Hands-On High Performance with Spring 5 E-Book

Chintan Mehta

• Herausgeber: Packt Publishing
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 418

Veröffentlichungsjahr: 2018

Beschreibung

While writing an application, performance is paramount. Performance tuning for real-world applications often involves activities geared toward detecting bottlenecks. The recent release of Spring 5.0 brings major advancements in the rich API provided by the Spring framework, which means developers need to master its tools and techniques to achieve high performance applications.

Hands-On High Performance with Spring 5 begins with the Spring framework's core features, exploring the integration of different Spring projects. It proceeds to evaluate various Spring specifications to identify those adversely affecting performance. You will learn about bean wiring configurations, aspect-oriented programming, database interaction, and Hibernate to focus on the metrics that help identify performance bottlenecks. You will also look at application monitoring, performance optimization, JVM internals, and garbage collection optimization. Lastly, the book will show you how to leverage the microservice architecture to build a high performance and resilient application.

By the end of the book, you will have gained an insight into various techniques and solutions to build and troubleshoot high performance Spring-based applications.

Leseprobe

Hands-On High Performance with Spring 5

Techniques for scaling and optimizing Spring and Spring Boot applications

Chintan Mehta Subhash Shah Pritesh ShahPrashant Goswami Dinesh Radadiya

BIRMINGHAM - MUMBAI

Hands-On High Performance with Spring 5

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Contributors

About the authors

Chintan Mehta is a co-founder of KNOWARTH Technologies and heads the cloud/RIMS/DevOps team. He has rich, progressive experience in server administration of Linux, AWS Cloud, DevOps, RIMS, and on open source technologies. He is also an AWS Certified Solutions Architect. Chintan has authored MySQL 8 for Big Data, Mastering Apache Solr 7.x, MySQL 8 Administrator's Guide, and Hadoop Backup and Recovery Solutions. Also, he has reviewed Liferay Portal Performance Best Practices and Building Serverless Web Applications.

Subhash Shah works as a Principal Consultant at KNOWARTH Technologies. He holds a degree in Information Technology from HNGU. He is experienced in developing web-based solutions using various software platforms. He is a strong advocate of open source software development and its use by businesses to reduce risk and cost. His interests include designing sustainable software solutions. His technical skills include requirement analysis, architecture design, project delivery, application setup, and execution processes. He admires quality code and test-driven development.

Pritesh Shahis a Solutions Architect at CentralBOS LLC. Pritesh is responsible for integrating technologies with best practices to translate business requirements into business change. He holds a degree in Computer Engineering from Dharmsinh Desai University. His expertise lies in, but is not limited to, designing, developing, deploying, and testing N-tier applications, and leading teams. He is very good at debugging problems and finding the best solution. Pritesh believes in constant improvement by quickly adapting new technologies suitable for building solutions.

Prashant Goswami works as a Senior Consultant at KNOWARTH Technologies and handles enterprise projects with regard to software design, development, deployment, and building processes to provide customers with affordable software solutions. He holds a master's degree in Computer Applications from Gujarat Technological University. He is able to adapt quickly to any technology and has a keen desire for constant improvement. Prashant has proven experience in working with various technologies in web application development, design patterns, enterprise architectures, and open source technologies.

Dinesh Radadiya works as a Lead Consultant and Architect at KNOWARTH Technologies, a leading open source software development company. He is a software architect with over 10 years of professional experience in developing web-based applications using various software platforms. He has proven expertise in leading and delivering software projects with varying degrees of complexity in domains such as ERP, HR, healthcare, CRM, and manufacturing. He has a keen interest in requirement analysis, progressive design, high-quality code, microservices, and refactoring.

About the reviewer

Mohamed Sanaulla is a software developer with more than 7 years of experience in developing enterprise applications and Java-based backend solutions for e-commerce applications. His interests include enterprise software development, refactoring and redesigning applications, designing and implementing RESTful web services, troubleshooting Java applications for performance issues, and TDD. He is also a Sun-Certified Java programmer for the Java 6 platform. He is a moderator for JavaRanch, and he likes to share his findings on his blog. He has co-authored Java 9 Cookbook.

