The /atg/endeca/assembler/AssemblerPipelineServlet component is part of Oracle ATG’s request handling pipeline and it is of class atg.endeca.assembler.AssemblerPipelineServlet. AssemblerPipelineServlet’s primary task is to invoke the Assembler, passing in a ContentInclude (for a page request) or a ContentSlotConfig (for a content collection request). AssemblerPipelineServlet is started when the ATG server is started. The /Initial.properties file under DAF.Endeca.Assembler configures this behavior by adding AssemblerPipelineServlet to its initial services.
initialServices+=\ /atg/endeca/assembler/AssemblerPipelineServlet
On invocation of the AssemblerPipelineServlet.service() method, several items are checked to determine whether or not the servlet should execute:
The
AssemblerPipelineServlet.enableproperty: If this property is set tofalse, the servlet is disabled and the request will be passed. This property defaults totrue.The
atg.assemblercontext parameter: A web application must explicitly set theatg.assemblercontext parameter to true in itsweb.xmlfile, otherwise theAssemblerPipelineServletwill pass the request. To set theatg.assemblercontext parameter totrue, add the following to the application’sweb.xmlfile:<context-param>
<param-name>atg.assembler</param-name>
<param-value>true</param-value>
</context-param>Applications that never have a need to invoke the Assembler, should set
atg.assemblertofalseto bypass the servlet and avoid making requests to the Assembler.The MIME type of the request:
AssemblerPipelineServletuses the request URI to determine the MIME type of the request. IfAssemblerPipelineServletis not allowed to process the specified MIME type, it passes the request. By default, theAssemblerPipelineServletcomponent passes all known MIME types and only executes for a null MIME type. See Bypassing or Invoking the Assembler Based On MIME Type for more information on customizing the MIME types that theAssemblerPipelineServletis allowed to execute.The
AssemblerPipelineServlet.ignoreRequestURIPatternproperty: This optional property contains a regular expression that defines a pattern for URIs that should be disallowed. When this property is set, the request URI is compared against the specified regular expression and, if the current URI matches the regular expression, the request is passed. Out of the box, this property is not set.
If all of the above checks pass, AssemblerPipelineServlet executes. Its first task is to determine whether the request is a page request or a content collection request. AssemblerPipelineServlet makes this determination based on the URL, as described in the following sections.
Content Collection Request Identification and Handling
The URL for a content collection request has some additional requirements that the URL for a page request does not have. Specifically, the URL for a content collection must have an /assembler sub-path and an assemblerContentCollection request parameter, for example:
/crs/storeus/assembler/?assemblerContentCollection=Search Box Auto Suggest Content
The /assembler sub-path can take any of these forms:
/assembler<context-root>/assembler(for example,crs/assembler)<site.productionURL>/assembler(for example,/crs/storeus/assembler)
The assemblerContentCollection request parameter must specify the name of a content collection. If these content collection URL conditions are met, AssemblerPipelineServlet creates a ContentSlotConfig object and passes it to the Assembler:
contentItem = new ContentSlotConfig(content, ruleLimit);
A content collection URL may also include the optional assemblerRuleLimit request parameter. This is an integer value that is used as an argument to the ContentSlotConfig constructor. It determines the number of items to return from the content collection. If assemblerRuleLimit is not set or is an invalid value, then the default value of 1 is used.
/crs/storeus/assembler/?assemblerContentCollection=Search Box Auto Suggest Content&assemblerRuleLimit=3
If the content collection does not exist, the Assembler returns a content item whose contents value is empty. For example, this URL:
http://localhost:8080/assembler/assembler?assemblerContentCollection=/content/BrowsePageCollection&format=json
Results in this data:
{"@type":"ContentSlot","contents":[],"ruleLimit":1,"contentCollection":"\/content\/BrowsePageCollection"}Page Request Identification and Handling
If the URL does not fit the requirements for a content collection request, the AssemblerPipelineServlet component assumes that this is a page request. A page request must be transformed into a form that the NucleusAssembler class can accept. To do this, the AssemblerPipelineServlet component calls the AssemblerTools.getContentPath() method to transform the page request URL into a URI and store it in a ContentInclude that can be passed to the NucleusAssembler class. The NucleusAssembler class can then match this URI to the URIs of the pages defined Experience Manager. See the AssemblerTools section for specific details on how the URL transformation is done.
Bypassing or Invoking the Assembler Based On MIME Type
By default, the AssemblerPipelineServlet limits its Assembler invocation to request paths that do not match a known MIME type. It does this via a reference to the /atg/dynamo/servlet/pipeline/MimeTyper component, which is part of the ATG Platform system that routes and executes requests based on matching MIME types. This configuration prevents the AssemblerPipelineServlet from intercepting requests for JSP, CSS, HTML, and JavaScript files, among others.
You can add allowed MIME types or disable Assembler invocation for unknown MIME types using the following AssemblerPipelineServlet configurable properties:
# Whether to invoke the Assembler for a potential match on a request # that doesn't match a known MIME type (typically a directory). # # assembleUnknownMimeTypes=true # A String array of allowed MIME types. Defaults to null, but # can be set to a MIME type if you want to pass certain extensions to # the Assembler (for example, ".asm" or ".endeca"). # # allowedMimeTypes=
See the ATG Platform Programming Guide for more information on the MimeTyper component.
