Mule has three layers - application, integration, and transport. It allows you to develop or reuse services and business logic, configure message processors to orchestrate services, and integrate applications using various transports and connectors. Key aspects that can be configured include flows, services, routers, filters, and transformers to route, filter, transform messages between services and transports. Mule also provides APIs to extend and customize its capabilities.

1. WORKING OF MULE

2. Layers :
 There are three layers in the architecture :
 The application layer,
 The integration layer,
 The transport layer.

3. Architechture :

4. General types of tasks you can perform to
configure and customize your Mule deployment:
 Service Component Development: Developing or reuse
existing POJOs, services, Cloud Connectors, or Spring beans
that contain the business logic and will consume, process, or
enrich messages.
 Service Orchestration: Configuring message processors,
routers, transformers, and filters that provide the service
mediation and orchestration capabilities required to allow
composition of loosely coupled services using a Mule Flow.
 Integration: A key requirement of service mediation is
decoupling services from the underlying protocols. Mule
provides transports to allow dispatching and receiving
messages on different protocol connectors. These connectors
are configured in the Mule configuration and then can be
referenced from the orchestration layer.

5. Create a Service Component :
 A service component is a class, web service, or
other application that contains the business logic
you want to plug in to the Mule service bus. You
can use any existing :
 Java class,
 Spring bean,
 Groovy script,
 Cloud Connector, or create a new component.
 Your service component does not need to contain
any Mule-specific code. All the Mule-specific
instructions will be configured on the service that
wraps the service component.

6. Configure the Mule Instance :
 The Mule configuration file allows you to configure
all the elements you need in your Mule instance.
 <configuration> element is used to set global
configuration options such as the threading
profile.
 Then define the connectors, transformers, and
endpoints to be used in different flows. Lastly,
configure flows or service models, which act as
containers for services and orchestration
elements and apply settings such as the queue
profile and error handling to all the services in that
flow or service model.

7. Configure the Flow :
 Configure a flow using the <flow> element in the
Mule configuration file.
 The flow creates a composition around the service
component(s) that will allow to define how
messages are routed, filtered, transformed and
enriched before or after processing by one or a
series of service components.
 Flows are more flexible and robust than the
traditional service model in Mule, allowing a more
natural and compact means of describing service
orchestration.

8. Configure the Service :
 Service can be configured within
a <model> element in the Mule configuration
file.
 The service points to the service component,
routers, filters, and transformers.
 It also specifies the endpoint on which this
service will receive messages and the
outbound endpoint where messages will go
next.

9. Message Processors :
 Message Processors are the basic building
blocks in Mule and in fact, components, routers,
filters, and transformers are all message
processors.
 There are also other special message processors
that do not fall in one of those categories.
 These include a number of specialized modules
like CXF and Jersey Web Services, BPM, as well
as a few specialized integration elements
like <poll>, <content-enricher>, and <logger>.
 Custom message processor can also be created
easily.

10. Routers :
 Router types :
 Inbound routers
 Outbound routers
 Default routers (many)
 Inbound routers specify how messages are routed
to a service.
 Outbound routers specify how messages are
routed after the service has finished processing
them.
 There are several default routers that come with
Mule that you can use, or you can create your
own routers.

11. Filters :
 Filters specify conditions that must be met for
a message to be routed to a service.
 There are several default filters that come with
Mule that you can use, or you can create your
own filters.

12. Transformers :
 Transformers convert incoming payload data
to the type required by the service component.
 After the service has finished processing the
message, they can also convert the message
to a different type as needed by the outbound
transport.
 There are several default transformers you can
use, or create your own.

13. Transports and Connectors :
 Mule provides default transports for many different
channels, including :
 File,
 FTP,
 HTTP,
 JMS,
 JDBC,
 Quartz, and many more.
 Transports communicate with the channel using a
connector.
 There are also many community-contributed
transports and Cloud Connectors on Mule Forge.

14. Cloud Connectors :
 Cloud Connectors are actually message
processors that are used to speak to
application APIs over existing transports -
almost always HTTP.
 Cloud Connectors typically connect
 SaaS applications,
 Social media,
 Cloud infrastructure services,
 Cloud-based data services.

15. Extend Mule :
 Mule provides a complete set of APIs for
extending Mule. Typical custom extensions
include:
 Cloud Connectors
 Transports
 Custom Message Processors
 Custom Transformers
 Configuration Patterns

16.  Still more to learn!!!!!!!!!!!! STAY TUNED!!!!!!