我最近开始使用Spring引导，并且遇到了一些问题。之前，当我刚刚使用Spring数据与hibernate和JPA时，我可以创建一个hibernate.cfg.xml文件，该文件将提供一系列可以传递给配置对象的配置，然后创建一个SessionFactory对象来创建一个可用于将查询传递给hibernate的会话对象：
package util; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; 导入org.hibernate.cfg.Configuration; public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory（）; private static SessionFactory buildSessionFactory（）{ try { //从hibernate.cfg.xml创建SessionFactory Configuration configuration = new Configuration（）。configure（hibernate.cfg .XML）;返回configuration.buildSessionFactory（new StandardServiceRegistryBuilder（）。applySettings（configuration.getProperties（））.build（））; } catch（Throwable ex）{ //确保您记录异常，因为它可能被吞噬System.err.println（Initial SessionFactory creation failed。+ ex）;抛出新的ExceptionInInitializerError（ex）; public static SessionFactory getSessionFactory（）{return sessionFactory; } }hibernate.cfg.xml
<？xml version ='1.0'encoding ='utf-8'？> <！DOCTYPE hibernate-configuration PUBLIC - // Hibernate / Hibernate配置DTD 3.0 // ENwww.hibernate/dtd/hibernate-configuration -3.0.dtd> < hibernate-configuration> < session-factory> <！ - 数据库连接设置 - > < property name =connection.driver_class> com.mysql.jdbc.Driver< / property> < property name =connection.url> jdbc：mysql：// localhost：3306 / hello-world< / property> < property name =connection.username> root< / property> < property name =connection.password>密码< / property> <！ - - SQL方言 - > < property name =dialect> org.hibernate.dialect.MySQLDialect< / property> <！ - 使用映射元数据自动创建/更新表格 - > < property name =hbm2ddl.auto>更新< / property> <！ - 使用基于注解的映射元数据 - > < mapping class =entity.Author/> < mapping class =entity.Article/> < / session-factory> < / hibernate-configuration>Main.java public class HelloWorldClient { public static void main（String [] args）{ Session session = HibernateUtil.getSessionFactory（）。openSession（）; Transaction txn = session.getTransaction（）; EntityManagerFactory emf = Persiscance.createEntityManagerFactory（hibernate.cfg.xml）; EntityManager em = emf.createEntityManager（）; EntityTransaction txn = em.getTransaction（）; 尝试{ txn.begin（）; 作者author = new Author（name，listOfArticlesWritten）; 文章文章=新文章（文章标题，作者）; session.save（作者）; session.save（article）; Query query = session.createQuery（从文章s 中选择不同的a.authorName，其中s.author像Joe％和title ='Spring boot'）; List< Article> articles = query.list（）; txnmit（）; } catch（Exception e）{ if（txn！= null）{txn.rollback（）;} e.printStackTrace（）; } finally { if（session！= null）{session.close（）;}} } }
这是问题出现的地方，我不知道如何避免为自定义查询创建一个hibernate.cfg.xml文件或会话工厂，在Spring指南页面以及我已经完成的一些教程中，他们采用DAO并扩展了CrudRepository接口，该接口已经提供了一堆方法，以及一种方法来命名该方法，以便Hibernate可以自行构建SQL。
我是什么试图完成，至少在这篇文章是能够在春季启动执行上述查询。我可以创建一个属性文件
application.properties
＃= ============================== ＃=数据源＃======= ======================== ＃设置数据库连接的配置 spring.datasource.url = jdbc：mysql：// localhost：3306 / spring-boot-demo spring.datasource.username = test spring.datasource.password = test ＃Mysql connector spring.datasource.driverClassName = com.mysql.jdbc.Driver ＃================== ============= ＃= JPA / HIBERNATE ＃======================= ======== ＃指定DBMS spring.jpa.database = MYSQL ＃显示或不记录每个sql查询 spring.jpa.show-sql = true ＃必须将Ddl auto设置为create以确保Hibernate将在应用程序启动时运行＃import.sql文件 ＃create-drop |更新|验证| none spring.jpa.hibernate.ddl-auto =更新 ＃用于生成优化查询的SQL方言 spring.jpa.properties.hibernate.dialect = org.hibernate.dialect .MySQL5Dialect ＃=============================== ＃= THYMELEAF ＃=============================== spring.thymeleaf.cache = false ＃debug = true我可以将所有映射移至属性文件，但那么我不清楚如何编写查询，因为不再有会话对象。
解决方案如果您使用Spring Boot + Spring Data JPA，然后通过使用配置您的数据源（您现在放入 hibernate.cfg.xml ）到 application.properties a href =docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html =noreferrer> spring.datasource。 * 属性。
这应该会自动创建一个为您提供实体经理。如果您需要使用查询，则可以使用Spring Data JPA的存储库，例如：
public interface ArticleRepository扩展了JpaRepository< Article，龙> { @Query（从第s条中选择s，其中s.author喜欢？1和s.title =？2） List< Article> findByAuthorAndTitle（String author，String title）; $ / code>现在您可以自动装入资源库并使用给定的查询，如下所示：
列表< Article> articles = repository.findByAuthorAndTitle（Joe％，Spring boot）;如果您确实需要自定义查询，则可以使用JPA的Predicate / Criteria API。 Spring提供了这些谓词的包装版本，称为 Specifications 。为此，您将 ArticleRepository 扩展为另一个称为 JpaSpecificationExecutor< Article> 的接口。这为您的存储库添加了一些额外的方法：
规范< Article> （（root，query，cb） - > { return cb.and（ cb.like（root.get（author），Joe％ ）， cb.equal（root.get（title），Spring boot））; }）; 列表<文章> articles = repository.findAll（spec）;这允许您动态创建查询，但从您的问题看，它并不像您真正需要它。
I have recently started using Spring boot, and have run into a bit of a problem. before, when i was just using Spring data with hibernate and JPA, I could create a hibernate.cfg.xml file that would give a bunch of configuration that could be passed to a config object and then ultimately create a SessionFactory object that would create a Session object that could be used to pass the query to hibernate:
