Mulesoft ESB Interview Questions & Answers

Introduction

If you're looking for MuleSoft Interview Questions for Experienced & Freshers, you are at right place. There are lot of opportunities from many reputed companies in the world. According to research MuleSoft has a market share of about 5.9%. So, You still have opportunity to move ahead in your career in Mule ESB. There are different positions open as Mule ESB Developer, Mule ESB architect, Mule ESB engineer, Mule ESB consultant, Mule ESB expert, etc across many top IT hubs.

Overview

What is ESB?

An enterprise service bus (ESB) is software architecture for middleware that provides fundamental services for more complex architectures. For example, an ESB incorporates the features required to implement a service-oriented architecture (SOA). In a general sense, an ESB can be thought of as a mechanism that manages access to applications and services (especially legacy versions) to present a single, simple, and consistent interface to end-users via Web- or forms-based client-side front ends.

What Is Mule ESB?

Mule is a lightweight event-driven enterprise service bus (ESB) and an integration platform. It is a lightweight and modular solution that could scale from an application-level messaging framework to an enterprise-wide highly distributable object broker.

What are the features of Mule ESB/ESB ?

Transport: applications can accept input from a variety of means, from the file system to the network.

Data format: speaking the right protocol is only part of the solution, as applications can use almost any form of representation for the data they exchange.

Invocation styles: synchronous, asynchronous, or batch call semantics entail very different integration strategies.

Lifecycles: applications of different origins that serve varied purposes tend to have disparate development, maintenance, and operational lifecycles.

Why Mule Was Designed ?

Mule’s core was designed as an event-driven framework combined with a unified representation of messages, expandable with pluggable modules. These modules would provide support for a wide range of transports or add extra features, such as distributed transactions, security, or management. Mule was also designed as a programmatic framework offering programmers the means to graft additional behavior such as specific message processing or custom data transformation.

What Are Differences Between Mule And Other Commercial Esbs ?

Prescriptive deployment model, whereas Mule supports a wide variety of deployment strategies. Prescriptive SOA methodology, whereas Mule can embrace the architectural style and SOA practices in place where it is deployed. Mainly focused on higher-level concerns, whereas Mule deals extensively with all the details of integration. Strict full-stack web service orientation, whereas Mule’s capacities as an integration framework open it to all sorts of other protocols. Comprehensive documentation, a subject on which MuleSource has made huge progress recently.

What Is Model Layer In Mule ?

The first logical layer is the model layer. A Mule model represents the runtime environment that hosts services. It defines the behavior of Mule when processing requests handled by services. The model provides services with supporting features, such as exception strategies. It also provides services with default values that simplify their configuration.

What Is Service Layer In Mule ?

A Mule service is composed of all the Mule entities involved in processing particular requests in predefined manners.A service is defined by a specific configuration. This configuration determines the different elements, from the different layers of responsibility, that will be mobilized to process the requests that it will be open to receive. Depending on the type of input channel it uses, a service may or may not be publicly accessible outside of the ESB.

What Is Transport Layer In Mule ?

The transport layer is in charge of receiving or sending messages. This is why it is involved with both inbound and outbound communications. A transport manifests itself in the configuration by the following elements: connectors, endpoints and transformers.

A transport also defines one message adapter. A message adapter is responsible for extracting all the information available in a particular request (data, meta information, attachments, and so on) and storing them in transport-agnostic fashion in a Mule message.

What Is Connector In Mule ?

A connector is in charge of controlling the usage of a particular protocol. It is configured with parameters that are specific to this protocol and holds any state that can be shared with the underlying entities in charge of the actual communications.

For example: a JMS connector is configured with a Connection, which is shared by the different entities in charge of the actual communication.

What Is Endpoint In Mule ?

An endpoint represents the specific usage of a protocol, whether it is for listening/polling, reading from, or writing to a particular target destination. Hence it controls what underlying entities will be used with the connector they depend on. The target destination itself is defined as a URI. Depending on the connector, the URI will bear a different meaning; for example, it can represent a URL or a JMS destination.

What Is Transformer In Mule ?

A transformer takes care of translating the content of a message from one form to another. It is possible to chain transformers to cumulate their effects. Transformers can kick in at different stages while a message transits through a service.

