Querying in AEM

What can we query for ..?

In a relational database one can query against table columns. But in a hierarchical content repository what can we query for.. ?

Well a tree structure has nodes and node can properties as well as child nodes as shown in picture.And every node will have an absolute path which determines its location on the tree structure.

We can create conditions with these things and that is nothing but our query.

Query is simply a set of the conditions alias predicates. Predicates available within AEM are listed below

Query Predicates	Example
Node Name Wild Card : * Case Sensitive	nodename=myapp nodename=myapp* // searches for any or no character after myapp nodename=myapp? // searches for any character  after myapp
Node Type	type=cq:Page type=nt:unstructured
Property Wild card : % Case Sensitive	property=jcr:title property.value=catalog property.operation=equals (default if not provided) property=jcr:title property.value=cat%  property.operation=like
Path	path=/content/myapp/products/catalog/en
Full Text (Performs a word search in the  entire repository, or within a path if provided) Wild Card: * Non Case Sensitive	fulltext=catalog path=/content/myapp/products fulltext=cat* fulltext.relPath=jcr:title Full text searches all the content, if we need to search for a particular property relPath can be used

How do we Query ? 

AEM provides us Query Builder API to write the queries. Query Builder is very easy to use and it is a wrapper around the actual query language like XPATH, SQL2 etc. 

You just require all of our query parameters put to a map and Java Query Builder API does the rest. 

 Map<String,String> map = new HashMap<String,String> ();
 map.put("path", "/content/myapp/products");
 map.put("type", "nt:file");

 Query query = builder.createQuery(PredicateGroup.create(map), session);
 SearchResult searchResult   =  query.getResult();

 List<Hit> resultHits   =  searchResult .getHits();

Now we can iterate through the result hits and achieve what we want.

You can find a bit more at Query Builder API