![Question 1: What's happening in the background?
Question 1: What's happening in the background?
Let's Debug:
Identified candidate component class: file [GameRunner.class]
Identified candidate component class: file [MarioGame.class]
Creating shared instance of singleton bean 'gameRunner'
Creating shared instance of singleton bean 'marioGame'
Autowiring by type from bean name 'gameRunner' via constructor to bean named
'marioGame'
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean
with name 'gameRunner' defined in file [GameRunner.class]
Unsatisfied dependency expressed through constructor parameter 0;
nested exception is:org.springframework.beans.factory.NoUniqueBeanDefinitionException
No qualifying bean of type 'com.in28minutes.learnspringframework.game.GamingConsole' available
expected single matching bean but found 3: marioGame,pacManGame,superContraGame
29](https://image.slidesharecdn.com/javaprogrammingforbeginners-presentation-221221131844-545cb519/85/JavaProgrammingForBeginners-Presentation-pdf-30-320.jpg)
![Hands-on: Understand Power of Spring Boot
Hands-on: Understand Power of Spring Boot
Let's Build a Hello World App using Spring Initializr
Setup BooksController
// http://localhost:8080/courses
[
{
"id": 1,
"name": "Learn Microservices",
"author": "in28minutes"
}
]
41](https://image.slidesharecdn.com/javaprogrammingforbeginners-presentation-221221131844-545cb519/85/JavaProgrammingForBeginners-Presentation-pdf-42-320.jpg)
JavaProgrammingForBeginners-Presentation.pdf
- 1. Java Programming Java Programming For Beginners For Beginners New Sections: Java New Features (10,..,15,16,..), Spring, Spring Boot and REST API 1
- 3. GOAL: Help YOU learn Programming Basics and Best Practices Problem Solving Simple Design and Debugging Help you have fun! APPROACH: Hands-on Step By Step Learn Problem Solving Practice 200+ Code Examples Test Your Learning: Exercises Learn to Debug Programs : Github Page Build real world applications By the end of the course, you will be a really good programmer! Learn Java Programming Learn Java Programming 2
- 4. YOUR Success = OUR Success YOUR Success = OUR Success 98,000+ Learners with 46% 5 STAR Reviews Last Year: 42,000+ active learners & 14 million learning minutes "Great mix of theory and exercises!" "Interactive learning with the help of puzzles" "Never thought taking an online course will be so helpful. " "Builds confidence in people who fear programming" RECOMMENDATION: Bit of Patience in the first hour! 3
- 5. Step 01: Installing Java on Windows Step 02: Installing Java on MacOS Step 03: Installing Java on Linux Step 04: Troubleshooting Alternative: Installing Java Installing Java https://tryjshell.org/ 4
- 6. I love programming: You get to solve new problems every day. Learn something new everyday! Steps in Problem Solving: Step I: Understand the Problem Step II: Design Break the Problem Down Step III: Write Your Program (and Test) Express Your Solution: Language Specifics (Syntax) Let's solve multiple problems step by step! Learning to Program = Learning to ride a bike First steps are the most difficult Pure Fun a erwards! Programming and Problem Solving Programming and Problem Solving 5
- 7. Challenge 1 : Print Multiplication Table Challenge 1 : Print Multiplication Table 5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 25 5 * 6 = 30 5 * 7 = 35 5 * 8 = 40 5 * 9 = 45 5 * 10 = 50 6
- 8. Where do we start? : Print Multiplication Table Where do we start? : Print Multiplication Table Step 1: Calculate value of "5 * 5" Step 2: Print "5 * 5 = 25" Step 3: Do this 10 times 5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 25 5 * 6 = 30 5 * 7 = 35 5 * 8 = 40 5 * 9 = 45 5 * 10 = 50 7
- 9. Do you know?: How do Python programmers start learning Python? Python shell: That's why Python is easy to learn From Java 9: Java is equally easy to learn - JShell Java REPL (Read Eval Print Loop) Type in a one line of code and see the output Makes learning fun (Make a mistake and it immediately tells you whats wrong!) All great programmers make use of JShell In this course: We use JShell to get started By Section 5, you will be comfortable with Java syntax We will start using Eclipse as the Java IDE! JShell JShell 8
