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.

Also see:

java.net.URLConnection#getURL()
java.net.URLConnection#url

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.

Also see:

java.net.URLConnection#getDoInput()
java.net.URLConnection#setDoInput(boolean)

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.

Also see:

java.net.URLConnection#getDoOutput()
java.net.URLConnection#setDoOutput(boolean)

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.

Also see:

java.net.URLConnection#getAllowUserInteraction()
java.net.URLConnection#setAllowUserInteraction(boolean)
java.net.URLConnection#setDefaultAllowUserInteraction(boolean)

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.

Also see:

java.net.URLConnection#setUseCaches(boolean)
java.net.URLConnection#getUseCaches()
java.net.URLConnection#setDefaultUseCaches(boolean)

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.

Also see:

java.net.URLConnection#getIfModifiedSince()
java.net.URLConnection#setIfModifiedSince(long)

 protected URLConnection(URL url) 
{
        this.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  void addRequestProperty(String key,
    String value) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        if (key == null)
            throw new NullPointerException ("key is null");
        if (requests == null)
            requests = new MessageHeader();
        requests.add(key, value);
}

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

 abstract public  void connect() throws IOException
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.

 public boolean getAllowUserInteraction() 
{
        return allowUserInteraction;
}

Returns the value of the allowUserInteraction field for this object.

 public int getConnectTimeout() 
{
        return connectTimeout;
}

Returns setting for connect timeout.

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

 public Object getContent() throws IOException 
{
        // Must call getInputStream before GetHeaderField gets called
        // so that FileNotFoundException has a chance to be thrown up
        // from here without being caught.
        getInputStream();
        return getContentHandler().getContent(this);
}

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.

 public Object getContent(Class[] classes) throws IOException 
{
        // Must call getInputStream before GetHeaderField gets called
        // so that FileNotFoundException has a chance to be thrown up
        // from here without being caught.
        getInputStream();
        return getContentHandler().getContent(this, classes);
}

Retrieves the contents of this URL connection.

 public String getContentEncoding() 
{
        return getHeaderField("content-encoding");
}

Returns the value of the content-encoding header field.

 synchronized ContentHandler getContentHandler() throws UnknownServiceException 
{
        String contentType = stripOffParameters(getContentType());
        ContentHandler handler = null;
        if (contentType == null)
            throw new UnknownServiceException("no content-type");
        try {
            handler = (ContentHandler) handlers.get(contentType);
            if (handler != null)
                return handler;
        } catch(Exception e) {
        }
        if (factory != null)
            handler = factory.createContentHandler(contentType);
        if (handler == null) {
            try {
                handler = lookupContentHandlerClassFor(contentType);
            } catch(Exception e) {
                e.printStackTrace();
                handler = UnknownContentHandler.INSTANCE;
            }
            handlers.put(contentType, handler);
        }
        return handler;
}

Gets the Content Handler appropriate for this connection.

 public int getContentLength() 
{
        long l = getContentLengthLong();
        if (l  > Integer.MAX_VALUE)
            return -1;
        return (int) l;
}

Returns the value of the content-length header field.

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

 public long getContentLengthLong() 
{
        return getHeaderFieldLong("content-length", -1);
}

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

 public String getContentType() 
{
        return getHeaderField("content-type");
}

Returns the value of the content-type header field.

 public long getDate() 
{
        return getHeaderFieldDate("date", 0);
}

Returns the value of the date header field.

 public static boolean getDefaultAllowUserInteraction() 
{
        return defaultAllowUserInteraction;
}

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.

 public static String getDefaultRequestProperty(String key) 
{
        return null;
}

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

 public boolean getDefaultUseCaches() 
{
        return defaultUseCaches;
}

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.

 public boolean getDoInput() 
{
        return doInput;
}

Returns the value of this URLConnection's doInput flag.

 public boolean getDoOutput() 
{
        return doOutput;
}

Returns the value of this URLConnection's doOutput flag.

 public long getExpiration() 
{
        return getHeaderFieldDate("expires", 0);
}

Returns the value of the expires header field.

 public static synchronized FileNameMap getFileNameMap() 
{
        if ((fileNameMap == null) && !fileNameMapLoaded) {
            fileNameMap = sun.net.www.MimeTable.loadTable();
            fileNameMapLoaded = true;
        }
        return new FileNameMap() {
            private FileNameMap map = fileNameMap;
            public String getContentTypeFor(String fileName) {
                return map.getContentTypeFor(fileName);
            }
        };
}

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.

 public String getHeaderField(String name) 
{
        return null;
}

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.

 public String getHeaderField(int n) 
{
        return null;
}

Returns the value for the n^th 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.

 public long getHeaderFieldDate(String name,
    long Default) 
{
        String value = getHeaderField(name);
        try {
            return Date.parse(value);
        } catch (Exception e) { }
        return 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.

