_METHOD
public static final int HTTP_NOT_ACCEPTABLE
public static final int HTTP_PROXY_AUTH
public static final int HTTP_CLIENT_TIMEOUT
public static final int HTTP_CONFLICT
public static final int HTTP_GONE
public static final int HTTP_LENGTH_REQUIRED
public static final int HTTP_PRECON_FAILED
public static final int HTTP_ENTITY_TOO_LARGE
public static final int HTTP_REQ_TOO_LONG
public static final int HTTP_UNSUPPORTED_TYPE
@Deprecated public static final int HTTP_SERVER_ERROR
public static final int HTTP_INTERNAL_ERROR
public static final int HTTP_NOT_IMPLEMENTED
public static final int HTTP_BAD_GATEWAY
public static final int HTTP_UNAVAILABLE
public static final int HTTP_GATEWAY_TIMEOUT
public static final int HTTP_VERSION
protected HttpURLConnection(URL u)
u
- the URLpublic String getHeaderFieldKey(int n)
n
th header field.
Some implementations may treat the 0
th
header field as special, i.e. as the status line returned by the HTTP
server. In this case, getHeaderField(0)
returns the status
line, but getHeaderFieldKey(0)
returns null.getHeaderFieldKey
in class URLConnection
n
- an index, where n >=0.n
th header field,
or null
if the key does not exist.public void setFixedLengthStreamingMode(int contentLength)
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.
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.
This method must be called before the URLConnection is connected.
NOTE: setFixedLengthStreamingMode(long)
is recommended
instead of this method as it allows larger content lengths to be set.
contentLength
- The number of bytes which will be written
to the OutputStream.IllegalStateException
- if URLConnection is already connected
or if a different streaming mode is already enabled.IllegalArgumentException
- if a content length less than
zero is specified.setChunkedStreamingMode(int)
public void setFixedLengthStreamingMode(long contentLength)
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.
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.
This method must be called before the URLConnection is connected.
The content length set by invoking this method takes precedence
over any value set by setFixedLengthStreamingMode(int)
.
contentLength
- The number of bytes which will be written to the OutputStream.IllegalStateException
- if URLConnection is already connected or if a different
streaming mode is already enabled.IllegalArgumentException
- if a content length less than zero is specified.public void setChunkedStreamingMode(int chunklen)
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.
This method must be called before the URLConnection is connected.
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.IllegalStateException
- if URLConnection is already connected
or if a different streaming mode is already enabled.setFixedLengthStreamingMode(int)
public String getHeaderField(int n)
n
th header field.
Some implementations may treat the 0
th
header field as special, i.e. as the status line returned by the HTTP
server.
This method can be used in conjunction with the
getHeaderFieldKey
method to iterate through all
the headers in the message.
getHeaderField
in class URLConnection
n
- an index, where n>=0.n
th header field,
or null
if the value does not exist.getHeaderFieldKey(int)
public static void setFollowRedirects(boolean set)
If there is a security manager, this method first calls
the security manager's checkSetFactory
method
to ensure the operation is allowed.
This could result in a SecurityException.
set
- a boolean
indicating whether or not
to follow HTTP redirects.SecurityException
- if a security manager exists and its
checkSetFactory
method doesn't
allow the operation.SecurityManager.checkSetFactory()
,
getFollowRedirects()
public static boolean getFollowRedirects()
boolean
indicating
whether or not HTTP redirects (3xx) should
be automatically followed.true
if HTTP redirects should
be automatically followed, false if not.setFollowRedirects(boolean)
public void setInstanceFollowRedirects(boolean followRedirects)
HttpURLConnection
instance.
The default value comes from followRedirects, which defaults to true.
followRedirects
- a boolean
indicating
whether or not to follow HTTP redirects.instanceFollowRedirects
,
getInstanceFollowRedirects()
public boolean getInstanceFollowRedirects()
HttpURLConnection
's
instanceFollowRedirects
field.HttpURLConnection
's
instanceFollowRedirects
field.instanceFollowRedirects
,
setInstanceFollowRedirects(boolean)
public void setRequestMethod(String method) throws ProtocolException
method
- the HTTP methodProtocolException
- if the method cannot be reset or if
the requested method isn't valid for HTTP.SecurityException
- if a security manager is set and the
method is "TRACE", but the "allowHttpTrace"
NetPermission is not granted.getRequestMethod()
public String getRequestMethod()
setRequestMethod(java.lang.String)
public int getResponseCode() throws IOException
HTTP/1.0 200 OK HTTP/1.0 401 UnauthorizedIt 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).
IOException
- if an error occurred connecting to the server.public String getResponseMessage() throws IOException
HTTP/1.0 200 OK HTTP/1.0 404 Not FoundExtracts the Strings "OK" and "Not Found" respectively. Returns null if none could be discerned from the responses (the result was not valid HTTP).
null
IOException
- if an error occurred connecting to the server.public long getHeaderFieldDate(String name, long Default)
URLConnection
This form of getHeaderField
exists because some
connection types (e.g., http-ng
) have pre-parsed
headers. Classes for that connection type can override this method
and short-circuit the parsing.
getHeaderFieldDate
in class URLConnection
name
- the name of the header field.Default
- a default value.Default
argument is returned if the field is
missing or malformed.public abstract void disconnect()
public abstract boolean usingProxy()
public Permission getPermission() throws IOException
SocketPermission
object representing the
permission necessary to connect to the destination host and port.getPermission
in class URLConnection
SocketPermission
object representing the
permission necessary to connect to the destination
host and port.IOException
- if an error occurs while computing
the permission.public InputStream getErrorStream()
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.