Rewrites URIs in links to a value determined by an InputModule.
The URI scheme identifies the InputModule to use, and the rest of the URI is
used as the attribute name.
Example
For instance, if we had an
org.apache.cocoon.components.modules.input.XMLFileModule , configured to
read values from an XML file:
<site>
<faq>
<how_to_boil_eggs href="faq/eggs.html"/>
</faq>
</site>
mapped to the prefix 'site:', then <link
href="site:/site/faq/how_to_boil_eggs/@href"> would be replaced
with <link href="faq/eggs.html">
InputModule Configuration
InputModules are configured twice; first statically in
cocoon.xconf, and then dynamically at runtime, with dynamic
configuration (if any) taking precedence. Transformer allows
you to pass a dynamic configuration to used InputModules as follows.
First, a template Configuration is specified in the static
<map:components> block of the sitemap within <input-module> tags:
<map:transformer name="linkrewriter"
src="org.apache.cocoon.transformation.LinkRewriterTransformer">
<link-attrs>href src</link-attrs>
<schemes>site ext</schemes>
<input-module name="site">
<file src="cocoon://samples/link/linkmap" reloadable="true"/>
</input-module>
<input-module name="mapper">
<input-module name="site">
<file src="{src}" reloadable="true"/>
</input-module>
<prefix>/site/</prefix>
<suffix>/@href</suffix>
</input-module>
</map:transformer>
Here, we have first configured which attributes to examine, and which URL
schemes to consider rewriting. In this example, <a href="site:index">
would be processed. See below for more configuration options.
Then, we have established dynamic configuration templates for two modules,
'site' (an
org.apache.cocoon.components.modules.input.XMLFileModule and 'mapper' (A
org.apache.cocoon.components.modules.input.SimpleMappingMetaModule . All
other InputModules will use their static configs. Note that, when
configuring a meta InputModule like 'mapper', we need to also configure the
'inner' module (here, 'site') with a nested <input-module>.
There is one further twist; to have really dynamic configuration,
we need information available only when the transformer actually runs. This
is why the above config was called a "template" configuration; it needs to
be 'instantiated' and provided extra info, namely:
- The {src} string will be replaced with the map:transform @src attribute value.
- Any other {variables} will be replaced with map:parameter values
With the above config template, we can have a matcher like:
<map:match pattern="**welcome">
<map:generate src="index.xml"/>
<map:transform type="linkrewriter" src="cocoon:/{1}linkmap"/>
<map:serialize type="xml"/>
</map:match>
Which would cause the 'mapper' XMLFileModule to be configured with a
different XML file, depending on the request.
Similarly, we could use a dynamic prefix:
<prefix>{prefix}</prefix>
in the template config, and:
<map:parameter name="prefix" value="/site/"/>
in the map:transform
A live example of LinkRewriterTransformer can be found in the Apache Forrest sitemap.
Transformer Configuration
The following configuration entries in map:transformer block are recognised:
- link-attrs
- Space-separated list of attributes to consider links (to be
transformed). The whole value of the attribute is considered link and
transformed.
- link-attr
- 0..n of these elements each specify an attribute containing link(s)
(to be transformed) and optionally a regular expression to locate
substring(s) of the attribute value considered link(s). Has two
attributes:
- name
- (required) name of the attribute whose value contains link(s).
- pattern
- (optional) regular expression such that when matched against the
attribute value, all parenthesized expressions (except number 0) will
be considered links that should be transformed. If absent, the whole value
of the attribute is considered to be a link, as if the attribute was
included in 'link-attrs'.
- schemes
- Space-separated list of URI schemes to explicitly include.
If specified, all URIs with unlisted schemes will not be converted.
- exclude-schemes
- Space-separated list of URI schemes to explicitly exclude.
Defaults to 'http https ftp news mailto'.
- bad-link-str
- String to use for links with a correct InputModule prefix, but no value
therein. Defaults to the original URI.
- namespace-uri
- The namespace uri of elements whose attributes are considered for
transformation. Defaults to the empty namespace ("").
The attributes considered to contain links are a set of the attributes
specified in 'link-attrs' element and all 'link-attr' elements. Each attribute
should be specified only once either in 'link-attrs' or 'link-attr'; i.e. an
attribute can have at most 1 regular expression associated with it. If neither
'link-attrs' nor 'link-attr' configuration is present, defaults to 'href'.
Below is an example of regular expression usage that will transform links
x1 and x2 in
<action target="foo url(x1) bar url(x2)"/>:
<map:transformer name="linkrewriter"
src="org.apache.cocoon.transformation.LinkRewriterTransformer">
<link-attr name="target" pattern="(?:url\((.*?)\).*?){1,2}$"/>
<!-- additional configuration ... -->
</map:transformer>
When matched against the value of target attribute above,
the parenthesized expressions are:
$0 = url(x1) bar url(x2)
$1 = x1
$2 = x2
Expression number 0 is always discarded by the transformer and the rest
are considered links and re-written.
If present, map:parameter's from the map:transform block override the
corresponding configuration entries from map:transformer. As an exception,
'link-attr' parameters are not recognised; 'link-attrs' parameter overrides
both 'link-attrs' and 'link-attr' configuration.
version:
$Id: LinkRewriterTransformer.java 433543 2006-08-22 06:22:54Z crossley $ | 