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Preface

The mission of this book is to introduce developers to application monitoring and performance tuning to create highly performant applications. The book starts with the basic details of Spring Framework, including various Spring modules and projects, Spring bean and BeanFactory implementation, and aspect-oriented programming. It also explores Spring Framework as an IoC bean container. We will be discussing Spring MVC, which is a commonly used Spring module for building a user interface in detail with Spring Security authentication part with a stateless API. This book also emphasizes the importance of building optimized Spring applications for interacting with relational databases. Then, we will walk through some of the advanced ways of accessing databases using object-relational mapping (ORM) frameworks, such as Hibernate. The book moves on to the details of new Spring features, such as Spring Boot and reactive programming, with best practices suggestions. An important aspect of the book is its focus on building highly performant applications. The latter part of the book includes details for application monitoring, performance optimization, JVM internals, and garbage collection optimization. Finally, how to build microservices is explained to help you understand the challenges faced in the process and how to monitor its performance.

Who this book is for

This book is suitable for Spring developers who would like to build high-performance applications and have more control over their application's performance in production and development. This book requires developers to have some familiarity with Java, Maven, and Eclipse.

What this book covers

Chapter 1, Exploring Spring Concepts, focuses on gaining a clear understanding of the core features of Spring Framework. It briefly outlines the Spring modules and explores the integration of different Spring projects, and gives a clear explanation of the Spring IoC container. It ends by introducing the new features of Spring 5.0.

Chapter 2, Spring Best Practices and Bean Wiring Configurations, explores different bean wiring configurations with Java, XML, and annotations. The chapter also helps us learn different best practices when it comes to bean wiring configuration. It also helps us understand performance assessment with different configurations, as well as DI pitfalls.

Chapter 3, Tuning Aspect-Oriented Programming, explores the concepts of the Spring Aspect-Oriented Programming (AOP) module and its various terminologies. It also covers the concept of proxy. It ends by going through the best practices for achieving quality and performance with the Spring AOP module.

Chapter 4, Spring MVC Optimization, starts by giving a clear understanding of the Spring MVC module with different Spring MVC configuration methods. It also covers the concept of asynchronous processing in Spring. Then it explains Spring Security configuration and authentication part with a stateless API. It finishes by going through the monitoring part of Tomcat with JMX, and Spring MVC performance improvements.

Chapter 5, Understanding Spring Database Interactions, helps us learn about database interaction with Spring Framework. It then walks through Spring transaction management and optimal connection pooling configuration. It ends by going through database design best practices.

Chapter 6, Hibernate Performance Tuning and Caching, describes some of the advanced ways of accessing the database using ORM frameworks, such as Hibernate. It ends by explaining how we can remove the boilerplate code of implementing the Data Access Object (DAO) interface using Spring Data.

Chapter 7, Optimizing Spring Messaging, starts by exploring the concepts of messaging in Spring and talks through its advantages. It then walks through the RabbitMQ configuration for using messaging in the Spring application. Finally, it describes the parameters for improving the performance and scalability to maximize throughput.

Chapter 8, Multithreading and Concurrent Programming, covers the core concepts of Java threads and advanced thread support. It also covers the concept of Java thread pooling to improve performance. Before its close, it will explore Spring transaction management with threads and various best practices for programming threads.

Chapter 9, Profiling and Logging, focuses on concepts surrounding profiling and logging. This chapter starts by defining profiling and logging and how they are useful for assessing application performance. In the latter part of the chapter, the focus will be on learning about software tools that can be used to study application performance.

Chapter 10, Application Performance Optimization, focuses on optimizing application performance. It also covers details for identifying the symptoms of performance issues, the performance tuning life cycle, and JMX support in Spring.

Chapter 11, Inside JVM, walks through the insides of JVM and tuning JVM to achieve high performance. It also covers the topics related to memory leaks and common misunderstandings related to garbage collection, before moving onto different garbage collection methods and discussion of their importance.

Chapter 12, Spring Boot Microservice Performance Tuning, covers the concept of Spring Boot microservices and their performance tuning. It also clearly describes how to use actuators and health checks in order to monitor Spring Boot applications. It also covers the different techniques in order to tune the performance of Spring Boot applications.

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This book requires developers to have some familiarity with Java, Maven, and Eclipse.

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Exploring Spring Concepts

TheSpring Frameworkprovides extensive support for managing large enterprise Java applications and also addresses the complexities of enterprise application development. Spring provides a complete set of API and configuration models for modern enterprise applications so that programmers just need to focus on the business logic of the application.

