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Summary

Bio::DB::WebDBSeqI - Object Interface to generalize Web Databases
for retrieving sequences

Package variables

Included modules

Inherit

Bio::DB::RandomAccessI

Synopsis

   # get a WebDBSeqI object somehow
   # assuming it is a nucleotide db
   my $seq = $db->get_Seq_by_id('ROA1_HUMAN')

Description

Provides core set of functionality for connecting to a web based
database for retriving sequences.
Users wishing to add another Web Based Sequence Dabatase will need to
extend this class (see Bio::DB::SwissProt or Bio::DB::NCBIHelper for
examples) and implement the get_request method which returns a
HTTP::Request for the specified uids (accessions, ids, etc depending
on what query types the database accepts).

Methods

Methods description

 Title   : _sleep
 Usage   : $self->_sleep
 Function: sleep for a number of seconds indicated by the delay policy
 Returns : none
 Args    : none

 Title   : authentication
 Usage   : $db->authentication($user,$pass)
 Function: Get/Set authentication credentials
 Returns : Array of user/pass 
 Args    : Array or user/pass

 Title   : default_format
 Usage   : my $format = $self->default_format
 Function: Returns default sequence format for this module
 Returns : string
 Args    : none

 Title   : delay
 Usage   : $secs = $self->delay([$secs])
 Function: get/set number of seconds to delay between fetches
 Returns : number of seconds to delay
 Args    : new value

 Title   : delay_policy
 Usage   : $secs = $self->delay_policy
 Function: return number of seconds to delay between calls to remote db
 Returns : number of seconds to delay
 Args    : none

 Title   : get_Seq_by_acc
 Usage   : $seq = $db->get_Seq_by_acc('X77802');
 Function: Gets a Bio::Seq object by accession number
 Returns : A Bio::Seq object
 Args    : accession number (as a string)
 Throws  : "acc does not exist" exception

 Title   : get_Seq_by_gi
 Usage   : $seq = $db->get_Seq_by_gi('405830');
 Function: Gets a Bio::Seq object by gi number
 Returns : A Bio::Seq object
 Args    : gi number (as a string)
 Throws  : "gi does not exist" exception

 Title   : get_Seq_by_id
 Usage   : $seq = $db->get_Seq_by_id('ROA1_HUMAN')
 Function: Gets a Bio::Seq object by its name
 Returns : a Bio::Seq object
 Args    : the id (as a string) of a sequence
 Throws  : "id does not exist" exception

 Title   : get_Seq_by_version
 Usage   : $seq = $db->get_Seq_by_version('X77802.1');
 Function: Gets a Bio::Seq object by sequence version
 Returns : A Bio::Seq object
 Args    : accession.version (as a string)
 Throws  : "acc.version does not exist" exception

  Title   : get_Stream_by_acc
  Usage   : $seq = $db->get_Stream_by_acc([$acc1, $acc2]);
  Function: Gets a series of Seq objects by accession numbers
  Returns : a Bio::SeqIO stream object
  Args    : $ref : a reference to an array of accession numbers for
                   the desired sequence entries
  Note    : For GenBank, this just calls the same code for get_Stream_by_id()

  Title   : get_Stream_by_gi
  Usage   : $seq = $db->get_Stream_by_gi([$gi1, $gi2]);
  Function: Gets a series of Seq objects by gi numbers
  Returns : a Bio::SeqIO stream object
  Args    : $ref : a reference to an array of gi numbers for
                   the desired sequence entries
  Note    : For GenBank, this just calls the same code for get_Stream_by_id()

  Title   : get_Stream_by_id
  Usage   : $stream = $db->get_Stream_by_id( [$uid1, $uid2] );
  Function: Gets a series of Seq objects by unique identifiers
  Returns : a Bio::SeqIO stream object
  Args    : $ref : a reference to an array of unique identifiers for
                   the desired sequence entries

  Title   : get_Stream_by_query
  Usage   : $stream = $db->get_Stream_by_query($query);
  Function: Gets a series of Seq objects by way of a query string or oject
  Returns : a Bio::SeqIO stream object
  Args    : $query :   A string that uses the appropriate query language
            for the database or a Bio::DB::QueryI object.  It is suggested 
            that you create the Bio::DB::Query object first and interrogate
            it for the entry count before you fetch a potentially large stream.

