Question

我正在使用JPA（Hibernate的实现）来注释实体类以持久化到关系数据库（MySQL或SQL Server）。有没有一种简单的方法可以从带注释的类中自动生成数据库模式（表创建脚本）？

我仍处于原型设计阶段，并预计频繁的架构更改。我希望能够从带注释的代码中指定和更改数据模型。 Grails类似于它从域类生成数据库。

Answer 1

您可以使用Hibernate中的hbm2ddl。文档为here。

Answer 2

为给定的JPA实体生成创建和删除脚本

我们使用此代码生成drop和create语句：只需使用所有实体类构造此类并调用create / dropTableScript。

如果需要，您可以使用persitence.xml和persitance单元名称。随便说点我也发布了这段代码。

import java.util.Collection;
import java.util.Properties;

import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.dialect.Dialect;
import org.hibernate.ejb.Ejb3Configuration;

/**
 * SQL Creator for Tables according to JPA/Hibernate annotations.
 *
 * Use:
 *
 * {@link #createTablesScript()} To create the table creationg script
 *
 * {@link #dropTablesScript()} to create the table destruction script
 * 
 */
public class SqlTableCreator {

    private final AnnotationConfiguration hibernateConfiguration;
    private final Properties dialectProps;

    public SqlTableCreator(final Collection<Class<?>> entities) {

        final Ejb3Configuration ejb3Configuration = new Ejb3Configuration();
        for (final Class<?> entity : entities) {
            ejb3Configuration.addAnnotatedClass(entity);
        }

        dialectProps = new Properties();
        dialectProps.put("hibernate.dialect", "org.hibernate.dialect.SQLServerDialect");

        hibernateConfiguration = ejb3Configuration.getHibernateConfiguration();
    }

    /**
     * Create the SQL script to create all tables.
     * 
     * @return A {@link String} representing the SQL script.
     */
    public String createTablesScript() {
        final StringBuilder script = new StringBuilder();

        final String[] creationScript = hibernateConfiguration.generateSchemaCreationScript(Dialect
                .getDialect(dialectProps));
        for (final String string : creationScript) {
            script.append(string).append(";\n");
        }
        script.append("\ngo\n\n");

        return script.toString();
    }

    /**
     * Create the SQL script to drop all tables.
     * 
     * @return A {@link String} representing the SQL script.
     */
    public String dropTablesScript() {
        final StringBuilder script = new StringBuilder();

        final String[] creationScript = hibernateConfiguration.generateDropSchemaScript(Dialect
                .getDialect(dialectProps));
        for (final String string : creationScript) {
            script.append(string).append(";\n");
        }
        script.append("\ngo\n\n");

        return script.toString();
    }
}

Answer 3

作为相关说明：可以找到使用EclipseLink JPA生成数据库模式的文档here。

Answer 4

由于Hibernate 4.3+现在实现了JPA 2.1，生成DDL脚本的适当方法是使用以下一组JPA 2.1属性：

<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"/>

由于它将在运行时运行，您可能希望在构建时执行此DDL生成。 Hibernate4不再支持官方maven插件了，因为Hibernate团队正在转向Gradle。

无论如何，这是以编程方式生成此脚本的JPA 2.1方法：

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);
    }

}

你可以看到它非常简单！

您现在可以在AntTask或MAVEN这样的构建中使用它（对于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 5

这里有一个关于如何使用hibernate SchemaExport类来完成你想要的内容的解释。

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

Answer 6

如果您更喜欢在Spring中进行配置，那么这应该会有所帮助：

 <!-- 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>

Answer 7

您可以使用maven插件来实现此目的。

       <plugin>
            <!-- run command "mvn hibernate3:hbm2ddl" to generate DLL -->
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>hibernate3-maven-plugin</artifactId>
            <version>3.0</version>
            <configuration>
                <hibernatetool>
                    <classpath>
                        <path location="${project.build.directory}/classes" />
                        <path location="${project.basedir}/src/main/resources/META-INF/" />                                               
                    </classpath>   

                    <jpaconfiguration persistenceunit="galleryPersistenceUnit" />                     
                    <hbm2ddl create="true" export="false" destdir="${project.basedir}/target" drop="true" outputfilename="mysql.sql" format="true" console="true"/>
                </hibernatetool>
            </configuration>
        </plugin>

Answer 8

<property name="hibernate.hbm2ddl.auto" value="update"/>

在properties标记下的persistence.xml中添加上述代码。 “update”将在您第一次运行代码时创建表，之后，只有在域对象发生任何更改时才更新表结构。

Answer 9

使用EclipseLink，您应该添加属性：

<property name="eclipselink.ddl-generation" value="create-tables"/>

正如这里所说： http://www.eclipse.org/eclipselink/documentation/2.4/jpa/extensions/p_ddl_generation.htm

我的persistence.xml：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="appDB" transaction-type="JTA">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <jta-data-source>LocalMySQL</jta-data-source>
        <class>entity.Us</class>
        <class>entity.Btl</class>
        <class>entity.Co</class>
        <properties>
            <property name="eclipselink.ddl-generation" value="create-tables"/>
        </properties>
    </persistence-unit>
</persistence>

从JPA带注释的实体类自动生成数据模式

9 个答案: