我正在使用 JPA（Hibernate 的实现）来注释实体类以持久保存到关系数据库（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，预计会频繁更改架构。我希望能够从带注释的代码中指定和更改数据模型。Grails 的相似之处在于它从域类生成数据库。
Steve Kuo
问问题
89125 次
9 回答
13
为给定的 JPA 实体生成创建和删除脚本
我们使用这段代码来生成 drop 和 create 语句：只需使用所有实体类构造这个类并调用 create/dropTableScript。
如果需要，您可以改用 persitence.xml 和持久性单元名称。说点什么，我也发布代码。
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();
}
}
于 2009-07-01T08:39:09.493 回答
10
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 JPA 2.1 属性集：
<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 不再支持官方的 maven 插件，这可能是因为 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);
}
}
如您所见，它非常简单！
您现在可以在 AntTask 或 MAVEN 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="${persistenceUnitName}" />
<arg value="target/jpa/sql/schema-create.sql" />
<!-- reference to the passed-in classpath reference -->
<classpath refid="maven.compile.classpath" />
</java>
</target>
</configuration>
</execution>
</executions>
</plugin>
于 2014-12-05T10:22:41.877 回答
9
作为相关说明：可以在此处找到使用 EclipseLink JPA 生成数据库模式的文档。
于 2008-12-04T19:33:02.460 回答
6
这里解释了如何使用 hibernate SchemaExport 类来做你想做的事。
http://jandrewthompson.blogspot.com/2009/10/how-to-generate-ddl-scripts-from.html
于 2009-10-28T15:08:45.937 回答
2
如果您更喜欢在 Spring 中进行配置，那么这应该会有所帮助：
<!-- CONTAINER-MANAGED JPA Entity manager factory (No need for persistence.xml)-->
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="jpaVendorAdapter" ref="jpaVendorAdapter"/>
<!-- Fine Grained JPA properties Create-Drop Records -->
<property name="jpaProperties">
<props>
<prop key="hibernate.hbm2ddl.auto">create</prop>
</props>
</property>
</bean>
<!-- The JPA vendor -->
<bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<!-- <property name="database" value="MySQL"/> -->
<property name="showSql" value="true"/>
<!-- <property name="generateDdl" value="true"/> -->
<property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="emf" />
</bean>
于 2012-10-19T08:36:27.120 回答
2
您可以使用 maven 插件来实现这一点。
<plugin>
<!-- run command "mvn hibernate3:hbm2ddl" to generate DLL -->
<groupId>org.codehaus.mojo</groupId>
<artifactId>hibernate3-maven-plugin</artifactId>
<version>3.0</version>
<configuration>
<hibernatetool>
<classpath>
<path location="${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>
于 2013-08-27T12:25:50.357 回答
1
<property name="hibernate.hbm2ddl.auto" value="update"/>
在 properties 标签下的 persistence.xml 添加上述代码。“更新”将在您第一次运行代码时创建表，之后仅在域对象发生任何更改时更新表结构。
于 2013-08-30T04:28:15.240 回答
1
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>
于 2015-11-03T13:32:36.320 回答