What Is Router In Mule ?

Routers play a crucial role in controlling the trajectory a message will follow when it transits in Mule. They are the gatekeepers of the endpoints of a service, taking care of keeping messages on the right succession of tracks so they can reach their intended destinations. Certain routers act like the big classification yards: they can split, sort, or regroup messages based on certain conditions.

What Is Filter In Mule ?

Filters are a powerful complement to the routers. Filters provide the brains routers need to make smart decisions about what to do with messages in transit. Some filters go as far as deeply analyzing the content of a message for a particular value on which their outcome will be based.

What Is Component In Mule ?

Components are the centerpiece of Mule’s services. Each service is organized with a component at its core and inbound and outbound routers around it. Components are used to implement a specific behavior in a service. This behavior can be as simple as logging messages or can go as far as invoking other services. Components can also have no behavior at all; in that case they are pass-through and make the service act as a bridge between its inbound and outbound routers.

How Message In Mule Is Composed ?

Ø A Mule message is composed of different parts: The payload, which is the main data content carried by the message.

Ø The properties, which contain the meta information much like the header of a SOAP envelope or the properties of a JMS message. Optionally, multiple named attachments, to support the notion of multipart messages.

Ø Optionally, an exception payload, which holds any error that occurred during the processing of the event.

What Are Configuration Builders In Mule ?

Mule uses configuration builders that can translate a human-authored configuration file into the complex graph of objects that constitutes a running node of this ESB. The main builders are of two kinds: a Spring-driven builder, which works with XML files, and a script builder, which can accept scripting language files.

Why Spring-driven Configuration Builder Is Important Than Script Builder ?

The advantages of Spring-driven configuration builder

Ø It is the most popular — you are more likely to find examples using this syntax.

Ø It is the most user friendly — Spring takes care of wiring together all the moving parts of the ESB, something you must do by hand with a script builder.

Ø It is the most expressive — dedicated XML schemas define the domain-specific language of Mule, allowing you to handle higher-level concepts than the scripting approach does.

What Is Bridge Component In Mule ?

A bridge component is used to pass the messages from the inbound router to the outbound one. A bridge is a neutral component: it does not perform any action or modify messages that it processes.

What Tags Are Used To Configure Spring Elements In Mule ?

Tags like <spring:bean/> <spring:entry/> etc. are used to configure spring stuff.

What Are Available Approaches Used For Modularizing Configurations In Mule ?

There are different following approaches that can be used when modularizing a configuration.

Independent configurations – a Mule instance can load several independent configuration files side by side.

Inherited configurations – main idea is to express a formal parent-child dependency between two configurations. By strongly expressing this dependency, you will have the guarantee at boot time that no configuration file has been omitted. Simply by using the same name for the parent and child models and by flagging the child as being an heir, as shown here:

Imported configurations – You can easily import external Spring application context files into your Mule configuration files. The following illustrates how instance.xml would import its Spring context file:

<spring:beans>

<spring:import resource="instance-beans.xml" />

</spring:beans>

Heterogeneous configurations – It is possible to mix several styles of Mule configuration in an instance. An instance can be configured with a Groovy script and Spring XML configuration builders.

Give An Example Of Stdio Connector In Mule ?

<stdio:connector name="SystemStreamConnector" promptMessage="Please enter something: " messageDelayTime="1000"/>

Give An Example Of Http Connector In Mule ?

<http:connector name="HttpConnector"proxyHostname="proxyHostname"

proxyPort="proxyPort"

proxyUsername="proxyUsername"proxyPassword="proxyPassword"/>

When Does Mule Instantiates A Connector ?

If Mule figures out that one of our endpoints needs a particular connector, it will automatically instantiate one for us, using all the default values for its different configuration parameters. This is a perfectly viable approach if we are satisfied with the behavior of the connector when it uses its default configuration. This is often the case for the VM or HTTP transports.

What Is Transport Service Descriptor In Mule ?

The connector has a technical configuration known as the Transport Service Descriptor (TSD). This hidden configuration is automatically used for each instance of the connector. It defines technical parameters such as what classes to use for the message receivers, requesters, and dispatchers; or the default transformers to use in inbound, outbound, and response routers. Knowing these default values is essential to grasping the behavior of a transport.

How Many Endpoints Are There In Mule ?

There are two endpoints :

Ø Inbound

Ø Outbound.

You will use inbound and outbound endpoints to communicate between components and services inside Mule as well as with the outside world.

What Is An Outbound Endpoint In Mule ?

Outbound endpoints are used to send data. An outbound endpoint is used to do things such as send SOAP messages, write to file streams, and send email messages.

What Is Global Endpoint In Mule ?

An endpoint destination that is shared by several routers, it is worth creating a global endpoint. A global endpoint is not typified for inbound or outbound routing, making it usable in many different places in a configuration file. It must be named so it can actually be used in a service, which will reference the global endpoint by its name. A global endpoint can also help clarify the usage of a particular destination.

Why Does An Endpoint In Mule Offer An Address Attribute ?

This allows us to configure a generic endpoint using the Mule 1.x style of URI-based destination addresses instead of the dedicated attributes of the specific endpoint element.

Give An Example Of File Endpoint In Mule ?

<file:endpoint name="tmpPoller" path="/tmp" fileAge="1000"pollingFrequency="2000"/>

What Is Streaming Property In File Connector In Mule ?

The value of this streaming property can be either true or false. If it is set to true then we are actually working on stream of file data otherwise we are working with file itself.

What Is Pollingfrequency Property In File Connector In Mule ?

When we want file inbound endpoints to poll their source directories for new content. This is accomplished by setting the pollingFrequency to some milliseconds value.

What Is Autodelete Property In File Connector In Mule ?

The default value of autoDelete is true. Therefore, a file inbound endpoint will, by default, remove the file from the source directory once it is read by the inbound endpoint. If you do not want to delete file automatically then you can set autoDelete property to false.

What Is Fileage Property In File Connector In Mule ?

The fileAge property specifies how long the endpoint should wait before reading the file again. For instance, a fileAge of 60000 indicates Mule should wait a minute before processing the file again.

How To Send Only Certain Types Of File From One Directory To Another In Mule ?

Use the below element in file inbound to filter certain types of files.

<file:filename-wildcard-filter pattern="file*.xml"/></file:inbound-endpoint>

pattern indicates what pattern of file names should move from one directory to another directory.

What Is Vm Transport In Mule ?

The VM transport is a special kind of transport that you’ll use to send messages via memory. These messages never leave the JVM the Mule instance is running in.

What Is Multicasting Router In Mule ?

The multicasting router can send messages to multiple endpoints over different transports. The multicasting router allows you to easily move the same messages across these different endpoints.

What Is Mule Transformer ?

It is an event, more specifically an instance of org.mule.api.MuleEvent. This object carries not only the actual content of the message but also the context of the event.

What Is Mule Context ?

The Mule context is composed of references to different objects, including security credentials, if any, the session in which the request is processed. All internals of the ESB are accessible through Mule context

What Is Payload In Mule ?

The content of a message, also known as payload. It is wrapped in an instance of org.mule.api.MuleMessage, which provides different means of accessing the payload under different forms. A MuleMessage also contains properties, much like the header of a SOAP envelope or the properties of a JMS message, and can also have multiple named attachments.

What Are Different Type Of Messages In Mule ?

Ø Bridge messages: Pass messages from inbound to outbound routers.

Ø Echo and log messages: Log messages and move them from inbound to outbound routers.

Ø Build messages: Create messages from fixed or dynamic values

Why Mule Esb?

Mule ESB is lightweight but highly scalable, allowing you to start small and connect more applications over time. Mule manages all the interactions between applications and components transparently, regardless of whether they exist in the same virtual machine or over the Internet, and regardless of the underlying transport protocol used.

There are currently several commercial ESB implementations on the market. However, many of these provide limited functionality or are built on top of an existing application server or messaging server, locking you into that specific vendor. Mule is vendor-neutral, so different vendor implementations can plug in to it. You are never locked in to a specific vendor when you use Mule.

What are Batch Jobs in Mule ESB ?

A batch job is a top-level element in Mule which exists outside all Mule flows. Batch jobs split large messages into records which Mule processes asynchronously in a batch job; just as flows process messages, batch jobs process records.

