在Spring引导中编写自定义查询 [英] writing custom queries in Spring boot
问题描述
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; }
}
<？xml version ='1.0'encoding ='utf-8'？>
<！DOCTYPE hibernate-configuration PUBLIC
- // Hibernate / Hibernate配置DTD 3.0 // EN
http://www.hibernate.org/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（）;
txn.commit（）;
} 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。
如果您使用Spring Boot + Spring Data JPA，然后通过使用<数据JPA>配置您的数据源（您现在放入 hibernate.cfg.xml ）到 application.properties a href =http://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"
"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(); } }
}
}
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=true
I 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.
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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