jdk.net.URLConnection — clojure-interop/java.net 1.0.0

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

The connection object is created by invoking the openConnection method on a URL. The setup parameters and general request properties are manipulated. The actual connection to the remote object is made, using the connect method. 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

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.

*get-default-allow-user-interaction? clj

(*get-default-allow-user-interaction?)

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. - boolean

*get-default-request-property clj

(*get-default-request-property key)

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

key - the keyword by which the request is known (e.g., Accept). - java.lang.String

returns: the value of the default request property for the specified key. - java.lang. java.lang.String

*get-file-name-map clj

(*get-file-name-map)

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.

returns: the FileNameMap - java.net.FileNameMap

*guess-content-type-from-name clj

(*guess-content-type-from-name 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.

fname - a filename. - java.lang.String

returns: a guess as to what the content type of the object is, based upon its file name. - java.lang.String

*guess-content-type-from-stream clj

(*guess-content-type-from-stream 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.

is - an input stream that supports marks. - java.io.InputStream

returns: a guess at the content type, or null if none can be determined. - java.lang.String

throws: java.io.IOException - if an I/O error occurs while reading the input stream.

*set-content-handler-factory clj

(*set-content-handler-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.

fac - the desired factory. - java.net.ContentHandlerFactory

throws: java.lang.Error - if the factory has already been defined.

*set-default-allow-user-interaction clj

(*set-default-allow-user-interaction defaultallowuserinteraction)

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

defaultallowuserinteraction - the new value. - boolean

*set-default-request-property clj

(*set-default-request-property key value)

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

key - the keyword by which the request is known (e.g., Accept). - java.lang.String value - the value associated with the key. - java.lang.String

returns: java.lang. void

*set-file-name-map clj

(*set-file-name-map 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.

map - the FileNameMap to be set - java.net.FileNameMap

throws: java.lang.SecurityException - if a security manager exists and its checkSetFactory method doesn't allow the operation.

add-request-property clj

(add-request-property this 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.

key - the keyword by which the request is known (e.g., Accept). - java.lang.String value - the value associated with it. - java.lang.String

throws: java.lang.IllegalStateException - if already connected

connect clj

(connect this)

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: java.net.SocketTimeoutException - if the timeout expires before the connection can be established

get-allow-user-interaction? clj

(get-allow-user-interaction? this)

Returns the value of the allowUserInteraction field for this object.

returns: the value of the allowUserInteraction field for this object. - boolean

get-connect-timeout clj

(get-connect-timeout this)

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 - int

get-content clj

(get-content this)

(get-content this classes)

Retrieves the contents of this URL connection.

classes - the Class array indicating the requested types - java.lang.Class[]

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. - java.lang.Object

throws: java.io.IOException - if an I/O error occurs while getting the content.

get-content-encoding clj

(get-content-encoding this)

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. - java.lang.String

get-content-length clj

(get-content-length this)

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. - int

get-content-length-long clj

(get-content-length-long this)

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. - long

get-content-type clj

(get-content-type this)

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. - java.lang.String

get-date clj

(get-date this)

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. - long

get-default-use-caches? clj

(get-default-use-caches? this)

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. - boolean

get-do-input? clj

(get-do-input? this)

Returns the value of this URLConnection's doInput flag.

returns: the value of this URLConnection's doInput flag. - boolean

get-do-output? clj

(get-do-output? this)

Returns the value of this URLConnection's doOutput flag.

returns: the value of this URLConnection's doOutput flag. - boolean

get-expiration clj

(get-expiration this)

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. - long

get-header-field clj

(get-header-field this 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.

name - the name of a header field. - java.lang.String

returns: the value of the named header field, or null if there is no such field in the header. - java.lang.String

get-header-field-date clj

(get-header-field-date this name 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.

name - the name of the header field. - java.lang.String default - a default value. - long

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. - long

get-header-field-int clj

(get-header-field-int this name 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.