Introduced as a lightweight framework, the Spring Framework was aimed at providing a way of making the development of Java enterprise applications easy and simple.

This chapter will help you gain a better understanding of the core features of the Spring Framework. We will start with an introduction to the Spring Framework. This chapter will also give you a clear understanding of every major module of the Spring Framework. After having a quick look at the important modules in the Spring Framework, we will dive into the world of Spring projects. We will also have a clear understanding of the Spring Inversion of Control (IoC) container. At the end, we will have a look at the new features and enhancements introduced in Spring 5.0.

In this chapter, we will be looking at the following topics:

Introducing the Spring Framework

Understanding Spring modules

Spring projects

Spring IoC container

New features in Spring Framework 5.0

Introducing the Spring Framework

The Spring Framework is one of the most popular open source Java application frameworks and IoC containers. Spring was originally developed by Rod Johnson and Jurgen Holler. The first milestone version of Spring Framework was released in March 2004. Though it has been a decade and a half, the Spring Framework remains the framework of choice to build any Java application.

The Spring Framework provides comprehensive infrastructure support for developing enterprise Java applications. So, developers don't need to worry about the infrastructure of the application; they can focus on the business logic of the application, rather than handling the configuration of the application.

All infrastructure, configuration, and meta configuration files, either Java-based or XML-based, are handled by the Spring Framework. So, this framework gives you more flexibility in building an application with a Plain Old Java Object (POJO) programming model rather than a non-invasive programming model.

The Spring IoC container forms the core of the entire framework by putting together any application's various components. Spring Model-View-Controller (MVC) components can be used to build a very flexible web tier. The IoC container simplifies the development of the business layer with POJOs.

Problems with EJB

In the early days, it was very difficult for programmers to manage enterprise applications, because the enterprise Java technologies like Enterprise JavaBeans (EJB) were much heavier to provide the enterprise solutions to programmers.

When EJB technology was first announced, it was offering a distributed component model that would allow the developers to focus only on the business side of the system while ignoring the middleware requirements, such as wiring of components, transaction management, persistence operations, security, resource pooling, threading, distribution, remoting, and so on; however, it was a very cumbersome process for developing, unit testing, and deploying EJB applications. Some of the following complexities were faced while using EJB:

Forcing implementation of unnecessary interfaces and methods

Making unit testing difficult, especially outside the EJB container

Inconveniences in managing deployment descriptors

Tedious exception handling

At that time, Spring was introduced as an alternative technology especially made for EJB, because Spring provided a very simple, leaner, and lighter programming model compared with other existing Java technologies. Spring makes it possible to overcome the preceding complexities, and also to avoid the use of some other heavier enterprise technologies by using many available design patterns. The Spring Framework focused on the POJO programming model rather than a non-invasive programming model. This model provided the simplicity to the Spring Framework. It also empowered ideas such as the dependency injection (DI) pattern and Aspect-Oriented Programming (AOP), using the proxy pattern and decorator pattern.

Simplifying implementation using POJO

The most important advantage of the POJO programming model is that coding application classes is very fast and simple. This is because classes don't need to depend on any particular API, implement any special interface, or extend from a particular framework class. You do not have to create any special callback methods until you really need them.

Benefits of the Spring Framework

The important benefits of the Spring Framework are as follows:

No need to reinvent the wheel

Ease of unit testing

Reduction in implementing code

Inversion of control and API

Consistency in transaction management

Modular architecture

Up to date with time

Let's discuss each in detail.

No need to reinvent the wheel

No need to reinvent the wheel is one of the most important benefits that developers can leverage from the Spring Framework. It facilitates the practical use of the well-known technologies, ORM frameworks, logging frameworks, JEE, JDK timers, Quartz, and so on. So, developers don't have to learn any new technologies or frameworks.

It facilitates good programming practices, such as programming using interfaces instead of classes. Spring enables developers to develop enterprise applications using POJO and Plain Old Java Interface (POJI) model programming.

Ease of unit testing

If you want to test the applications developed using Spring, it is quite easy. The main reason behind this is that the environment-dependent code is available in this framework. Earlier versions of EJBs were very difficult to unit test. It was difficult to even run EJBs outside the container (as of version 2.1). The only way to test them was to deploy them in a container.