  Title   : get_Stream_by_version
  Usage   : $seq = $db->get_Stream_by_version([$version1, $version2]);
  Function: Gets a series of Seq objects by accession.versions
  Returns : a Bio::SeqIO stream object
  Args    : $ref : a reference to an array of accession.version strings for
                   the desired sequence entries
  Note    : For GenBank, this is implemeted in NCBIHelper

 Title   : get_request
 Usage   : my $url = $self->get_request
 Function: returns a HTTP::Request object
 Returns : 
 Args    : %qualifiers = a hash of qualifiers (ids, format, etc)

 Title   : get_seq_stream
 Usage   : my $seqio = $self->get_seq_sream(%qualifiers)
 Function: builds a url and queries a web db
 Returns : a Bio::SeqIO stream capable of producing sequence
 Args    : %qualifiers = a hash qualifiers that the implementing class 
           will process to make a url suitable for web querying

 Title   : postprocess_data
 Usage   : $self->postprocess_data ( 'type' => 'string',
				     'location' => \$datastr);
 Function: process downloaded data before loading into a Bio::SeqIO
 Returns : void
 Args    : hash with two keys - 'type' can be 'string' or 'file'
                              - 'location' either file location or string 
                                           reference containing data

 Title   : proxy
 Usage   : $httpproxy = $db->proxy('http')  or 
           $db->proxy(['http','ftp'], 'http://myproxy' )
 Function: Get/Set a proxy for use of proxy
 Returns : a string indicating the proxy
 Args    : $protocol : an array ref of the protocol(s) to set/get
           $proxyurl : url of the proxy to use for the specified protocol
           $username : username (if proxy requires authentication)
           $password : password (if proxy requires authentication)

 Title   : request_format
 Usage   : my ($req_format, $ioformat) = $self->request_format;
           $self->request_format("genbank");
           $self->request_format("fasta");
 Function: Get/Set sequence format retrieval. The get-form will normally not
           be used outside of this and derived modules.
 Returns : Array of two strings, the first representing the format for
           retrieval, and the second specifying the corresponding SeqIO format.
 Args    : $format = sequence format

 Title   : retrieval_type
 Usage   : $self->retrieval_type($type);
           my $type = $self->retrieval_type
 Function: Get/Set a proxy for retrieval_type (pipeline, io_string or tempfile)
 Returns : string representing retrieval type
 Args    : $value - the value to store

   pipeline  Perform a fork in an attempt to begin streaming
             while the data is still downloading from the remote
             server.  Disk, memory and speed efficient, but will
             not work on Windows or MacOS 9 platforms.

   io_string Store downloaded database entry(s) in memory.  Can be
             problematic for batch downloads because entire set
             of entries must fit in memory.  Alll entries must be
             downloaded before processing can begin.

   tempfile  Store downloaded database entry(s) in a temporary file.
             All entries must be downloaded before processing can
             begin.

 Title   : ua
 Usage   : my $ua = $self->ua or 
           $self->ua($ua)
 Function: Get/Set a LWP::UserAgent for use
 Returns : reference to LWP::UserAgent Object
 Args    : $ua - must be a LWP::UserAgent

 Title   : url_base_address
 Usage   : my $address = $self->url_base_address or 
           $self->url_base_address($address)
 Function: Get/Set the base URL for the Web Database
 Returns : Base URL for the Web Database 
 Args    : $address - URL for the WebDatabase

 Title   : url_params
 Usage   : my $params = $self->url_params or 
           $self->url_params($params)
 Function: Get/Set the URL parameters for the Web Database
 Returns : url parameters for Web Database
 Args    : $params - parameters to be appended to the URL for the WebDatabase

Methods code

BEGIN {

    $MODVERSION = '0.8';
    %RETRIEVAL_TYPES = ( 'io_string' => 1,
			 'tempfile'  => 1,
			 'pipeline'  => 1,
		       );
    $DEFAULT_RETRIEVAL_TYPE = 'pipeline';
    $DEFAULTFORMAT = 'fasta';
    $LAST_INVOCATION_TIME = 0;

}

sub _request {

    my ($self, $url,$tmpfile) = @_;
    my ($resp);
    if( defined $tmpfile && $tmpfile ne '' ) { 
	$resp =  $self->ua->request($url, $tmpfile);
    } else { $resp =  $self->ua->request($url); } 

    if( $resp->is_error  ) {
	$self->throw("WebDBSeqI Request Error:\n".$resp->as_string);
    }
    return $resp;
}

