= Velocity Response Writer
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The VelocityResponseWriter is an optional plugin available in the `contrib/velocity` directory. It powers the /browse user interfaces when using some example configurations such as "techproducts" and "example/files".

[WARNING]
====
The VelocityResponseWriter and associated /browse UI is deprecated and will be removed in 9.0.

The functionality has been replaced by a 3rd party plugin available at https://github.com/erikhatcher/solritas.
====

Its JAR and dependencies must be added (via `<lib>` or solr/home lib inclusion), and must be registered in `solrconfig.xml` like this:

[source,xml]
----
<queryResponseWriter name="velocity" class="solr.VelocityResponseWriter">
  <str name="template.base.dir">${velocity.template.base.dir:}</str>

<!--
  <str name="init.properties.file">velocity-init.properties</str>
  <lst name="tools">
    <str name="mytool">com.example.MyCustomTool</str>
  </lst>
-->
</queryResponseWriter>
----

== Configuration & Usage

=== Template Rendering Protections

Velocity template rendering is largely controlled by the `trusted` configset flag.  Templates built into (the `/browse` ones) the component library are always available
with this component.  In a trusted configset, templates in the `velocity/` subdirectory of the configset are renderable.  Also in a trusted configset, when `template.base.dir`
is specified those templates are renderable.

=== VelocityResponseWriter Initialization Parameters

`template.base.dir`::
If specified and exists as a file system directory, a file resource loader will be added for this directory. Templates in this directory will override "solr" resource loader templates.

`init.properties.file`:: Specifies a properties file name which must exist in the Solr `conf/` directory (*not* under a `velocity/` subdirectory) or root of a JAR file in a <lib>.

`tools`::
External "tools" can be specified as list of string name/value (tool name / class name) pairs. Tools, in the Velocity context, are simply Java objects. Tool classes are constructed using a no-arg constructor (or a single-SolrCore-arg constructor if it exists) and added to the Velocity context with the specified name.
+
A custom registered tool can override the built-in context objects with the same name, except for `$request`, `$response`, `$page`, and `$debug` (these tools are designed to not be overridden).

=== VelocityResponseWriter Request Parameters

`v.template`::
Specifies the name of the template to render.

`v.layout`::
Specifies a template name to use as the layout around the main, `v.template`, specified template.
+
The main template is rendered into a string value included into the layout rendering as `$content`.

`v.layout.enabled`::
Determines if the main template should have a layout wrapped around it. The default is `true`, but requires `v.layout` to specified as well.

`v.contentType`::
Specifies the content type used in the HTTP response. If not specified, the default will depend on whether `v.json` is specified or not.
+
The default without `v.json=wrf`: `text/html;charset=UTF-8`.
+
The default with `v.json=wrf`: `application/json;charset=UTF-8`.

`v.json`::
Specifies a function name to wrap around the response rendered as JSON. If specified, the content type used in the response will be "application/json;charset=UTF-8", unless overridden by `v.contentType`.
+
Output will be in this format (with `v.json=wrf`):
+
`wrf("result":"<Velocity generated response string, with quotes and backslashes escaped>")`

`v.locale`::
Locale to use with the `$resource` tool and other LocaleConfig implementing tools. The default locale is `Locale.ROOT`. Localized resources are loaded from standard Java resource bundles named `resources[_locale-code].properties`.
+
Resource bundles can be added by providing a JAR file visible by the SolrResourceLoader with resource bundles under a velocity sub-directory. Resource bundles are not loadable under `conf/`, as only the class loader aspect of SolrResourceLoader can be used here.


=== VelocityResponseWriter Context Objects

// TODO: Change column width to %autowidth.spread when https://github.com/asciidoctor/asciidoctor-pdf/issues/599 is fixed

[cols="30,70",options="header"]
|===
|Context Reference |Description
|`request` |{solr-javadocs}solr-core/org/apache/solr/request/SolrQueryRequest.html[SolrQueryRequest] javadocs
|`response` |{solr-javadocs}solr-core/org/apache/solr/response/SolrQueryResponse.html[QueryResponse] most of the time, but in some cases where QueryResponse doesn't like the request handler's output (https://cwiki.apache.org/confluence/display/solr/AnalysisRequestHandler[AnalysisRequestHandler], for example, causes a ClassCastException parsing "response"), the response will be a SolrResponseBase object.
|`esc` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#EscapeTool[EscapeTool] instance
|`date` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#ComparisonDateTool[ComparisonDateTool] instance
|`math` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#MathTool[MathTool] instance
|`number` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#NumberTool[NumberTool] instance
|`sort` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#SortTool[SortTool] instance
|`display` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#DisplayTool[DisplayTool] instance
|`resource` |A Velocity http://velocity.apache.org/tools/{ivy-velocity-tools-version}/tools-summary.html#ResourceTool[ResourceTool] instance
|`engine` |The current VelocityEngine instance
|`page` |An instance of Solr's PageTool (only included if the response is a QueryResponse where paging makes sense)
|`debug` |A shortcut to the debug part of the response, or null if debug is not on. This is handy for having debug-only sections in a template using `#if($debug)...#end`
|`content` |The rendered output of the main template, when rendering the layout (`v.layout.enabled=true` and `v.layout=<template>`).
|[custom tool(s)] |Tools provided by the optional "tools" list of the VelocityResponseWriter registration are available by their specified name.
|===

=== VelocityResponseWriter Usage

To see results in an HTML user interface on your own collection, try http://localhost:8983/solr/<my collection>/select?q=*:*&wt=velocity&v.template=browse&v.layout=layout

Or try `/browse` in the examples techproducts or example/files.