Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class HttpURLConnection - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.net
Class HttpURLConnection

java.lang.Object
  |
  +--java.net.URLConnection
        |
        +--java.net.HttpURLConnection

public abstract class HttpURLConnection
extends URLConnection

A URLConnection with support for HTTP-specific features. See the spec for details.

Since:: JDK1.1

Field Summary

static int HTTP_ACCEPTED


static int HTTP_BAD_GATEWAY


static int HTTP_BAD_METHOD


static int HTTP_BAD_REQUEST
          4XX: client error

static int HTTP_CLIENT_TIMEOUT


static int HTTP_CONFLICT


static int HTTP_CREATED


static int HTTP_ENTITY_TOO_LARGE


static int HTTP_FORBIDDEN


static int HTTP_GATEWAY_TIMEOUT


static int HTTP_GONE


static int HTTP_INTERNAL_ERROR


static int HTTP_LENGTH_REQUIRED


static int HTTP_MOVED_PERM


static int HTTP_MOVED_TEMP


static int HTTP_MULT_CHOICE
          3XX: relocation/redirect

static int HTTP_NO_CONTENT


static int HTTP_NOT_ACCEPTABLE


static int HTTP_NOT_AUTHORITATIVE


static int HTTP_NOT_FOUND


static int HTTP_NOT_MODIFIED


static int HTTP_OK
          2XX: generally "OK"

static int HTTP_PARTIAL


static int HTTP_PAYMENT_REQUIRED


static int HTTP_PRECON_FAILED


static int HTTP_PROXY_AUTH


static int HTTP_REQ_TOO_LONG


static int HTTP_RESET


static int HTTP_SEE_OTHER


static int HTTP_SERVER_ERROR
          5XX: server error

static int HTTP_UNAUTHORIZED


static int HTTP_UNAVAILABLE


static int HTTP_UNSUPPORTED_TYPE


static int HTTP_USE_PROXY


static int HTTP_VERSION


protected String method


protected int responseCode


protected String responseMessage


Fields inherited from class java.net.URLConnection

allowUserInteraction, connected, doInput, doOutput, ifModifiedSince, url, useCaches

Constructor Summary

protected HttpURLConnection(URL u)
          Constructor for the URLStreamHandler.

Method Summary

abstract void disconnect()
          Close the connection to the server.

InputStream getErrorStream()
          Returns the error stream if the connection failed but the server sent useful data nonetheless.

static boolean getFollowRedirects()


Permission getPermission()
          Returns a permission object representing the permission necessary to make the connection represented by this object.

String getRequestMethod()
          Get the request method.

int getResponseCode()
          Gets HTTP response status.

String getResponseMessage()
          Gets the HTTP response message, if any, returned along with the response code from a server.

static void setFollowRedirects(boolean set)
          Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this class.

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.

Methods inherited from class java.net.URLConnection

connect, getAllowUserInteraction, getContent, getContentEncoding, getContentLength, getContentType, getDate, getDefaultAllowUserInteraction, getDefaultRequestProperty, getDefaultUseCaches, getDoInput, getDoOutput, getExpiration, getFileNameMap, getHeaderField, getHeaderField, getHeaderFieldDate, getHeaderFieldInt, getHeaderFieldKey, getIfModifiedSince, getInputStream, getLastModified, getOutputStream, getRequestProperty, getURL, getUseCaches, guessContentTypeFromName, guessContentTypeFromStream, setAllowUserInteraction, setContentHandlerFactory, setDefaultAllowUserInteraction, setDefaultRequestProperty, setDefaultUseCaches, setDoInput, setDoOutput, setFileNameMap, setIfModifiedSince, setRequestProperty, setUseCaches, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

method

protected String method

responseCode

protected int responseCode

responseMessage

protected String responseMessage

HTTP_OK

public static final int HTTP_OK

2XX: generally "OK"

