hibernate源码（1）--- schema创建

sessionFactory

配置项：

hibernate的核心是sessionFactory，那我们看看如何构建session Factory。
参考官网：

plugins {id("java")
}
group = "com.atai.hibernatespy"
version = "1.0-SNAPSHOT"
repositories {mavenCentral()
}
dependencies {// the GOAT ORMimplementation("org.hibernate.orm:hibernate-core:6.3.0.Final")// Hibernate Validator)implementation("org.hibernate.validator:hibernate-validator:8.0.0.Final")implementation("org.glassfish:jakarta.el:4.0.2")// Agroal connection pool)implementation("org.hibernate.orm:hibernate-agroal:6.3.0.Final")implementation("io.agroal:agroal-pool:2.1")// logging via Log4j)implementation("org.apache.logging.log4j:log4j-core:2.20.0")//JPA Metamodel Generator)annotationProcessor("org.hibernate.orm:hibernate-jpamodelgen:6.3.0.Final")runtimeOnly("com.h2database:h2:2.1.214")
// Compile-time checking for HQL//implementation 'org.hibernate : query-validator: 2.O-SNAPSHOT'//annotationProcessor 'org.hibernate: query-validator: 2.O-SNAPSHOT'
// H2 database
//    runtimeonly( 'com.h2database:h2:2.1.214')testImplementation(platform("org.junit:junit-bom:5.9.1"))testImplementation("org.junit.jupiter:junit-jupiter")
}
tasks.test {useJUnitPlatform()
}

package org.example;import com.atai.entity.Book;
import org.hibernate.cfg.Configuration;import static java.lang.Boolean.TRUE;
import static java.lang.System.out;
import static org.hibernate.cfg.JdbcSettings.*;
import static org.hibernate.cfg.JdbcSettings.HIGHLIGHT_SQL;public class Main {public static void main(String[] args) {var sessionFactory = new Configuration().addAnnotatedClass(Book.class).setProperty(URL, "jdbc:h2:mem:db1").setProperty(USER, "sa").setProperty(PASS, "")// use Agroal connection pool.setProperty("hibernate.agroal.maxSize", "20")//display sQL in console.setProperty(SHOW_SQL, TRUE.toString()).setProperty(FORMAT_SQL, TRUE.toString()).setProperty(HIGHLIGHT_SQL, TRUE.toString()).buildSessionFactory();// export the inferred database schemasessionFactory.getSchemaManager().exportMappedObjects(true);// persist an entitysessionFactory.inTransaction(session -> {session.persist(new Book("9781932394153", "Hibernate in Action"));});// query data using HQLsessionFactory.inSession(session -> {out.println(session.createSelectionQuery(" select isbn||': '||title from Book").getSingleResult());});// query data using criteria APIsessionFactory.inSession(session -> {var builder = sessionFactory.getCriteriaBuilder();var query = builder.createQuery(String.class);var book = query.from(Book.class);query.select(builder.concat(builder.concat(book.get("isbn"), builder.literal(": ")), book.get("title")));out.println(session.createSelectionQuery(query).getSingleResult());});}
}

可以通过Configuration来进行创建，参数配置在property中，buildSessionFactory（） 创建出sf。
有了sf，即可以连接数据库处理。

schema相关

前面的例子中，已经有了比较好的实例，通过sf的schemaManager创建：

sessionFactory.getSchemaManager().exportMappedObjects(true);

