URLConnection

public abstract class URLConnection extends Object
Known Direct Subclasses
Known Indirect Subclasses

The abstract class URLConnection is the superclass of all classes that represent a communications link between the application and a URL. Instances of this class can be used both to read from and to write to the resource referenced by the URL. In general, creating a connection to a URL is a multistep process:

openConnection() connect()
Manipulate parameters that affect the connection to the remote resource. Interact with the resource; query header fields and contents.
---------------------------->
time
  1. The connection object is created by invoking the openConnection method on a URL.
  2. The setup parameters and general request properties are manipulated.
  3. The actual connection to the remote object is made, using the connect method.
  4. The remote object becomes available. The header fields and the contents of the remote object can be accessed.

The setup parameters are modified using the following methods:

  • setAllowUserInteraction
  • setDoInput
  • setDoOutput
  • setIfModifiedSince
  • setUseCaches

and the general request properties are modified using the method:

  • setRequestProperty

Default values for the AllowUserInteraction and UseCaches parameters can be set using the methods setDefaultAllowUserInteraction and setDefaultUseCaches.

Each of the above set methods has a corresponding get method to retrieve the value of the parameter or general request property. The specific parameters and general request properties that are applicable are protocol specific.

The following methods are used to access the header fields and the contents after the connection is made to the remote object:

  • getContent
  • getHeaderField
  • getInputStream
  • getOutputStream

Certain header fields are accessed frequently. The methods:

  • getContentEncoding
  • getContentLength
  • getContentType
  • getDate
  • getExpiration
  • getLastModifed

provide convenient access to these fields. The getContentType method is used by the getContent method to determine the type of the remote object; subclasses may find it convenient to override the getContentType method.

In the common case, all of the pre-connection parameters and general request properties can be ignored: the pre-connection parameters and request properties default to sensible values. For most clients of this interface, there are only two interesting methods: getInputStream and getContent, which are mirrored in the URL class by convenience methods.

More information on the request properties and header fields of an http connection can be found at:

 http://www.ietf.org/rfc/rfc2616.txt
 
Note about fileNameMap: In versions prior to JDK 1.1.6, field fileNameMap of URLConnection was public. In JDK 1.1.6 and later, fileNameMap is private; accessor and mutator methods getFileNameMap and setFileNameMap are added to access it. This change is also described on the Compatibility page. Invoking the close() methods on the InputStream or OutputStream of an URLConnection after a request may free network resources associated with this instance, unless particular protocol specifications specify different behaviours for it.

Field Summary

protected boolean allowUserInteraction If true, this URL is being examined in a context in which it makes sense to allow user interactions such as popping up an authentication dialog.
protected boolean connected If false, this connection object has not created a communications link to the specified URL.
protected boolean doInput This variable is set by the setDoInput method.
protected boolean doOutput This variable is set by the setDoOutput method.
protected long ifModifiedSince Some protocols support skipping the fetching of the object unless the object has been modified more recently than a certain time.
protected URL url The URL represents the remote object on the World Wide Web to which this connection is opened.
protected boolean useCaches If true, the protocol is allowed to use caching whenever it can.

Protected Constructor Summary

URLConnection(URL url)
Constructs a URL connection to the specified URL.