The Spring Framework introduced the DI concept. We will discuss DI in complete detail in Chapter 2, Spring Best Practices and Bean Wiring Configurations. The DI enables unit testing. This is done by replacing the dependencies with their mocks. The entire application need not be deployed to unit test.

Unit testing has multiple benefits:

Improving the productivity of programmers

Detecting defects at earlier stages, thereby saving the cost of fixing them

Preventing future defects by automating unit tests in applications that are running in

continuous integration

(

CI

) builds

Inversion of control and API

Spring also helps developers to get rid of the necessity of writing a separate compilation unit, or a separate class loader to handle exceptions. Spring converts technology-dependent exceptions, particularly thrown by Java Database Connectivity (JDBC), Hibernate or Java Data Objects (JDO), into unchecked and consistent exceptions. Spring does this magic using inversion of control and APIs.

Also, it uses IoC for DI, which means aspects can be configured normally. If we want to add our own behavior, we need to extend the classes of the framework or plug in our own classes. The following is a list of advantages for this kind of architecture:

Decoupling the execution of a task from its implementation

Making it easier to switch between different implementations

Greater modularity of a program

Greater ease in testing a program by isolating a component or mocking it

Dependencies and allowing components to communicate through contracts

Consistency in transaction management

Spring also provides support for transaction management with consistency. It provides an easy and flexible way to configure local transactions for small applications as well as global transactions for large applications using the Java Transaction API (JTA). So we do not need to use any third-party transactional API to execute a database transaction; Spring will take care of it with the transaction management feature.

Modular architecture

Spring provides a modular architecture that helps developers to identify the packages or classes which are to be used and which are to be ignored. Hence, in this way, we can keep only those things which we really need. So that makes it easy to identify and utilize the usable packages or classes even if there are many packages or classes.

Spring is a powerful framework that addresses many common problems in Jakarta EE. It includes support for managing business objects and exposing their services to presentation tier components.

Spring instantiates the beans and injects the dependencies of your objects into the application it serves as a life cycle manager of the beans.

Up to date with time

When the first version of the Spring Framework was built, its main focus was to make applications testable. There were also new challenges in the later versions, but the Spring Framework managed to evolve and stay ahead and on track with the architectural flexibility and modules that are offered. Some examples are listed as follows:

The Spring Framework introduced a number of abstractions ahead of Jakarta EE to keep the application decoupled from the specific implementation

The Spring Framework also provided transparent caching support in Spring 3.1

Jakarta EE was introduced with JSR-107 for JCache in 2014, so it was provided in Spring 4.1

Another major evolution that Spring was involved with was to provide different Spring projects. The Spring Framework is just one of the many projects among Spring projects. The following example illustrates how the Spring Framework managed to remain up to date in terms of Spring projects:

As architecture evolved toward cloud and microservices, Spring came up with new cloud-oriented Spring projects. The Spring Cloud project simplifies development and deployment of microservices.

To build

Java

batch applications, a new approach was introduced as the

Spring Batch project

by the Spring Framework.

In the next section, we will dive deep into the different Spring Framework modules.

Understanding Spring modules

Spring provides a modular architecture that is one of the most important reasons for the popularity of the Spring Framework. Its layered architecture enables integration of other frameworks easily and without hassle. These modules provide everything that a developer may need to use in enterprise application development. The Spring Framework is organized into 20 different modules that are built on the top of its Core Container.

The following diagram illustrates different Spring modules organized in a layered architecture:

Spring Framework modules

We will start with discussing the Core Container before moving on to other modules.

Core Container

The Spring Core Container provides the core features of the Spring Framework, namely as Core, Beans, Context, and Expression Language, the details of which are as follows:

Artifact

Module Usage

spring-core

This module facilitates all the utilities used by other modules and it also provides a way for managing the different bean life cycle operations.

spring-beans

This module is mainly used to decouple code dependencies from your actual business logic and eliminates the use of singleton classes using DI and IoC features.

spring-context

This module provides features like internationalization, and resource loading, and also underpins Java EE features like EJB, JMS, and remoting.

spring-expression

This module provides support for accessing properties of beans at runtime and also allows us to manipulate them.

