映射MongoDB _id字段的几种常见方式

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "my_entities")
public class MyEntity {

    @Id
    private String id; // 将映射到 MongoDB 的 _id 字段

    private String name;

    // Constructors, getters, setters
    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

MyEntity entity = new MyEntity();
entity.setName("Test Entity");
mongoTemplate.save(entity); // entity.getId() 现在会有一个自动生成的 ObjectId 字符串
System.out.println(entity.getId()); // 例如："60c72b941f4b1a3e4c8e4f3a"

import org.bson.types.ObjectId;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "products")
public class Product {

    @Id
    private ObjectId id; // 直接使用 ObjectId 类型

    private String productName;

    // Constructors, getters, setters
    public ObjectId getId() {
        return id;
    }

    public void setId(ObjectId id) {
        this.id = id;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }
}

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
import java.math.BigInteger;

@Document(collection = "items")
public class Item {

    @Id
    private Long itemId; // 使用 Long 类型，需要自己保证唯一性并赋值

    // 或者
    // @Id
    // private BigInteger itemId; // 使用 BigInteger，需要自己保证唯一性并赋值

    private String description;

    // Constructors, getters, setters
    public Long getItemId() {
        return itemId;
    }

    public void setItemId(Long itemId) {
        this.itemId = itemId;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

Item item = new Item();
item.setItemId(12345L); // 必须手动设置 ID
item.setDescription("Custom ID Item");
mongoTemplate.save(item);

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "books")
public class Book {

    @Id
    private String bookIsbn; // Java 字段名为 "bookIsbn"，但它映射到 MongoDB 的 _id

    private String title;

    // Getters and setters
    public String getBookIsbn() {
        return bookIsbn;
    }

    public void setBookIsbn(String bookIsbn) {
        this.bookIsbn = bookIsbn;
    }
    // ...
}