Public Method Summary

void
addRequestProperty(String key, String value)
Adds a general request property specified by a key-value pair.
abstract void
connect()
Opens a communications link to the resource referenced by this URL, if such a connection has not already been established.
boolean
getAllowUserInteraction()
Returns the value of the allowUserInteraction field for this object.
int
getConnectTimeout()
Returns setting for connect timeout.
Object
getContent()
Retrieves the contents of this URL connection.
Object
getContent(Class[] classes)
Retrieves the contents of this URL connection.
String
getContentEncoding()
Returns the value of the content-encoding header field.
int
getContentLength()
Returns the value of the content-length header field.
long
getContentLengthLong()
Returns the value of the content-length header field as a long.
String
getContentType()
Returns the value of the content-type header field.
long
getDate()
Returns the value of the date header field.
static boolean
getDefaultAllowUserInteraction()
Returns the default value of the allowUserInteraction field.
static String
getDefaultRequestProperty(String key)
This method was deprecated. The instance specific getRequestProperty method should be used after an appropriate instance of URLConnection is obtained.
boolean
getDefaultUseCaches()
Returns the default value of a URLConnection's useCaches flag.
boolean
getDoInput()
Returns the value of this URLConnection's doInput flag.
boolean
getDoOutput()
Returns the value of this URLConnection's doOutput flag.
long
getExpiration()
Returns the value of the expires header field.
synchronized static FileNameMap
getFileNameMap()
Loads filename map (a mimetable) from a data file.
String
getHeaderField(String name)
Returns the value of the named header field.
String
getHeaderField(int n)
Returns the value for the nth header field.
long
getHeaderFieldDate(String name, long Default)
Returns the value of the named field parsed as date.
int
getHeaderFieldInt(String name, int Default)
Returns the value of the named field parsed as a number.
String
getHeaderFieldKey(int n)
Returns the key for the nth header field.
long
getHeaderFieldLong(String name, long Default)
Returns the value of the named field parsed as a number.
Map<StringList<String>>
getHeaderFields()
Returns an unmodifiable Map of the header fields.
long
getIfModifiedSince()
Returns the value of this object's ifModifiedSince field.
InputStream
getInputStream()
Returns an input stream that reads from this open connection.
long
getLastModified()
Returns the value of the last-modified header field.
OutputStream
getOutputStream()
Returns an output stream that writes to this connection.
Permission
getPermission()
Returns a permission object representing the permission necessary to make the connection represented by this object.
int
getReadTimeout()
Returns setting for read timeout.
Map<StringList<String>>
getRequestProperties()
Returns an unmodifiable Map of general request properties for this connection.
String
getRequestProperty(String key)
Returns the value of the named general request property for this connection.
URL
getURL()
Returns the value of this URLConnection's URL field.
boolean
getUseCaches()
Returns the value of this URLConnection's useCaches field.
static String
guessContentTypeFromName(String fname)
Tries to determine the content type of an object, based on the specified "file" component of a URL.
static String
guessContentTypeFromStream(InputStream is)
Tries to determine the type of an input stream based on the characters at the beginning of the input stream.
void
setAllowUserInteraction(boolean allowuserinteraction)
Set the value of the allowUserInteraction field of this URLConnection.
void
setConnectTimeout(int timeout)
Sets a specified timeout value, in milliseconds, to be used when opening a communications link to the resource referenced by this URLConnection.
synchronized static void
setContentHandlerFactory(ContentHandlerFactory fac)
Sets the ContentHandlerFactory of an application.
static void
setDefaultAllowUserInteraction(boolean defaultallowuserinteraction)
Sets the default value of the allowUserInteraction field for all future URLConnection objects to the specified value.
static void
setDefaultRequestProperty(String key, String value)
This method was deprecated. The instance specific setRequestProperty method should be used after an appropriate instance of URLConnection is obtained. Invoking this method will have no effect.
void
setDefaultUseCaches(boolean defaultusecaches)
Sets the default value of the useCaches field to the specified value.
void
setDoInput(boolean doinput)
Sets the value of the doInput field for this URLConnection to the specified value.
void
setDoOutput(boolean dooutput)
Sets the value of the doOutput field for this URLConnection to the specified value.
static void
setFileNameMap(FileNameMap map)
Sets the FileNameMap.
void
setIfModifiedSince(long ifmodifiedsince)
Sets the value of the ifModifiedSince field of this URLConnection to the specified value.
void
setReadTimeout(int timeout)
Sets the read timeout to a specified timeout, in milliseconds.
void
setRequestProperty(String key, String value)
Sets the general request property.
void
setUseCaches(boolean usecaches)
Sets the value of the useCaches field of this URLConnection to the specified value.
String
toString()
Returns a String representation of this URL connection.

Inherited Method Summary

Fields

protected boolean allowUserInteraction

If true, this URL is being examined in a context in which it makes sense to allow user interactions such as popping up an authentication dialog. If false, then no user interaction is allowed.