public interface SchemaManager {/*** Export database objects mapped by Hibernate entities.* <p>* Programmatic way to run {@link org.hibernate.tool.schema.spi.SchemaCreator}.** @param createSchemas if {@code true}, attempt to create schemas,*                      otherwise, assume the schemas already exist*/void exportMappedObjects(boolean createSchemas);/*** Drop database objects mapped by Hibernate entities, undoing the* {@linkplain #exportMappedObjects(boolean) previous export}.* <p>* Programmatic way to run {@link org.hibernate.tool.schema.spi.SchemaDropper}.** @param dropSchemas if {@code true}, drop schemas,*                    otherwise, leave them be*/void dropMappedObjects(boolean dropSchemas);/*** Validate that the database objects mapped by Hibernate entities* have the expected definitions.* <p>* Programmatic way to run {@link org.hibernate.tool.schema.spi.SchemaValidator}.*/void validateMappedObjects();/*** Truncate the database tables mapped by Hibernate entities, and* then re-import initial data from any configured* {@linkplain org.hibernate.cfg.AvailableSettings#JAKARTA_HBM2DDL_LOAD_SCRIPT_SOURCE* load script}.* <p>* Programmatic way to run {@link org.hibernate.tool.schema.spi.SchemaTruncator}.*/void truncateMappedObjects();
}

另一个与schema关系较大的类就是：SchemaManagementToolCoordinator

   List<Class> classes = Arrays.asList(AccessconfigEntity.class);Properties p = new Properties();// 数据库方言，最终输出的方言p.put(AvailableSettings.DIALECT, MySQL5InnoDBDialect.class.getName());// 自动执行的动作p.put(AvailableSettings.HBM2DDL_AUTO, ddlAuto);// 分隔符，默认为空p.put(AvailableSettings.HBM2DDL_DELIMITER, ";");// 是否展示SQLp.put(AvailableSettings.SHOW_SQL, true);p.put("hibernate.connection.driver_class", dataSource.getDriverClassName());p.put("hibernate.connection.url", urlTena);p.put("hibernate.connection.username", dataSource.getUsername());p.put("hibernate.connection.password", dataSource.getPassword());// 是否使用默认的jdbc元数据，默认为true，读取项目自身的元数据p.put("hibernate.temp.use_jdbc_metadata_defaults", true);
//                p.put("hibernate.temp.use_jdbc_metadata_defaults", false);ConfigurationHelper.resolvePlaceHolders(p);ServiceRegistry registry = new StandardServiceRegistryBuilder().applySettings(p).build();
//                registry.getMap settings = registry.getService(ConfigurationService.class).getSettings();MetadataSources metadataSources = new MetadataSources(registry);entities.forEach(new Consumer<EntityType<?>>() {@Overridepublic void accept(EntityType<?> entityType) {metadataSources.addAnnotatedClass(entityType.getJavaType());}});classes.forEach(metadataSources::addAnnotatedClass);Metadata metadata = metadataSources.buildMetadata();HashMap properties = new HashMap<>();properties.putAll(registry.getService(ConfigurationService.class).getSettings());SchemaManagementToolCoordinator.process(metadata, registry, settings, null);

如果做代码跟踪，就会发现是否使用默认的use_jdbc_metadata_defaults 配置项将会建立连接，获取数据库的表信息。

SchemaExport

schemaexport是另一个与schema相关的类，可以控制台输出，脚本文件输出与数据库创建：

        Configuration cfn = new Configuration();cfn.setProperty("hibernate.connection.driver_class", "com.mysql.jdbc.Driver");cfn.setProperty("hibernate.connection.url", "jdbc:mysql://10.110.87.204:3306/corps?useOldAliasMetadataBehavior=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF-8&useSSL=false&nullCatalogMeansCurrent=true");cfn.setProperty("hibernate.connection.username", "root");cfn.setProperty("hibernate.connection.password", "liugeba?68");cfn.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5InnoDBDialect");cfn.configure();ServiceRegistry registry = new StandardServiceRegistryBuilder().applySettings(cfn.getProperties()).build();
//        System.out.println(cfn.toString());
//
//        ServiceRegistry registry = new StandardServiceRegistryBuilder().configure().build();
//        registry.Metadata metadata = new MetadataSources(registry).buildMetadata();SchemaExport export = new SchemaExport();export.create(EnumSet.of(TargetType.DATABASE), metadata);

实际操作的也就是下面的几个类：