Category Archives: H2

In MemoryDatabase H2 with SpringBoot


An in memory database is created when an application starts up and destroyed when the application is stopped.
That means there is no persistence of data and every time you restart or stop you application your saved data will be lost.

H2

H2 is one of the popular in memory databases. Spring Boot has very good integration for H2.

H2 is a relational database management system written in Java. It can be embedded in Java applications or run in the client-server mode.

H2 also provides a web console to maintain the database.



Setting up a Spring Boot Project with H2


Spring Initializer http://start.spring.io/ is great tool to bootstrap your Spring Boot projects.





As shown in the image above, following steps have to be done

Launch Spring Initializer and choose the following

1. Choose com.rks as Group
2. Choose H2-console as Artifact
3. Choose following dependencies

  • Web
  • JPA
  • H2
  • DevTools


Click Generate Project.


Import the project into Eclipse.


File -> Import -> Existing Maven Project.



Create a simple Employee Entity with a primary key id.


package com.rks.h2console;
import javax.persistence.*;
@Entity
@Table(name = "employee")
public class Employee {

    @Id
    @Column
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @Column
    private String firstName;
    @Column
    private String lastName;
    @Column
    private String email;

    public int getId() {
        return id;
    }

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

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

Edit properties file placed in 

/src/main/resources/application.properties
# Enabling H2 Console

spring.h2.console.enabled=true

# Show all queries
spring.jpa.show-sql=true

#DB configurations

spring.datasource.url=jdbc:h2:mem:rksdb

spring.datasource.driverClassName=org.h2.Driver

spring.datasource.username=test

spring.datasource.password=test

spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

Run your application from file EmployeePortalApplication.

Right click -> RunAs ->JavaApplication

package com.rks.h2console;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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


When you reload the application, you can launch up H2 Console at http://localhost:8080/h2-console.



 As soon as Spring Boot sees H2 in the class path, it auto configures a data source It knows that you are using an in memory database H2 and it uses the default url if you don’t provide one.


All tables will automatically get created by hibernate corresponding to the beans you have created but if you want to create table using sql scripts

You can also populate some data into student table by adding a file called data.sql

/src/main/resources/data.sql



create table student
(
   id integer not null,
   name varchar(255) not null,
   email varchar(255) not null,
   primary key(id)
);

insert into student
values(101,'Rakesh', 'rks@r.com');

insert into student
values(102,'Moni', 'moni@m.com');  

commit;



Source code


https://github.com/rsinghania/H2-Console-Db.git



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