The value of this field can be set by the setAllowUserInteraction method. Its value is returned by the getAllowUserInteraction method. Its default value is the value of the argument in the last invocation of the setDefaultAllowUserInteraction method.

protected boolean connected

If false, this connection object has not created a communications link to the specified URL. If true, the communications link has been established.

protected boolean doInput

This variable is set by the setDoInput method. Its value is returned by the getDoInput method.

A URL connection can be used for input and/or output. Setting the doInput flag to true indicates that the application intends to read data from the URL connection.

The default value of this field is true.

protected boolean doOutput

This variable is set by the setDoOutput method. Its value is returned by the getDoOutput method.

A URL connection can be used for input and/or output. Setting the doOutput flag to true indicates that the application intends to write data to the URL connection.

The default value of this field is false.

protected long ifModifiedSince

Some protocols support skipping the fetching of the object unless the object has been modified more recently than a certain time.

A nonzero value gives a time as the number of milliseconds since January 1, 1970, GMT. The object is fetched only if it has been modified more recently than that time.

This variable is set by the setIfModifiedSince method. Its value is returned by the getIfModifiedSince method.

The default value of this field is 0, indicating that the fetching must always occur.

protected URL url

The URL represents the remote object on the World Wide Web to which this connection is opened.

The value of this field can be accessed by the getURL method.

The default value of this variable is the value of the URL argument in the URLConnection constructor.

See Also

protected boolean useCaches

If true, the protocol is allowed to use caching whenever it can. If false, the protocol must always try to get a fresh copy of the object.

This field is set by the setUseCaches method. Its value is returned by the getUseCaches method.

Its default value is the value given in the last invocation of the setDefaultUseCaches method.

Protected Constructors

protected URLConnection (URL url)

Constructs a URL connection to the specified URL. A connection to the object referenced by the URL is not created.

Parameters
url the specified URL.

Public Methods

public void addRequestProperty (String key, String value)

Adds a general request property specified by a key-value pair. This method will not overwrite existing values associated with the same key.

Parameters
key the keyword by which the request is known (e.g., "Accept").
value the value associated with it.
Throws
IllegalStateException if already connected
NullPointerException if key is null

public abstract void connect ()

Opens a communications link to the resource referenced by this URL, if such a connection has not already been established.

If the connect method is called when the connection has already been opened (indicated by the connected field having the value true), the call is ignored.

URLConnection objects go through two phases: first they are created, then they are connected. After being created, and before being connected, various options can be specified (e.g., doInput and UseCaches). After connecting, it is an error to try to set them. Operations that depend on being connected, like getContentLength, will implicitly perform the connection, if necessary.

Throws
SocketTimeoutException if the timeout expires before the connection can be established
IOException if an I/O error occurs while opening the connection.

public boolean getAllowUserInteraction ()

Returns the value of the allowUserInteraction field for this object.

Returns
  • the value of the allowUserInteraction field for this object.

public int getConnectTimeout ()

Returns setting for connect timeout.

0 return implies that the option is disabled (i.e., timeout of infinity).

Returns
  • an int that indicates the connect timeout value in milliseconds

public Object getContent ()

Retrieves the contents of this URL connection.

This method first determines the content type of the object by calling the getContentType method. If this is the first time that the application has seen that specific content type, a content handler for that content type is created:

  1. If the application has set up a content handler factory instance using the setContentHandlerFactory method, the createContentHandler method of that instance is called with the content type as an argument; the result is a content handler for that content type.
  2. If no content handler factory has yet been set up, or if the factory's createContentHandler method returns null, then the application loads the class named:
             sun.net.www.content.<contentType>
         
    where <contentType> is formed by taking the content-type string, replacing all slash characters with a period ('.'), and all other non-alphanumeric characters with the underscore character '_'. The alphanumeric characters are specifically the 26 uppercase ASCII letters 'A' through 'Z', the 26 lowercase ASCII letters 'a' through 'z', and the 10 ASCII digits '0' through '9'. If the specified class does not exist, or is not a subclass of ContentHandler, then an UnknownServiceException is thrown.

