在上篇springBoot生成SQL文件-使用Hibernate5的SchemaExport实现01中已经知道从Hibernate5.0.x开始通过程序生成SQL的方式已变成：
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build();MetadataImplementor metadata = (MetadataImplementor) new MetadataSources( serviceRegistry ).buildMetadata();SchemaExport schemaExport = new SchemaExport(metadata);schemaExport.create(true, true);下面我们看下在springBoot中如何在启动过程中生成SQL。这里通过两种方式实现，第一种为最初版本，第二种是第一种的精简版，两种套餐可酌情使用。
目录
初版
初版中通过手动注入关键been实现获取Hibernate的Config配置。分成了两个文件HibernateJavaConfig.java和GenerateDDLApplicationRunner.java
HibernateJavaConfig.java
这个文件用于实现Hibernate的配置，类似hibernate.cfg.xml。通过显式创建been手动获取了如下对象：
org.hibernate.boot.Metadataorg.hibernate.boot.registry.StandardServiceRegistryjavax.persistence.spi.PersistenceUnitInfo
完整文件如下：
package com.windcoder.qycms.core.basis.test.Hibernate.ddl;
import org.hibernate.boot.Metadata;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.springframework.boot.autoconfigure.AutoConfigureAfter;import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;import org.springframework.boot.autoconfigure.domain.EntityScan;import org.springframework.boot.autoconfigure.domain.EntityScanPackages;import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager;
import javax.persistence.spi.PersistenceUnitInfo;import java.util.List;import java.util.Map;
@Configuration@EntityScan("com.windcoder.qycms.*")@AutoConfigureAfter({HibernateJpaAutoConfiguration.class})public class HibernateJavaConfig {
/** * 生成元数据Metadata * 在这里将要解析的类加在进Metadata中 * @param standardServiceRegistry * @param persistenceUnitInfo * @return */ @ConditionalOnMissingBean({Metadata.class}) @Bean public Metadata getMetadata(StandardServiceRegistry standardServiceRegistry, PersistenceUnitInfo persistenceUnitInfo) { MetadataSources metadataSources = new MetadataSources(standardServiceRegistry);
List<String> managedClassNames = persistenceUnitInfo.getManagedClassNames(); for (String managedClassName : managedClassNames) { metadataSources.addAnnotatedClassName(managedClassName); }
Metadata metadata = metadataSources.buildMetadata(); return metadata; } /** * 该实例将配置信息合并到一组工作服务 * @param jpaProperties * @return */ @ConditionalOnMissingBean({StandardServiceRegistry.class}) @Bean public StandardServiceRegistry getStandardServiceRegistry(JpaProperties jpaProperties) { StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder(); Map<String, String> properties = jpaProperties.getProperties(); ssrb.applySettings(properties);
StandardServiceRegistry ssr = ssrb.build();
return ssr; } /** * PersistenceUnitInfo接口由容器实现并由创建一个javax.persistence.EntityManagerFactory时的persistence提供者使用， * 这里用于生成PersistenceUnitInfo的Been,用于代替persistence.xml * @param entityScanPackages * @return */ @ConditionalOnMissingBean({PersistenceUnitInfo.class}) @Bean public PersistenceUnitInfo getPersistenceUnitInfo(EntityScanPackages entityScanPackages) { List<String> packagesToScan = entityScanPackages.getPackageNames();
DefaultPersistenceUnitManager persistenceUnitManager = new DefaultPersistenceUnitManager();
String[] packagesToScanArr = (String[]) packagesToScan.toArray(new String[packagesToScan.size()]); persistenceUnitManager.setPackagesToScan(packagesToScanArr); persistenceUnitManager.afterPropertiesSet();
PersistenceUnitInfo persistenceUnitInfo = persistenceUnitManager.obtainDefaultPersistenceUnitInfo(); return persistenceUnitInfo; }}这里需要@EntityScan("com.windcoder.qycms.*")设置扫描范围，以便entityScanPackages可以自动生成默认been，不添加可能会报错找不到可用的entityScanPackages。
GenerateDDLApplicationRunner.java
package com.windcoder.qycms.core.basis.test.Hibernate.ddl;
import org.hibernate.boot.Metadata;import org.hibernate.boot.spi.MetadataImplementor;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.springframework.boot.ApplicationArguments;import org.springframework.boot.ApplicationRunner;import org.springframework.stereotype.Component;
import java.io.File;import java.text.MessageFormat;import java.text.SimpleDateFormat;import java.util.Calendar;
/** * 最终用于生成SQL的类 * Hibernate基础可参考： * http://docs.jboss.org/hibernate/orm/5.0/quickstart/html/ */@Componentpublic class GenerateDDLApplicationRunner implements ApplicationRunner { private Metadata metadata;