 public int getHeaderFieldInt(String name,
    int Default) 
{
        String value = getHeaderField(name);
        try {
            return Integer.parseInt(value);
        } catch (Exception e) { }
        return 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.

 public String getHeaderFieldKey(int n) 
{
        return null;
}

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

 public long getHeaderFieldLong(String name,
    long Default) 
{
        String value = getHeaderField(name);
        try {
            return Long.parseLong(value);
        } catch (Exception e) { }
        return 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.

 public Map<String> getHeaderFields() 
{
        return Collections.EMPTY_MAP;
}

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.

 public long getIfModifiedSince() 
{
        return ifModifiedSince;
}

Returns the value of this object's ifModifiedSince field.

 public InputStream getInputStream() throws IOException 
{
        throw new UnknownServiceException("protocol doesn't support input");
}

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.

 public long getLastModified() 
{
        return getHeaderFieldDate("last-modified", 0);
}

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

 public OutputStream getOutputStream() throws IOException 
{
        throw new UnknownServiceException("protocol doesn't support output");
}

Returns an output stream that writes to this connection.

 public Permission getPermission() throws IOException 
{
        return SecurityConstants.ALL_PERMISSION;
}

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.

 public int getReadTimeout() 
{
        return readTimeout;
}

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

 public Map<String> getRequestProperties() 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        if (requests == null)
            return Collections.EMPTY_MAP;
        return requests.getHeaders(null);
}

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.

 public String getRequestProperty(String key) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        if (requests == null)
            return null;
        return requests.findValue(key);
}

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

 public URL getURL() 
{
        return url;
}

Returns the value of this URLConnection's URL field.

 public boolean getUseCaches() 
{
        return useCaches;
}

Returns the value of this URLConnection's useCaches field.

 public static String guessContentTypeFromName(String fname) 
{
        return getFileNameMap().getContentTypeFor(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.

 public static String guessContentTypeFromStream(InputStream is) throws IOException 
{
        // If we can't read ahead safely, just give up on guessing
        if (!is.markSupported())
            return null;
        is.mark(16);
        int c1 = is.read();
        int c2 = is.read();
        int c3 = is.read();
        int c4 = is.read();
        int c5 = is.read();
        int c6 = is.read();
        int c7 = is.read();
        int c8 = is.read();
        int c9 = is.read();
        int c10 = is.read();
        int c11 = is.read();
        int c12 = is.read();
        int c13 = is.read();
        int c14 = is.read();
        int c15 = is.read();
        int c16 = is.read();
        is.reset();
        if (c1 == 0xCA && c2 == 0xFE && c3 == 0xBA && c4 == 0xBE) {
            return "application/java-vm";
        }
        if (c1 == 0xAC && c2 == 0xED) {
            // next two bytes are version number, currently 0x00 0x05
            return "application/x-java-serialized-object";
        }
        if (c1 == '< ') {
            if (c2 == '!'
                || ((c2 == 'h' && (c3 == 't' && c4 == 'm' && c5 == 'l' ||
                                   c3 == 'e' && c4 == 'a' && c5 == 'd') ||
                (c2 == 'b' && c3 == 'o' && c4 == 'd' && c5 == 'y'))) ||
                ((c2 == 'H' && (c3 == 'T' && c4 == 'M' && c5 == 'L' ||
                                c3 == 'E' && c4 == 'A' && c5 == 'D') ||
                (c2 == 'B' && c3 == 'O' && c4 == 'D' && c5 == 'Y')))) {
                return "text/html";
            }
            if (c2 == '?' && c3 == 'x' && c4 == 'm' && c5 == 'l' && c6 == ' ') {
                return "application/xml";
            }
        }
        // big and little (identical) endian UTF-8 encodings, with BOM
        if (c1 == 0xef &&  c2 == 0xbb &&  c3 == 0xbf) {
            if (c4 == '< ' &&  c5 == '?' &&  c6 == 'x') {
                return "application/xml";
            }
        }
        // big and little endian UTF-16 encodings, with byte order mark
        if (c1 == 0xfe && c2 == 0xff) {
            if (c3 == 0 && c4 == '< ' && c5 == 0 && c6 == '?' &&
                c7 == 0 && c8 == 'x') {
                return "application/xml";
            }
        }
        if (c1 == 0xff && c2 == 0xfe) {
            if (c3 == '< ' && c4 == 0 && c5 == '?' && c6 == 0 &&
                c7 == 'x' && c8 == 0) {
                return "application/xml";
            }
        }
        // big and little endian UTF-32 encodings, with BOM
        if (c1 == 0x00 &&  c2 == 0x00 &&  c3 == 0xfe &&  c4 == 0xff) {
            if (c5  == 0 && c6  == 0 && c7  == 0 && c8  == '< ' &&
                c9  == 0 && c10 == 0 && c11 == 0 && c12 == '?' &&
                c13 == 0 && c14 == 0 && c15 == 0 && c16 == 'x') {
                return "application/xml";
            }
        }
        if (c1 == 0xff &&  c2 == 0xfe &&  c3 == 0x00 &&  c4 == 0x00) {
            if (c5  == '< ' && c6  == 0 && c7  == 0 && c8  == 0 &&
                c9  == '?' && c10 == 0 && c11 == 0 && c12 == 0 &&
                c13 == 'x' && c14 == 0 && c15 == 0 && c16 == 0) {
                return "application/xml";
            }
        }
        if (c1 == 'G' && c2 == 'I' && c3 == 'F' && c4 == '8') {
            return "image/gif";
        }
        if (c1 == '#' && c2 == 'd' && c3 == 'e' && c4 == 'f') {
            return "image/x-bitmap";
        }
        if (c1 == '!' && c2 == ' ' && c3 == 'X' && c4 == 'P' &&
                        c5 == 'M' && c6 == '2') {
            return "image/x-pixmap";
        }
        if (c1 == 137 && c2 == 80 && c3 == 78 &&
                c4 == 71 && c5 == 13 && c6 == 10 &&
                c7 == 26 && c8 == 10) {
            return "image/png";
        }
        if (c1 == 0xFF && c2 == 0xD8 && c3 == 0xFF) {
            if (c4 == 0xE0) {
                return "image/jpeg";
            }
            /**
             * File format used by digital cameras to store images.
             * Exif Format can be read by any application supporting
             * JPEG. Exif Spec can be found at:
             * http://www.pima.net/standards/it10/PIMA15740/Exif_2-1.PDF
             */
            if ((c4 == 0xE1) &&
                (c7 == 'E' && c8 == 'x' && c9 == 'i' && c10 =='f' &&
                 c11 == 0)) {
                return "image/jpeg";
            }
            if (c4 == 0xEE) {
                return "image/jpg";
            }
        }
        if (c1 == 0xD0 && c2 == 0xCF && c3 == 0x11 && c4 == 0xE0 &&
            c5 == 0xA1 && c6 == 0xB1 && c7 == 0x1A && c8 == 0xE1) {
            /* Above is signature of Microsoft Structured Storage.
             * Below this, could have tests for various SS entities.
             * For now, just test for FlashPix.
             */
            if (checkfpx(is)) {
                return "image/vnd.fpx";
            }
        }
        if (c1 == 0x2E && c2 == 0x73 && c3 == 0x6E && c4 == 0x64) {
            return "audio/basic";  // .au format, big endian
        }
        if (c1 == 0x64 && c2 == 0x6E && c3 == 0x73 && c4 == 0x2E) {
            return "audio/basic";  // .au format, little endian
        }
        if (c1 == 'R' && c2 == 'I' && c3 == 'F' && c4 == 'F') {
            /* I don't know if this is official but evidence
             * suggests that .wav files start with "RIFF" - brown
             */
            return "audio/x-wav";
        }
        return null;
}

