URIs, MIMEs, & URI Processing on Android

Vladimir Kulyukin

www.vkedco.blogspot.com

Outline● Uniform Resource Identifiers (URIs)● Multipurpose Internet Mail Extensions (MIMEs)● URI Processing on Android

URI Elements URI Matching Codes & Mimes Matching URIs

Non-Standard MIME Subtypes on Android

● A Content provider must list which columns it supports● There is no standard way of listing columns● Typical methods of listing columns:

Constants and documentation Interfaces and documentation

● Documentation or naming conventions should be used to indicate column types, because there is no formal way to indicate column types

Uniform Resource Identifiers

Uniform Resource Identifier (URI)● A URI is a string of characters that identifies a resource● Uniform – means that different types of resource identifiers can

be used in the same context even when their access mechanisms are different

● Resource – means anything that has an identity (e.g., a document, an image, a service)

● Identifier – means that it is a reference to a resource with an identity (e.g., a sequence of characters with specific syntactic restrictions)

Common Abbreviations: URI, URL, URN

● URL – Uniform Resource Locator● URN – Uniform Resource Name● Although the terms URI, URL, & URN are frequently used

interchangeably, URL and URN are technically subsets of URI● URL is the subset of URIs that identify resources via their

primary access mechanisms (aka protocols) (http, ftp, gopher, etc.)

● URN is the subset of URIs that are required to remain globally unique and persistent (even when the resources cease to exist)

URI Examples

● ftp://ftp.org.sample/rfc/rfc1001.txt● gopher://univ.edu/classes/cs● http://some_server:8080/public/home.html● telnet://my_company.net/● mailto:user12345@gmail.com● news:comp.infosystems.www.servers.unix

Hierarchical & Relative URIs● Absolute URI refers to a resource

regardless of the context in which it is used● Relative URI refers to a resource within a

specific namespace (e.g., absolute vs. relative file paths)

● Some URI schemes support hierarchical naming systems

● URI naming hierarchies use the “/” delimiters

Generic URI Syntax

<scheme>://<authority><path>?<query>

Example 01

● ftp://org.vkedco.mobappdev/resources/README.txt ● SCHEME: ftp● AUTHORITY: org.vkedco.mobappdev● PATH: /resources/README.txt● PATH_SEGMENTS: resources; README.txt● PORT: -1 // not specified so defaults to -1● QUERY: null // not specified so defaults to null

Example 02content://org.vkedco.mobappdev.content_providers.books/book_title/id

● SCHEME: content● AUTHORITY: org.vkedco.mobappdev.content_providers.books● PATH: /book_title/id● PATH_SEGMENTS: book_title; id● PORT: -1 // not specified, defaults to -1● QUERY: null // not specified, defaults to null

Example 03content://org.vkedco.mobappdev.content_providers.books/book_title/id/10

● SCHEME: content● AUTHORITY: org.vkedco.mobappdev.content_providers.books

● PATH: /book_title/id/10● PATH_SEGMENTS: book_title; id ; 10● PORT: -1● QUERY: null

Example 04content://org.vkedco.mobappdev.content_providers.books/book_title?title=essential_rumi

● SCHEME: content● AUTHORITY: org.vkedco.mobappdev.content_providers.books

● PATH: /book_title● PATH_SEGMENTS: book_title● PORT: -1● QUERY: title=essential_rumi

Example 05http://vkedco_content_server:8080/book_title?title=essential_rumi&author=rumi

● SCHEME: http● AUTHORITY: vkedco_content_server:8080

● PATH: /book_title● PATH_SEGMENTS: book_title● PORT: 8080● QUERY: title=essential_rumi&author=rumi

URI Member Access

<scheme>://<authority><path>?<query>

● Uri.getScheme()● Uri.getAuthority()● Uri.getPath()● Uri.getPathSegments()● Uri.getPort()● Uri.getQuery()● Uri.getQueryParameter()

Getting URI ElementsString getUriInfo(Uri uri) {

StringBuilder sb = new StringBuilder(""); sb.append("URI: " + uri.toString() + "\n");

sb.append("SCHEME: " + uri.getScheme() + "\n"); sb.append("AUTHORITY: " + uri.getAuthority() + "\n");

sb.append("PATH=" + uri.getPath() + "\n"); sb.append("PATH SEGMENTS:\n");