- 10. Java Primitive Types Java Primitive Types Type of Values Java Primitive Type Size (in bits) Range of Values Example Integral byte 8 -128 to 127 byte b = 5; Integral short 16 -32,768 to 32,767 short s = 128; Integral int 32 -2,147,483,648 to 2,147,483,647 int i = 40000; Integral long 64 -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 long l = 2222222222; Float float 32 ±3.40282347E+38F. NOT precise float f = 4.0f Float double 64 ±1.79769313486231570E+308. NOT precise double d = 67.0 Character char 16 'u0000 to 'uffff char c = 'A'; Boolean boolean 1 true or false boolean isTrue = false; 9
- 11. Print Multiplication Table - Solution 1 Print Multiplication Table - Solution 1 jshell> int i i ==> 0 jshell> for (i=0; i<=10; i++) { ...> System.out.printf("%d * %d = %d", 5, i, 5*i).println(); ...> } 5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 2 5 * 6 = 30 5 * 7 = 35 5 * 8 = 40 5 * 9 = 45 5 * 10 = 50 10
- 12. JVM, JRE And JDK JVM, JRE And JDK JRE = JVM + Libraries + Other Components JVM runs your program bytecode Libraries are built-in Java utilities that can be used within any program you create. System.out.println() was a method in java.lang, one such utility. Other Components include tools for debugging and code profiling (for memory management and performance) JDK = JRE + Compilers + Debuggers JDK refers to the Java Development Kit. It's an acronym for the bundle needed to compile (with the compiler) and run (with the JRE bundle) your Java program. Remember: JDK is needed to Compile and Run Java programs JRE is needed to Run Java Programs JVM is needed to Run Bytecode generated from Java programs 11
- 13. Most Popular Open Source Java IDE Download: Recommended: "Eclipse IDE for Enterprise Java and Web Developers" Troubleshooting Use 7Zip if you have problems with unzipping Unzip to root folder "C:Eclipse" instead of a long path Guide: Installing Eclipse Installing Eclipse https://www.eclipse.org/downloads/packages/ https://wiki.eclipse.org/Eclipse/Installation#Troubleshooting 12
- 14. Print Multiplication Table - Solution 2 Print Multiplication Table - Solution 2 public class MultiplicationTable { public static void print() { for(int i=1; i<=10;i++) { System.out.printf("%d * %d = %d", 5, i, 5*i).println(); } } public static void print(int number) { for(int i=1; i<=10;i++) { System.out.printf("%d * %d = %d", number, i, number*i).println(); } } public static void print(int number, int from, int to) { for(int i=from; i<=to;i++) { System.out.printf("%d * %d = %d", number, i, number*i).println(); } } } 13
- 15. Print Multiplication Table - Refactored (No Duplication) Print Multiplication Table - Refactored (No Duplication) package com.in28minutes.firstjavaproject; public class MultiplicationTable { public static void print() { print(5, 1, 10); } public static void print(int number) { print(number, 1, 10); } public static void print(int number, int from, int to) { for(int i=from; i<=to;i++) { System.out.printf("%d X %d = %d", number, i, number*i).println(); } } } 14
- 16. Object Oriented Programming (OOP) Object Oriented Programming (OOP) A class is a template. In above example, Planet is a class An object is an instance of a class. earth and venus are objects. name, location and distanceFromSun compose object state. rotate() and revolve() define object's behavior. Fields are the elements that make up the object state. Object behavior is implemented through Methods. class Planet name, location, distanceFromSun // data / state / fields rotate(), revolve() // actions / behavior / methods earth : new Planet venus : new Planet 15
- 17. Object Oriented Programming (OOP) - 2 Object Oriented Programming (OOP) - 2 Each Planet has its own state: name: "Earth", "Venus" location : Each has its own orbit distanceFromSun : They are at unique, different distances from the sun Each Planet has its own unique behavior: rotate() : They rotate at different rates (and in fact, different directions!) revolve() : They revolve round the sun in different orbits, at different speeds class Planet name, location, distanceFromSun // data / state / fields rotate(), revolve() // actions / behavior / methods earth : new Planet venus : new Planet 16
