Modifying Content - The SlingPostServlet has been edited by Felix Meschberger (May 15, 2008).

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Content:

Modifying Content: The SlingPostServlet

Work In Progress

This page is work in progress to explain how the SlingPostServlet works after the refactoring as per SLING-422

Multiple Ways to Modify Content

As always in life there is more than one way to do it. So to modify content in a JCR repository underlying Sling, you have multiple options, two of which are WebDAV and the Sling default POST Servlet also called the SlingPostServlet. This page is about how you can modify - create, modify, copy, move, delete - content through the SlingPostServlet. In addition it also explains how to extend the SlingPostServlet with new operations.

What is Content anyway ? In the following discussion, I use the terms Content and Item interchangeably. With Content I just mean some data to be stored in the JCR repository to be later used as the basis for some presentation. In this sense Content is a rather conceptual term. Item is the name of the parent interface of the JCR Node and Property interfaces. When speaking of Items we mean some actual data stored in the repository ignoring whether the data is actually stored as a Node with child nodes and properties or just a single Property.

Quickstart: Creating Content

To create content you simply send an HTTP request using the path of the node to store the content in and include the actual content as request parameters. So one possibility to do just that is by having an HTML Form like the following:

<form method="POST" action="" class="code-quote">"http://host/some/new/content" >
   <input type="text" name="title" value="" />
   <input type="text" name="text" value="" />
</form>


This simple form will set the title and text properties on a node at /some/new/content. If this node does not exist it is just created otherwise the existing content would be modified.

Similarly you can do this using the curl command line tool:

$ curl -Ftitle="some title text" -Ftext="some body text content" http://host/some/new/content

You might want to use a specific JCR node type for a newly created node. This is possibly by simply setting a jcr:primaryType property on the request, e.g.

$ curl -F"jcr:primaryType=nt:unstructured" -Ftitle="some title text" -Ftext="some body text content" http://host/some/new/content

Similary you may assing JCR mixin node types using the jcr:mixinTypes property and a Sling resource type using the sling:resourceType property. For example:

$ curl -F"sling:resourceType=sling:sample" -Ftitle="some title text" -Ftext="some body text content" http://host/some/new/content

SlingPostServlet Operations

The SlingPostServlet is actually just a frontend to the actual operations. To select the actual operation to execute, the :operation request parameter is used. Out of the box, the SlingPostServlet supports the following operations:

  • property not set or empty – Create new content or modify existing content
  • delete – Remove existing content
  • move – Move existing content to a new location
  • copy – Copy existing content to a new location

All these operations always operate on the resource of the request as returned by SlingHttpServletRequest.getResource(). Some operations require additional parameters to be set to operate completely.

Content Creation or Modification

The simplest and most common use case, probably, is content creation and modification. We already saw an example above in the quickstart section. In this section we elaborate more on the concrete stuff.

First, the request URL indicates the actual repository node to be handled. If the URL addresses an existing node, the request parameters just provide values for the properties to be set on the existing node.

If the resource of the request is a synthetic resource, e.g. NonExistingResource or StarResource, a new item is created. The path (including name) of the item to be created is derived from the resource path:

  • If the resource path ends with a /* or / the name of the item is automatically created using a name creation algorithm taking into account various request parameters.
  • Otherwise the resource path is used as the path and name of the new item.

In both cases the path may still include selectors and extensions, which are cut off the path before finding out, what to do.

To illustrate this algorithm, lets look at some examples:

Resource Path Item path
/content/new /content/new
/content/new.html /content/new
/content/new.print.a4.html /content/new
/content/ /content/xxx where xxx is a generated name
/content/* /content/xxx where xxx is a generated name
/content/*.html /content/xxx where xxx is a generated name
/content/*.print.a4.html /content/xxx where xxx is a generated name

TDB: How parameters are used to define content to be stored.

Response Status

The delete operation has the following status responses:

Status Explanation
200/OK An existing node has been updated with content
201/CREATED A new node has been created and filled with content
500/INTERNAL SERVER ERROR Some exception, for example a RepositoryException, occurred while processing the request

Content Removal

To remove existing content just address the item to be removed and set the :operation parameter to delete. For example the following command line removes the /content/sample page:

$ curl -F":operation=delete" http://host/content/sample

Response Status

The delete operation has the following status responses:

Status Explanation
200/OK The resource (and all its descendents) has been removed
404/NOT FOUND The request URL does not address an existing repository item
500/INTERNAL SERVER ERROR Some exception, for example a RepositoryException, occurred while processing the request

Copying Content

To copy existing content to a new location, the copy operation is specified. This operation copies the item addressed by the request URL to a new location indicated by the :dest parameter. The :dest parameter is the absolute or relative path to which the resource is copied. If the path is relative it is assumed to be below the same parent as the request resource. If it is terminated with a / character the request resource is copied to an item of the same name under the destination path.

To illustrate the :dest parameter handling, lets look at a few examples. All examples are based on addressing the /content/sample item:

:dest Parameter Destination Absolute Path
/content/newSample /content/newSample
different/newSample /content/different/newSample
/content/different/ /content/different/sample
different/ /content/different/sample

If an item already exists at the location derived from the :dest parameter, the copy operation fails unless the :replace parameter is set to true (case is ignored when checking the parameter value).

Status Explanation
200/OK The node has been copied to the new location replacing an existing item at the destination
201/CREATED The node has been copied to the new location creating a new item at the destination
412/PRECONDITION FAILED An item already exists at the destination and the :replace parameter is not set to true
500/INTERNAL SERVER ERROR Some exception, for example a RepositoryException, occurred while processing the request

Moving Content

To move existing content to a new location, the move operation is specified. This operation moves the item addressed by the request URL to a new location indicated by the :dest parameter. The :dest parameter is the absolute or relative path to which the resource is moved. If the path is relative it is assumed to be below the same parent as the request resource. If it is terminated with a / character the request resource is moved to an item of the same name under the destination path.

To illustrate the :dest parameter handling, lets look at a few examples. All examples are based on addressing the /content/sample item:

:dest Parameter Destination Absolute Path
/content/newSample /content/newSample
different/newSample /content/different/newSample
/content/different/ /content/different/sample
different/ /content/different/sample

If an item already exists at the location derived from the :dest parameter, the move operation fails unless the :replace parameter is set to true (case is ignored when checking the parameter value).

Status Explanation
200/OK The node has been moved to the new location replacing an existing item at the destination
201/CREATED The node has been moved to the new location creating a new item at the destination
412/PRECONDITION FAILED An item already exists at the destination and the :replace parameter is not set to true
500/INTERNAL SERVER ERROR Some exception, for example a RepositoryException, occurred while processing the request

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