# send web request to stdout for streaming purposes

}

sub _sleep {

   my $self = shift;
   my $last_invocation = $LAST_INVOCATION_TIME;
   if (time - $LAST_INVOCATION_TIME < $self->delay) {
      my $delay = $self->delay - (time - $LAST_INVOCATION_TIME);
      warn "sleeping for $delay seconds\n" if $self->verbose;
      sleep $delay;
   }
   $LAST_INVOCATION_TIME = time;
}

1;

}

sub _stream_request {

  my $self    = shift;
  my $request = shift;

  # fork so as to pipe output of fetch process through to
  # postprocess_data method call.
  my $child = open (FETCH,"-|");
  $self->throw("Couldn't fork: $!") unless defined $child;

  if ($child) {
    local ($/) = "//\n";  # assume genbank/swiss format
    $| = 1;
    my $records = 0;
    while (my $record = <FETCH>) {
      $records++;
      $self->postprocess_data('type'     => 'string',
			      'location' =>\$ record);
      print STDOUT $record;
    }
    $/ = "\n"; # reset to be safe;
    close(FETCH);
    close STDOUT; 
    close STDERR;
    kill 9=>$$;  # to prevent END{} blocks from executing in forked children
    sleep;
  }
  else {
    $| = 1;
    my $resp =  $self->ua->request($request,
				   sub { print shift }
				   );
    if( $resp->is_error  ) {
      $self->throw("WebDBSeqI Request Error:\n".$resp->as_string);
    }

    close STDOUT; close STDERR;
    kill 9=>$$;  # to prevent END{} blocks from executing in forked children
    sleep;
  }
  exit 0;

}

sub authentication {

   my ($self,$u,$p) = @_;

   if( defined $u && defined $p ) {
       $self->{'_authentication'} = [ $u,$p];
   }
   return @{$self->{'_authentication'}};

}

sub db {

  my $self = shift;
  my $d    = $self->{_db};
  $self->{_db} = shift if @_;
  $d;

}

sub default_format {

    return $DEFAULTFORMAT;
}

# sorry, but this is hacked in because of BioFetch problems...

}

sub delay {

   my $self = shift;
   my $d = $self->{'_delay'};
   $self->{'_delay'} = shift if @_;
   $d;

}

sub delay_policy {

   my $self = shift;
   return 0;

}

sub get_Seq_by_acc {

   my ($self,$seqid) = @_;
   $self->_sleep;
   my $seqio = $self->get_Stream_by_acc($seqid);
   $self->throw("acc does not exist") if( ! defined $seqio );
   my @seqs;
   while( my $seq = $seqio->next_seq() ) { push @seqs, $seq; }
   $self->throw("acc does not exist") unless @seqs;
   if( wantarray ) { return @seqs } else { return shift @seqs }

}

sub get_Seq_by_gi {

   my ($self,$seqid) = @_;
    $self->_sleep;
   my $seqio = $self->get_Stream_by_gi($seqid);
   $self->throw("gi does not exist") if( !defined $seqio );
   my @seqs;
   while( my $seq = $seqio->next_seq() ) { push @seqs, $seq; }
   $self->throw("gi does not exist") unless @seqs;
   if( wantarray ) { return @seqs } else { return shift @seqs }

}

sub get_Seq_by_id {

    my ($self,$seqid) = @_;
    $self->_sleep;
    my $seqio = $self->get_Stream_by_id([$seqid]);
    $self->throw("id does not exist") if( !defined $seqio ) ;
    my @seqs;
    while( my $seq = $seqio->next_seq() ) { push @seqs, $seq; }
    $self->throw("id does not exist") unless @seqs;
    if( wantarray ) { return @seqs } else { return shift @seqs }

}

sub get_Seq_by_version {

   my ($self,$seqid) = @_;
    $self->_sleep;
   my $seqio = $self->get_Stream_by_version($seqid);
   $self->throw("accession.version does not exist") if( !defined $seqio );
   my @seqs;
   while( my $seq = $seqio->next_seq() ) { push @seqs, $seq; }
   $self->throw("accession.version does not exist") unless @seqs;
   if( wantarray ) { return @seqs } else { return shift @seqs }
}

