Spring Java. Deep Dive into Spring Internals.2024 (Bennett C) (Z-Library) (1)

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spring Java Deep Dive into Spring Internals - Understand the Inner Workings of Spring Framework to Optimize Performance and Customize Behavior Like a True Spring Ninja Caleb Bennett & Riley Foster

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Spring Java Deep Dive into Spring Internals - Understand the Inner Workings of Spring Framework to Optimize Performance and Customize Behavior Like a True Spring Ninja

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Caleb Bennett & Riley Foster

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© Copyright 2023 - All rights reserved. The contents of this book may not be reproduced, duplicated or transmitted without direct written permis­ sion from the author. Under no circumstances will any legal responsibility or blame be held against the publisher for any repara­ tion, damages, or monetary loss due to the information herein, either directly or indirectly. Legal Notice: This book is copyright protected. This is only for personal use. You cannot amend, dis-tribute, sell, use, quote or paraphrase any part or the content within this book without the consent of the author. Disclaimer Notice: Please note the information contained within this document is for educational and entertainment pur­ poses only. Every attempt has been made to provide accurate, up to date and reliable complete information. Readers acknowledge that the author is not engaging in the rendering of legal, financial, medical or pro­ fessional advice. The content of this book has been derived from various sources. Please consult a licensed professional before attempting any techniques outlined in this book. By reading this document, the reader agrees that under no circumstances is the author responsible for any losses, direct or indirect, which are incurred as a result of the use of information contained within this document.

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Table of Contents Introduction Chapter One : Bean Creation and Initialization Chapter Two : Spring Application Context Internals Chapter Thr ee: Classpath Scanning and Component Discovery Chapter Fou r: Resource Handling and Spring's Resource Abstraction Chapter Fiv e: Advanced Spring AOP Internals Chapter Six : Transaction Management Deep Dive Chapter Sev en: Spring Boot Auto-Configuration Magic Unveiled Chapter Eig ht: Spring Boot Starters and Initializr Internals

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Chapter Nin e: Performance Tuning of Spring Applications Chapter Ten: Advanced Spring Cloud Internals Chapter Elev en: Exploring Reactive Spring Chapter Twel ve: Microservices Patterns and Best Practices Conclusion

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Introduction Delving into the Inner Workings of Spring Framework "Exploring the Depths of Spring Framework" delves into the intricate inner workings that form the backbone of Spring's prowess within Java development. Spring stands tall as a cornerstone framework, renowned for its ability to streamline application development through its sophisticated architecture, par­ ticularly in managing dependencies and promoting modular design. At its essence, Spring operates on the principle of Inversion of Control (loC), a paradigm shift that redefines how Java applications are structured. loC relinquishes control over object instantiation and dependency resolution to the framework, facilitating a more modular and loosely coupled architecture. Central to Spring's loC container is the BeanFactory, a lightweight entity tasked with overseeing the cre­ ation and lifecycle management of beans—fundamental building blocks within Spring applications. Beans, essentially Java objects, are configured through various means such as XML, annotations, or Java-based configuration classes. Consider the following code snippet as a practical demonstration:

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java import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration; ©Configurationpublic class AppConfig { ©Beanpublic MyService myService() {return new MyServiceImpl();1 Here, the AppConfig class, annotated with ©Configuration, serves as a repository of bean definitions. The myService() method, annotated with ©Bean, signifies that it should be managed as a bean by the Spring container. The method returns an instance of MyServicelmpl, which implements the MyService interface. During application initialization, Spring's loC container parses the configuration metadata, instantiates beans as required, and resolves dependencies between them—a process commonly referred to as bean wiring or dependency injection.

