Spring Boot | Database Access | Hello World

Database Access

Add spring-boot-starter-jdbc and the database dependency, such as org.hsqldb:hsqldb.
The configured database can then run in memory.
Because data is stored in memory, it is lost when the JVM stops.
H2 and Derby can also be used as embedded databases.

Writing the Code

build.gradle

dependencies {
    compile 'org.hsqldb:hsqldb'
    compile 'org.springframework.boot:spring-boot-starter-jdbc'
}

src/main/java/sample/springboot/Main.java

package sample.springboot;

import java.util.List;
import java.util.Map;

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

@SpringBootApplication
public class Main {

    public static void main(String[] args) {
        try (ConfigurableApplicationContext ctx = SpringApplication.run(Main.class, args)) {
            Main m = ctx.getBean(Main.class);
            m.method();
        }
    }

    @Autowired
    private JdbcTemplate jdbc;

    public void method() {
        this.jdbc.execute("CREATE TABLE TEST_TABLE (ID INTEGER NOT NULL IDENTITY, VALUE VARCHAR(256))");

        this.jdbc.update("INSERT INTO TEST_TABLE (VALUE) VALUES (?)", "hoge");
        this.jdbc.update("INSERT INTO TEST_TABLE (VALUE) VALUES (?)", "fuga");
        this.jdbc.update("INSERT INTO TEST_TABLE (VALUE) VALUES (?)", "piyo");

        List<Map<String, Object>> list = this.jdbc.queryForList("SELECT * FROM TEST_TABLE");
        list.forEach(System.out::println);
    }
}

Result

{ID=0, VALUE=hoge}
{ID=1, VALUE=fuga}
{ID=2, VALUE=piyo}

Storing Data in a File

Define spring.datasource.url in the properties file to specify a JDBC connection URL.
For HSQLDB, the URL determines whether data is stored in a file. The following setting enables file storage.

application.properties

spring.datasource.url=jdbc:hsqldb:file:./db/testdb;shutdown=true