# implementing class must define these

}

sub get_Stream_by_acc {

    my ($self, $ids ) = @_;
    return $self->get_seq_stream('-uids' => $ids, '-mode' => 'single');

}

sub get_Stream_by_gi {

    my ($self, $ids ) = @_;
    return $self->get_seq_stream('-uids' => $ids, '-mode' => 'gi');

}

sub get_Stream_by_id {

    my ($self, $ids) = @_;
    my ($webfmt,$localfmt) = $self->request_format;
    return $self->get_seq_stream('-uids' => $ids, '-mode' => 'single',
				 '-format' => $webfmt);
}

*get_Stream_by_batch = sub {
  my $self = shift;
  $self->deprecated('get_Stream_by_batch() is deprecated; use get_Stream_by_id() instead');
  $self->get_Stream_by_id(@_) 
};

}

sub get_Stream_by_query {

    my ($self, $query ) = @_;
    return $self->get_seq_stream('-query' => $query, '-mode'=>'query');

}

sub get_Stream_by_version {

    my ($self, $ids ) = @_;
#    $self->throw("Implementing class should define this method!"); 
    return $self->get_seq_stream('-uids' => $ids, '-mode' => 'version'); # how it should work

}

sub get_request {

    my ($self) = @_;
    my $msg = "Implementing class must define method get_request in class WebDBSeqI";
    $self->throw($msg);
}

# class methods

}

sub get_seq_stream {

  my ($self, %qualifiers) = @_;
  my ($rformat, $ioformat) = $self->request_format();
  my $seen = 0;
  foreach my $key ( keys %qualifiers ) {
    if( $key =~ /format/i ) {
      $rformat = $qualifiers{$key};
      $seen = 1;
    }
  }
  $qualifiers{'-format'} = $rformat if( !$seen);
  ($rformat, $ioformat) = $self->request_format($rformat);

  my $request = $self->get_request(%qualifiers);
  $request->proxy_authorization_basic($self->authentication)
    if ( $self->authentication);
  $self->debug("request is ". $request->as_string(). "\n");

  # workaround for MSWin systems
  $self->retrieval_type('io_string') if $self->retrieval_type =~ /pipeline/ && $^O =~ /^MSWin/;

  if ($self->retrieval_type =~ /pipeline/) {
    # Try to create a stream using POSIX fork-and-pipe facility.
    # this is a *big* win when fetching thousands of sequences from
    # a web database because we can return the first entry while 
    # transmission is still in progress.
    # Also, no need to keep sequence in memory or in a temporary file.
    # If this fails (Windows, MacOS 9), we fall back to non-pipelined access.

    # fork and pipe: _stream_request()=><STREAM>
    my $result =  eval { open(STREAM,"-|") };

    if (defined $result) {
      $DB::fork_TTY = '/dev/null'; # prevents complaints from debugger
      if (!$result) {	# in child process
	$self->_stream_request($request); 
	kill 9=>$$; # to prevent END{} blocks from executing in forked children
	exit 0;
      }
      else {
	  return Bio::SeqIO->new('-verbose' => $self->verbose,
			       '-format'  => $ioformat,
			       '-fh'      =>\* STREAM);
      }
    }
    else {
      $self->retrieval_type('io_string');
    }
  }

  if ($self->retrieval_type =~ /temp/i) {
    my $dir = $self->io->tempdir( CLEANUP => 1);
    my ( $fh, $tmpfile) = $self->io()->tempfile( DIR => $dir );
    close $fh;
    my $resp = $self->_request($request, $tmpfile);		
    if( ! -e $tmpfile || -z $tmpfile || ! $resp->is_success() ) {
      $self->throw("WebDBSeqI Error - check query sequences!\n");
    }
    $self->postprocess_data('type' => 'file',
			    'location' => $tmpfile);	
    # this may get reset when requesting batch mode
    ($rformat,$ioformat) = $self->request_format();
    if( $self->verbose > 0 ) {
      open(ERR, "<$tmpfile");
      while(<ERR>) { $self->debug($_);}
    }

    return Bio::SeqIO->new('-verbose' => $self->verbose,
			   '-format' => $ioformat,
			   '-file'   => $tmpfile);
  }

  if ($self->retrieval_type =~ /io_string/i ) {
    my $resp = $self->_request($request);
    my $content = $resp->content_ref;
    $self->debug( "content is $$content\n");
    if (!$resp->is_success() || length($$content) == 0) {
      $self->throw("WebDBSeqI Error - check query sequences!\n");	
    }
    ($rformat,$ioformat) = $self->request_format();
    $self->postprocess_data('type'=> 'string',
			    'location' => $content);
    $self->debug( "str is $$content\n");
    return Bio::SeqIO->new('-verbose' => $self->verbose,
			   '-format' => $ioformat,
			   '-fh'   => new IO::String($$content));
  }

