Auto generate data schema from JPA annotated entity classes

Question

I\'m using JPA (Hibernate\'s implementation) to annotate entity classes to persist to a relational database (MySQL or SQL Server). Is there an easy way to auto generate the

Answer 1

Here's an explaination of how to use the hibernate SchemaExport class to do exactly what you want.

http://jandrewthompson.blogspot.com/2009/10/how-to-generate-ddl-scripts-from.html

Answer 2

As Hibernate 4.3+ now implements JPA 2.1 the appropriate way to generate DDL scripts is to use following set of JPA 2.1 properties :

<property name="javax.persistence.schema-generation.scripts.action" value="create"/>
<property name="javax.persistence.schema-generation.create-source" value="metadata"/>
<property name="javax.persistence.schema-generation.scripts.create-target" value="target/jpa/sql/create-schema.sql"/>

As it will be run at runtime, you may want to execute this DDL generation at build. There is no supported official maven plugin anymore for Hibernate4 probably because Hibernate team is moving to Gradle.

Anyway, this is the JPA 2.1 approach to generate this script programmatically :

import java.io.IOException;
import java.util.Properties;

import javax.persistence.Persistence;

import org.hibernate.jpa.AvailableSettings;

public class JpaSchemaExport {

    public static void main(String[] args) throws IOException {
        execute(args[0], args[1]);
        System.exit(0);
    }

    public static void execute(String persistenceUnitName, String destination) {
        System.out.println("Generating DDL create script to : " + destination);

        final Properties persistenceProperties = new Properties();

        // XXX force persistence properties : remove database target
        persistenceProperties.setProperty(org.hibernate.cfg.AvailableSettings.HBM2DDL_AUTO, "");
        persistenceProperties.setProperty(AvailableSettings.SCHEMA_GEN_DATABASE_ACTION, "none");

        // XXX force persistence properties : define create script target from metadata to destination
        // persistenceProperties.setProperty(AvailableSettings.SCHEMA_GEN_CREATE_SCHEMAS, "true");
        persistenceProperties.setProperty(AvailableSettings.SCHEMA_GEN_SCRIPTS_ACTION, "create");
        persistenceProperties.setProperty(AvailableSettings.SCHEMA_GEN_CREATE_SOURCE, "metadata");
        persistenceProperties.setProperty(AvailableSettings.SCHEMA_GEN_SCRIPTS_CREATE_TARGET, destination);

        Persistence.generateSchema(persistenceUnitName, persistenceProperties);
    }

}

As you can see it's very simple !

You can now use this in an AntTask, or MAVEN build like this (for MAVEN) :

            <plugin>
                <artifactId>maven-antrun-plugin</artifactId>
                <version>1.7</version>
                <executions>
                    <execution>
                        <id>generate-ddl-create</id>
                        <phase>process-classes</phase>
                        <goals>
                            <goal>run</goal>
                        </goals>
                        <configuration>
                            <target>
                                <!-- ANT Task definition -->
                                <java classname="com.orange.tools.jpa.JpaSchemaExport"
                                    fork="true" failonerror="true">
                                    <arg value="${persistenceUnitName}" />
                                    <arg value="target/jpa/sql/schema-create.sql" />
                                    <!-- reference to the passed-in classpath reference -->
                                    <classpath refid="maven.compile.classpath" />
                                </java>
                            </target>
                        </configuration>

                    </execution>
                </executions>
            </plugin>

Answer 3

If you prefer configuring in Spring then this should be helpful:

 <!-- CONTAINER-MANAGED JPA Entity manager factory (No need for persistence.xml)-->
    <bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="jpaVendorAdapter" ref="jpaVendorAdapter"/>
    <!-- Fine Grained JPA properties Create-Drop Records -->
    <property name="jpaProperties">
    <props>
    <prop key="hibernate.hbm2ddl.auto">create</prop>
    </props>
    </property> 
    </bean> 
     <!-- The JPA vendor -->
    <bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
    <!-- <property name="database" value="MySQL"/> -->
    <property name="showSql" value="true"/>
    <!--  <property name="generateDdl" value="true"/>  -->
    <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/>      
    </bean> 
     <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="emf" />
     </bean>