- 18. Java keeps improving: Java 10, Java 11, Java 12, ..., Java 17, Java 18 ... Developing Java Applications is Evolving as well: Spring Spring Boot REST API How about building a Real World Java Project? REST API with Spring and Spring Boot Let's get started! Next Few Sections Next Few Sections 17
- 19. Java Versioning Java Versioning Version Release Data Notes JDK 1.0 January 1996 J2SE 5.0 September 2004 5 Releases in 8 years Java SE 8 (LTS) March 2014 Most important Java Release Java SE 9 September 2017 4 Releases in 13 years Java SE 10 March 2018 Time-Based Release Versioning Java SE 11 (LTS) September 2018 Long Term Support Version (Every 3 years) Java SE 12 March 2019 ... Java SE 16 March 2021 Java SE 17 (LTS) September 2021 18
- 20. Java New Features Java New Features Version Release Data Important New Features J2SE 5.0 Sep 2004 Enhanced For Loop, Generics, Enums, Autoboxing Java SE 8 (LTS) Mar 2014 Functional Programming - Lambdas & Streams, Static methods in interface Java SE 9 Sep 2017 Modularization (Java Platform Module System) Java SE 10 Mar 2018 Local Variable Type Inference Java SE 14 Mar 2020 Switch Expressions (Preview in 12 and 13) Java SE 15 Sep 2020 Text Blocks (Preview in 13) Java SE 16 Mar 2021 Record Classes (Preview in 14 and 15) All Java Versions - API Improvements, Performance and Garbage Collection Improvements 19
- 21. Introduced in Java 9 Goals: Modularize JDK (IMPORTANT) rt.jar grew to 60+ MB by Java 8 Modularize applications Modularizing JDK: java --list-modules java.base java.logging java.sql java.xml jdk.compiler jdk.jartool jdk.jshell java -d java.sql Java Modularization - Overview Java Modularization - Overview 20
- 22. Java Modularization - Remember Java Modularization - Remember Module Descriptor - module-info.java: Defines metadata about the module: requires module.a; - I need module.a to do my work! requires transitive module.a; - I need module.a to do my work AND my users also need access to module.a exports - Export package for use by other modules opens package.b to module.a - Before Java 9, reflection can be used to find details about types (private, public and protected). From Java 9, you can decide which packages to expose: Above statement allows module.a access to perform reflection on public types in package.b Advantages Compile Time Checks For availability of modules Better Encapsulation Make only a subset of classes from a module available to other modules Smaller Java Runtime Use only the modules of Java that you need! 21
- 23. Local Variable Type Inference Local Variable Type Inference Java compiler infers the type of the variable at compile time Introduced in Java 10 You can add final if you want var can also be used in loops Remember: You cannot assign null var is NOT a keyword Best Practices: Good variable names Minimize Scope Improve readability for chained expressions // List<String> numbers = new ArrayList<>(list); var numbers = new ArrayList<>(list); 22
- 24. Switch Expression Switch Expression Create expressions using switch statement Released in JDK 14 Preview - JDK 12 and 13 Remember: No fallthrough Use yield or -> to return value String monthName = switch (monthNumber) { case 1 -> { System.out.println("January"); // yield statement is used in a Switch Expression // break,continue statements are used in a Switch Statement yield "January"; // yield mandatory! } case 2 -> "February"; case 3 -> "March"; case 4 -> "April"; default -> "Invalid Month"; }; 23
- 25. Text Blocks Text Blocks Simplify Complex Text Strings Released in JDK 15 Preview - JDK 13 and 14 Remember: First Line : """ Followed by line terminator """abc or """abc""" in First Line are NOT valid Automatic Alignment is done Trailing white space is stripped You can use text blocks where ever you can use a String System.out.println(""First Line"nSecond LinenThird Line"); System.out.println(""" "First Line" Second Line Third Line""" ); 24