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Beyond its core loC container, Spring encompasses an extensive ecosystem of modules, each tailored to address specific concerns spanning web development, data access, security, and integration. Noteworthy modules include Spring MVC for web development, Spring Data for simplified data access, Spring Security for robust security measures, and Spring Integration for seamless system integration. Spring's modular architecture empowers developers to selectively incorporate components based on their application's needs, fostering a flexible and customizable development experience. Mastery of Spring Framework not only equips developers with the tools to navigate complex application architectures but also opens doors to a realm of possibilities in enterprise Java development. Setting the Stage for In-Depth Exploration of Spring Internals "Getting Ready for the Inner Workings of the Spring Framework serves as a first step in understanding the complex mechanisms that power Spring, and prepares you for further in-depth exploration. This section serves as an introduction and provides the basics needed to understand the intricacies of this versatile framework. The Spring Framework is based on the core principles of simplicity, modularity, and extensibility that guide its architecture and design. Before delving into the details of its internal mechanisms, it is important to understand the overarching goals and architectural concepts that shape its development.

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The most important of these concepts are Dependency Injection (DI) and Aspect-Oriented Programming (AOP), which form the basis of Spring's Inversion of Control (loC) container. These paradigms fundamentally change the way control is done within applications, promoting modular­ ity and flexibility. Dependency injection redefines how dependencies are managed within an application, with Spring taking care of object creation and assembly. This promotes loosely coupled, modular design, improving testability and maintainability. Aspect-oriented programming complements dependency injection by addressing cross-cutting issues such as logging and transaction management in a modular and reusable way. Spring's AOP support allows developers to modularize these concerns and apply them declaratively throughout the application. For instance, consider the following code snippet: java ©Componentpublic class MyService { private final MyRepository repository;

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©Autowiredpublic MyService(MyRepository repository) { this.repository = repository;} ©Transactionalpublic void doSomethingO {// Business logic} Here, MyService demonstrates dependency injection through constructor-based injection, with the My Repository dependency injected into the constructor. Additionally, the ©Transactional annotation showcases aspect-oriented programming by declaring transaction management concerns at the method level. As we embark on this exploration of Spring's internals, it's important to maintain a mindset of curiosity and inquiry. Understanding not just how Spring operates, but why it operates the way it does, is essential. This journey will involve examining the inner workings of the Spring loC container, as well as exploring its core modules, such as Spring MVC and Spring Security.

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In conclusion, "Preparing for a Comprehensive Dive into Spring Framework's Inner Workings" acts as a foundational stepping stone, equipping us with the necessary understanding to navigate the complexities of Spring with confidence and clarity.

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Chapter One Bean Creation and Initialization The Anatomy of Bean Creation "The Anatomy of Bean Creation" explores the intricate steps involved in Spring Framework's handling of beans, the essential components of Spring applications. Understanding this process is pivotal for develop­ ers aiming to harness the full capabilities of Spring's dependency injection mechanism. At the core of Spring's bean creation lies the Inversion of Control (loC) container, which oversees the lifecy­ cle of beans and their dependencies. Configuration metadata, specified through XML, Java annotations, or configuration classes, drives this container. The journey of bean creation encompasses several pivotal stages: 1. Definition of Beans: Before instantiation, beans require detailed configuration. This metadata includes class information, dependencies, and lifecycle instructions. In XML configurations, bean definitions are typically enclosed in <bean> tags, while in Java, annotations or configura­ tion classes serve this purpose.

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2 <bean id="myBean" class="com.example.MyBean'7> java ©Componentpublic class MyBean {// Bean properties and methods 1. Instantiation of Beans: Once defined, beans undergo instantiation. The loC container gener­ ates a new instance based on the bean's class, utilizing either a no-argument constructor or one with arguments, depending on the configuration. 2. Injection of Dependencies: Post-instantiation, the container injects necessary dependencies into the bean. This can be achieved through constructor injection, setter injection, or field in­ jection, adapting to the bean's configuration and dependency types. java

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3 ©Componentpublic class MyBean {private Dependency dependency; ©Autowiredpublic MyBean(Dependency dependency) { this.dependency = dependency; 4. Initialization Process: With dependencies resolved, the bean enters the initialization phase. Here, any specified initialization methods, such as ©PostConstruct methods or custom callbacks, are invoked. java 4 ©Componentpublic class MyBean { ©PostConstruct public void init() {// Initialization logic

