What is the difference between ResourceResolver and ResourceResolverFactory interface?

When working to get a JCR session - you typically inject a ResoureResolverFactory instance into your code to get a ResourceResolver object. See this code:

//Inject a Sling ResourceResolverFactory

@Reference

private ResourceResolverFactory resolverFactory;

public String getCustomerData(String filter) {

Customer cust = null;

List<Customer> custList = new ArrayList<Customer>();

Map<String, Object> param = new HashMap<String, Object>();

param.put(ResourceResolverFactory.SUBSERVICE, "datawrite");

ResourceResolver resolver = null;

try {

    //Invoke the adaptTo method to create a Session used to create a QueryManager

    resolver = resolverFactory.getServiceResourceResolver(param);

    session = resolver.adaptTo(Session.class);

ResourceResolverFactory is like any other service that is available in OSGI framework. It's most frequent use is accessing resource resolver. You can see its detailed use in  your felix console, /system/console/configMgr. Search for "Apache Sling Resource Resolver Factory".

Now, coming to your second part of the question...

It depends on where you need to get the handle of resourceResolver. In Servlet OR In Java code(non servlet), In OSGI service or In WorkflowProcess class., In JSP .. etc.  The most straight forward way is to handle it in the servlet where we have request and resource objects available. So, its request.getResourceResolver() and resource.getResourceResolver(); In case of WorkflowProcess class OR in OSGI service,  you could inject a @Reference object for ResourceResolverFactory and get resourceResolver.

Finally, In case of JSP, if you have sling:defineObjects tag included, then resourceResolver becomes an implicit object and you could use it as is. I hope i have answered your question. Please let me know if you have any more questions or clarifications with respect to this question.

Nice explanation!

ResourceResolver Interface

• Purpose: The ResourceResolver interface is used to resolve and access resources within the repository. It acts as your main tool for finding resources, adapting them to different types, and navigating the resource tree.

• Functionality:

  • Resolving Resources: It maps HTTP requests or paths to resources stored in the repository.
  • Accessing Resource Properties: Allows for reading properties of resources.
  • Adapting Resources: Enables adapting resources to other types, like adapting a Resource to a ValueMap for property access or to a custom model class.
  • Querying: Supports querying the repository using SQL, XPath, or the Query Builder API.

• Lifecycle: A ResourceResolver instance is typically obtained per request or session and must be closed after use to release any underlying resources and sessions.

ResourceResolverFactory Interface

• Purpose: The ResourceResolverFactory is a factory interface used to create and obtain instances of ResourceResolver. It provides the methods to get a new ResourceResolver instance based on different types of authentication and access requirements.

• Functionality:

  • Creating ResourceResolvers: Offers methods to create new ResourceResolver instances, such as getServiceResourceResolver for service users or getAdministrativeResourceResolver (deprecated and not recommended for use due to security concerns) for administrative access.
  • Parameterized Resolver Creation: Allows for the creation of ResourceResolver instances with specific attributes or requirements, using Map<String, Object> parameters to define the creation context.

• Service User Mapping: In AEM, ResourceResolverFactory is often used in conjunction with service users, which are predefined users with specific permissions. This practice is part of AEM's security best practices, ensuring that code executes with only the permissions it requires.