springboot整合mongodbid自增

在Spring Boot中整合MongoDB实现自增ID可以通过自定义序列来实现。以下是一种常见的实现方式：

1. 首先，创建一个名为Sequence的实体类，用于保存自增ID的当前值：

package com.example.entity;

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

@Document(collection = "sequences")
public class Sequence {
    @Id
    private String id;
    private long value;

    public String getId() {
        return id;
    }

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

    public long getValue() {
        return value;
    }

    public void setValue(long value) {
        this.value = value;
    }
}

2. 接下来，创建一个名为SequenceGenerator的自定义序列生成器类，用于生成自增ID：

package com.example.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.data.mongodb.core.query.FindAndModifyOptions;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.data.mongodb.core.query.Update;
import org.springframework.stereotype.Service;
import com.example.entity.Sequence;

@Service
public class SequenceGenerator {
    private final MongoOperations mongoOperations;

    @Autowired
    public SequenceGenerator(MongoOperations mongoOperations) {
        this.mongoOperations = mongoOperations;
    }

    public long generateSequence(String seqName) {
        Query query = new Query().addCriteria(Criteria.where("_id").is(seqName));
        Update update = new Update().inc("value", 1);
        FindAndModifyOptions options = new FindAndModifyOptions().returnNew(true).upsert(true);
        Sequence sequence = mongoOperations.findAndModify(query, update, options, Sequence.class);
        return sequence.getValue();
    }
}

3. 最后，在需要生成自增ID的实体类中使用@Autowired注入SequenceGenerator，并使用@PrePersist注解在保存实体之前生成自增ID：

package com.example.entity;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.annotation.Id;
import org.springframework.data.annotation.PrePersist;
import org.springframework.data.mongodb.core.mapping.Document;
import com.example.service.SequenceGenerator;

@Document(collection = "users")
public class User {
    @Id
    private long id;
    private String name;
    private int age;

    @Autowired
    private SequenceGenerator sequenceGenerator;

    public User() {
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @PrePersist
    public void generateId() {
        this.id = sequenceGenerator.generateSequence(User.SEQUENCE_NAME);
    }
}

通过以上方式，就可以在Spring Boot整合MongoDB中实现自增ID的功能。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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