小编典典

在Spring Boot中编写自定义查询

spring-boot

我最近开始使用Spring
Boot,但是遇到了一些问题。以前,当我仅将Spring数据与hibernate和JPA一起使用时,我可以创建一个hibernate.cfg.xml文件,该文件将提供一堆可以传递给config对象的配置,然后最终创建一个SessionFactory对象,该对象将创建一个可用于将查询传递给hibernate状态的会话对象:

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" 
    "http://www.hibernate.org/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();

            txn.commit();
        } catch(Exception e) {
            if(txn != null) { txn.rollback(); }
            e.printStackTrace();
        } finally {
            if(session != null) { session.close(); } }
    } 
}

这是出现问题的地方。我不知道如何避免为自定义查询创建hibernate.cfg.xml文件或会话工厂。在Spring指南页面中,以及我已经完成的一些教程中,他们采用了DAO并扩展了CrudRepository接口,该接口已经提供了许多方法,以及一种命名方法的方法,以便Hibernate可以自行构建sql。

我要完成的工作,至少在这篇文章中是要能够在Spring Boot中执行上述查询。我可以创建一个属性文件

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=true

我可以将除映射之外的所有内容移动到属性文件,但是由于不再有会话对象,因此我不清楚如何编写查询。


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2020-05-30

共1个答案

小编典典

如果您使用Spring Boot + Spring Data JPA,则可以通过使用属性将数据源(现在将其放入 hibernate.cfg.xml中
)配置到中。application.propertiesspring.datasource.*

这将自动为您创建一个实体管理器。如果需要使用查询,可以使用Spring Data JPA的存储库,例如:

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);
}

现在,您可以自动连接存储库并使用给定的查询,如下所示:

List<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中的Predicate / Criteria
API。Spring提供了这些谓词的包装版本,称为Specification

为此,您可以ArticleRepository使用另一个接口扩展您的接口JpaSpecificationExecutor<Article>。这为您的存储库添加了一些额外的方法:

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);

这使您可以动态创建查询,尽管从您的问题来看,它似乎并不是您真正需要的。

2020-05-30