com.upokecenter.mail.ContentDisposition

# com.upokecenter.mail.ContentDisposition

public class ContentDisposition extends Object

Specifies how a message body should be displayed or handled by a mail user agent. This type is immutable; its contents can't be changed after it's created. To create a changeable disposition object, use the ContentDisposition.Builder class.

About the "filename" parameter

The "filename" parameter of a content disposition suggests a name to use when saving data to a file. For the "filename" parameter, the GetParameter method and Parameters property( getParameters) method in Java) do not adapt that parameter's value using the ContentDisposition.MakeFilename method. Thus, for example, the "filename" parameter, if any, returned by this method could have an arbitrary length, be encoded using RFC 2047 encoded words (which some email and HTTP implementations still like to write out in headers, even though that RFC says encoded words "MUST NOT appear within a 'quoted-string'"; see ContentDisposition.MakeFilename), or not be usable as is as a file name.

Example: An example of RFC 2047 encoded words is:

=?UTF-8?Q?test?=

Content-Disposition header fields like the following have appeared in practice:

Content-Disposition: attachment; filename==?UTF-8?Q?example?=

Content-Disposition: attachment; filename==?UTF-8?Q?test.png?=

Content-Disposition: attachment; filename="=?UTF-8?Q?test.png?="

In this implementation, the first and second of these are syntactically invalid, so they trigger parse errors, while the third of these is syntactically valid, but the "filename" parameter is treated as "=?UTF-8?Q?test.png?=", not "test.png" or something else -- RFC 2047 encoded words are not decoded at the moment a content disposition is parsed (using the Parse method).

Nested Classes

• static final class  ContentDisposition.Builder
  A mutable data type that allows a content disposition to be built.

Fields

• static final ContentDisposition Attachment
  The content disposition value “attachment” .

• static final ContentDisposition Inline
  The content disposition value “inline” .

Methods

• boolean equals(Object obj)
  Determines whether this object and another object are equal.

• int[] GetCreationDate()
  Gets the date and time extracted from this content disposition’s “creation-date” parameter, which specifies the date of creation of a file (RFC 2183 sec.

• final String getDispositionType()
  Gets a string containing this object’s disposition type, such as “inline” or “attachment”.

• String GetFilename()
  Gets an adapted version of the “filename” parameter in this content disposition object by using the “MakeFilename” method.

• int[] GetModificationDate()
  Gets the date and time extracted from this content disposition’s “modification-date” parameter, which specifies the date of last modification of a file (RFC 2183 sec.

• String GetParameter(String name)
  Gets a parameter from this disposition object.

• final Map<String,String> getParameters()
  Gets a list of parameter names associated with this object and their values.

• int[] GetReadDate()
  Gets the date and time extracted from this content disposition’s “read-date” parameter, which specifies the date at which a file was last read (RFC 2183 sec.

• int hashCode()
  Calculates the hash code of this object.

• final boolean isAttachment()
  Gets a value indicating whether the disposition type is attachment.

• final boolean isInline()
  Gets a value indicating whether the disposition type is inline.

• static String MakeFilename(String str)
  Converts a file name from the Content-Disposition header field (or another string representing a title and an optional file extension) to a suitable name for saving data to a file.

• static ContentDisposition Parse(String dispoValue)
  Creates a new content disposition object from the value of a Content-Disposition header field.

• static ContentDisposition Parse(String dispositionValue, ContentDisposition defaultValue)
  Parses a content disposition string and returns a content disposition object, or the default value if the string is invalid.

• String ToSingleLineString()
  Converts this content disposition to a text string form suitable for inserting in HTTP headers.

• String toString()
  Converts this content disposition to a text string form suitable for inserting in email headers.

Field Details

Attachment

public static final ContentDisposition Attachment

The content disposition value “attachment” .

Inline

public static final ContentDisposition Inline

The content disposition value “inline” .

Method Details

getDispositionType

public final String getDispositionType()

Gets a string containing this object’s disposition type, such as “inline” or “attachment”. Note that under RFC 6266 sec. 4.2 and RFC 2183 sec. 2.8, unrecognized disposition types should be treated as “attachment”. (There is no default content disposition in a message has no Content-Disposition header field.) The resulting string will be in lowercase; that is, with its basic uppercase letters (“A” to “Z”) converted to basic lowercase letters (“a” to “z”).

Returns:

• A string containing this object’s disposition type, such as “inline” or “attachment”.

equals

public boolean equals(Object obj)

Determines whether this object and another object are equal.

Overrides:

• equals in class Object

Parameters:

• obj - The parameter obj is an arbitrary object.

Returns:

• true if the objects are equal; otherwise, false. In this method, two objects are not equal if they don’t have the same type or if one is null and the other isn’t.

hashCode

public int hashCode()

Calculates the hash code of this object. The exact algorithm used by this method may change between versions of this library, and no application or process IDs are used in the hash code calculation.

