Spring Boot JDBC: Hello World Application

Step 1: Open Eclipse. Create new maven project ‘springJDBC’.

Open Eclipse. File -> New -> Other.

Search for maven and select ‘Maven Project’ and click Next button.

Select the check box ‘Create a simple project (skip archetype selection)’.

Click on Next button.

Give Group Id and Artifact Id as 'springJDBC', version as 1  and click on Finish button.

Total project structure created like below.

Step 2: Update dependencies in pom.xml

pom.xml

<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>
    <groupId>springJDBC</groupId>
    <artifactId>springJDBC</artifactId>
    <version>1</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

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

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>
    </dependencies>

</project>

Step 3: Define an Employee entity class.

package com.sample.app.entity;

public class Employee {
    private int id;
    private String firstName;
    private String lastName;

    public Employee(int id, String firstName, String lastName) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    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;
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("Employee [id=").append(id).append(", firstName=").append(firstName).append(", lastName=")
                .append(lastName).append("]");
        return builder.toString();
    }

}

Step 4: Create application.properties file under ‘src/main/resources’ folder and configure data source condfigurations.

application.properties    

logging.level.root=WARN

## H2 specific properties
spring.h2.console.enabled=true
spring.h2.console.path=/h2

spring.datasource.url=jdbc:h2:file:~/db/myOrg.db;DB_CLOSE_ON_EXIT=FALSE;DB_CLOSE_DELAY=-1;

spring.datasource.username=krishna
spring.datasource.password=password123

spring.datasource.driverClassName=org.h2.Driver


## Database connection pooling properties
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.max-wait=10000

# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.tomcat.max-active=10
spring.datasource.tomcat.max-idle=5
spring.datasource.tomcat.min-idle=3

Step 5: Define App.java like below.

App.java    

package com.sample.app;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.core.JdbcTemplate;

import com.sample.app.entity.Employee;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@SpringBootApplication
public class App {
    private static final Logger log = LoggerFactory.getLogger(App.class);

    @Autowired
    JdbcTemplate jdbcTemplate;

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

    @Bean
    public CommandLineRunner demo() {
        return (args) -> {
            log.info("Creating tables");

            jdbcTemplate.execute("DROP TABLE employees IF EXISTS");
            jdbcTemplate
                    .execute("CREATE TABLE employees(" + "id SERIAL, first_name VARCHAR(255), last_name VARCHAR(255))");

            jdbcTemplate
                    .execute("INSERT INTO employees(id, first_name, last_name) VALUES (1, 'Rama Krishna', 'Gurram')");
            
            
            System.out.println("Printing Employees\n");
            
            jdbcTemplate.query(
                    "SELECT id, first_name, last_name FROM employees",
                    (rs, rowNum) -> new Employee(rs.getInt("id"), rs.getString("first_name"),
                            rs.getString("last_name"))
            ).forEach(customer -> System.out.println(customer));

        };
    }

}

'execute' method of JdbcTemplate is used to execute SQL queries.

Example

jdbcTemplate.execute("DROP TABLE employees IF EXISTS");

jdbcTemplate.execute("CREATE TABLE employees(" + "id SERIAL, first_name VARCHAR(255), last_name VARCHAR(255))");

jdbcTemplate.execute("INSERT INTO employees(id, first_name, last_name) VALUES (1, 'Rama Krishna', 'Gurram')");

'query' method is used to extract the information from given tables.

Example

List<Employee> emps = jdbcTemplate.query("SELECT id, first_name, last_name FROM employees", (rs, rowNum) -> new Employee(rs.getInt("id"), rs.getString("first_name"), rs.getString("last_name")));

Total project structure looks like below.

Run App.java, you can see below messages in console.

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.6.RELEASE)

Printing Employees

Employee [id=1, firstName=Rama Krishna, lastName=Gurram]

You can download complete working application from this link.

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