A batch job contains one or more batch steps which, in turn, contain any number of message processors that act upon records as they move through the batch job. During batch processing, you can use record-level variables (recordVars) and MEL expressions to enrich, route or otherwise act upon records.

What are the different types of Flow Processing Strategies ?

There are six different types of Flow Processing Strategies. They are

Ø Asynchronous Flow Processing Strategy.

Ø Custom Processing Strategy.

Ø Thread Per Processing Strategy.

Ø Queued Asynchronous Flow Processing Strategy.

Ø Synchronous Flow Processing Strategy.

Ø Non-blocking Flow Processing Strategy.

Ø Queued Flow Processing Strategy.

Why the Mulesoft is preferred than other ESB implementations ?

Mule is lightweight but highly scalable, allowing you to start small and connect more applications over time. The ESB manages all the interactions between applications and components transparently, regardless of whether they exist in the same virtual machine or over the Internet, and regardless of the underlying transport protocol used.

Several commercial ESB implementation provide limited functionality or built on top of an existing application server or messaging server, locking you into that specific vendor. Mule is vendor-neutral, so different vendor implementations can plug in to it. You are never locked in to a specific vendor when you use Mule.

What Is Filter In Mule ?

What are the different types of Web services ?

There are mainly two types of web services.

Ø SOAP web services.

Ø RESTful web services.

How to add classes/jars to the Mule class path ?

Use the MULE_LIB variable (generally set in the run script)

To include JAR file(s) in a mule class path, declare each dependent jar file in the MULE_LIB entry.

For spring resource, if the XML bean declaration is placed within a project, include the project JAR file in the class path too (i.e., if not included, Mule will throw a **.xml not found on class path)

What is Mule Data Integrator ?

Mule has released a data integrator tool, it is a visual mapping tool which supports flat file, java object, XML mappings, etc. Coding complex mappings can be very tedious and additionally difficult to maintain, the mule data integrator with drag and drop facilities makes building and maintaining mappings very simple.

The mapping is done in eclipse (plugins required) and executed on a data integrator runtime which sits on top of Mule ESB – this requires a license.

Where to find the class Abstract Mule TestCase ?

This is in 1.4/1.4.1 distributions but was missing from the 1.3.3 distribution – the class is defined in /lib/mule/mule-core-.jar.

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Mule won’t start? Check your Environment ?

The java and mule environment variables must be setup correctly for mule to start. If you are experiencing problems check the following variables:

MULE_HOME – should be the location of the mule install

JAVA_HOME – should be the location of the JDK

PATH – should have both JAVA_HOME\bin and MULE_HOME\bin in the path.

Check all of the above carefully. Some systems with multiple JDK’s installed can end up with incorrect mappings between the PATH and the JAVA_HOME, which will stop mule from loading.

What are Web Services ?

Web service is a functionality or a small piece of program in any programming language that can be accessed over HTTP. Message format can be XML or JSON or any other program as long as the other programs can understand and communicate.

A Web service can be of synchronous or asynchronous type. Any web service has a server-client relationship and it can have multiple clients.

How can we create and consume SOAP service in Mule ?

Creating SOAP Service – We can create a SOAP service same as we create Mule Project With RAML, the only change is instead of RAML we need to import Concert WSDL.

Consuming SOAP Service – We can use Web Service Consumer or CXF component in our mule flow to access/consume SOAP service.

The different types of variables in Mule ESB are:

Ø Flow Variable

Ø Session Variable

Ø Record Variable

What are the various types of Exception Handling in Mule ESB ?

The types of exception handling in Mule ESB are:

Ø Default Exception Handling

Ø Global Exception Handling

Ø Catch Exception Handling

Ø Choice Exception Handling

What are the Features of Mule ESB ?

An ESB is a used for integration using a service-oriented approach. Its main features are:

Ø Set of Service Container

Ø Message Transformation Service

Ø Message Routing Service

Ø Web Service Security

What is the difference between SOAP and REST ?

SOAP -> REST

ü SOAP is a protocol. -> REST is an architectural style.

ü SOAP stands for Simple Object Access Protocol. -> REST stands for REpresentational State Transfer.

