The entites that I define a java class are not appearing in my h2 database. Why is this happening?

Question

I was trying to use a spring boot initializer using intelij IDEA. I used dependancies like spring-web, spring data-JPA and H2 sql. Afrter implementing the necessary steps I was able to get the H2 console running and sucessfull database connection. But, the entity I created is not apearing in the database. [h2_console after running my java application]

I tried the following steps:

1. create my project by adding the dependancies I mentioned above.(The main application class)

    ```java
   
    package com.example.demo;
   
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
   
    @SpringBootApplication
    public class Demo5Application {
   
        public static void main(String[] args) {
            SpringApplication.run(Demo5Application.class, args);
        }
   
    }
   
    ```
   

2. create the packege for defining my entity nemed "entity".[package_entity]

3. Then I created a class called "Book" to define my entity properties.[entity_properties]

    ```java
    package com.example.demo.entity;
   
    import javax.persistence.*;
   
    @Entity
    public class Book {
   
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private Integer id;
        private String name;
        private String category;
        private String sector;
        private String type;
   
        public Integer getId() {
        return id;
    }
   
    public void setId(Integer id) {
        this.id = id;
    }
   
    public String getName() {
        return name;
    }
   
    public void setName(String name) {
        this.name = name;
    }
   
    public String getCategory() {
        return category;
    }
   
    public void setCategory(String category) {
        this.category = category;
    }
   
    public String getSector() {
        return sector;
    }
   
    public void setSector(String sector) {
        this.sector = sector;
    }
   
    public String getType() {
        return type;
    }
   
    public void setType(String type) {
        this.type = type;
      }
     }
     ```
   

4. provide them their getters and setters.(as shown above)

5. Use the proper annotaions for each parts.(@Entity, @ID, @GeneratedValue) 6- Then, I go to the application.properties to add more information about my H2 database.[application_properties]

    spring.datasource.driver-class-name=org.h2.Driver
    spring.datasource.url=jdbc:h2:mem:sarita
    spring.datasource.username=SA
    spring.datasource.password=
   
    spring.h2.console.enabled=true
    spring.h2.console.path=/h2
   
    spring.jpa.show-sql=true
    spring.jpa.hibernate.ddl-auto=create  
   

After all those steps I run my application. The connection is showing my success.[successfull_h2_db_connection]

But, when I hit connect it will get inside. However, there is no table created inside as I expected!!![no_table_created]

In all the tutorials I saw they were able to see this table in their H2 console. What mistake did I made for my failure?

Thanks!!!

Answer 1

As other has mentioned, you didn't mentioned hibernate/jpa to create your database tables. You have only created a connection to your in-memory database.

you need to define your jpa actions (like using jpa template: https://www.baeldung.com/the-persistence-layer-with-spring-data-jpa) to have a crud (create, read, update, delete). However, you need to create your database structure (unless you tell jpa to create your database schema).

A common library that is supported under spring is liquibase(https://www.baeldung.com/liquibase-refactor-schema-of-java-app). it will create your schema every time you run your app.

Another option is to have your h2 pointing to a file persisted database. you may use some responses from How to store H2 database file into project directory.

Answer 2

Add data.sql and schema.sql under src/resources folder in your project. schema.sql should have create table sql queries

data.sql should have the insert queries.

This should help jpa to create and populate data in your in memory db.