Table of contents
Velocity template rendering
This release of Elda includes the ability to use Velocity templates for rendering. This feature is provisional; it may change significantly in future releases.
To use the Velocity renderer to generate HTML, attach this formatter to your API spec:
<yourSpec> api:defaultFormatter [a elda:VelocityFormatter ; api:name "html" ; elda:className "com.epimorphics.lda.renderers.VelocityRendererFactory" ; api:mimeType "text/html" ]
By default, this will render the template
page-shell.vm found in {_velocityRoot}
if _velocityRoot is defined, or in
{_resourceRoot/vm} otherwise. (_resourceRoot
has a default value.)
(Previous versions of Elda loaded templates from
webapp/WEB-INF/classes, but with the split between
elda-common and elda-assets, the templates have been moved out
of the Elda code webapp.)
To change the
rendered template, set the elda:velocityTemplate
property of the formatter to the name of the desired
template.
You may choose to specify a Velocity formatter as a property of an endpoint rather than as the API-wide default.
You can change the associated suffix of the formatter by changing the
value of its api:name property, and change the content-type
of the generated page by changing the value of the api:mimeType property.
Elda looks for {_resourceRoot}/velocity.properties
and, if it exists and is non-empty, uses it as its Velocity
configuration. If there's no such file, or it contains no
property definitions, Elda uses a default configuration that
fetches templates from {_velocityRoot} if it
is defined and from {_resourceRoot}/vm if not.
The example Velocity renderer
The Elda title bar links to the RDF specification, the Elda documentation, the Linked Data API specification, and the Epimorphics web page.
Underneath that is the list of available formats that this endpoint can display information in; clicking on list items rerenders this page in the format. Since Elda's XSLT-driven HTML renderer and the Velocity renderer both generate HTML but only one can be called HTML, the original renderer gets the "html" name and the new one is named "vhtml".
Below the format list the page is displayed in two columns; the left one for search results (information about selected items) and the right one for additional viewing information (map, filters, views and viewing properties).
At the top of the search results Elda displays links to the items on this page, and buttons to move through the item list. Each item entry names the item (displaying its preferred label) and shows selected properties of that item. Values that are themselves resources with properties have their properties displayed unless they have already appeared in an outer display box. Clicking on an item's name will restrict the display to that single item.
Clicking on the operator symbols (<<=>>) toward the right of the search results will restrict the search to items that have the specified value for the specified property. These filters will then appear in the filters section of the viewing column, where they can be snipped away using the cancel icon.
The properties section of viewing shows properties that have been explicitly selected for display. Those properties can be discarded using the cancel icon, extended with ".*" using the star icon, or have a trailing ".*" cut away using the reduce icon. The star icon on the properties title introduces the wildcard property chain "*" into the proeprties if it's not already present.
The views section displays the available views (ie, named sets of properties) for this endpoint. Clicking on the expand icon will toggle displaying the properties of that view; clicking on the plus icon of that property will add it to the properties display. Clicking on the plus icon of the view will set it (and hence all its properties) as the current view.
If there are any items in the top-level of the search results that
have both a lat and long property, then
a map is displayed in the viewing column with markers at
those locations.
Names in the Velocity context
When rendering a page using Velocity, Elda binds several names in the context:
| name | value |
|---|---|
| thisPage | A WrappedNode for a resource with the URI of this page. |
| isItemEndpoint | A boolean, true iff this page is for an item endpoint. |
| isListEndpoint | A boolean, true iff this page is for a list endpoint. |
| primaryTopic | A WrappedNode for the primary topic of this page, only defined if this page is for an item endpoint. |
| names |
a map from resources to their short names, passed
when needed to methods on WrappedNodes.
|
| formats | a list of Format objects in order of their names. Each Format has a getName and getLink method; a format's Link is the URI needed to fetch the version of the current page in this format. |
| items |
the list of selected items. Each item is a
WrappedNode.
|
| meta |
A map from string pathnames to WrappedNode
values. Each pathname is the dot-separated concatenation
of the short names of the properties in the path. The
proeprty chains are those of the metadata in the result
model, disregarding the termBindings and
the variableValues since these have their own
context variables.
|
| vars |
A map from LDA variable names to WrappedNodes
representing their values.
|
| filters | A map of the name=parameter query parameter values (discarding all the ones that start with "_"). |
| ids |
An IdMap object which contains a map from Resources to their
identifiers for use in HTML id= attributes.