package util; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { // Create the SessionFactory from hibernate.cfg.xml Configuration configuration = new Configuration().configure("hibernate.cfg.xml"); return configuration.buildSessionFactory( new StandardServiceRegistryBuilder().applySettings( configuration.getProperties() ).build() ); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } }hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "www.hibernate/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/hello-world</property> <property name="connection.username">root</property> <property name="connection.password">password</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- Create/update tables automatically using mapping metadata --> <property name="hbm2ddl.auto">update</property> <!-- Use Annotation-based mapping metadata --> <mapping class="entity.Author"/> <mapping class="entity.Article"/> </session-factory> </hibernate-configuration>Main.java
public class HelloWorldClient { public static void main(String[] args) { Session session = HibernateUtil.getSessionFactory().openSession(); Transaction txn = session.getTransaction(); EntityManagerFactory emf = Persiscance.createEntityManagerFactory("hibernate.cfg.xml"); EntityManager em = emf.createEntityManager(); EntityTransaction txn = em.getTransaction(); try { txn.begin(); Author author = new Author("name", listOfArticlesWritten); Article article = new Article("Article Title", author); session.save(author); session.save(article); Query query = session.createQuery("select distinct a.authorName from Article s where s.author like "Joe%" and title = 'Spring boot'); List<Article> articles = query.list(); txnmit(); } catch(Exception e) { if(txn != null) { txn.rollback(); } e.printStackTrace(); } finally { if(session != null) { session.close(); } } } }This is where the issue appears. I don't know how to avoid creating a hibernate.cfg.xml file or session factory for custom queries. in the Spring guides page, and some tutorials i have worked through, they take their DAO and extend the CrudRepository interface which gives a bunch of methods already, as well as a way to name the method so that Hibernate can build the sql on its own.
what i am trying to accomplish, at least in this post is to be able to execute the above query in spring boot. I can create a properties file
application.properties
# =============================== # = DATA SOURCE # =============================== # Set here configurations for the database connection spring.datasource.url = jdbc:mysql://localhost:3306/spring-boot-demo spring.datasource.username = test spring.datasource.password = test # Mysql connector spring.datasource.driverClassName = com.mysql.jdbc.Driver # =============================== # = JPA / HIBERNATE # =============================== # Specify the DBMS spring.jpa.database = MYSQL # Show or not log for each sql query spring.jpa.show-sql = true # Ddl auto must be set to "create" to ensure that Hibernate will run the # import.sql file at application startup #create-drop| update | validate | none spring.jpa.hibernate.ddl-auto = update # SQL dialect for generating optimized queries spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect # =============================== # = THYMELEAF # =============================== spring.thymeleaf.cache = false #debug=trueI can move all but the mapping to a properties file, but then I am unclear how to write the query because there is no longer a session object.
解决方案If you use Spring Boot + Spring Data JPA, then you configure your datasource (which you now put in hibernate.cfg.xml) into the application.properties, by using the spring.datasource.* properties.
This should automatically create an entity manager for you. If you need to use queries, you can use Spring Data JPA's repositories, for example:
public interface ArticleRepository extends JpaRepository<Article, Long> { @Query("select s from Article s where s.author like ?1 and s.title = ?2") List<Article> findByAuthorAndTitle(String author, String title); }Now you can autowire the repository and use the given query, like this:
List<Article> articles = repository.findByAuthorAndTitle("Joe%", "Spring boot");If you really need custom queries, you can use the Predicate/Criteria API from JPA. Spring offers a wrapped version of these predicates, called Specifications.
To do that, you extend your ArticleRepository with another interface called JpaSpecificationExecutor<Article>. This adds some extra methods to your repository:
Specification<Article> spec = Specifications.<Article>where((root, query, cb) -> { return cb.and( cb.like(root.get("author"), "Joe%"), cb.equal(root.get("title"), "Spring boot")); }); List<Article> articles = repository.findAll(spec);This allows you to dynamically create queries, though from your question it doesn't look like you really need it.
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