Class: ActiveFedora::NokogiriDatastream

Inherits:
Datastream show all
Includes:
MetadataDatastreamHelper, OM::XML::Document, Solrizer::XML::TerminologyBasedSolrizer
Defined in:
lib/active_fedora/nokogiri_datastream.rb

Overview

this class represents a MetadataDatastream, a special case of ActiveFedora::Datastream

Instance Attribute Summary collapse

Attributes included from MetadataDatastreamHelper

#fields

Attributes inherited from Datastream

#dirty, #fields, #last_modified

Attributes inherited from Fedora::BaseObject

#attributes, #blob, #errors, #new_object, #uri

Class Method Summary collapse

Instance Method Summary collapse

Methods included from MetadataDatastreamHelper

included, #save, #set_blob_for_save, #to_solr

Methods inherited from Datastream

#after_save, #before_save, #check_concurrency, #content, #content=, #delete, delete, #dirty?, #dsid=, #last_modified_in_repository, #pid, #pid=, #save, #size, #to_param

Methods inherited from Fedora::Datastream

#control_group, #control_group=, #dsid, #label, #label=, #mime_type, #mime_type=, #pid, #uri, #url

Methods inherited from Fedora::BaseObject

#[], #new_object?

Constructor Details

#initialize(attrs = nil) ⇒ NokogiriDatastream

constructor, calls up to ActiveFedora::Datastream’s constructor



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 20

def initialize(attrs=nil)
  super
  @fields={}
  self.class.from_xml(blob, self)
end

Instance Attribute Details

#internal_solr_doc ⇒ Object

Returns the value of attribute internal_solr_doc.



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 17

def internal_solr_doc
  @internal_solr_doc
end

#ng_xml ⇒ Object

Returns the value of attribute ng_xml.



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 17

def ng_xml
  @ng_xml
end

Class Method Details

.from_xml(xml, tmpl = self.new) ⇒ Object

Create an instance of this class based on xml content Careful! If you call this from a constructor, be sure to provide something ‘ie. self’ as the @tmpl. Otherwise, you will get an infinite loop!

Parameters:

  • xml (String, File, Nokogiri::XML::Node) —

    the xml content to build from

  • tmpl (ActiveFedora::MetadataDatastream) (defaults to: self.new) —

    the Datastream object that you are building @default a new instance of this class



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 30

def self.from_xml(xml, tmpl=self.new) # :nodoc:
  if xml.nil?
    tmpl.ng_xml = self.xml_template
  elsif xml.kind_of? Nokogiri::XML::Node || xml.kind_of?(Nokogiri::XML::Document)
    tmpl.ng_xml = xml
  else
    tmpl.ng_xml = Nokogiri::XML::Document.parse(xml)
  end    
  tmpl.send(:dirty=, false)
  return tmpl
end

.xml_template ⇒ Object 



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 42

def self.xml_template
  Nokogiri::XML::Document.parse("<xml/>")
end

Instance Method Details

#from_solr(solr_doc) ⇒ Object

** Experimental **

This method is called by ActiveFedora::Base.load_instance_from_solr in order to initialize a nokogiri datastreams values from a solr document. This method merely sets the internal_solr_doc to the document passed in. Then any calls to get_values get values from the solr document on demand instead of directly from the xml stored in Fedora. This should be used for read-only purposes only, and instances where you want to improve performance by getting data from solr instead of Fedora.

See ActiveFedora::Base.load_instance_from_solr and get_values_from_solr for more information.



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 97

def from_solr(solr_doc)
  #just initialize internal_solr_doc since any value retrieval will be done via lazy loading on this doc on-demand
  @internal_solr_doc = solr_doc
end

#generate_solr_symbol(base, data_type) ⇒ Object 



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 240

def generate_solr_symbol(base, data_type)
  Solrizer::XML::TerminologyBasedSolrizer.default_field_mapper.solr_name(base.to_sym, data_type)
end

#get_values(field_key, default = []) ⇒ Object 



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 317

def get_values(field_key,default=[])
  term_values(*field_key)
end

#get_values_from_solr(*term_pointer) ⇒ Array

** Experimental ** This method is called by get_values if this datastream has been initialized by calling from_solr method via ActiveFedora::Base.load_instance_from_solr. This method retrieves values from a preinitialized @internal_solr_doc instead of xml. This makes the datastream read-only and this method is not intended to be used in any other case.

