Setting up a Liquibase project with Maven and PostgreSQL

The purpose of this document is to guide you through the process of creating a new Maven project with PostgreSQL on a Linux/Unix/Mac machine. In this tutorial, you will generate an example project and follow the instructions to apply and learn concepts associated with creating new Liquibase Projects within Maven.

Prerequisites

Install Liquibase with Maven on Linux/Unix/Mac if you have not done so already.

Maven – Liquibase Project Tutorial

To create a Liquibase project within Maven that uses a PostgreSQL database, begin with the following steps:

1. Create a new project folder and name it MavenPostgreSQL.
2. Create a new plain-text file named dbchangelog.xml in the MavenPostgeSQL directory. This file will be your changelog, a file that will keep track of all the changes you make to your database structure. You can learn more about them on the Database Change Log File page. In this tutorial, you will manually add a single change. We will start with an empty changelog file.
3. Open the dbchangelog.xml file and update it with the following text. This is a basic empty changelog file.

 <?xml version="1.0" encoding="UTF-8"?>
 <databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
                    xmlns:pro="http://www.liquibase.org/xml/ns/pro"
                    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.8.xsd">
 </databaseChangeLog>
 

4. Create another plain text file in the same directory, named liquibase.properties
5. Edit the liquibase.properties file to add the following properties:

 changeLogFile: dbchangelog.xml
 url: jdbc:postgresql://localhost:5432/MYDATABASE
 username: postgres
 password: password
 

Note: If you have a Liquibase Pro key and want to apply it to your project, add the following property to your liquibase.properties file. liquibaseProLicenseKey: <paste license key>

6. Add a changeset to the changelog. In the dbchangelog.xml file line 9 to 20 add a new changeset. This changeset will have one change in it, to create a table named “department”.

 <?xml version="1.0" encoding="UTF-8"?>
 
 <databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
                    xmlns:pro="http://www.liquibase.org/xml/ns/pro"
                    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.8.xsd">
 
     <changeSet id="1" author="bob">
         <createTable tableName="department">
             <column name="id" type="int">
                 <constraints primaryKey="true" nullable="false"/>
             </column>
             <column name="name" type="varchar(50)">
                 <constraints nullable="false"/>
             </column>
             <column name="active" type="boolean" defaultValueBoolean="true"/>
         </createTable>
    </changeSet>
 </databaseChangeLog>
 

7. Now, we create the maven POM file for the project. Create a new plain-text file in the same directory named pom.xml.
8. Edit the pom.xml file and update it to have the following contents:

 <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>com.my-group.app</groupId>
   <artifactId>LiquiPostgreSQL-app</artifactId>
   <version>1.0-SNAPSHOT</version>
   <build>
       <pluginManagement>
           <plugins>
               <plugin>
                   <groupId>org.liquibase</groupId>
                   <artifactId>liquibase-maven-plugin</artifactId>
                   <version>3.8.0</version>
                   <configuration>
                       <propertyFile>liquibase.properties</propertyFile>
                   </configuration>
                   <dependencies>
                     <dependency>
                         <groupId>postgresql</groupId>
                         <artifactId>postgresql</artifactId>
                         <version>9.1-901-1.jdbc4</version>
                     </dependency>
                 </dependencies>
               </plugin>
           </plugins>
       </pluginManagement>
   </build>
 </project>
 

9. Open the command prompt and navigate to the MavenPostgreSQL directory.
10. Run the following command: mvn liquibase:update
11. From a database UI Tool, for example: “pgAdmin” check your database changes under “MYDATABASE”. You should see a new “department” table added to the database.

Also, you should see two more tables:

1. DATABASECHANGELOG - This table keeps a record of all the changesets that have been deployed. The next time you run the update command, the changesets in the changelog will be compared with the DATABASECHANGELOG tracking table, and only the new changesets not found in the DATABASECHANGELOG will be deployed. You will notice that a new row was created in that table with the changeset information we have just deployed.
2. DATABASECHANGELOGLOCK - This table is used internally by Liquibase to manage access to the changelog table during deployment.