Apache

Basic Ideas

Collections

SlingQuery class represents a collection of resources. Basic collection can be created explicitly via a dollar method:

$(resource1, resource2, resource3)

Above method creates a new SlingQuery object that consists of 3 resources. This object implements Iterable<Resource> interface, so can be used in foreach statements directly:

for (Resource resource in $(...)) { }

Operations

SlingQuery class defines a number of methods which can be used to transform current collection into a new one. Following code:

$(resource1, resource2).parent()

will replace each resource with its direct parent. If some resource is a repository root, it will be skipped. Some methods replace each resource with another resource (eg. parent() or closest()). Other methods can replace each resource with a set of resources:

$(resource1, resource2).children();

Resulting object will contain direct children of both resource1 and resource2 objects. There are also methods that doesn't add any new resources, but removes existing:

$(resource1, resource2).first();

Methods can be chained to create more complex query. Eg. following code will return last direct child of the resource:

$(resource).children().last();

Laziness

All operations are lazy (except prev() and sometimes not()). It means that SlingQuery won't read any resources until it's actually necessary. Example:

$(resource).children().children().first();

children().children() construction reads all grand-children of the given resource. However, the last method limits the output to the first found resource. As a result, SlingQuery won't iterate over all children and grand-children, but it will simply take the first child of the resource and return its first child.

Immutability

SlingQuery object is immutable and each operation creates a new one. We can "freeze" some collection before performing more operations on it:

SlingQuery children = $(resource).children();
SlingQuery firstChild = children.first();
for (Resource child : children) { /* will display all children */ }
for (Resource child : firstChild) { /* will display the first child */ }

Selectors

Some operations may take an additional string selector parameter that defines a filtering. Selector could be used to define resource type, resource attributes and additional modifiers. Example selector could look like this:

"cq:Page"

It will match all resources with the given resource type. Example:

$(resource).children("cq:Page")

will return only children with cq:Page resource type. You could also filter these resources defining any number of attributes in the square brackets:

$(resource).children("cq:Page[jcr:title=Some title][jcr:description=Some desc]")

And finally, you could add some modifiers at the end:

$(resource).children("cq:Page[jcr:content/cq:template=my/template]:even")

Above resources will find cq:Page children of the resource, using template my/template and return not all of them, but only those with even indices (eg. if matching children of the resource are page_0, page_1 and page_2, only the first and the last will be returned).

All parts of the selector are optional. In fact, an empty string ("") is a valid selector, accepting all resources. However, the defined order (resource type, attributes in square brackets and modifiers) has to be followed. Example selectors:

"foundation/components/richtext" // resource type
"foundation/components/richtext:first" // resource type with modifier
"[property=value][property2=value2]" // two attributes
":even" // modifier
":even:not(:first)" // two modifiers, the second one is nested