Values are retrieved from the @internal_solr_doc on-demand instead of via xml preloaded into memory.

A term_pointer is passed in and if it contains hierarchical indexes it will detect which solr field values need to be returned.

Example 1 (non-hierarchical term_pointer):

term_pointer = [:image, :title_set, :title]

Returns value of "image_title_set_title_t" in @internal_solr_doc

Example 2 (hierarchical term_pointer that contains one or more indexes):

term_pointer = [:image, {:title_set=>1}, :title]

relevant xml:  
      <image>
        <title_set>
          <title>Title 1</title>
        </title_set>
      </image>
      <image>
        <title_set>
          <title>Title 2</title>
        </title_set>
        <title_set>
          <title>Title 3</title>
        </title_set>
      </image>

Repeating element nodes are indexed and will be stored in solr as follows:
  image_0_title_set_0_title_t = "Title 1"
  image_1_title_set_0_title_t = "Title 2"
  image_1_title_set_1_title_t = "Title 3"

Even though no image element index is specified, only the second image element has two title_set elements so the expected return value is
  ["Title 3"]

While loading from solr the xml hierarchy is not immediately apparent so we must detect first how many image elements with a title_set element exist
and then check which of those elements have a second title element.

As this nokogiri datastream is indexed in solr, a value at each level in the tree will be stored independently and therefore 
if 'image_0_title_set_0_title_t' exists in solr 'image_0_title_set_t' will also exist in solr.  
So, we will build up the relevant solr names incrementally for a given term_pointer.  The last element in the
solr_name will not contain an index.

It then will do the following:
  Because no index is supplied for :image it will detect which indexes exist in solr
     image_0_title_set_t   (found key and add 'image_0_title_set' to base solr_name list)
     image_1_title_set_t   (found key and add 'image_0_title_set' to base solr_name list)
     image_2_title_set_t   (not found and stop checking indexes for image)
  After iteration 1:
     bases = ["image_0_title_set","image_1_title_set"]

  Two image nodes were found and next sees index of 1 supplied for title_set so just uses index of 1 building off bases found in previous iteration
     image_0_title_set_1_title_t (not found remove 'image_0_title_set' from base solr_name list)
     image_1_title_set_1_title_t (found and replace 'image_1_title_set' with new base 'image_1_title_set_1_title') 

  After iteration 2:
     bases = ["image_1_title_set_1_title"]
  It always looks ahead one element so we check if any elements are after title.  There are not any other elements so we are done iterating.
     returns @internal_solr_doc["image_1_title_set_1_title_t"]

Parameters:

  • term_pointer (Array) —

    Term pointer similar to an xpath ie. [:image, :title_set, :title]

Returns:

  • (Array) —

    If no values are found an empty Array is returned.