Crosscutting concerns

Crosscutting concerns are applicable to all the layers of an application, including logging and security, among others. Important Spring modules related to crosscutting concerns are as follows:

Artifact

Module Usage

spring-aop

This module is mainly used to perform the tasks which are common amongst different parts of a system like transaction management, logging, and security. To enable this we can implement method-interceptors and pointcuts.

spring-aspects

This module is used to integrate any custom object type. It is possible using AspectJ, and the main use of this module is to integrate the objects which are not in the control of the container.

spring-instrument

This module is used to measure the application's performance and also helps to perform error diagnosis using trace information.

spring-test

This module is used to integrate testing support in a Spring application.

Data Access/Integration

The Data Access/Integration layer in applications interacts with the database and/or the external interfaces. It consists of JDBC, ORM, OXM, JMS, and Transaction modules. These modules are spring-jdbc, spring-orm, spring-oxm, spring-jms, and spring-tx.

Web

The Web layer contains the Web, Web-MVC, Web-Socket, and other Web-Portlet modules. The respective module names are spring-web, spring-webmvc, spring-websocket, spring-webmvc-portlet.

In the next section, we will go through different kinds of Spring projects.

Spring projects

The Spring Framework provides different kinds of projects for different infrastructure needs, and also helps to explore solutions to other problems in the enterprise application: deployment, cloud, big data, and security, among others.

Some of the important Spring projects are listed as follows:

Spring Boot

Spring Data

Spring Batch

Spring Cloud

Spring Security

Spring HATEOAS

Let's discuss them in detail.

Spring Boot

Spring Boot provides support to create standalone, production-grade, Spring-based applications that you can just run.

Spring Boot also provides some of the following features out of the box, by taking an opinionated view of how applications have to be developed:

Provides support for developing standalone Spring applications

Embeds Tomcat, Jetty, or Undertow directly, with no need to deploy WAR files

Allow us to externalize configuration to work in different environments with the same application code

Simplifies Maven configuration by providing opinionated starter POMs

Eliminates the need for code generation and the requirement for XML configuration

Provides support for production features like metrics, health checks, and application monitoring

We will look at Spring Boot in depth in Chapter 12, Spring Boot Microservice Performance Tuning.

Spring Data

The main goal of the Spring Data project is to provide an easy and consistent Spring-based model to access data and other special features, to manipulate SQL-and NoSQL-based data stores. It also tries to provide an easy way to use data access technologies, map-reduce frameworks, relational and non-relational databases, and cloud-based data services.

Some of the important features are as follows:

Provides support for integration with custom repository code

Provides repository and object-mapping abstractions by deriving dynamic queries using repository method names

Advanced integration support with Spring MVC controllers

Advanced support for transparent auditing features such as created by, created date, last changed by, and last changed date

Experimental integration support for cross-store persistence

Spring Data provides integration support for the following data sources:

JPA

JDBC

LDAP

MongoDB

Gemfire

REST

Redis

Apache Cassandra

Apache Solr

Spring Batch

Spring Batch facilitates essential processing for large volumes of records, including logging/tracing, transaction management, job processing statistics, job restart, skip, and resource management, by providing reusable functions. It also provides more advanced technical services and features that will enable extremely high-volume and high-performance batch jobs using optimization and partitioning techniques.

Important features of Spring Batch are as follows:

The ability to process data in chunks

The ability to start, stop and restart jobs, including the ability to restart, in the case of failed jobs, from the point where they failed

The ability to retry steps or to skip steps on failure

Web-based administration interface

Spring Cloud

It is not an overstatement to say the world is moving to the cloud.

Spring Cloud provides tools for developers to build common patterns in distributed systems. Spring Cloud enables developers to quickly build services and applications that implement common patterns to work in any distributed environment.

Some of the common patterns implemented in Spring Cloud are as follows:

Distributed configuration

Service registration and discovery

Circuit breakers

Load balancing

Intelligent routing

Distributed messaging

Global locks

Spring Security

Authentication and authorization are the essential parts of enterprise applications, both web applications and web services. SpringSecurityis a powerful and highly customizable authentication and access control framework. Spring Security focuses on providing declarative authentication and authorization to Java applications.