- 26. Records Records Eliminate verbosity in creating Java Beans Public accessor methods, constructor, equals, hashcode and toString are automatically created You can create custom implementations if you would want Released in JDK 16 Preview - JDK 14 and 15 Remember: Compact Constructors are only allowed in Records You can add static fields, static initializers, and static methods BUT you CANNOT add instance variables or instance initializers HOWEVER you CAN add instance methods record Person(String name, String email, String phoneNumber) { } 25
- 27. Build a Loose Coupled Hello World Gaming App with Modern Spring Approach Get Hands-on with Spring and understand: Why Spring? Terminology Tight Coupling and Loose Coupling IOC Container Application Context Component Scan Dependency Injection Spring Beans Auto Wiring Getting Started with Spring Framework - Goals Getting Started with Spring Framework - Goals 26
- 28. Design Game Runner to run games: Mario, Super Contra, PacMan etc Iteration 1: Tightly Coupled GameRunner class Game classes: Mario, Super Contra, PacMan etc Iteration 2: Loose Coupling - Interfaces GameRunner class GamingConsole interface Game classes: Mario, Super Contra, PacMan etc Iteration 3: Loose Coupling - Spring Spring framework will manage all our objects! GameRunner class GamingConsole interface Game classes: Mario, Super Contra, PacMan etc Loose Coupling with Spring Framework Loose Coupling with Spring Framework 27
- 29. Question 1: What's happening in the background? Let's debug! Question 2: What about the terminology? How does it relate to what we are doing? Dependency, Dependency Injection, IOC Container, Application Context, Component Scan, Spring Beans, Auto Wiring etc! Question 3: Does the Spring Framework really add value? We are replacing 3 simple lines with 3 complex lines! Question 4: What if I want to run Super Contra game? Question 5: How is Spring JAR downloaded? Magic of Maven! Spring Framework - Questions Spring Framework - Questions 28
- 30. Question 1: What's happening in the background? Question 1: What's happening in the background? Let's Debug: Identified candidate component class: file [GameRunner.class] Identified candidate component class: file [MarioGame.class] Creating shared instance of singleton bean 'gameRunner' Creating shared instance of singleton bean 'marioGame' Autowiring by type from bean name 'gameRunner' via constructor to bean named 'marioGame' org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'gameRunner' defined in file [GameRunner.class] Unsatisfied dependency expressed through constructor parameter 0; nested exception is:org.springframework.beans.factory.NoUniqueBeanDefinitionException No qualifying bean of type 'com.in28minutes.learnspringframework.game.GamingConsole' available expected single matching bean but found 3: marioGame,pacManGame,superContraGame 29
- 31. @Component (..): Class managed by Spring framework Dependency: GameRunner needs GamingConsole impl! GamingConsole Impl (Ex: MarioGame) is a dependency of GameRunner Component Scan: How does Spring Framework find component classes? It scans packages! (@ComponentScan("com.in28minutes")) Dependency Injection: Identify beans, their dependencies and wire them together (provides IOC - Inversion of Control) Spring Beans: An object managed by Spring Framework IoC container: Manages the lifecycle of beans and dependencies Types: ApplicationContext (complex), BeanFactory (simpler features - rarely used) Autowiring: Process of wiring in dependencies for a Spring Bean Question 2: Spring Framework - Important Terminology Question 2: Spring Framework - Important Terminology 30
- 32. - In Game Runner Hello World App, we have very few classes BUT Real World applications are much more complex: Multiple Layers (Web, Business, Data etc) Each layer is dependent on the layer below it! Example: Business Layer class talks to a Data Layer class Data Layer class is a dependency of Business Layer class There are thousands of such dependencies in every application! With Spring Framework: INSTEAD of FOCUSING on objects, their dependencies and wiring You can focus on the business logic of your application! Spring Framework manages the lifecycle of objects: Mark components using annotations: @Component (and others..) Mark dependencies using @Autowired Allow Spring Framework to do its magic! Ex: Controller > BusinessService (sum) > DataService (data)! Question 3: Does the Spring Framework really add value? Question 3: Does the Spring Framework really add value? 31