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 169

def get_values_from_solr(*term_pointer)
  values = []
  solr_doc = @internal_solr_doc
  return values if solr_doc.nil?
  begin
   term = self.class.terminology.retrieve_term(*OM.pointers_to_flat_array(term_pointer, false))
   #check if hierarchical term pointer
   if is_hierarchical_term_pointer?(*term_pointer)
     # if we are hierarchical need to detect all possible node values that exist
     # we do this by building up the possible solr names parent by parent and/or child by child
     # if an index is supplied for any node in the pointer it will be used
     # otherwise it will include all nodes and indexes that exist in solr
     bases = []
     #add first item in term_pointer as start of bases
     # then iterate through possible nodes that might exist
     term_pointer.first.kind_of?(Hash) ? bases << term_pointer.first.keys.first : bases << term_pointer.first
     for i in 1..(term_pointer.length-1)
       #iterate in reverse so that we can modify the bases array while iterating
       (bases.length-1).downto(0) do |j|
         current_last = (term_pointer[i].kind_of?(Hash) ? term_pointer[i].keys.first : term_pointer[i])
         if (term_pointer[i-1].kind_of?(Hash))
           #just use index supplied instead of trying possibilities
           index = term_pointer[i-1].values.first
           solr_name_base = OM::XML::Terminology.term_hierarchical_name({bases[j]=>index},current_last)
           solr_name = generate_solr_symbol(solr_name_base, term.data_type)
           bases.delete_at(j)
           #insert the new solr name base if found
           bases.insert(j,solr_name_base) if has_solr_name?(solr_name,solr_doc)
         else
           #detect how many nodes exist
           index = 0
           current_base = bases[j]
           bases.delete_at(j)
           solr_name_base = OM::XML::Terminology.term_hierarchical_name({current_base=>index},current_last)
           solr_name = generate_solr_symbol(solr_name_base, term.data_type)
           #check for indexes that exist until we find all nodes
           while has_solr_name?(solr_name,solr_doc) do
             #only reinsert if it exists
             bases.insert(j,solr_name_base)
             index = index + 1
             solr_name_base = OM::XML::Terminology.term_hierarchical_name({current_base=>index},current_last)
             solr_name = generate_solr_symbol(solr_name_base, term.data_type)
           end
         end
       end
     end

     #all existing applicable solr_names have been found and we can now grab all values and build up our value array
     bases.each do |base|
       field_name = generate_solr_symbol(base.to_sym, term.data_type)
       value = (solr_doc[field_name].nil? ? solr_doc[field_name.to_s]: solr_doc[field_name])
       unless value.nil?
         value.is_a?(Array) ? values.concat(value) : values << value
       end
     end
   else
     #this is not hierarchical and we can simply look for the solr name created using the terms without any indexes
     generic_field_name_base = OM::XML::Terminology.term_generic_name(*term_pointer)
     generic_field_name = generate_solr_symbol(generic_field_name_base, term.data_type)
     value = (solr_doc[generic_field_name].nil? ? solr_doc[generic_field_name.to_s]: solr_doc[generic_field_name])
     unless value.nil?
       value.is_a?(Array) ? values.concat(value) : values << value
     end
   end
  rescue Exception => e
    #just do nothing since term does not exist and return emtpy values
    raise e
  end
  values
end

#has_solr_name?(name, solr_doc = Hash.new) ⇒ Boolean

** Experimental **

Parameters:

  • name (String) —

    Name of key to look for

  • solr_doc (Solr::Document) (defaults to: Hash.new) —

    Solr doc to query

Returns:

  • (Boolean) —

    true if either the key for name exists in solr or if its string value exists



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 248

def has_solr_name?(name, solr_doc=Hash.new)
  !solr_doc[name].nil? || !solr_doc[name.to_s].nil?
end

#is_hierarchical_term_pointer?(*term_pointer) ⇒ Boolean

** Experimental **

Example:

[:image, {:title_set=>1}, :title] return true
[:image, :title_set, :title]      return false

Returns:

  • (Boolean) —

    true if the term_pointer contains an index



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 257

def is_hierarchical_term_pointer?(*term_pointer)
  if term_pointer.length>1
    term_pointer.each do |pointer|
      if pointer.kind_of?(Hash)
        return true
      end
    end
  end
  return false
end

#om_term_values ⇒ Object

extend(OM::XML::Container::ClassMethods)



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 14

alias_method(:om_term_values, :term_values)

#om_update_values ⇒ Object 



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 15

alias_method(:om_update_values, :update_values)

#term_values(*term_pointer) ⇒ Object

override OM::XML::term_values so can lazy load from solr if this datastream initialized using from_solr



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 338

def term_values(*term_pointer)
  if @internal_solr_doc
    #lazy load values from solr on demand
    get_values_from_solr(*term_pointer)
  else
    om_term_values(*term_pointer)
  end
end