Returns
  • the object fetched. The instanceof operator should be used to determine the specific kind of object returned.
Throws
IOException if an I/O error occurs while getting the content.
UnknownServiceException if the protocol does not support the content type.

public Object getContent (Class[] classes)

Retrieves the contents of this URL connection.

Parameters
classes the Class array indicating the requested types
Returns
  • the object fetched that is the first match of the type specified in the classes array. null if none of the requested types are supported. The instanceof operator should be used to determine the specific kind of object returned.
Throws
IOException if an I/O error occurs while getting the content.
UnknownServiceException if the protocol does not support the content type.

public String getContentEncoding ()

Returns the value of the content-encoding header field.

Returns
  • the content encoding of the resource that the URL references, or null if not known.

public int getContentLength ()

Returns the value of the content-length header field.

Note: getContentLengthLong() should be preferred over this method, since it returns a long instead and is therefore more portable.

Returns
  • the content length of the resource that this connection's URL references, -1 if the content length is not known, or if the content length is greater than Integer.MAX_VALUE.

public long getContentLengthLong ()

Returns the value of the content-length header field as a long.

Returns
  • the content length of the resource that this connection's URL references, or -1 if the content length is not known.

public String getContentType ()

Returns the value of the content-type header field.

Returns
  • the content type of the resource that the URL references, or null if not known.

public long getDate ()

Returns the value of the date header field.

Returns
  • the sending date of the resource that the URL references, or 0 if not known. The value returned is the number of milliseconds since January 1, 1970 GMT.

public static boolean getDefaultAllowUserInteraction ()

Returns the default value of the allowUserInteraction field.

Ths default is "sticky", being a part of the static state of all URLConnections. This flag applies to the next, and all following URLConnections that are created.

Returns
  • the default value of the allowUserInteraction field.

public static String getDefaultRequestProperty (String key)

This method was deprecated.
The instance specific getRequestProperty method should be used after an appropriate instance of URLConnection is obtained.

Returns the value of the default request property. Default request properties are set for every connection.

Parameters
key the keyword by which the request is known (e.g., "Accept").
Returns
  • the value of the default request property for the specified key.

public boolean getDefaultUseCaches ()

Returns the default value of a URLConnection's useCaches flag.

Ths default is "sticky", being a part of the static state of all URLConnections. This flag applies to the next, and all following URLConnections that are created.

Returns
  • the default value of a URLConnection's useCaches flag.

public boolean getDoInput ()

Returns the value of this URLConnection's doInput flag.

Returns
  • the value of this URLConnection's doInput flag.

public boolean getDoOutput ()

Returns the value of this URLConnection's doOutput flag.

Returns
  • the value of this URLConnection's doOutput flag.

public long getExpiration ()

Returns the value of the expires header field.

Returns
  • the expiration date of the resource that this URL references, or 0 if not known. The value is the number of milliseconds since January 1, 1970 GMT.

public static synchronized FileNameMap getFileNameMap ()

Loads filename map (a mimetable) from a data file. It will first try to load the user-specific table, defined by "content.types.user.table" property. If that fails, it tries to load the default built-in table at lib/content-types.properties under java home.

Returns
  • the FileNameMap

public String getHeaderField (String name)

Returns the value of the named header field.

If called on a connection that sets the same header multiple times with possibly different values, only the last value is returned.

Parameters
name the name of a header field.
Returns
  • the value of the named header field, or null if there is no such field in the header.

public String getHeaderField (int n)

Returns the value for the nth header field. It returns null if there are fewer than n+1fields.

This method can be used in conjunction with the getHeaderFieldKey method to iterate through all the headers in the message.

Parameters
n an index, where n>=0
Returns
  • the value of the nth header field or null if there are fewer than n+1 fields

public long getHeaderFieldDate (String name, long Default)

Returns the value of the named field parsed as date. The result is the number of milliseconds since January 1, 1970 GMT represented by the named field.

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.

Parameters
name the name of the header field.
Default a default value.
Returns
  • the value of the field, parsed as a date. The value of the Default argument is returned if the field is missing or malformed.

public int getHeaderFieldInt (String name, int Default)

Returns the value of the named field parsed as a number.

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.