ü SOAP can’t use REST because it is a protocol. -> REST can use SOAP web services because it is a concept and can use any protocol like HTTP, SOAP.

ü SOAP uses services interfaces to expose the business logic. -> REST uses URI to expose business logic.

ü SOAP defines standards to be strictly followed. -> REST does not define too much standards like SOAP.

ü SOAP requires more bandwidth and resource than REST. -> REST requires less bandwidth and resource than SOAP.

ü SOAP defines its own security. -> RESTful web services inherit security measures from the underlying transport.

ü SOAP permits XML data format only. -> REST permits different data format such as Plain text, HTML, XML, JSON etc.

ü SOAP is less preferred than REST. -> REST more preferred than SOAP.

What is Shared Resource in Mule and how they have been used?

We can make connectors as an reusable component by defining them as common resources and expose them to all applications deployed under a same domain, these resources are known as shared resources. These shared resource needs to be defined inside Mule Domain Project and then referred to each of the projects that are meant to use the elements in it.

What are the different ESBs in the market?

There are various ESB's available in the market. Some are opensource, some licenced:

Ø Talend

Ø Mule ESB

Ø JBoss Fuse ESB

Ø IBM WESB

Ø Opensource ESB

Ø WSO2

Explain ESB Integration core principles?

Transformation - Data transformation between canonical data formats and specific data formats required by each ESB connector.

Transportation - Transport protocol negotiation between multiple formats. Such as HTTP, JMS, JDBC.

Mediation - Providing multiple interfaces for the purpose of a) supporting multiple versions of a service for backwards compatibility or alternatively, b) to allow for multiple channels to the same underlying component implementation. This second requirement may involve providing multiple interfaces to the same component, one legacy interface (flat file) and one standards compliant (SOAP/XML) interface.

Non-functional consistency - For a typical ESB initiative, this can include consistency around the way security and monitoring policies are applied and implemented.

How to select an ESB?

Usability: How complicated is the installation process? The learning curve of the ESB should not be long.

Maintainability: How to monitor the product? If any GUI terminal is available for monitoring the services.

Community: Is there active community for the ESB. Various discussion forums, tutorials etc.

Enterprose Support- Is the product support reliable. What services are available.

Flexibility: Can the ESB be configured to meet the business requirements.

Reliability: The reliablity of the ESB. Its current users and various case studies if available.

Cost: The cost of the ESB. Its Licence policies. Support cose. etc.

What are the advantages of using an ESB?

Provides a way for end points to connect to each other without having to directly talk to each other. It simplifies the communications for the end points as they only have to conform to a standard communication interface, the bus.

An ESB provides a single place to get some key end point metrics: frequency, availability, and performance.

An ESB tends to provide more than one communication interface. However, a developer only needs to choose the easiest one to get and receive the data from the bus.

What is REST?

REST stands for Representaional State Transfer or RESTful web service. REST is a client-server architecture which means each unique URL is representation of some object or resource. Any REST API developed uses HTTP methods explicitly and in a way that’s consistent with the protocol definition. This basic REST design principle establishes a one-to-one mapping between create, read, update, and delete (CRUD) operations and HTTP methods. According to this mapping:

Ø To create a resource on the server, use POST.

Ø To retrieve a resource, use GET.

Ø To change the state of a resource or to update it, use PUT.

Ø To remove or delete a resource, use DELETE.

What is RAML and why we use it?

RAML – REST ful API Modeling Language

RAML is similar to WSDL, it contains endpoint URL, request/response schema, HTTP methods and query and URI parameter.

RAML helps client (a consumer of the service) know, what the service is and what/how all operations can be invoked.

RAML helps the developer in creating the initial structure of this API. RAML can also be used for documentation purpose.

What are the Message Sources in Mule ESB?

Message sources in Mule are usually Anypoint Connectors, elements which provide connectivity to a specific external source, either via a standard protocol (such as HTTP, FTP, SMTP) or a third-party API (such as Salesforce.com, Twitter, or MongoDB).

What is the difference between ESB and JMS?

ESB provides the middleware and interfaces that allow businesses to connect their applications without writing code.

JMS provides messaging capability and facilitates communication between the modules/applications.

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