private static final String SCHEMA_SQL2 = "db/base/update-2-ddl_%s.sql"; public GenerateDDLApplicationRunner(Metadata metadata) { this.metadata = metadata; } /** * */ public void run(ApplicationArguments args) throws Exception { File dropAndCreateDdlFile = new File(getOutputFilename()); deleteFileIfExists(dropAndCreateDdlFile);
SchemaExport schemaExport = new SchemaExport((MetadataImplementor) metadata);
schemaExport.setDelimiter(";"); schemaExport.setFormat(false); schemaExport.setOutputFile(dropAndCreateDdlFile.getAbsolutePath());
schemaExport.execute(true, false, false, false);
} /** * 检测输出路径将要生成的文件，若存在则删除 */ private void deleteFileIfExists(File dropAndCreateDdlFile) { if (dropAndCreateDdlFile.exists()) { if (!dropAndCreateDdlFile.isFile()) { String msg = MessageFormat.format("File is not a normal file {0}", dropAndCreateDdlFile); throw new IllegalStateException(msg); }
if (!dropAndCreateDdlFile.delete()) { String msg = MessageFormat.format("Unable to delete file {0}", dropAndCreateDdlFile); throw new IllegalStateException(msg); } } }
/** * 格式化输出路径 */ private static String getOutputFilename() { SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss"); String currentDate = sdf.format(Calendar.getInstance().getTime());
return String.format(SCHEMA_SQL2, currentDate); }}化繁为简
通过上面两个文件的配置与实现，实现原则了解的也差不多了，现在开始做精简，整个文件：
package com.windcoder.qycms.core.basis.test.Hibernate.ddl;
import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.boot.spi.MetadataImplementor;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.ApplicationArguments;import org.springframework.boot.ApplicationRunner;import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;import org.springframework.stereotype.Component;
import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.List;@Componentpublic class JPASchemaExtractor2 implements ApplicationRunner { private static final String SCHEMA_SQL2 = "db/base/create-ddl_2_%s.sql";
@Autowired LocalContainerEntityManagerFactoryBean fb;
@Override public void run(ApplicationArguments args) throws Exception {
StandardServiceRegistry standardServiceRegistry = new StandardServiceRegistryBuilder() .applySettings(fb.getJpaPropertyMap()) .build();
MetadataSources metadata = new MetadataSources(standardServiceRegistry); List<String> managedClassNames = fb.getPersistenceUnitInfo().getManagedClassNames(); for (String managedClassName : managedClassNames) { metadata.addAnnotatedClassName(managedClassName); }
MetadataImplementor metadataImplementor = (MetadataImplementor) metadata.getMetadataBuilder().build(); SchemaExport schemaExport = new SchemaExport(metadataImplementor); String outputFile = getOutputFilename(); schemaExport.setOutputFile(outputFile); schemaExport.setDelimiter(";"); schemaExport.setFormat(false); schemaExport.execute(true, false, false, false); }
private static String getOutputFilename() { SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss"); String currentDate = sdf.format(Calendar.getInstance().getTime());
return String.format(SCHEMA_SQL2, currentDate); }}通过对比可知，LocalContainerEntityManagerFactoryBean代替了之前的显式代码实现。
根据官方定义可知：
该FactoryBean根据JPA的标准容器引导程序约定创建JPA EntityManagerFactory。
这是在Spring应用程序上下文中设置共享JPA EntityManagerFactory的最强大的方法;之后可以通过依赖注入将EntityManagerFactory传递给基于JPA的DAO。
注意：可以通过配置，切换到JNDI查找或切换到LocalEntityManagerFactoryBean definition。
与LocalEntityManagerFactoryBean一样，配置设置通常根据常规JPA配置约定从驻留在类路径中的META-INF / persistence.xml配置文件中读取。
但是，这个FactoryBean更灵活，你可以覆盖persistence.xml文件的位置，指定要链接的JDBC DataSources等。此外，它允许通过Spring的LoadTimeWeaver抽象实现可插入的类检测，而不是绑定到 JVM启动时指定的特殊VM代理。
在内部，此FactoryBean解析persistence.xml文件本身并创建相应的PersistenceUnitInfo对象（包含其他配置，例如JDBC DataSources和Spring LoadTimeWeaver），以传递给选定的JPA PersistenceProvider。 这是一个完全支持标准JPA容器约定的本地JPA容器。
公开的EntityManagerFactory对象将实现如下两个接口：
- PersistenceProvider返回的底层（underlying ）原生（native ）EntityManagerFactory的所有接口；
- 由此FactoryBean组装的其他元数据的EntityManagerFactoryInfo接口；
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