  # if we got here, we don't know how to handle the retrieval type
  $self->throw("retrieval type " . $self->retrieval_type . 
		 " unsupported\n");

}

sub io {

    my ($self,$io) = @_;

    if(defined($io) || (! exists($self->{'_io'}))) {
	$io = Bio::Root::IO->new() unless $io;
	$self->{'_io'} = $io;
    }
    return $self->{'_io'};

}

sub new {

    my ($class, @args) = @_;
    my $self = $class->SUPER::new(@args);
    my ($baseaddress, $params, $ret_type, $format,$delay,$db) =
	$self->_rearrange([qw(BASEADDRESS PARAMS RETRIEVALTYPE FORMAT DELAY DB)],
			  @args);

    $ret_type = $DEFAULT_RETRIEVAL_TYPE unless ( $ret_type);
    $baseaddress   && $self->url_base_address($baseaddress);
    $params        && $self->url_params($params);
    $db            && $self->db($db);
    $ret_type      && $self->retrieval_type($ret_type);
    $delay          = $self->delay_policy unless defined $delay;
    $self->delay($delay);

    # insure we always have a default format set for retrieval
    # even though this will be immedietly overwritten by most sub classes
    $format = $self->default_format unless ( defined $format && 
					     $format ne '' );

    $self->request_format($format);
    my $ua = new LWP::UserAgent;
    $ua->agent(ref($self) ."/$MODVERSION");
    $self->ua($ua);  
    $self->{'_authentication'} = [];
    return $self;
}

# from Bio::DB::RandomAccessI

}

sub postprocess_data {

    my ( $self, %args) = @_;
    return;
}

# private methods

}

sub proxy {

    my ($self,$protocol,$proxy,$username,$password) = @_;
    return undef if ( !defined $self->ua || !defined $protocol 
		      || !defined $proxy );
    $self->authentication($username, $password) 	
	if ($username && $password);
    return $self->ua->proxy($protocol,$proxy);

}

sub request_format {

    my ($self, $value) = @_;

    if( defined $value ) {
	$self->{'_format'} = [ $value, $value];
    }
    return @{$self->{'_format'}};

}

sub retrieval_type {

    my ($self, $value) = @_;
    if( defined $value ) {
	$value = lc $value;
	if( ! $RETRIEVAL_TYPES{$value} ) {
	    $self->warn("invalid retrieval type $value must be one of (" . 
			join(",", keys %RETRIEVAL_TYPES), ")"); 
	    $value = $DEFAULT_RETRIEVAL_TYPE;
	}
	$self->{'_retrieval_type'} = $value;
    }
    return $self->{'_retrieval_type'};

}

sub ua {

    my ($self, $ua) = @_;
    if( defined $ua && $ua->isa("LWP::UserAgent") ) {
	$self->{'_ua'} = $ua;
    }
    return $self->{'_ua'};

}

sub url_base_address {

    my $self = shift;
    my $d = $self->{'_baseaddress'};
    $self->{'_baseaddress'} = shift if @_;
    $d;

}

sub url_params {

    my ($self, $value) = @_;
    if( defined $value ) {
	$self->{'_urlparams'} = $value;
    }

}

General documentation

User feedback is an integral part of the
evolution of this and other Bioperl modules. Send
your comments and suggestions preferably to one
of the Bioperl mailing lists. Your participation
is much appreciated.

  bioperl-l@bioperl.org              - General discussion
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Report bugs to the Bioperl bug tracking system to
help us keep track the bugs and their resolution.
Bug reports can be submitted via email or the
web:

  bioperl-bugs@bio.perl.org
  http://bugzilla.bioperl.org/

Email < jason@bioperl.org >

The rest of the documentation details each of the
object methods. Internal methods are usually
preceded with a _