Parameters
name the name of the header field.
Default the default value.
Returns
  • the value of the named field, parsed as an integer. The Default value is returned if the field is missing or malformed.

public String getHeaderFieldKey (int n)

Returns the key for the nth header field. It returns null if there are fewer than n+1 fields.

Parameters
n an index, where n>=0
Returns
  • the key for the nth header field, or null if there are fewer than n+1 fields.

public long getHeaderFieldLong (String name, long Default)

Returns the value of the named field parsed as a number.

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.

Parameters
name the name of the header field.
Default the default value.
Returns
  • the value of the named field, parsed as a long. The Default value is returned if the field is missing or malformed.

public Map<StringList<String>> getHeaderFields ()

Returns an unmodifiable Map of the header fields. The Map keys are Strings that represent the response-header field names. Each Map value is an unmodifiable List of Strings that represents the corresponding field values.

Returns
  • a Map of header fields

public long getIfModifiedSince ()

Returns the value of this object's ifModifiedSince field.

Returns
  • the value of this object's ifModifiedSince field.

public InputStream getInputStream ()

Returns an input stream that reads from this open connection. A SocketTimeoutException can be thrown when reading from the returned input stream if the read timeout expires before data is available for read.

Returns
  • an input stream that reads from this open connection.
Throws
IOException if an I/O error occurs while creating the input stream.
UnknownServiceException if the protocol does not support input.

public long getLastModified ()

Returns the value of the last-modified header field. The result is the number of milliseconds since January 1, 1970 GMT.

Returns
  • the date the resource referenced by this URLConnection was last modified, or 0 if not known.

public OutputStream getOutputStream ()

Returns an output stream that writes to this connection.

Returns
  • an output stream that writes to this connection.
Throws
IOException if an I/O error occurs while creating the output stream.
UnknownServiceException if the protocol does not support output.

public Permission getPermission ()

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.

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.

public int getReadTimeout ()

Returns setting for read timeout. 0 return implies that the option is disabled (i.e., timeout of infinity).

Returns
  • an int that indicates the read timeout value in milliseconds

public Map<StringList<String>> getRequestProperties ()

Returns an unmodifiable Map of general request properties for this connection. The Map keys are Strings that represent the request-header field names. Each Map value is a unmodifiable List of Strings that represents the corresponding field values.

Returns
  • a Map of the general request properties for this connection.
Throws
IllegalStateException if already connected

public String getRequestProperty (String key)

Returns the value of the named general request property for this connection.

Parameters
key the keyword by which the request is known (e.g., "Accept").
Returns
  • the value of the named general request property for this connection. If key is null, then null is returned.
Throws
IllegalStateException if already connected

public URL getURL ()

Returns the value of this URLConnection's URL field.

Returns
  • the value of this URLConnection's URL field.
See Also

public boolean getUseCaches ()

Returns the value of this URLConnection's useCaches field.

Returns
  • the value of this URLConnection's useCaches field.

public static String guessContentTypeFromName (String fname)

Tries to determine the content type of an object, based on the specified "file" component of a URL. This is a convenience method that can be used by subclasses that override the getContentType method.

Parameters
fname a filename.
Returns
  • a guess as to what the content type of the object is, based upon its file name.
See Also

public static String guessContentTypeFromStream (InputStream is)

Tries to determine the type of an input stream based on the characters at the beginning of the input stream. This method can be used by subclasses that override the getContentType method.

Ideally, this routine would not be needed. But many http servers return the incorrect content type; in addition, there are many nonstandard extensions. Direct inspection of the bytes to determine the content type is often more accurate than believing the content type claimed by the http server.

Parameters
is an input stream that supports marks.
Returns
  • a guess at the content type, or null if none can be determined.
Throws
IOException if an I/O error occurs while reading the input stream.

public void setAllowUserInteraction (boolean allowuserinteraction)

Set the value of the allowUserInteraction field of this URLConnection.

Parameters
allowuserinteraction the new value.
Throws
IllegalStateException if already connected

public void setConnectTimeout (int timeout)

Sets a specified timeout value, in milliseconds, to be used when opening a communications link to the resource referenced by this URLConnection. If the timeout expires before the connection can be established, a java.net.SocketTimeoutException is raised. A timeout of zero is interpreted as an infinite timeout.