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.

 public  void setAllowUserInteraction(boolean allowuserinteraction) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        allowUserInteraction = allowuserinteraction;
}

Set the value of the allowUserInteraction field of this URLConnection.

 public  void setConnectTimeout(int timeout) 
{
        if (timeout <  0) {
            throw new IllegalArgumentException("timeout can not be negative");
        }
        connectTimeout = 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().

 public static synchronized  void setContentHandlerFactory(ContentHandlerFactory fac) 
{
        if (factory != null) {
            throw new Error("factory already defined");
        }
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkSetFactory();
        }
        factory = 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.

 public static  void setDefaultAllowUserInteraction(boolean defaultallowuserinteraction) 
{
        defaultAllowUserInteraction = defaultallowuserinteraction;
}

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

 public static  void setDefaultRequestProperty(String key,
    String value) 
{

}

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

 public  void setDefaultUseCaches(boolean defaultusecaches) 
{
        defaultUseCaches = defaultusecaches;
}

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

 public  void setDoInput(boolean doinput) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        doInput = 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.

 public  void setDoOutput(boolean dooutput) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        doOutput = 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.

 public static  void setFileNameMap(FileNameMap map) 
{
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) sm.checkSetFactory();
        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.

 public  void setIfModifiedSince(long ifmodifiedsince) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        ifModifiedSince = ifmodifiedsince;
}

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

 public  void setReadTimeout(int timeout) 
{
        if (timeout <  0) {
            throw new IllegalArgumentException("timeout can not be negative");
        }
        readTimeout = 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().

 public  void setRequestProperty(String key,
    String value) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        if (key == null)
            throw new NullPointerException ("key is null");
        if (requests == null)
            requests = new MessageHeader();
        requests.set(key, 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.

 public  void setUseCaches(boolean usecaches) 
{
        if (connected)
            throw new IllegalStateException("Already connected");
        useCaches = 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.

 public String toString() 
{
        return this.getClass().getName() + ":" + url;
}

Returns a String representation of this URL connection.