List<String> pathSegments = uri.getPathSegments();

for(int i = 0; i < pathSegments.size(); i++) {

sb.append("path_sgmnt[" + i + "]=" + pathSegments.get(i) + "\n");

}

sb.append("PORT: " + uri.getPort() + "\n");

sb.append("QUERY: " + uri.getQuery() + "\n");

sb.append("TITLE_PARAM: " + uri.getQueryParameter("title") + "\n");

sb.append("AUTHOR_PARAM: " + uri.getQueryParameter("author") + "\n");

return sb.toString();

}

URI Design Criteria● URI should be a sequence of characters and not always

a sequence of octets (in CS, octet is a sequence of 8 bits, aka byte)

● URI may be transcribed from a non-network source and should consist of characters sensitive to constraints imposed by keyboards and locales

● URI should be remembered by people (should have meaningful components)

URI Design Steps● Choose the scheme, e.g., content, http, etc.● Design an authority● Design MIMEs (Multipurpose Internet Mail Extensions)

or use existing ones● Design match codes to manage uri matching● Use UriMatcher objects to add and match URIs

Logical URI Matching Steps● Publish Authority & Paths● Publish URI Matching Codes● Publish Mimes● Create a UriMatcher and add to it a URI described as

a triple <AUTHORITY, PATH, MATCH_CODE>● An input URI is given to the UriMatcher, if a match is

successful, MATCH_CODE is returned● A MATCH_CODE is used to return an associated type

Multipurpose Internet Mail Extensions (aka MIMEs)

MIME Types● A Web site returns a MIME type for a given URL● A Browser starts a URL handling program depending on

the URL's MIME type● MIME types work on Android in the same way they work in

HTTP: a content provider can be asked for the MIME type of a given URI

● When asked about the MIME type, the provider returns a two-part string according to the standard web MIME conventions

MIME Types ● RFC document on the MIME standards is available at

http://tools.ietf.org/html/rfc2046● A MIME type has two parts: a type and a subtype:

text/html text/css application/pdf

● Complete list of registered types and subtypes are at http://www.iana.org/assignments/media-types

MIME Types

● Primary registered content types are application, audio, example, image, message, model, multipart, text, video

● Each primary type has subtypes● If a vendor has proprietary data formats, the subtype

name begins with vnd: application/vnd.ms-excel● If it is a standard data format, the subtype does not start

with any prefix: text/html or application/pdf

Non-Standard MIME Subtypes ● Subtypes that start with x- refer to non-standard types that

do not have to be registered● These two types are typically defined bilaterally defined by

collaborating applications/agents application/x-tar audio/x-aiff video/x-msvideo

Non-Standard MIME Subtypes on Android ● For a single record, the Android MIME type is as follows:

vnd.android.cursor.item/vnd.yourcompany.contenttype

● For a collection of records, the Android MIME type is as follows:

vnd.android.cursor.dir/vnd.yourcompany.contenttype

● Examples: vnd.android.cursor.item/vnd.google.note vnd.android.cursor.dir/vnd.google.note

URI Processing

source code is in UriTestActivity.java

Sample Problem

Suppose we want to create a resource that allows its clients to retrieve books, book titles, and book authors. What URIs do we need to support this resource?

URIs: Scheme, Authority, Paths● Scheme: content● Authority: org.vkedco.mobappdev.content_providers.books● Paths:

book_title/id // retrieve all book ids

book_title/id/# // retreive a specific book title id

// (e.g., book_title/ids/1, book_title/ids/2, etc)

book_author/author // retrieve all authors

book_author/author/# // retrieve a specific book author whose id is #

book_cover_image/cover_image // retrieve all images

book_cover_image/cover_image/# // retrieve a specific image

Publishing Authority & Paths

// AUTHORITY & PATHS

static final String AUTHORITY = "org.vkedco.mobappdev.content_providers.books";

static final String BOOK_ID_PATH = "book_title" + "/id";

static final String BOOK_TITLE_PATH = "book_title" + "/title";

static final String BOOK_AUTHOR_PATH = "book_author" + "/author";

static final String BOOK_COVER_PATH = "book_cover" + "/cover_image";

