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执行 CRUD 操作

Overview

在本指南中，您可以学习；了解如何使用MongoDB Extension for Hibernate ORM 在MongoDB集合上运行创建、读取、更新和删除(增删改查 ) 操作。

样本数据

The examples in this guide use the Movie entity, which represents the sample_mflix.movies collection from the Atlas sample datasets. The Movie entity has the following definition:

import com.mongodb.hibernate.annotations.ObjectIdGenerator;
import org.bson.types.ObjectId;
import java.util.List;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
@Entity
@Table(name = "movies")
public class Movie {
   @Id
   @ObjectIdGenerator
   private ObjectId id;
   private String title;
   private String plot;
   private int year;
   private List<String> cast;
   public Movie(String title, String plot, int year, List<String> cast) {
      this.title = title;
      this.plot = plot;
      this.year = year;
      this.cast = cast;
   }
   public Movie() {
   }
   public ObjectId getId() {
      return id;
   }
   public String getTitle() {
      return title;
   }
   public void setTitle(String title) {
      this.title = title;
   }
   public String getPlot() {
      return plot;
   }
   public void setPlot(String plot) {
      this.plot = plot;
   }
   public int getYear() {
      return year;
   }
   public void setYear(int year) {
      this.year = year;
   }
   public List<String> getCast() {
      return cast;
   }
   public void setCast(List<String> cast) {
      this.cast = cast;
   }
}

要学习如何创建Java应用程序以使用MongoDB Extension for Hibernate ORM与此MongoDB示例集合交互，请参阅入门教程。

重要

持久性上下文

启用Hibernate ORM 能够与数据库交互，您必须使用 Hibernate Session 或 Jakarta Persistence EntityManager 在持久性上下文中运行操作。您还必须在ACID 事务中运行写入操作，才能修改MongoDB数据并保持数据完整性。

Before running the examples in this guide, ensure that you add persistence context and transaction management code to your application that resembles the following code:

var sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
Transaction tx = session.beginTransaction();
// ... Perform CRUD operations here
tx.commit();
session.close();
sf.close();

要使用会话，您必须创建一个配置HibernateUtil.java 的SessionFactory 文件。要学习；了解更多信息，请参阅入门教程中的配置应用程序步骤。

 // Replace <persistence unit> with the name of your persistence unit in the persistence.xml file
 EntityManagerFactory emf = Persistence.createEntityManagerFactory("<persistence unit>");
 EntityManager entityManager = entityManagerFactory.createEntityManager();
 entityManager.getTransaction().begin();
 // ... Perform CRUD operations here
entityManager.getTransaction().commit();
entityManager.close();
emf.close;

要使用EntityManager ，您必须创建一个声明持久性单元的persistence.xml 文件。要学习；了解更多信息，请参阅 Hibernate ORM 文档中的使用 JPA 标准 API 的教程。

插入文档

要将文档插入集合，请创建一个新的实体实例。然后，您可以将此实例作为参数传递给以下方法，以将其作为文档保存到MongoDB集合中：

org.hibernate.Session.persist()：使用 Hibernate API应用更改应用于数据库
jakarta.persistence.EntityManager.persist()：使用 Jakarta Persistence API应用更改应用于数据库

提示

要学习；了解有关创建实体实例并将其持久保存到数据库的更多信息，请参阅 Hibernate ORM 用户指南中的持久化实体。

例子

The following example creates a new Movie entity instance and uses the persist() method to insert a corresponding document into the sample_mflix.movies collection:

var myMovie = new Movie();
myMovie.setTitle("Knives Out");
myMovie.setYear(2019);
myMovie.setCast(List.of("Ana de Armas", "Daniel Craig", "Chris Evans"));
myMovie.setPlot("Detective Benoit Blanc investigates the mysterious death of crime novelist Harlan Thrombey, " +
        "unraveling lies as every Thrombey family member becomes a suspect.");
session.persist(myMovie);

var myMovie = new Movie();
myMovie.setTitle("Knives Out");
myMovie.setYear(2019);
myMovie.setCast(List.of("Ana de Armas", "Daniel Craig", "Chris Evans"));
myMovie.setPlot("Detective Benoit Blanc investigates the mysterious death of crime novelist Harlan Thrombey, " +
        "unraveling lies as every Thrombey family member becomes a suspect.");
entityManager.persist(myMovie);

读取文档

要从集合中检索文档，请将查询条件传递给 createQuery() 方法。以下 API 均提供 createQuery() 方法：

Hibernate 的 Session API：使用 Hibernate 查询语言 (HQL) 语法定义查询
Jakarta Persistence 的 EntityManager API：使用 Jakarta Persistence Query Language (JPQL) 语法（HQL 的子集）来定义查询

提示

要学习有关使用 HQL 和 JPQL 语法检索数据的更多信息，请参阅 Hibernate ORM 查询指南中的 Select 声明。

注意

本部分介绍如何使用 HQL 和 JPQL 读取文档，但您也可以使用条件构建器或原生查询来检索数据。要学习；了解详情，请参阅以下指南：

返回一个文档示例

To retrieve only one document that matches your query criteria, chain the getSingleResult() method to the createQuery() method. The following example retrieves one document that has a title value of "Boyhood" from the sample_mflix.movies collection:

var singleResult = session.createQuery("from Movie where title = :t", Movie.class)
                          .setParameter("t", "Boyhood")
                          .getSingleResult();
System.out.println("Title: " + singleResult.getTitle() + ", Year: " + singleResult.getYear());