- 33. Try it as an exercise @Primary Playing with Spring: Exercise: Dummy implementation for PacMan and make it Primary! Debugging Problems: Remove @Component and Play with it! Question 4: What if I want to run Super Contra game? Question 4: What if I want to run Super Contra game? 32
- 34. What happens if you manually download Spring JAR? Remember: Spring JAR needs other JARs What if you need to upgrade to a new version? Maven: Manage JARs needed by apps (application dependencies) Once you add a dependency on Spring framework, Maven would download: Spring Framework and its dependencies All configuration in pom.xml Maven artifacts: Identified by a Group Id, an Artifact Id! Important Features: Defines a simple project setup that follows best practices Enables consistent usage across all projects Manages dependency updates and transitive dependencies Terminology Warning: Spring Dependency vs Maven Dependency Question 5 Question 5: How is Spring JAR downloaded? (Maven) : How is Spring JAR downloaded? (Maven) 33
- 35. Constructor-based : Dependencies are set by creating the Bean using its Constructor Setter-based : Dependencies are set by calling setter methods on your beans Field: No setter or constructor. Dependency is injected using reflection. Which one should you use? Spring team recommends Constructor-based injection as dependencies are automatically set when an object is created! Exploring Spring - Dependency Injection Types Exploring Spring - Dependency Injection Types 34
- 36. Spring Modules Spring Modules Spring Framework is divided into modules: Core: IoC Container etc Testing: Mock Objects, Spring MVC Test etc Data Access: Transactions, JDBC, JPA etc Web Servlet: Spring MVC etc Web Reactive: Spring WebFlux etc Integration: JMS etc Each application can choose the modules they want to make use of They do not need to make use of all things everything in Spring framework! 35
- 37. Spring Projects Spring Projects Spring Projects: Spring keeps evolving (REST API > Microservices > Cloud) Spring Boot: Most popular framework to build microservices Spring Cloud: Build cloud native applications Spring Data: Integrate the same way with different types of databases : NoSQL and Relational Spring Integration: Address challenges with integration with other applications Spring Security: Secure your web application or REST API or microservice 36
- 38. Loose Coupling: Spring manages beans and dependencies Make writing unit tests easy! Provides its own unit testing project - Spring Unit Testing Reduced Boilerplate Code: Focus on Business Logic Example: No need for exception handling in each method! All Checked Exceptions are converted to Runtime or Unchecked Exceptions Architectural Flexibility: Spring Modules and Projects You can pick and choose which ones to use (You DON'T need to use all of them!) Evolution with Time: Microservices and Cloud Spring Boot, Spring Cloud etc! Why is Spring Popular? Why is Spring Popular? 37
- 39. Spring JDBC - Example Spring JDBC - Example JDBC example JDBC example Spring JDBC example Spring JDBC example public void deleteTodo(int id) { PreparedStatement st = null; try { st = db.conn.prepareStatement(DELETE_TODO_QUERY); st.setInt(1, id); st.execute(); } catch (SQLException e) { logger.fatal("Query Failed : " + DELETE_TODO_QUERY, e); } finally { if (st != null) { try {st.close();} catch (SQLException e) {} } } } public void deleteTodo(int id) { jdbcTemplate.update(DELETE_TODO_QUERY, id); } 38
- 40. Goal: 10,000 Feet overview of Spring Framework Help you understand the terminology! Dependency Dependency Injection (and types) Autowiring Spring Beans Component Scan IOC Container (Application Context) We will play with other Spring Modules and Projects later in the course Advantages: Loosely Coupled Code (Focus on Business Logic), Architectural Flexibility and Evolution with time! Spring Framework - Review Spring Framework - Review 39