Overrides:

• hashCode in class Object

Returns:

• A 32-bit hash code.

isInline

public final boolean isInline()

Gets a value indicating whether the disposition type is inline.

Returns:

• true If the disposition type is inline; otherwise, false.

isAttachment

public final boolean isAttachment()

Gets a value indicating whether the disposition type is attachment.

Returns:

• true If the disposition type is attachment; otherwise, false.

getParameters

public final Map<String,String> getParameters()

Gets a list of parameter names associated with this object and their values. Each parameter name will be in lowercase; that is, with its basic uppercase letters ("A" to "Z") converted to basic lowercase letters ("a" to "z").

For the "filename" parameter, the value of that parameter is not adapted with the ContentDisposition.MakeFilename method; see the documentation for the ContentDisposition class.

Returns:

• A read-only list of parameter names associated with this object and their values. NOTE: Previous versions erroneously stated that the list will be sorted by name. In fact, the names will not be guaranteed to appear in any particular order; this is at least the case in version 0.10.0.

toString

public String toString()

Converts this content disposition to a text string form suitable for inserting in email headers. Notably, the string contains the value of a Content-Disposition header field (without the text necessarily starting with “Content-Disposition” followed by a space), and consists of one or more lines.

Overrides:

• toString in class Object

Returns:

• A text string form of this content disposition.

ToSingleLineString

public String ToSingleLineString()

Converts this content disposition to a text string form suitable for inserting in HTTP headers. Notably, the string contains the value of a Content-Disposition header field (without the text necessarily starting with “Content-Disposition” followed by a space), and consists of a single line.

Returns:

• A text string form of this content disposition.

MakeFilename

public static String MakeFilename(String str)

Converts a file name from the Content-Disposition header field (or another string representing a title and an optional file extension) to a suitable name for saving data to a file. This method is idempotent; that is, calling the method again on the result doesn't change that result. The method avoids characters and combinations of characters that are problematic to use in certain file systems, and leaves the vast majority of file names seen in practice untouched.

Examples of how this method works follows:

"=?utf-8?q?hello=2Etxt?=" ->"hello.txt" (RFC 2047 encoding).

"=?utf-8?q?long_filename?=" ->"long filename" (RFC 2047 encoding).

"utf-8'en'hello%2Etxt" ->"hello.txt" (RFC 2231 encoding).

"nul.txt" ->"_nul.txt" (Reserved name).

"dir1/dir2/file" ->"dir1_dir2_file" (Directory separators).

Remarks:

• This method should be used only to prepare a file name for the purpose of suggesting a name by which to save data. It should not be used to prepare file names of existing files for the purpose of reading them, since this method may replace certain characters with other characters in some cases, such that two different inputs may map to the same output.
• File Name Support. For recommendations on file name support, see " File Name Support in Applications ".
• Guarantees. The exact file name conversion used by this method is not guaranteed to remain the same between versions of this library, with the exception that the return value will be in normalization form C, will not contain base + slash code points, will not be null, and will be an empty string only if the parameter str is null or empty.

• 'Name' and 'Filename' Parameters. Email and HTTP headers may specify suggested filenames using the Content-Disposition header field's filename parameter or, in practice, the Content-Type header field's name parameter.

  Although RFC 2047 encoded words appearing in both parameters are written out by some implementations, this practice is often discouraged (especially since the RFC itself says that encoded words "MUST NOT appear within a 'quoted-string'"). Nevertheless, the MakeFilename method has a basis in the RFCs to decode RFC 2047 encoded words (and RFC 2231 encoding) in file names passed to this method.

  RFC 2046 sec. 4.5.1 (application/octet-stream subtype in Content-Type header field) cites an earlier RFC 1341, which "defined the use of a 'NAME' parameter which gave a suggested file name to be used if the data were written to a file". Also, RFC 2183 sec. 2.3 (filename parameter in Content-Disposition) confirms that the " suggested filename" in the filename parameter "should be used as a basis for the actual filename, where possible", and that that file name should "not.get(be) blindly use.get(d)". See also RFC 6266, section 4.3, which discusses the use of that parameter in Hypertext Transfer Protocol (HTTP).

  To the extent that the "name" parameter is not allowed in message bodies other than those with the media type "application/octet-stream" or treated as that media type, this is a deviation of RFC 2045 and 2046 (see also RFC 2045 sec. 5, which says that "[t]here are NO globally meaningful parameters that apply to all media types"). (Some email implementations may still write out the "name" parameter, even for media types other than application/octet-stream and even though RFC 2046 has deprecated that parameter.)

.

Parameters:

• str - A string representing a file name. Can be null.

Returns:

• A string with the converted version of the file name. Among other things, encoded words under RFC 2047 are decoded (since they occur so frequently in Content-Disposition filenames); the value is decoded under RFC 2231 if possible; characters unsuitable for use in a filename (including the directory separators slash and backslash) are replaced with underscores; spaces and tabs are collapsed to a single space; leading and trailing spaces and tabs are removed; and the filename is truncated if it would otherwise be too long. Also, for reasons stated in the remarks, a character that is the combined form of a base character and a combining slash is replaced with “!” followed by the base character. The returned string will be in normalization form C. Returns the empty string if str is null or empty.