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5. Lifecycle Management: Throughout the bean's lifecycle, the container manages its state, executing any defined lifecycle callbacks such as ©PreDestroy methods or custom destruction call­ backs. When the bean is no longer needed, it may be destroyed, freeing up any held resources. java ©Componentpublic class MyBean {©PreDestroypublic void destroyO {// Cleanup logic1 Spring offers extensive flexibility in configuring bean creation and initialization, allowing developers to customize various aspects such as bean scopes, lazy initialization, and conditional bean creation. By understanding "The Anatomy of Bean Creation," developers gain insight into Spring's loC container, en­ abling them to effectively manage bean instantiation, wiring, and lifecycle management. This knowledge

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empowers developers to build adaptable, modular, and maintainable applications using Spring's depen­ dency injection mechanism. Leveraging BeanPostProcessors for Custom Initialization "Leveraging BeanPostProcessors for Custom Initialization" encapsulates an advanced aspect of Spring Framework's bean lifecycle management, offering developers a mechanism to intervene in the bean instan­ tiation process and perform custom initialization tasks. Understanding and utilizing BeanPostProcessors is pivotal for extending Spring's capabilities and tailoring bean behavior to specific application requirements. BeanPostProcessors, as the name suggests, are special beans within the Spring loC container that intercept the instantiation process of other beans. They enable developers to execute custom logic before and after the instantiation of individual beans. By employing BeanPostProcessors, developers can inject additional behavior into bean instantiation without modifying the bean classes themselves, promoting modularity and flexibility in Spring applications. To effectively leverage BeanPostProcessors for custom initialization, developers must comprehend their role in the bean lifecycle and how to implement them in their applications. The bean lifecycle consists of several key phases:

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1. Instantiation: The bean is created by the loC container, typically through invoking its con­ structor. 2. Population of Properties: Dependencies and properties of the bean are injected by the con­ tainer. 3. Initialization: The bean is initialized, and any initialization logic specified in the bean's con­ figuration is executed. 4. Destruction: When the bean is no longer needed, the container may destroy it, invoking any destruction logic specified in the bean's configuration. BeanPostProcessors primarily intervene during the initialization phase of the bean lifecycle, enabling de­ velopers to execute custom logic before or after the bean's initialization. This can be useful for tasks such as setting up resources, performing validation, or applying custom behavior to beans. Implementing a BeanPostProcessor involves creating a class that implements the BeanPostProcessor in­ terface and overriding its postProcessBeforeInitialization() and postProcessAfterInitialization() meth­ ods. These methods receive the bean instance and its name as parameters, allowing developers to inspect and modify the bean as needed.

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Consider the following example of a BeanPostProcessor that logs a message before and after initializing beans: java nport org.springframework.beans.BeansException;nport org.springframework.beans.factory.config.BeanPostProcessor; ublic class CustomBeanPostProcessor implements BeanPostProcessor { ©Overridepublic Object postProcessBefore!nitialization(Object bean, String beanName) throws BeansException { System.out.println("Initializing bean:" + beanName);return bean;} ©Overridepublic Object postProcessAfter!nitialization(Object bean, String beanName) throws BeansException { System.out.println("Bean initialized:" + beanName);return bean;}

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In this example, the CustomBeanPostProcessor class implements the BeanPostProcessor interface and provides custom logic in the postProcessBefore!nitialization() and postProcessAfterInitialization() methods to log messages before and after initializing beans. To enable the BeanPostProcessor in the Spring application context, it must be declared as a bean itself. This can be done either through XML configuration or Java-based configuration. XML Configuration: xml <bean class="com.example.CustomBeanPostProcessor"/> Java-based Configuration: java port org.springframework.context.annotation.Bean;port org.springframework.context.annotation.Configuration;