- 41. Build a Hello World App in Modern Spring Boot Approach Get Hands-on with Spring Boot Why Spring Boot? Terminology Spring Initializr Auto Configuration Starter Projects Actuator Developer Tools Getting Started with Spring Boot - Goals Getting Started with Spring Boot - Goals 40
- 42. Hands-on: Understand Power of Spring Boot Hands-on: Understand Power of Spring Boot Let's Build a Hello World App using Spring Initializr Setup BooksController // http://localhost:8080/courses [ { "id": 1, "name": "Learn Microservices", "author": "in28minutes" } ] 41
- 43. World Before Spring Boot! World Before Spring Boot! Setting up Spring Web Projects before Spring Boot was NOT easy! Define maven dependencies and manage versions for frameworks spring-webmvc, jackson-databind, log4j etc Define web.xml (/src/main/webapp/WEB-INF/web.xml) Define Front Controller for Spring Framework (DispatcherServlet) Define a Spring context XML file (/src/main/webapp/WEB-INF/todo-servlet.xml) Define a Component Scan (<context:component-scan base-package="com.in28minutes" />) Install Tomcat or use tomcat7-maven-plugin plugin (or any other web server) Deploy and Run the application in Tomcat How does Spring Boot do its Magic? Spring Boot Starter Projects Spring Boot Auto Configuration https://github.com/in28minutes/SpringMvcStepByStep/blob/master/Step15.md#pomxml 42
- 44. Goal of Starter Projects: Help you get a project up and running quickly! Web Application - Spring Boot Starter Web REST API - Spring Boot Starter Web Talk to database using JPA - Spring Boot Starter Data JPA Talk to database using JDBC - Spring Boot Starter JDBC Secure your web application or REST API - Spring Boot Starter Security Manage list of maven dependencies and versions for different kinds of apps: Spring Boot Starter Web: Frameworks needed by typical web applications spring-webmvc, spring-web, spring-boot-starter-tomcat, spring-boot-starter-json Spring Boot Starter Projects Spring Boot Starter Projects 43
- 45. Spring Boot provides Auto Configuration Basic configuration to run your application using the frameworks defined in your maven dependencies Auto Configuration is decided based on: Which frameworks are in the Class Path? What is the existing configuration (Annotations etc)? An Example: (Enable debug logging for more details): If you use Spring Boot Starter Web, following are auto configured: Dispatcher Servlet (DispatcherServletAutoConfiguration) Embedded Servlet Container - Tomcat is the default (EmbeddedWebServerFactoryCustomizerAutoConfiguration) Default Error Pages (ErrorMvcAutoConfiguration) Bean to/from JSON conversion (JacksonHttpMessageConvertersConfiguration) Spring Boot Auto Configuration Spring Boot Auto Configuration 44
- 46. How do you deploy your application? Step 1 : Install Java Step 2 : Install Web/Application Server Tomcat/WebSphere/WebLogic etc Step 3 : Deploy the application WAR (Web ARchive) This is the OLD WAR Approach Complex to setup! Embedded Server - Simpler alternative Step 1 : Install Java Step 2 : Run JAR file Make JAR not WAR (Credit: Josh Long!) Embedded Server Examples: spring-boot-starter-tomcat spring-boot-starter-jetty spring-boot-starter-undertow Spring Boot Embedded Servers Spring Boot Embedded Servers 45
- 47. Spring Boot Actuator: Monitor and manage your application in your production Provides a number of endpoints: beans - Complete list of Spring beans in your app health - Application health information metrics - Application metrics mappings - Details around Request Mappings Spring Boot DevTools: Increase developer productivity Why do you need to restart the server for every code change? More Spring Boot Features More Spring Boot Features 46
- 48. Spring Boot vs Spring MVC vs Spring Spring Boot vs Spring MVC vs Spring Spring Framework Core Feature: Dependency Injection @Component, @Autowired, IOC Container, ApplicationContext, Component Scan etc.. Spring Modules and Spring Projects: Good Integration with Other Frameworks (Hibernate/JPA, JUnit & Mockito for Unit Testing) Spring MVC (Spring Module): Build web applications in a decoupled approach Dispatcher Servlet, ModelAndView and View Resolver etc Spring Boot (Spring Project): Build production ready applications quickly Starter Projects - Make it easy to build variety of applications Auto configuration - Eliminate configuration to setup Spring, Spring MVC and other projects! Enable production ready non functional features: Actuator : Enables Advanced Monitoring and Tracing of applications. Embedded Servers - No need for separate application servers! Default Error Handling 47