#to_xml(xml = self.ng_xml) ⇒ Object 



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 64

def to_xml(xml = self.ng_xml)
  ng_xml = self.ng_xml
  if ng_xml.respond_to?(:root) && ng_xml.root.nil? && self.class.respond_to?(:root_property_ref) && !self.class.root_property_ref.nil?
    ng_xml = self.class.generate(self.class.root_property_ref, "")
    if xml.root.nil?
      xml = ng_xml
    end
  end

  unless xml == ng_xml || ng_xml.root.nil?
    if xml.kind_of?(Nokogiri::XML::Document)
        xml.root.add_child(ng_xml.root)
    elsif xml.kind_of?(Nokogiri::XML::Node)
        xml.add_child(ng_xml.root)
    else
        raise "You can only pass instances of Nokogiri::XML::Node into this method.  You passed in #{xml}"
    end
  end
  
  return xml.to_xml {|config| config.no_declaration}
end

#update_indexed_attributes(params = {}, opts = {}) ⇒ Object

Update field values within the current datastream using #update_values, which is a wrapper for OM::TermValueOperators#update_values Ignores any fields from params that this datastream’s Terminology doesn’t recognize

Example: 

@mods_ds.update_indexed_attributes( {[{":person"=>"0"}, "role"]=>{"0"=>"role1", "1"=>"role2", "2"=>"role3"} })
=> {"person_0_role"=>{"0"=>"role1", "1"=>"role2", "2"=>"role3"}}

@mods_ds.to_xml # (the following is an approximation)
<mods>
  <mods:name type="person">
  <mods:role>
    <mods:roleTerm>role1</mods:roleTerm>
  </mods:role>
  <mods:role>
    <mods:roleTerm>role2</mods:roleTerm>
  </mods:role>
  <mods:role>
    <mods:roleTerm>role3</mods:roleTerm>
  </mods:role>
  </mods:name>
</mods>

Parameters:

  • params (Hash) (defaults to: {}) —

    The params specifying which fields to update and their new values. The syntax of the params Hash is the same as that expected by term_pointers must be a valid OM Term pointers (ie. [:name]). Strings will be ignored.

  • opts (Hash) (defaults to: {}) —

    This is not currently used by the datastream-level update_indexed_attributes method



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# File 'lib/active_fedora/nokogiri_datastream.rb', line 293

def update_indexed_attributes(params={}, opts={})    
  if self.class.terminology.nil?
    raise "No terminology is set for this NokogiriDatastream class.  Cannot perform update_indexed_attributes"
  end
  # remove any fields from params that this datastream doesn't recognize    
  # make sure to make a copy of params so not to modify hash that might be passed to other methods
  current_params = params.clone
  current_params.delete_if do |term_pointer,new_values| 
    if term_pointer.kind_of?(String)
      logger.warn "WARNING: #{dsid} ignoring {#{term_pointer.inspect} => #{new_values.inspect}} because #{term_pointer.inspect} is a String (only valid OM Term Pointers will be used).  Make sure your html has the correct field_selector tags in it."
      true
    else
      !self.class.terminology.has_term?(*OM.destringify(term_pointer))
    end
  end

  result = {}
  unless current_params.empty?
    result = update_values( current_params )
  end
  
  return result
end

#update_values(params = {}) ⇒ Object

Update values in the datastream’s xml This wraps OM::TermValueOperators#update_values so that returns an error if we have loaded from solr since datastreams loaded that way should be read-only

Examples:

Updating multiple values with a Hash of Term pointers and values

ds.update_values( {[{":person"=>"0"}, "role", "text"]=>{"0"=>"role1", "1"=>"role2", "2"=>"role3"}, [{:person=>1}, :family_name]=>"Andronicus", [{"person"=>"1"},:given_name]=>["Titus"],[{:person=>1},:role,:text]=>["otherrole1","otherrole2"] } )
=> {"person_0_role_text"=>{"0"=>"role1", "1"=>"role2", "2"=>"role3"}, "person_1_role_text"=>{"0"=>"otherrole1", "1"=>"otherrole2"}} 


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# File 'lib/active_fedora/nokogiri_datastream.rb', line 327

def update_values(params={})
  if @internal_solr_doc
    raise "No update performed, this object was initialized via Solr instead of Fedora and is therefore read-only.  Please utilize ActiveFedora::Base.load_instance to first load object via Fedora instead."
  else
    result = om_update_values(params)
    self.dirty= true
    return result
  end
end