JPA Schema Generator Plugin

Motivation

Why another tool to dump the JPA schema? All tools that we've found were related to legacy versions of Hibernate or were covering just simple cases, without options to configure dialect or naming strategy. Also all of the tools we've found are based on the SchemaExport class, which does not always correlate with the runtime schema - for example due to the lack of support for the Integrator services, used to register UserType classes like JodaTime or similar. We were also looking for a tool that is be able to handle further schema migrations, not just dump the current version.

Configuration parameters

• packages (required): list of packages containing JPA entities
• outputPath: output file for the generated schema. By default:
• for UPDATE action: BUILD_OUTPUT_DIR/generated-resources/scripts/
• for other actions: BUILD_OUTPUT_DIR/generated-resources/scripts/database.sql
• jpaProperties: additional properties like dialect or naming strategies which should be used in generation task. By default empty
• formatOutput: should the output be formatted. By default true
• skipSequences: should the generator skip sequences creation. By default false
• delimiter: delimiter used to separate statements. By default ;
• action: which statements should be generated. By default: CREATE. Possible values:
  • DROP
  • CREATE
  • DROP_AND_CREATE
  • UPDATE
• generationMode: schema generation mode. By default DATABASE. Possible values:
  • DATABASE: generation based on setting up embedded database and dumping the schema
  • METADATA: generation based on static metadata

Maven Plugin

You can run this plugin directly or integrate it into the default build lifecycle.

Simple configuration example

<build>
    <plugins>
        <plugin>
            <groupId>com.devskiller.jpa2ddl</groupId>
            <artifactId>jpa2ddl-maven-plugin</artifactId>
            <version>0.9.9</version>
            <extensions>true</extensions> <!-- required to run automatically -->
            <configuration>
                <packages>
                    <package>com.test.model</package>
                </packages>
            </configuration>
        </plugin>
    </plugins>
</build>

Generate schema

<build>
    <plugins>
        <plugin>
            <groupId>com.devskiller.jpa2ddl</groupId>
            <artifactId>jpa2ddl-maven-plugin</artifactId>
            <version>0.9.9</version>
            <configuration>
                <outputPath>${basedir}/src/main/resources/database.sql</outputPath>
                <packages>
                    <package>com.test.model</package>
                    <package>com.test.entities</package>
                </packages>
                <jpaProperties>
                    <property>
                        <name>hibernate.dialect</name>
                        <value>org.hibernate.dialect.MySQL57Dialect</value>
                    </property>
                    <property>
                        <name>hibernate.default_schema</name>
                        <value>prod</value>
                    </property>
                </jpaProperties>
                <formatOutput>true</formatOutput>
                <skipSequences>true</skipSequences>
                <delimiter>;</delimiter>
                <action>DROP_AND_CREATE</action>
            </configuration>
        </plugin>
    </plugins>
</build>

Generate migrations

It's also possible to generate automated migrations scripts. JPA2DDL supports Flyway naming patterns for versioned migrations.

All subsequent migration scripts are saved in the outputPath, in the following layout:

src/main/resources/migrations/
 v1__jpa2ddl.sql
 v2__jpa2ddl.sql
 ... next

Please note that after generation you can change the name of the file to make it more descriptive following the filename pattern v(N)__jpa2ddl(_custom_description).sql - for example v1__jpa2ddl_init.sql

Sample configuration:

<build>
    <plugins>
        <plugin>
            <groupId>com.devskiller.jpa2ddl</groupId>
            <artifactId>jpa2ddl-maven-plugin</artifactId>
            <version>0.9.9</version>
            <configuration>
                <outputPath>${basedir}/src/main/resources/migrations/</outputPath>
                <packages>
                    <package>com.test.model</package>
                    <package>com.test.entities</package>
                </packages>
                <jpaProperties>
                    <property>
                        <name>hibernate.dialect</name>
                        <value>org.hibernate.dialect.MySQL57Dialect</value>
                    </property>
                </jpaProperties>
                <formatOutput>true</formatOutput>
                <delimiter>;</delimiter>
                <action>UPDATE</action>
            </configuration>
        </plugin>
    </plugins>
</build>

Direct invocation

./mvnw com.devskiller.jpa2ddl:jpa2ddl-maven-plugin:0.9.9:generate

Gradle Plugin

Below you can find a sample build.gradle script configuration:

buildscript {
    repositories {
	    mavenCentral()
    }
    dependencies {
	    classpath "com.devskiller.jpa2ddl:jpa2ddl-gradle-plugin:0.9.9"
    }
}

apply plugin: 'com.devskiller.jpa2ddl'

jpa2ddl {
    packages = ['com.test.model']
}