Important features in Spring Security are as follows:

Comprehensive support for both authentication and authorization

Good support for integration with servlet APIs and Spring MVC

Module support for integration with

Security Assertion Markup Language

(

SAML

) and

Lightweight Directory Access Protocol

(

LDAP

)

Providing support for common security attacks such as

Cross-Site Forgery Request

(

CSRF

), session fixation, clickjacking, and so on

We will discuss how to secure web applications with Spring Security in Chapter 4, Spring MVC Optimization.

Spring HATEOAS

Themain purpose of Hypermedia As The Engine Of Application State (HATEOAS) is to decouple the server (the service provider) from the client (the service consumer). The server provides the client with information on other possible actions that can be performed on the resource.

Spring HATEOAS provides a HATEOAS implementation, especially for the REpresentational State Transfer (REST) services implemented with Spring MVC.

Spring HATEOAS has the following important features:

A simplified definition of links pointing to service methods, making the links less fragile

Support for

JSON

and

JAXB (XML-based)

integration

Support for hypermedia formats such as

Hypertext Application Language

(

HAL

)

In the next section, we will understand the mechanism of Spring's IoC container.

Spring's IoC container

Spring's IoC container is built as the core module of the Spring architecture. IoC is also known as DI. It is a design pattern which eliminates the dependency of the code to provide ease in managing and testing the application. In DI, the objects themselves characterize their dependencies with the other objects they work, just through constructor arguments, arguments to a factory method, or properties that are set on the object instance after it is created or returned from a factory method.

The container is then responsible to inject those dependencies when it creates the bean. This process is basically the inverse (so it is known as IoC) of the bean itself controlling the instantiation or location of its dependencies, by using the direct construction of classes, or a mechanism.

There are two main base packages of the Spring Framework's IoC container: org.springframework.beans, and org.springframework.context. The BeanFactory interface provides some of the advanced-level configuration mechanisms to manage any type of object. ApplicationContext includes all the functionalities of BeanFactory, and acts as a subinterface of it. In fact, ApplicationContext is also recommended over BeanFactory, and provides more supporting infrastructure that enables: easier integration with Spring's AOP features and transaction; message resource handling in terms of internationalization and event publication; and application layer-specific contexts such as WebApplicationContext for use in web applications.

The interface org.springframework.context.ApplicationContext is represented as the Spring IoC container, and it is in complete control of a bean's life cycle and responsible for instantiating, configuring, and assembling the beans.

The container gets all the instructions to instantiate, configure, and assemble, by scanning bean configuration metadata. The configuration metadata can be represented using the following methods:

XML-based configuration

Annotation-based configuration

Java-based configuration

We will learn these methods in more detail in Chapter 2, Spring Best Practices and Bean Wiring Configurations.

The following diagram represents a simple representation of the Spring Container process towards creating a fully configured application:

The Spring IoC container

The following example shows the basic structure of XML-based configuration metadata:

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <!-- All the bean configuration goes here --><bean id="..." class="..."></bean><!-- more bean definitions go here --></beans>

The id attribute is a string that you use to identify the individual bean definition. The class attribute defines the type of bean, and uses the fully qualified class name. The value of the id attribute refers to collaborating objects.

What are Spring beans?

You can consider a Spring bean as a simple Java object, instantiated, configured, and managed by a Spring IoC container. It is called a bean instead of an object or component because it is a replacement for complex and heavy enterprise JavaBeans with respect to the origin of the framework. We will learn more about Spring bean instantiation methods in Chapter 2, Spring Best Practices and Bean Wiring Configurations.

Instantiating a Spring container

For creating bean instances, we first need to instantiate a Spring IoC container by reading the configuration metadata. After initialization of an IoC container, we can get the bean instances using the bean name or ID.

Spring provides two types of IoC container implementations:

BeanFactory

ApplicationContext

ApplicationContext

The ApplicationContext container provides support to access application components using BeanFactory methods. This includes all functionality of BeanFactory. In addition, ApplicationContext can also perform more enterprise functionalities, like transaction, AOP, resolving text messages from properties files, and pushing application events to interested listeners. It also has the ability to publish events to the registered listeners.

The mostly-used implementations of ApplicationContext are FileSystemXmlApplicationContext, ClassPathXmlApplicationContext, and AnnotationConfigApplicationContext.

Spring also provides us with a web-aware implementation of the ApplicationContext interface, as shown:

XmlWebApplicationContext

AnnotationConfigWebApplicationContext

We can use either one of these implementations to load beans into a