创建实体

例子

此示例Movie.java 实体类定义了一个 Movie 实体，其中包含以下信息：

• @Entity 将该类标记为 Hibernate ORM 实体的注解

• @Table 注释，用于将实体映射到Atlas示例数据集中的 movies集合

• @Id 和 @ObjectIdGenerator 注解，用于将 id字段指定为主主键并配置自动 ObjectId 生成

• 表示电影数据的私有字段

• 用于实体实例化的默认构造函数和参数化构造函数

• 提供对实体字段访问权限权限的 Getter 和 setter 方法

package org.example;
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;
	}
}

一对一关系

A One-to-One relationship is when a record in one database is associated with exactly one record in another database. In MongoDB, you can create a collection with an embedded document field to model a One-to-One relationship. The Hibernate ORM extension allows you to create embedded document fields by using @Struct aggregate embeddables.

The example defines a field with a @Struct aggregate embeddable type in an entity similar to the Define an Entity example in this guide. The sample Movie.java entity class includes the following information:

• @Entity 和 @Table 注解，用于定义实体并将其映射到 movies集合

• @Id 以及将 id字段指定主键的@ObjectIdGenerator 注解

• 表示电影标题的字符串字段

• @Struct 聚合表示电影奖项和工作室信息的可嵌入式字段

The following example represents a One-to-One relationship because each Movie entity is associated with one Awards embeddable and one Studio embeddable:

@Entity
@Table(name = "movies")
public class Movie {
    @Id
    @ObjectIdGenerator
    private ObjectId id;
    private String title;
    private Awards awards;
    private Studio studio;
    public Movie(String title, Awards awards, Studio studio) {
        this.title = title;
        this.awards = awards;
        this.studio = studio;
    }
    public Movie() {
    }
    // Getter and setter methods
}

以下示例代码创建一个 Awards @Struct 聚合可嵌入对象：

@Embeddable
@Struct(name = "Awards")
public class Awards {
    private int wins;
    private int nominations;
    private String text;
    public Awards(int wins, int nominations, String text) {
       this.wins = wins;
       this.nominations = nominations;
       this.text = text;
    }
    public Awards() {
    }
    // Getter and setter methods
}

以下示例代码创建一个 Studio @Struct 聚合可嵌入对象：

@Embeddable
@Struct(name = "Studio")
public class Studio {
    private String name;
    private String location;
    private int foundedYear;
    public Studio(String name, String location, int foundedYear) {
        this.name = name;
        this.location = location;
        this.foundedYear = foundedYear;
    }
    public Studio() {
    }
    // Getter and setter methods
}

一对多关系

一对多关系是指一个数据库中的一条记录与另一个数据库中的多条记录相关联。在MongoDB中，您可以定义一个集合字段来存储嵌入式文档列表，以对一对多关系进行建模。 Hibernate ORM 扩展允许您使用 @Struct 聚合可嵌入对象的列表来创建嵌入式文档字段。

The example defines a field that stores a list of @Struct aggregate embeddables in an entity similar to the Define an Entity Example in this guide. The sample Movie.java entity class includes the following information:

• @Entity 和 @Table 注解，用于定义实体并将其映射到 movies集合

• @Id 以及将 id字段指定主键的@ObjectIdGenerator 注解

• 表示电影标题的字符串字段

• 存储多个 Writer @Struct 聚合可嵌入对象的列表字段，表示作者信息

The following example represents a One-to-Many relationship because each Movie entity is associated with multiple Writer embeddables:

@Entity
@Table(name = "movies")
public class Movie {
    @Id
    @ObjectIdGenerator
    @Column(name = "_id")
    private ObjectId id;
    private String title;
    private List<Writer> writers;
    public Movie(String title, List<Writer> writers) {
        this.title = title;
        this.writers = writers;
    }
    public Movie() {
    }
    // Getter and setter methods
}

以下示例代码创建一个 Writer @Struct 聚合可嵌入对象：

@Embeddable
@Struct(name = "Writer")
public class Writer {
    private String name;
    public Writer() {
    }
    public Writer(String name) {
        this.name = name;
    }
    // Getter and setter methods
}