Lazy Initialization :

hitarth's Vault // Exported at - 10:04:PM

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Scope :

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Post Construct and Pre Destroy :

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Evolution of Jakarta EE: vs J2EE vs Java EE

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Jakarta Contexts & Dependency Injection (CDI)

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package com.example.demo.examples.jakarta;

import com.example.demo.businessAssignment.components.DataService;
import jakarta.inject.Inject;
import jakarta.inject.Named;
import jdk.jfr.Name;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;

import java.util.Arrays;

//@Component
@Named // we can use @Named and @Inject instead of @Component and @Inject respectively 
class BusinessService {
	private DataService2 dataService;

//	@Autowired
	@Inject
	public void setDataService(DataService2 dataService) {
		System.out.println("Setter called");
		this.dataService = dataService;
	}

	public DataService2 getDataService() {
		System.out.println("Setter injection");
		return dataService;
	}

}

//@Component
@Named
class DataService2 {

}

@Configuration
@ComponentScan // performs a component scan on the current package
public class CdiContextLauncherApp {

	public static void main(String[] args) {
		var context = new AnnotationConfigApplicationContext(CdiContextLauncherApp.class);
		Arrays.stream(context.getBeanDefinitionNames()).forEach((System.out::println));
		System.out.println(context.getBean(BusinessService.class).getDataService());
	}

}

Spring Stereotype Annotations - @Component & more

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Quick Review of Important Spring Annotations

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Quick Review of Important Spring Concepts :

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Spring Boot Dev Tools :

Allows us to restart the server for every change made in the code.

<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
		</dependency>

Application Properties :

Logging Levels :

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Trace : Prints all the errors
Debug prints the errors listed below it
similarly info prints errors listed below it and so on...

To add a LOT of different configuration properties :

Picking up configs from application.properties file
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Running the .jar file :

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Monitor Applications using Spring Boot Actuator

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<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-actuator -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>

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Getting Started with JPA, Hibernate, Spring and Spring Boot :

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ignore the user=SA part
this is a dynamic url so it changes every time we restart the application, so lets configure a static url

JDBC vs Spring JDBC

Both the code blocks will perform the same task but the Spring JDBC requires less code compared to JDBC

indexing : command line runner, jdbc, sql, insert into, @Repository, JdbcTemplate

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Using Spring JDBC to execute SQL queries and much more :

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This approach is not so efficient and with a huge database things will start to fall apart. This is where Spring JPA comes into play :

Using JPA

we'll create a mapping between our java bean and the table and we'll use this mapping to insert or retrieve values.

Using Spring Data JPA :

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with this, we don't even have to worry about entity manager now.
in the image below, in <Course, Integer> integer is the ID type

Hibernate vs JPA :

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"myfirstwebapp" : ToDoList ☠️☠️ :

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or
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Model 1 :

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Model 2 :

<form method="post">...</form> is to be used whenever you want to transfer the data
- get method reveals the name and password in the URL

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Model 3 : To Do List :

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SessionAttributes are to be added like this :

JSTL Dependencies :

<dependency>  
    <groupId>jakarta.servlet.jsp.jstl</groupId>  
    <artifactId>jakarta.servlet.jsp.jstl-api</artifactId>  
</dependency>  
  
<dependency>  
    <groupId>org.eclipse.jetty</groupId>  
    <artifactId>glassfish-jstl</artifactId>  
</dependency>

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Validations :

Description: <input type="text" name="description" required/>

frontend validations can easily be abused by hackers that is why we'll use server side validations :
Spring Form Tag Libraries : https://docs.spring.io/spring-framework/docs/3.2.x/spring-framework-reference/html/view.html
We get these jakarta validation constraints on importing spring boot starter validation.
We can use them like this :

and

Predicate Object : Lambda Function :

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