GetFilename

public String GetFilename()

Gets an adapted version of the “filename” parameter in this content disposition object by using the “MakeFilename” method.

Returns:

• The adapted file name in the form of a string. Returns the empty string if there is no “filename” parameter or that parameter is empty.

GetCreationDate

public int[] GetCreationDate()

Gets the date and time extracted from this content disposition’s “creation-date” parameter, which specifies the date of creation of a file (RFC 2183 sec. 2.4). The parameter is parsed as though by MailDateTime.ParseDateString with obsolete time zones (including “GMT”) allowed. See that method’s documentation for information on the format of this method’s return value.

Returns:

• The extracted date and time as an 8-element array, or null if the “creation-date” parameter doesn’t exist, is an empty string, or is syntactically invalid, or if the parameter’s year would overflow a 32-bit signed integer.

GetModificationDate

public int[] GetModificationDate()

Gets the date and time extracted from this content disposition’s “modification-date” parameter, which specifies the date of last modification of a file (RFC 2183 sec. 2.5). The parameter is parsed as though by MailDateTime.ParseDateString with obsolete time zones (including “GMT”) allowed. See that method’s documentation for information on the format of this method’s return value.

Returns:

• The extracted date and time as an 8-element array, or null if the “modification-date” parameter doesn’t exist, is an empty string, or is syntactically invalid, or if the parameter’s year would overflow a 32-bit signed integer.

GetReadDate

public int[] GetReadDate()

Gets the date and time extracted from this content disposition’s “read-date” parameter, which specifies the date at which a file was last read (RFC 2183 sec. 2.6). The parameter is parsed as though by MailDateTime.ParseDateString with obsolete time zones (including “GMT”) allowed. See that method’s documentation for information on the format of this method’s return value.

Returns:

• The extracted date and time as an 8-element array, or null if the “read-date” parameter doesn’t exist, is an empty string, or is syntactically invalid, or if the parameter’s year would overflow a 32-bit signed integer.

GetParameter

public String GetParameter(String name)

Gets a parameter from this disposition object. For the “filename” parameter, the value of that parameter is not adapted with the ContentDisposition.MakeFilename method; see the documentation for the ContentDisposition class.

Parameters:

• name - The name of the parameter to get. The name will be matched using a basic case-insensitive comparison. (Two strings are equal in such a comparison, if they match after converting the basic uppercase letters A to Z (U+0041 to U+005A) in both strings to basic lowercase letters.). Can’t be null.

Returns:

• The value of the parameter, or null if the parameter does not exist.

Throws:

• NullPointerException - The parameter name is null.

• IllegalArgumentException - The parameter name is empty.

Parse

public static ContentDisposition Parse(String dispoValue)

Creates a new content disposition object from the value of a Content-Disposition header field.

Parameters:

• dispoValue - The parameter dispoValue is a text string.

Returns:

• A content disposition object, or ContentDisposition.Attachment” if dispoValue is empty or syntactically invalid.

Throws:

• NullPointerException - The parameter dispoValue is null.

Parse

public static ContentDisposition Parse(String dispositionValue, ContentDisposition defaultValue)

Parses a content disposition string and returns a content disposition object, or the default value if the string is invalid. This method checks the syntactic validity of the string, but not whether it has all parameters it's required to have or whether the parameters themselves are set to valid values for the parameter.

This method assumes the specified content disposition string was directly extracted from the Content-Disposition header field (as defined for email messages) and follows the syntax given in RFC 2183. Accordingly, among other things, the content disposition string can contain comments (delimited by parentheses).

RFC 2231 extensions allow each content disposition parameter to be associated with a character encoding and/or language, and support parameter values that span two or more key-value pairs. Parameters making use of RFC 2231 extensions have names with an asterisk ("*"). Such a parameter will be ignored if it is ill-formed because of RFC 2231's rules (except for illegal percent-decoding or undecodable sequences for the specified character encoding). Examples of RFC 2231 extensions follow (both examples encode the same "filename" parameter):

inline; filename*=utf-8'en'filename.txt

inline; filename*0*=utf-8'en'file; filename*1*=name%2Etxt

This implementation ignores keys (in parameter key-value pairs) that appear more than once in the content disposition. Nothing in RFCs 2045, 2183, 2231, 6266, or 7231 explicitly disallows such keys, or otherwise specifies error-handling behavior for such keys.

Parameters:

• dispositionValue - A text string that should be the value of a Content-Disposition header field.

• defaultValue - The value to return in case the disposition value is syntactically invalid. Can be null.

Returns:

• A ContentDisposition object.

Throws:

• NullPointerException - The parameter dispositionValue is null.

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