name - the name of the header field. - java.lang.String default - the default value. - int

returns: the value of the named field, parsed as an integer. The Default value is returned if the field is missing or malformed. - int

get-header-field-key clj

(get-header-field-key this n)

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

n - an index, where n>=0 - int

returns: the key for the nth header field, or null if there are fewer than n+1 fields. - java.lang.String

get-header-field-long clj

(get-header-field-long this name 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.

name - the name of the header field. - java.lang.String default - the default value. - long

returns: the value of the named field, parsed as a long. The Default value is returned if the field is missing or malformed. - long

get-header-fields clj

(get-header-fields this)

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 - java.util.Map<java.lang.String,java.util.List<java.lang.String>>

get-if-modified-since clj

(get-if-modified-since this)

Returns the value of this object's ifModifiedSince field.

returns: the value of this object's ifModifiedSince field. - long

get-input-stream clj

(get-input-stream this)

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. - java.io.InputStream

throws: java.io.IOException - if an I/O error occurs while creating the input stream.

get-last-modified clj

(get-last-modified this)

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. - long

get-output-stream clj

(get-output-stream this)

Returns an output stream that writes to this connection.

returns: an output stream that writes to this connection. - java.io.OutputStream

throws: java.io.IOException - if an I/O error occurs while creating the output stream.

get-permission clj

(get-permission this)

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. - java.security.Permission

throws: java.io.IOException - if the computation of the permission requires network or file I/O and an exception occurs while computing it.

get-read-timeout clj

(get-read-timeout this)

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 - int

get-request-properties clj

(get-request-properties this)

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. - java.util.Map<java.lang.String,java.util.List<java.lang.String>>

throws: java.lang.IllegalStateException - if already connected

get-request-property clj

(get-request-property this key)

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

key - the keyword by which the request is known (e.g., Accept). - java.lang.String

returns: the value of the named general request property for this connection. If key is null, then null is returned. - java.lang.String

throws: java.lang.IllegalStateException - if already connected

get-url clj

(get-url this)

Returns the value of this URLConnection's URL field.

returns: the value of this URLConnection's URL field. - java.net.URL

get-use-caches? clj

(get-use-caches? this)

Returns the value of this URLConnection's useCaches field.

returns: the value of this URLConnection's useCaches field. - boolean

set-allow-user-interaction clj

(set-allow-user-interaction this allowuserinteraction)

Set the value of the allowUserInteraction field of this URLConnection.

allowuserinteraction - the new value. - boolean

throws: java.lang.IllegalStateException - if already connected

set-connect-timeout clj

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

timeout - an int that specifies the connect timeout value in milliseconds - int

throws: java.lang.IllegalArgumentException - if the timeout parameter is negative

set-default-use-caches clj

(set-default-use-caches this defaultusecaches)

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

defaultusecaches - the new value. - boolean

set-do-input clj

(set-do-input this 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.

doinput - the new value. - boolean

throws: java.lang.IllegalStateException - if already connected

set-do-output clj

(set-do-output this 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.

dooutput - the new value. - boolean

throws: java.lang.IllegalStateException - if already connected

set-if-modified-since clj

(set-if-modified-since this ifmodifiedsince)

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

ifmodifiedsince - the new value. - long

throws: java.lang.IllegalStateException - if already connected

set-read-timeout clj

(set-read-timeout this 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().

timeout - an int that specifies the timeout value to be used in milliseconds - int

throws: java.lang.IllegalArgumentException - if the timeout parameter is negative

set-request-property clj

(set-request-property this 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-separated list syntax which enables multiple properties to be appended into a single property.

key - the keyword by which the request is known (e.g., Accept). - java.lang.String value - the value associated with it. - java.lang.String

throws: java.lang.IllegalStateException - if already connected

set-use-caches clj

(set-use-caches this 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.

usecaches - a boolean indicating whether or not to allow caching - boolean

throws: java.lang.IllegalStateException - if already connected

to-string clj

(to-string this)

Returns a String representation of this URL connection.

returns: a string representation of this URLConnection. - java.lang.String