Servlet is a Java programming language class that is used to extend the capabilities of servers that host applications accessed by means of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers.
Servlets can be registered as OSGi services. For a Servlet registered as an OSGi service to be used by the Sling Servlet Resolver, the following restrictions apply:
There are two ways of doing this
We should prefer @SlingServlet annotation.
You can register a Servlet using the two Standard approaches:
The resource type(s) supported by the servlet. The property value must either be a single String, an array of Strings or a Vector of Strings. This property is ignored if the sling.servlet.paths property is set. More on Register servlet by Resource Type watch this video
SlingSafeMethodsServlet - Helper base class for read-only Servlets used in Sling. This base class is actually just a better implementation of the Servlet API HttpServlet class which accounts for extensibility. So extensions of this class have great control over what methods to overwrite. It supports GET, HEAD, OPTIONS etc methods. Read more
SlingAllMethodsServlet - Helper base class for data modifying Servlets used in Sling. This class extends the SlingSafeMethodsServlet by support for the POST, PUT and DELETE methods. Read more
Suppose I have added sling.servlet.paths and sling.servlet.resourceTypes both in servlet. sling.servlet.resourceTypes property is ignored if the sling.servlet.paths property is set.
The ResourceResolver defines the service API which may be used to resolve Resource objects. The resource resolver is available to the request processing servlet through the SlingHttpServletRequest.getResourceResolver() method. A resource resolver can also be created through the ResourceResolverFactory. The ResourceResolver is also an Adaptable to get adapters to other types.Read more
Registering the servlet by resourceType is more preferential than path , because
The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named "serialVersionUID" that must be static, final, and of type long:
If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization