package com.app.EcommerceBackend.config;

import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp2.BasicDataSource;
import org.hibernate.SessionFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.orm.hibernate5.HibernateTransactionManager;
import org.springframework.orm.hibernate5.LocalSessionFactoryBuilder;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@ComponentScan(basePackages={"com.app.EcommerceBackend.dto"})
@EnableTransactionManagement
public class HibernateConfig {

    // Change the below based on the DBMS you choose
    private final static String DATABASE_URL = "jdbc:h2:tcp://localhost/~/ecommerce";
    private final static String DATABASE_DRIVER = "org.h2.Driver";
    private final static String DATABASE_DIALECT = "org.hibernate.dialect.H2Dialect";
    private final static String DATABASE_USERNAME = "sa";
    private final static String DATABASE_PASSWORD = "";

    // dataSource bean will be available
    @Bean
    public DataSource getDataSource() {

        BasicDataSource dataSource = new BasicDataSource();

        // Providing the database connection information
        dataSource.setDriverClassName(DATABASE_DRIVER);
        dataSource.setUrl(DATABASE_URL);
        dataSource.setUsername(DATABASE_USERNAME);
        dataSource.setPassword(DATABASE_PASSWORD);


        return dataSource;

    }

    // sessionFactory bean will be available

    @Bean
    public SessionFactory getSessionFactory(DataSource dataSource) {

        LocalSessionFactoryBuilder builder = new LocalSessionFactoryBuilder(dataSource);

        builder.addProperties(getHibernateProperties());
        builder.scanPackages("com.app.EcommerceBackend.dto");

        return builder.buildSessionFactory();

    }



    // All the hibernate properties will be returned in this method
    private Properties getHibernateProperties() {

        Properties properties = new Properties();


        properties.put("hibernate.dialect", DATABASE_DIALECT);
        properties.put("hibernate.show_sql", "true");
        properties.put("hibernate.format_sql", "true");

        //properties.put("hibernate.hbm2ddl.auto", "create");


        return properties;
    }

    // transactionManager bean
    @Bean
    public HibernateTransactionManager getTransactionManager(SessionFactory sessionFactory) {
        HibernateTransactionManager transactionManager = new HibernateTransactionManager(sessionFactory);
        return transactionManager;
    }


}

package com.app.EcommerceBackend.daoImpl;

    import java.util.ArrayList;
    import java.util.List;

    import org.hibernate.SessionFactory;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Repository;
    import org.springframework.transaction.annotation.Transactional;

    import com.app.EcommerceBackend.dao.CategoryDAO;
    import com.app.EcommerceBackend.dto.Category;

    @Repository("categoryDAO")
    @Transactional
    public class CategoryDAOImpl implements CategoryDAO
    {
        @Autowired
        private SessionFactory sessionFactory;

        private static List<Category> categories = new ArrayList<>();

        static {
            Category category = new Category();

            // Add First Element
            category.setId(1);
            category.setName("Television");
            category.setDescription("this is some desc for television");
            category.setImageURL("img1.jpg");

            categories.add(category);

            // Add Second Element
            category = new Category();
            category.setId(2);
            category.setName("Mobile");
            category.setDescription("this is some desc for Mobile");
            category.setImageURL("img2.jpg");

            categories.add(category);

            // Add Third Element
            category = new Category();
            category.setId(3);
            category.setName("Laptop");
            category.setDescription("this is some desc for Laptop");
            category.setImageURL("img3.jpg");

            categories.add(category);

        }

        @Override
        public List<Category> list() {
            return categories;

        }

        @Override
        public Category get(int id) {

            for (Category category : categories) {
                if (category.getId() == id)
                    return category;
            }
            return null;
        }

        @Override

        public boolean add(Category category) {

            //add the category to the databse table
            try
            {
                sessionFactory.getCurrentSession().persist(category);
                return true;
            }
            catch (Exception e)
            {
                e.printStackTrace();
                return false;
            }
        }

    }

**Category**

package com.app.EcommerceBackend.dto;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Category implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;
    private String description;

    @Column(name = "image_url")
    private String imageURL;

    @Column(name = "is_active")
    private boolean active = true;

    @Override
    public String toString() {
        return "Category [id=" + id + ", name=" + name + ", description=" + description + ", imageURL=" + imageURL
                + ", active=" + active + "]";
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getImageURL() {
        return imageURL;
    }

    public void setImageURL(String imageURL) {
        this.imageURL = imageURL;
    }

    public boolean isActive() {
        return active;
    }

    public void setActive(boolean active) {
        this.active = active;
    }
}

package com.app.EcommerceBackend.test;

import static org.junit.Assert.assertEquals;

import java.sql.SQLException;

import org.junit.BeforeClass;
import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.app.EcommerceBackend.dao.CategoryDAO;
import com.app.EcommerceBackend.dto.Category;

public class CategoryTestCase {

    private static AnnotationConfigApplicationContext context;

    private static CategoryDAO categoryDAO;

    private Category category;

    @BeforeClass
    public static void init() throws Exception {
        org.h2.tools.Server.createTcpServer().start();
        context = new AnnotationConfigApplicationContext();
        context.scan("com.app.EcommerceBackend");
        context.refresh();
        categoryDAO = (CategoryDAO) context.getBean("categoryDAO");
    }

    @Test
    public void testAddCategory() {

        category = new Category();

        category.setName("Laptop");
        category.setDescription("This is some description for laptop!");
        category.setImageURL("CAT_105.png");

        assertEquals("Successfully added a category inside the table!", true, categoryDAO.add(category));

    }
}

org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.exception.GenericJDBCException: Unable to acquire JDBC Connection
    at org.springframework.orm.hibernate5.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:542)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:447)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:277)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    at com.sun.proxy.$Proxy29.add(Unknown Source)
    at com.app.EcommerceBackend.test.CategoryTestCase.testAddCategory(CategoryTestCase.java:40)