import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootDemoApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootDemoApplication.class, args);
	}

}

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Size;


@Entity
public class Student {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    @Size(min = 4, message = "Name should have atleast 4 characters")
    private String name;

    @NotBlank(message = "passportNumber is mandatory")
    private String passportNumber;

    public Student() {
        super();
    }

    public Student(Long id, String name, String passportNumber) {
        super();
        this.id = id;
        this.name = name;
        this.passportNumber = passportNumber;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassportNumber() {
        return passportNumber;
    }

    public void setPassportNumber(String passportNumber) {
        this.passportNumber = passportNumber;
    }
}

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface StudentRepository extends JpaRepository<Student, Long>{

}

import jakarta.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.hateoas.EntityModel;
import org.springframework.hateoas.server.mvc.WebMvcLinkBuilder;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import java.net.URI;
import java.util.List;
import java.util.Optional;

import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.linkTo;
import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.methodOn;

@RestController
public class StudentController {

    @Autowired
    private StudentRepository studentRepository;

    @GetMapping("/students")
    public List<Student> retrieveAllStudents() {
        return studentRepository.findAll();
    }

    @GetMapping("/students/{id}")
    public EntityModel<Student> retrieveStudent(@PathVariable long id) {
        Optional<Student> student = studentRepository.findById(id);

        if (!student.isPresent())
            throw new StudentNotFoundException("id-" + id);

        EntityModel<Student> resource = EntityModel.of(student.get());

        WebMvcLinkBuilder linkTo = linkTo(methodOn(this.getClass()).retrieveAllStudents());

        resource.add(linkTo.withRel("all-students"));

        return resource;
    }

    @PostMapping("/students")
    public ResponseEntity<Object> createStudent(@Valid @RequestBody Student student) {
        Student savedStudent = studentRepository.save(student);

        URI location = ServletUriComponentsBuilder.fromCurrentRequest().path("/{id}")
                .buildAndExpand(savedStudent.getId()).toUri();

        return ResponseEntity.created(location).build();

    }

    @DeleteMapping("/students/{id}")
    public void deleteStudent(@PathVariable long id) {
        studentRepository.deleteById(id);
    }

    @PutMapping("/students/{id}")
    public ResponseEntity<Object> updateStudent(@Valid @RequestBody Student student, @PathVariable long id) {

        Optional<Student> studentOptional = studentRepository.findById(id);

        if (!studentOptional.isPresent())
            return ResponseEntity.notFound().build();

        student.setId(id);

        studentRepository.save(student);

        return ResponseEntity.noContent().build();
    }
}

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(HttpStatus.NOT_FOUND)
public class StudentNotFoundException extends RuntimeException {

    public StudentNotFoundException(String exception) {
        super(exception);
    }

}

spring.jpa.defer-datasource-initialization=true

insert into student values(10001,'Annie', 'E1234567');
insert into student values(20001,'John', 'A1234568');
insert into student values(30001,'David','C1232268');
insert into student values(40001,'Amy','D213458');

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.3</version>
    <relativePath/> <!-- lookup parent from repository -->
  </parent>

  <groupId>com.example</groupId>
  <artifactId>demo</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringBoot_Demo</name>
  <description>Demo project for Spring Boot</description>

  <properties>
    <java.version>17</java.version>
    <junit.version>4.13.2</junit.version>
    <rest-assured.version>5.3.2</rest-assured.version>
    <maven.compiler.plugin.version>3.12.1</maven.compiler.plugin.version>
    <maven.surefire.plugin.version>3.2.3</maven.surefire.plugin.version>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-hateoas</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-validation</artifactId>
    </dependency>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-devtools</artifactId>
      <scope>runtime</scope>
    </dependency>

    <dependency>
      <groupId>com.h2database</groupId>
      <artifactId>h2</artifactId>
      <scope>runtime</scope>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>${junit.version}</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>io.rest-assured</groupId>
      <artifactId>rest-assured</artifactId>
      <version>${rest-assured.version}</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>org.junit.vintage</groupId>
      <artifactId>junit-vintage-engine</artifactId>
      <scope>test</scope>
    </dependency>

  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>${maven.compiler.plugin.version}</version>
        <configuration>
          <source>${maven.compiler.source}</source>
          <target>${maven.compiler.target}</target>
        </configuration>
      </plugin>

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>${maven.surefire.plugin.version}</version>
        <configuration>
          <testFailureIgnore>true</testFailureIgnore>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

package org.example;

import io.restassured.RestAssured;
import io.restassured.http.ContentType;
import io.restassured.response.ValidatableResponse;
import org.json.JSONException;
import org.json.JSONObject;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.test.context.junit4.SpringRunner;

import static io.restassured.RestAssured.given;
import static org.hamcrest.Matchers.equalTo;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class SpringbootDemoTests {

    private final static String BASE_URI = "http://localhost";

    @LocalServerPort
    private int port;

    private ValidatableResponse validatableResponse;

    private ValidatableResponse validatableResponse1;

    @Before
    public void configureRestAssured() {
        RestAssured.baseURI = BASE_URI;
        RestAssured.port = port;
    }

    /* Get operation - Get the details of a Student */
    @Test
    public void listUsers() {

        validatableResponse = given()
                .contentType(ContentType.JSON)
                .when()
                .get("/students")
                .then()
                .assertThat().statusCode(200);

    }

    /* Get operation - Get the details of a Student */
    @Test
    public void listAUser() {

        validatableResponse = given()
                .contentType(ContentType.JSON)
                .when()
                .get("/students/30001")
                .then()
                .assertThat().log().all().statusCode(200)
                .body("id",equalTo(30001))
                .body("name",equalTo("David"))
                .body("passportNumber",equalTo("C1232268"));;
    }

    /* Create operation - Create a new Student */
    @Test
    public void createAUser() throws JSONException {

        JSONObject newStudent = new JSONObject();

        newStudent.put("name", "Timmy");
        newStudent.put("passportNumber", "ZZZ12345");

        validatableResponse = given()
                .contentType(ContentType.JSON).body(newStudent.toString())
                .when()
                .post("/students")
                .then()
                .log().all().assertThat().statusCode(201);

        /* Verify that a new Student is created */
        validatableResponse1 = given()
                .contentType(ContentType.JSON)
                .when()
                .get("/students/1")
                .then()
                .log().all().assertThat().statusCode(200)
                .body("id",equalTo(1))
                .body("name",equalTo("Timmy"))
                .body("passportNumber",equalTo("ZZZ12345"));

    }

    /* Update operation - Update PassportNumber of a Student */
    @Test
    public void updateAUser() throws JSONException {

        JSONObject newStudent = new JSONObject();

        newStudent.put("name", "John");
        newStudent.put("passportNumber", "YYYY1234");

        validatableResponse = given()
                .contentType(ContentType.JSON).body(newStudent.toString())
                .when()
                .put("/students/20001")
                .then()
                .log().all().assertThat().statusCode(204);

        /* Verify that the updated Student has updated PassportNumber */
        validatableResponse1 = given()
                .contentType(ContentType.JSON)
                .when()
                .get("/students/20001")
                .then()
                .log().all().assertThat().statusCode(200)
                .body("id",equalTo(20001))
                .body("name",equalTo("John"))
                .body("passportNumber",equalTo("YYYY1234"));

    }

    /* Delete operation - Delete a Student */
    @Test
    public void deleteAUser() throws JSONException {

        validatableResponse = given()
                .contentType(ContentType.JSON)
                .when()
                .delete("/students/10003")
                .then()
                .log().all().assertThat().statusCode(200);


        /* Verify that the deleted Student Request returns STATUS 404 */
        validatableResponse1 = given()
                .contentType(ContentType.JSON)
                .when()
                .get("/students/10003")
                .then()
                .log().all().assertThat().statusCode(404);

    }
}

mvn clean test