- 49. Goal: 10,000 Feet overview of Spring Boot Help you understand the terminology! Starter Projects Auto Configuration Actuator DevTools Advantages: Get started quickly with production ready features! Spring Boot - Review Spring Boot - Review 48
- 50. REST API REST API REST API: Architectural Style for the Web Resource: Any information (Example: Courses) URI: How do you identify a resource? (/courses, /courses/1) You can perform actions on a resource (Create/Get/Delete/Update). Different HTTP Request Methods are used for different operations: GET - Retrieve information (/courses, /courses/1) POST - Create a new resource (/courses) PUT - Update/Replace a resource (/courses/1) PATCH - Update a part of the resource (/courses/1) DELETE - Delete a resource (/courses/1) Representation: How is the resource represented? (XML/JSON/Text/Video etc..) Server: Provides the service (or API) Consumer: Uses the service (Browser or a Front End Application) 49
- 51. Spring and Spring Boot Release Cycles Spring and Spring Boot Release Cycles What is the difference between these? 2.5.0 (SNAPSHOT) 2.4.5 (M3) 2.4.4 Release Number: MAJOR.MINOR.FIX Spring and Spring Boot Release Cycle: SNAPSHOT (versions under development) > Mile Stones > Released Version Recommendation - Do NOT use SNAPSHOTs or M1 or M2 or M3 Prefer released versions! 50
- 52. JDBC Write a lot of SQL queries! And write a lot of Java code Spring JDBC Write a lot of SQL queries BUT lesser Java code JPA Do NOT worry about queries Just Map Entities to Tables! Spring Data JPA Let's make JPA even more simple! I will take care of everything! JDBC to Spring JDBC to JPA to Spring Data JPA JDBC to Spring JDBC to JPA to Spring Data JPA 51
- 53. JDBC to Spring JDBC JDBC to Spring JDBC JDBC example JDBC example Spring JDBC example Spring JDBC example public void deleteTodo(int id) { PreparedStatement st = null; try { st = db.conn.prepareStatement(DELETE_TODO_QUERY); st.setInt(1, id); st.execute(); } catch (SQLException e) { logger.fatal("Query Failed : " + DELETE_TODO_QUERY, e); } finally { if (st != null) { try {st.close();} catch (SQLException e) {} } } } public void deleteTodo(int id) { jdbcTemplate.update(DELETE_TODO_QUERY, id); } 52
- 54. JPA Example JPA Example Spring Data JPA Example Spring Data JPA Example @Repository @Transactional public class PersonJpaRepository { @PersistenceContext EntityManager entityManager; public Person findById(int id) { return entityManager.find(Person.class, id); } public Person update(Person person) { return entityManager.merge(person); } public Person insert(Person person) { return entityManager.merge(person); } public void deleteById(int id) {........ public interface TodoRepository extends JpaRepository<Todo, Integer>{ 53
- 55. We added Data JPA and H2 dependencies: Spring Boot Auto Configuration does some magic: Initialize JPA and Spring Data JPA frameworks Launch an in memory database (H2) Setup connection from App to in-memory database Launch a few scripts at startup (example: data.sql) Remember - H2 is in memory database Does NOT persist data Great for learning BUT NOT so great for production Let's see how to use MySQL next! Spring Boot Auto Configuration Magic - Data JPA Spring Boot Auto Configuration Magic - Data JPA 54
- 56. Java keeps improving: Java 10, Java 11, Java 12, ... Java Project - REST API in Modern Approach: Spring Spring Boot Do NOT forget to leave a Review! Congratulations Congratulations 55
- 57. What's Next? - Don't Stop Learning! What's Next? - Don't Stop Learning! Step I: Build more applications: REST API and Microservices Full Stack Applications (Angular and React) Mobile Applications Learn Unit Testing (JUnit and Mockito) and Clean Code Step II: Learn Java Frameworks in Depth: Spring & Spring Boot Hibernate and JPA Step III: Go Cloud (AWS, Azure and Google Cloud) Step IV: Learn DevOps https://github.com/in28minutes/learn 56