• Spring Security will be used later in this project.

spring.application.name=examtool  
server.port=8085
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• If a database is not connected to our application then we will not be able to run the application as we have included the MySQLDriver dependency.
  • Error that we get if we have not connected a database :
    

• Using the highlighted database.

package com.tool.erp.setup;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import java.util.Vector;

@Getter
@Setter
@NoArgsConstructor // Lombok will generate a constructor with no arguments
@AllArgsConstructor // Lombok will generate a constructor with all properties in the class
public class APIReturnModel {
    private String status = "fail";
    private String message = "Something Went Wrong !!";
    private Vector<?> data; // "?" means any type of data
    private int count = 0; // count of data
}

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• We are creating folders to organize our code. This is called Modular Approach, and it helps us in identifying the source of a bug/error.

• We want this model to be inserted into the database. To achieve this, we'll have to define some fields (like @Entity).

For data type validations, we use the spring-boot-starter-validation dependency (otherwise we'll have to separately use if and else conditions for validations) :

		<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
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package com.tool.erp.users.model;

import jakarta.persistence.*;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Size;
import lombok.*;
import org.hibernate.annotations.CreationTimestamp;

import java.util.Date;
@Data // This annotation is used to generate getters, setters, toString, equals, and hashCode methods
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Entity // This annotation is used to mark the class as a persistent Java class
@Table(name = "User")
// This annotation is used to specify the table name (Note: A name like "User Employee" will be converted to "user_employee" in the database)
public class UsersModel {
    @Id // This annotation is used to specify the primary key of an entity
    @GeneratedValue(strategy = GenerationType.AUTO)
    // This annotation is used to specify how the primary key should be generated
    private int userId;

    @NotBlank(message = "User Name can't be Null")
    @Column(unique = true, nullable = false, updatable = false)
    private String userName;

    @NotBlank(message = "First Name can't be Null")
    @Column(nullable = false, updatable = false)
    @Size(max = 20, min = 2, message = "First Name must be between 2 and 20 characters")
    private String firstName;

    private String lastName;

    @NotBlank(message = "Password can't be Null")
    @Column(nullable = false)
    @Size(max = 20, min = 2, message = "Password must be between 8 and 20 characters")
    private String password;

    private String email;

    private String phoneNo;

    @CreationTimestamp
    @Column(updatable = false, nullable = false)
    @Temporal(TemporalType.TIMESTAMP)// This annotation is used to specify the type of data of the property
    private Date createdDate;

    @CreationTimestamp
    @Column(nullable = false, updatable = true)
    private Date modifiedDate;

    private String createdBy;

    private String modifiedBy;
}
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• 
  Schema has been created.
  When we run our spring application now a new table will be created by JPA Hibernate itself.
  
  

• Service Classes are used to define how data is handled.

• To declare any class as a controller in spring boot, we use the @RestController annotation.
• To connect Service class to this class we'll make an instance of the Service class.

There are 2 ways, spring security handles 2 things : OAuth 2, and a "cheaper" version of OAuth 2 which is JWT and encrypted password.