Some non-standard implmentation of this method may ignore the specified timeout. To see the connect timeout set, please call getConnectTimeout().

Parameters
timeout an int that specifies the connect timeout value in milliseconds
Throws
IllegalArgumentException if the timeout parameter is negative

public static synchronized void setContentHandlerFactory (ContentHandlerFactory fac)

Sets the ContentHandlerFactory of an application. It can be called at most once by an application.

The ContentHandlerFactory instance is used to construct a content handler from a content type

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.

Parameters
fac the desired factory.
Throws
Error if the factory has already been defined.
SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.

public static void setDefaultAllowUserInteraction (boolean defaultallowuserinteraction)

Sets the default value of the allowUserInteraction field for all future URLConnection objects to the specified value.

Parameters
defaultallowuserinteraction the new value.

public static void setDefaultRequestProperty (String key, String value)

This method was deprecated.
The instance specific setRequestProperty method should be used after an appropriate instance of URLConnection is obtained. Invoking this method will have no effect.

Sets the default value of a general request property. When a URLConnection is created, it is initialized with these properties.

Parameters
key the keyword by which the request is known (e.g., "Accept").
value the value associated with the key.

public void setDefaultUseCaches (boolean defaultusecaches)

Sets the default value of the useCaches field to the specified value.

Parameters
defaultusecaches the new value.

public void setDoInput (boolean doinput)

Sets the value of the doInput field for this URLConnection to the specified value.

A URL connection can be used for input and/or output. Set the DoInput flag to true if you intend to use the URL connection for input, false if not. The default is true.

Parameters
doinput the new value.
Throws
IllegalStateException if already connected

public void setDoOutput (boolean dooutput)

Sets the value of the doOutput field for this URLConnection to the specified value.

A URL connection can be used for input and/or output. Set the DoOutput flag to true if you intend to use the URL connection for output, false if not. The default is false.

Parameters
dooutput the new value.
Throws
IllegalStateException if already connected
See Also

public static void setFileNameMap (FileNameMap map)

Sets the FileNameMap.

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.

Parameters
map the FileNameMap to be set
Throws
SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.

public void setIfModifiedSince (long ifmodifiedsince)

Sets the value of the ifModifiedSince field of this URLConnection to the specified value.

Parameters
ifmodifiedsince the new value.
Throws
IllegalStateException if already connected

public void setReadTimeout (int timeout)

Sets the read timeout to a specified timeout, in milliseconds. A non-zero value specifies the timeout when reading from Input stream when a connection is established to a resource. If the timeout expires before there is data available for read, a java.net.SocketTimeoutException is raised. A timeout of zero is interpreted as an infinite timeout.

Some non-standard implementation of this method ignores the specified timeout. To see the read timeout set, please call getReadTimeout().

Parameters
timeout an int that specifies the timeout value to be used in milliseconds
Throws
IllegalArgumentException if the timeout parameter is negative

public void setRequestProperty (String key, String value)

Sets the general request property. If a property with the key already exists, overwrite its value with the new value.

NOTE: HTTP requires all request properties which can legally have multiple instances with the same key to use a comma-seperated list syntax which enables multiple properties to be appended into a single property.

Parameters
key the keyword by which the request is known (e.g., "Accept").
value the value associated with it.
Throws
IllegalStateException if already connected
NullPointerException if key is null

public void setUseCaches (boolean usecaches)

Sets the value of the useCaches field of this URLConnection to the specified value.

Some protocols do caching of documents. Occasionally, it is important to be able to "tunnel through" and ignore the caches (e.g., the "reload" button in a browser). If the UseCaches flag on a connection is true, the connection is allowed to use whatever caches it can. If false, caches are to be ignored. The default value comes from DefaultUseCaches, which defaults to true.

Parameters
usecaches a boolean indicating whether or not to allow caching
Throws
IllegalStateException if already connected
See Also

public String toString ()

Returns a String representation of this URL connection.

Returns
  • a string representation of this URLConnection.