Title: Boyhood, Year: 2014

var singleResult = entityManager.createQuery("select m from Movie m where m.title = :t", Movie.class)
                          .setParameter("t", "Boyhood")
                          .getSingleResult();
System.out.println("Title: " + singleResult.getTitle() + ", Year: " + singleResult.getYear());

Title: Boyhood, Year: 2014

提示

查询语法

要学习；了解有关 HQL 和 JPQL 语法的更多信息，请参阅 Hibernate ORM 文档中的 Hibernate 查询语言指南。

返回多个文档示例

The following example calls the createQuery() method on a session to retrieve documents from the sample_mflix.movies collection. The code uses HQL and JPQL to return documents that have a year value of 1920 and prints their title values:

var results = session.createQuery("from Movie where year = :y", Movie.class)
                    .setParameter("y", 1920)
                    .getResultList();
results.forEach(movie -> System.out.println(movie.getTitle()));

High and Dizzy
One Week
The Saphead
The Daughter of Dawn

var results = entityManager.createQuery("select m from Movie m where m.year = :y", Movie.class)
                    .setParameter("y", 1920)
                    .getResultList();
results.forEach(movie -> System.out.println(movie.getTitle()));

High and Dizzy
One Week
The Saphead
The Daughter of Dawn

修改文档

您可以执行以下操作来修改集合中的文档：

更新一个文档：调用实体的 setter 方法来更改一个实体实例的字段值，然后使用会话或实体管理器来保存更改。
更新多个文档：将更新声明传递给会话或实体管理器上的createQuery() 或createMutationQuery() 方法。然后，调用executeUpdate() 方法将更改应用到数据库。

提示

要学习；了解有关使用 Hibernate ORM 修改数据的更多信息，请参阅以下资源：

Hibernate ORM 用户指南中的修改托管/持久状态
更新 Hibernate ORM查询指南中的语句

更新一个示例

The following example retrieves a document by its ObjectId value. Then, the example calls the Movie entity's setTitle() method to update the document's title value to "Jurassic Park I":

// Your ObjectId value might differ
Movie movieById = session.get(Movie.class, new ObjectId("573a1399f29313caabcedc5d"));
movieById.setTitle("Jurassic Park I");
session.persist(movieById);

// Your ObjectId value might differ
Movie movieById = entityManager.find(Movie.class, new ObjectId("573a1399f29313caabcedc5d"));
movieById.setTitle("Jurassic Park I");
entityManager.persist(movieById);

Update Multiple Example

The following example updates the title value of matching documents from "The Three Stooges" to "The 3 Stooges". Then, the example calls the executeUpdate() method to apply the changes to the database:

var updateResult = session.createMutationQuery(
    "update Movie set title = :new where title = :old")
    .setParameter("new", "The 3 Stooges")
    .setParameter("old", "The Three Stooges")
    .executeUpdate();
System.out.println("Number of movies updated: " + updateResult);

Number of movies updated: 2

var updateResult = entityManager.createQuery(
    "update Movie m set m.title = :new where m.title = :old")
    .setParameter("new", "The 3 Stooges")
    .setParameter("old", "The Three Stooges")
    .executeUpdate();
System.out.println("Number of movies updated: " + updateResult);

Number of movies updated: 2

Delete Documents

您可以执行以下操作从集合中删除文档：

删除一个文档：在会话或实体管理器上调用 remove()方法，并将要删除的实体实例作为参数传递。
删除多个文档：将删除声明传递给会话或实体经理上的 createQuery() 或 createMutationQuery() 方法。然后，调用 executeUpdate() 方法将更改应用到数据库。

提示

要学习；了解有关使用 Hibernate ORM 删除数据的更多信息，请参阅以下资源：

Hibernate ORM 用户指南中的删除实体
《Hibernate ORM查询指南》中的删除语句

删除一个示例

The following example retrieves a document by its ObjectId value. Then, the example calls the remove() method on a session to delete the corresponding document from the sample_mflix.movies collection:

// Your ObjectId value might differ
Movie movieToDelete = session.get(Movie.class, new ObjectId("573a1399f29313caabcedc5d"));
session.remove(movieToDelete);

// Your ObjectId value might differ
Movie movieToDelete = entityManager.find(Movie.class, new ObjectId("573a1399f29313caabcedc5d"));
entityManager.remove(movieToDelete);

Delete Multiple Example

The following example deletes all documents that have a year value of 1920 from the sample_mflix.movies collection. The example passes a delete statement to the createMutationQuery() method, and then calls the executeUpdate() method to apply the changes to the database:

var deleteResult = session.createMutationQuery(
    "delete Movie where year = :y")
    .setParameter("y", 1920)
    .executeUpdate();
System.out.println("Number of movies deleted: " + deleteResult);

Number of movies deleted: 4

var deleteResult = entityManager.createQuery(
    "delete Movie m where m.year = :y")
    .setParameter("y", 1920)
    .executeUpdate();
System.out.println("Number of movies deleted: " + deleteResult);

Number of movies deleted: 4