Publishing Authority & Paths

// AUTHORITY & PATHS

static final String AUTHORITY = "org.vkedco.mobappdev.content_providers.books";

static final String BOOK_ID_PATH = "book_title" + "/id";

static final String BOOK_TITLE_PATH = "book_title" + "/title";

static final String BOOK_AUTHOR_PATH = "book_author" + "/author";

static final String BOOK_COVER_PATH = "book_cover" + "/cover_image";

Publishing Matching Codes// URI Matching Codes; these are returned if a match is successful

static final int CODE_BOOK_ID_ALL = 0;

static final int CODE_BOOK_ID_SINGLE = 1;

static final int CODE_BOOK_TITLE_ALL = 2;

static final int CODE_BOOK_TITLE_SINGLE = 3;

static final int CODE_BOOK_AUTHOR_ALL = 4;

static final int CODE_BOOK_AUTHOR_SINGLE = 5;

static final int CODE_BOOK_COVER_ALL = 6;

static final int CODE_BOOK_COVER_SINGLE = 7;

Publishing MIMEs// This mime is associated with CODE_BOOK_ID_ALL

static final String BOOK_TITLE_ID_ALL_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_id_all";

// This mime is associated with CODE_BOOK_ID_SINGLE

static final String BOOK_TITLE_ID_SINGLE_MIME = "vnd.android.cursor.item/vnd.vkedco.mobappdev.book_id_single";

// This mime is associated with CODE_BOOK_TITLE_ALL

static final String BOOK_TITLE_ALL_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_title_all";

// This mime is associated with CODE_BOOK_TITLE_SINGLE

static final String BOOK_TITLE_SINGLE_MIME = "vnd.android.cursor.item/vnd.vkedco.mobappdev.book_title_single";

Publishing MIMEs// This mime is associated with CODE_BOOK_AUTHOR_ALL

static final String BOOK_AUTHOR_ALL_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_author_all";

// This mime is associated with CODE_BOOK_AUTHOR_SINGLE

static final String BOOK_AUTHOR_SINGLE_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_author_single";

// This mime is associated with CODE_BOOK_COVER_ALL

static final String BOOK_COVER_ALL_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_cover_all";

// This mime is associated with CODE_BOOK_COVER_SINGLE

static final String BOOK_COVER_SINGLE_MIME = "vnd.android.cursor.dir/vnd.vkedco.mobappdev.book_cover_single";

Adding URIs to UriMatcher

// 1. Create a UriMatcher

UriMatcher mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

// 2. add a new URI to the UriMatcher: AUTHORITY/BOOK_ID_PATH

// if a match is successful, then BOOK_ID_ALL is returned

mUriMatcher.addURI(AUTHORITY, BOOK_ID_PATH, BOOK_ID_ALL);

Basic URI Matching Patternvoid matchUri(Uri uri) {

int uri_match_code = mUriMatcher.match(uri);

switch ( uri_match_code ) {

case CODE_BOOK_ID_ALL:

// do something with this URI

break;

case CODE_BOOK_ID_SINGLE:

// do something with this URI

break;

// handle other cases

}

Getting Associated URI MIMEsstatic String getUriMIME(Uri uri) {

int uri_match_code = mUriMatcher.match(uri);

switch ( uri_match_code ) {

case CODE_BOOK_ID_ALL: return UriTestActivity.BOOK_AUTHOR_ALL_MIME;

case CODE_BOOK_ID_SINGLE: return UriTestActivity.BOOK_AUTHOR_SINGLE_MIME;

case CODE_BOOK_TITLE_ALL: return UriTestActivity.BOOK_TITLE_ALL_MIME;

case CODE_BOOK_TITLE_SINGLE: return UriTestActivity.BOOK_TITLE_SINGLE_MIME;

case CODE_BOOK_AUTHOR_ALL: return UriTestActivity.BOOK_AUTHOR_ALL_MIME;

case CODE_BOOK_AUTHOR_SINGLE: return UriTestActivity.BOOK_AUTHOR_SINGLE_MIME;

case CODE_BOOK_COVER_ALL: return UriTestActivity.BOOK_COVER_ALL_MIME;

case CODE_BOOK_COVER_SINGLE: return UriTestActivity.BOOK_COVER_ALL_MIME;

}

return "NONE";

}

References ● http://developer.android.com/guide/topics/providers/content-providers.html● http://tools.ietf.org/html/rfc2046● http://www.iana.org/assignments/media-types● http://www.faqs.org/rfcs/rfc2396.html