HTTP_CREATED

public static final int HTTP_CREATED

HTTP_ACCEPTED

public static final int HTTP_ACCEPTED

HTTP_NOT_AUTHORITATIVE

public static final int HTTP_NOT_AUTHORITATIVE

HTTP_NO_CONTENT

public static final int HTTP_NO_CONTENT

HTTP_RESET

public static final int HTTP_RESET

HTTP_PARTIAL

public static final int HTTP_PARTIAL

HTTP_MULT_CHOICE

public static final int HTTP_MULT_CHOICE

3XX: relocation/redirect

HTTP_MOVED_PERM

public static final int HTTP_MOVED_PERM

HTTP_MOVED_TEMP

public static final int HTTP_MOVED_TEMP

HTTP_SEE_OTHER

public static final int HTTP_SEE_OTHER

HTTP_NOT_MODIFIED

public static final int HTTP_NOT_MODIFIED

HTTP_USE_PROXY

public static final int HTTP_USE_PROXY

HTTP_BAD_REQUEST

public static final int HTTP_BAD_REQUEST

4XX: client error

HTTP_UNAUTHORIZED

public static final int HTTP_UNAUTHORIZED

HTTP_PAYMENT_REQUIRED

public static final int HTTP_PAYMENT_REQUIRED

HTTP_FORBIDDEN

public static final int HTTP_FORBIDDEN

HTTP_NOT_FOUND

public static final int HTTP_NOT_FOUND

HTTP_BAD_METHOD

public static final int HTTP_BAD_METHOD

HTTP_NOT_ACCEPTABLE

public static final int HTTP_NOT_ACCEPTABLE

HTTP_PROXY_AUTH

public static final int HTTP_PROXY_AUTH

HTTP_CLIENT_TIMEOUT

public static final int HTTP_CLIENT_TIMEOUT

HTTP_CONFLICT

public static final int HTTP_CONFLICT

HTTP_GONE

public static final int HTTP_GONE

HTTP_LENGTH_REQUIRED

public static final int HTTP_LENGTH_REQUIRED

HTTP_PRECON_FAILED

public static final int HTTP_PRECON_FAILED

HTTP_ENTITY_TOO_LARGE

public static final int HTTP_ENTITY_TOO_LARGE

HTTP_REQ_TOO_LONG

public static final int HTTP_REQ_TOO_LONG

HTTP_UNSUPPORTED_TYPE

public static final int HTTP_UNSUPPORTED_TYPE

HTTP_SERVER_ERROR

public static final int HTTP_SERVER_ERROR

5XX: server error

HTTP_INTERNAL_ERROR

public static final int HTTP_INTERNAL_ERROR

HTTP_BAD_GATEWAY

public static final int HTTP_BAD_GATEWAY

HTTP_UNAVAILABLE

public static final int HTTP_UNAVAILABLE

HTTP_GATEWAY_TIMEOUT

public static final int HTTP_GATEWAY_TIMEOUT

HTTP_VERSION

public static final int HTTP_VERSION

Constructor Detail

HttpURLConnection

protected HttpURLConnection(URL u)

Constructor for the URLStreamHandler.

Method Detail

setFollowRedirects

public static void setFollowRedirects(boolean set)

Sets whether HTTP redirects (requests with response code 3xx) should be automatically followed by this class. True by default. Applets cannot change this variable.

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.

Throws:: SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.
See Also:: SecurityManager.checkSetFactory()

getFollowRedirects

public static boolean getFollowRedirects()

setRequestMethod

public void setRequestMethod(String method)
                      throws ProtocolException

Set the method for the URL request, one of:

GET
POST
HEAD
OPTIONS
PUT
DELETE
TRACE

are legal, subject to protocol restrictions. The default method is GET.

Throws:: ProtocolException - if the method cannot be reset or if the requested method isn't valid for HTTP.

getRequestMethod

public String getRequestMethod()

Get the request method.

getResponseCode

public int getResponseCode()
                    throws IOException

Gets HTTP response status. From responses like:

 HTTP/1.0 200 OK
 HTTP/1.0 401 Unauthorized

Extracts the ints 200 and 401 respectively. Returns -1 if none can be discerned from the response (i.e., the response is not valid HTTP).

Throws:: IOException - if an error occurred connecting to the server.

getResponseMessage

public String getResponseMessage()
                          throws IOException

Gets the HTTP response message, if any, returned along with the response code from a server. From responses like:

 HTTP/1.0 200 OK
 HTTP/1.0 404 Not Found

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.

disconnect

public abstract void disconnect()

Close the connection to the server.

usingProxy

public abstract boolean usingProxy()

Indicates if the connection is going through a proxy.

getPermission

public Permission getPermission()
                         throws IOException

Description copied from class: URLConnection

Returns a permission object representing the permission necessary to make the connection represented by this object. This method returns null if no permission is required to make the connection. By default, this method returns java.security.AllPermission. Subclasses should override this method and return the permission that best represents the permission required to make a a connection to the URL. For example, a URLConnection representing a file: URL would return a java.io.FilePermission object.

The permission returned may dependent upon the state of the connection. For example, the permission before connecting may be different from that after connecting. For example, an HTTP sever, say foo.com, may redirect the connection to a different host, say bar.com. Before connecting the permission returned by the connection will represent the permission needed to connect to foo.com, while the permission returned after connecting will be to bar.com.

Permissions are generally used for two purposes: to protect caches of objects obtained through URLConnections, and to check the right of a recipient to learn about a particular URL. In the first case, the permission should be obtained after the object has been obtained. For example, in an HTTP connection, this will represent the permission to connect to the host from which the data was ultimately fetched. In the second case, the permission should be obtained and tested before connecting.

Overrides:: getPermission in class URLConnection

Tags copied from class: URLConnection

Returns:: the permission object representing the permission necessary to make the connection represented by this URLConnection.
Throws:: IOException - if the computation of the permission requires network or file I/O and an exception occurs while computing it.

getErrorStream

public InputStream getErrorStream()

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.

This method will not cause a connection to be initiated. If there the connection was not connected, or if the server did not have an error while connecting or if the server did have an error but there no error data was sent, this method will return null. This is the default.

Returns:: an error stream if any, null if there have been no errors, the connection is not connected or the server sent no useful data.