This is a Spring Boot application with Liquibase to manage the database migration.

These are some steps to guide the whole procedure:

To add the Liquibase into the project, open the build.gradle file and add it to the classpath:

buildscript {
	ext {
		springBootVersion = '1.5.8.RELEASE'
	}
	repositories {
		mavenCentral()
		mavenLocal()
	}
	dependencies {
		classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
		classpath "org.mariadb.jdbc:mariadb-java-client-jre7:1.6.1"
		classpath "org.liquibase:liquibase-gradle-plugin:1.2.4"
	}
}

At the same file, add the Liquibase dependency:

dependencies {
	compile group: 'org.springframework.boot', name: 'spring-boot-starter-web', version: '1.5.8.RELEASE'

	compile group: 'org.liquibase', name: 'liquibase-core', version: '3.5.3'
}

Finally, apply the liquibase plugin:

apply plugin: 'liquibase'

To avoid the Liquibase task execution during the application startup, open the application.properties file and add the following configuration on it:

liquibase.enabled=false

To create the Liquibase activity, open the build.gradle file and add a new section on it:

liquibase {
	activities {
		main {
			changeLogFile 'src/main/db/changelog.xml'
			url 'jdbc:mariadb://localhost:3306/testliquibase'
            username 'root'
            password 'root'

            referenceUrl 'jdbc:mariadb://localhost:3306/testliquibase_reference'
            referenceUsername 'root'
            referencePassword 'root'
		}
	}

	runList = 'main'
}

These are the parameters:

• changeLogFile: the XML file where the change sets will be created by Liquibase;
• url: the database destination address where the changes must be applied/compared;
• username: the username of the destination database where the changes must be applied/compared;
• password: the password of the destination database where the changes must be applied/compared;
• referenceUrl: the address of the reference database where the changes where performed;
• referenceUsername: the username of the reference database where the changes where performed;
• referencePassword: the password of the reference database where the changes where performed.

Add an entity model into the application, for instance:

@Entity
public class Product {

    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)
    private long id;

    @Column(length = 30, nullable = false)
    private String name;

    @Column(length = 30, nullable = false)
    private String model;

    @Column(nullable = false)
    private double price;
    
    //Getters and Setters
}

There are two main tasks to be performed in case of model creation or changes:

To populate the change log XML file with the changes from the models, execute the diffChangeLog task. This task will populate the change log file with the last changes, comparing the reference database with the base database schemas. These a example related to the creation of the Product entity:

    <changeSet author="paulo.cesar (generated)" id="1516704417378-1">
        <createTable tableName="product">
            <column autoIncrement="true" name="id" type="BIGINT">
                <constraints primaryKey="true"/>
            </column>
            <column name="model" type="VARCHAR(30)">
                <constraints nullable="false"/>
            </column>
            <column name="name" type="VARCHAR(30)">
                <constraints nullable="false"/>
            </column>
            <column name="price" type="DOUBLE">
                <constraints nullable="false"/>
            </column>
        </createTable>
    </changeSet>

The id parameter at the changeSet section must be used to uniquely identify the change set.

When more changes where performed in certain entity model, execute the diffChangeLog task again, to append one more change set at this file.

To generate the SQL statements to perform the changes, execute the updateSQL task. The SQL statements will be printed at execution log.

Use the SQL statements generated by the updateSQL task to update the DDL scripts.