|
| utils | Utility methods not appropriate for placing in WrappedNode or WrappedString. |
| utils.println(Object) | One-argument println to System.err, as a debugging aid. Output starts with ">>". |
| utils.println(Object, Object) | Two-argument space-separated println to System.err, as a debugging aid. Output starts with ">>". |
| utils.sort(Object c) | Sorts the sortable collection c in-place. |
| utils.join(Collection c, String infix) | Return an infix-separated concatenation of the toString() values of the elements of c. |
| utils.currentMillis() | Returns the current time in milliseconds since the Velocity renderer was initialised for this rendering, meant as a debugging/profiling aid. |
| utils |
Wrapped RDFNodes
WrappedNodes are wrappers round Jena RDFNodes. When they are created, they are given a ShortNames object to allow them to render their short names and an IdMap object to hold their allocated Id. They have the following methods:
| signature | description |
|---|---|
| boolean equals(Object other) | A WrappedNode is .equals to another object if that object is a WrappedNode and their underlying RDFNodes are equal. |
| String getId() | Answer the id of this WrappedNode, allocating a fresh one if necessary. |
| WrappedString getLabel() | Return this wrapped resource's preferred label; the first literal of (a) this resources skos:prefLabel, (b) an unlanguaged rdfs:label, (c) a languaged rdfs:label, (d) the local name of this resource. |
| WrappedString getLabel(String wantlanguage) |
If wantLanguage is "", return getLabel(). Otherwise,
return the lexical form of some label of this wrapped
resource which has wantLanguage. If there isn't
one, return some lexical form with no language. If there
isn't one, return the local name of the resource.
|
| boolean isJustALabel() |
Returns true if this WrappedNode is a Resource node
which has exactly one property, and that property
has predicate rdfs:label.
|
| WrappedString shortForm() | If this node is a wrapped Resource, return the shortname associated with that Resource or its localname if it has no shortname. If this node is a wrapped Literal, return the lexical form of that literal. |
| WrappedString getURI | If this WrappedNode is a Resource, return its URI. |
| boolean isLiteral | Return true iff this WrappedNode is a wrapped Literal. |
| boolean isResource | Return true iff this WrappedNode is a wrapped Resource (which may be a blank node). |
| boolean isAnon | Return true iff this WrappedNode is a blank node. |
| boolean isSelfQuoting | Return true iff this WrappedNode is a literal node that is "self-quoting", ie does not need to have quotes round its presentation. In E1.2.31 this means "has a numeric type". |
| String getLanguage | If this node is a wrapped Literal, return its language if any, otherwise return the empty string. |
| WrappedString getLiteralType() | Return the short form of the URI representing the type of this wrapped literal node. |
| Object getLiteralValue() | Return the unadorned value of this literal. |
| boolean isList | Return true iff this WrappedNode wraps a Resource representing an RDF list. |
| List<WrappedNode>asList | Return a Java list of WrappedNodes wrapping the elements of the RDF list represented by this WrappedNode. |
| List<WrappedNode> getProperties | Return a Java list of WrappedNodes which are the wrapped form of the different properties of this WrappedNode. |
| List<WrappedNode> getInverseProperties | Return a Java list of WrappedNodes which are the wrapped form of predicates P where there is some subject S such that (S, P, this wrapped node). |
| List<WrappedNode> getValues(WrappedNode property) |
Return a Java list of WrappedNodes which are the
objects of all statements for which this WrappedNode
is the subject and the argument property
is the predicate. (This argument will typically be
an element from the getProperties list.)
|
| List<WrappedNode> getInverseValues(WrappedNode property) |
Return a Java list of WrappedNodes which are the
subjects of all statements for which this WrappedNode
is the object and the argument property
is the predicate. (This argument will typically be
an element from the getInverseProperties list.)
|
| WrappedNode change(String prefix, WrappedNode p, WrappedNode v) |
Return a new WrappedNode wrapping a resource with the same URI
as this one, except that all query parameters whose name is
prefix prefixed onto p's shortname have been
discarded and replaced by a parameter with that name and with
value v.toString().
|
Where a String result might contain HTML-significant characters, WrappedNodes return a WrappedString object.
| signature | description |
|---|---|
| WrappedString cut() | Returns a new wrapped string who's content is the content of this wrapped string but with spaces inserted in place of runs of '_' and between a lower-case letter followed by an upper-case one, with that letter converted to lower-case. |
| String toString() | Return the content of this WrappedString, performing HTML escaping. |
| String raw() | Return the content of this WrappedString without escaping. |