我们如何使用 spring boot 为 mongodb 创建自动生成的字段 [英] How can we create Auto generated field for mongodb using spring boot

问题描述

我写了一些代码.我想将 BaseQuestion 类中的 questionId 字段设为自动生成.有什么解决方案吗?我没有使用 jpa jar.所以我不能使用 @Generatedvalue 注释.所以我们在这里如何显示这个字段是自动生成的.代码如下.

I write some code.I want to make questionId field in BaseQuestion Class as Autogenerated.Any solution for that? I am not using jpa jar.so i can't use @Generatedvalue annotation.So how we show here this field is auto generated. code is below.

pom.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>audit_project</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>2.11.0</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

BaseQuestion.java

package model;

import java.util.List;

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

@Document(collection = "basequestion")
public class BaseQuestion {
      @ID
    private String id;
    private int questionId;
    private String responseType;
    private boolean required;
    private boolean active;
    private String questionCode;
    private QuestionText questionText;
    private String category;
    private List<Responses> responses;

    public QuestionText getQuestionText() {
        return questionText;
    }

    public void setQuestionText(QuestionText questionText) {
        this.questionText = questionText;
    }

    public List<Responses> getResponses() {
        return responses;
    }

    public void setResponses(List<Responses> responses) {
        this.responses = responses;
    }

    public int getQuestionId() {
        return questionId;
    }

    public void setQuestionId(int questionId) {
        this.questionId = questionId;
    }

    public String getResponseType() {
        return responseType;
    }

    public void setResponseType(String responseType) {
        this.responseType = responseType;
    }

    public boolean getRequired() {
        return required;
    }

    public void setRequired(boolean required) {
        this.required = required;
    }

    public String getQuestionCode() {
        return questionCode;
    }

    public void setQuestionCode(String questionCode) {
        this.questionCode = questionCode;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public boolean isActive() {
        return active;
    }

    public void setActive(boolean active) {
        this.active = active;
    }
}

AuditProjectRepository.java

package repository;

import org.springframework.data.mongodb.repository.MongoRepository;

import model.BaseQuestion;

public interface AuditProjectRepository extends MongoRepository<BaseQuestion, String> {

    public BaseQuestion findByQuestionId(int questionId);

    public BaseQuestion findByQuestionCode(String questionCode);

    public Long deleteByQuestionId(int questionid);

}

推荐答案

MongoDB 提供了所有复杂的 ObjectId 生成功能，但通常您只是从关系数据库中跳槽，并且仍然想要一个易于阅读/交流的数字标识符字段每次插入新记录时自动递增.

MongoDB came with all sophisticated ObjectId generation feature, but often you just jumped the ship from relational database, and you still want an easy to read / communicate numeric identifier field which automatically increments every time new record is inserted.

MongoDB 教程的一个巧妙建议是使用以计数器名称"作为其 ID 的计数器集合，并使用seq"字段来存储上次使用的数字.

One neat suggestion from MongoDB tutorial is to use a counter collection with a ‘counter name’ as its id, and a ‘seq’ field to store the last used number.

在使用 Spring Data MongoDB 进行开发时，这个巧妙的技巧可以写成一个简单的服务.这里我使用集合名称作为计数器名称，以便于猜测/记住.

When developing using Spring Data MongoDB, this neat trick can be written as a simple service. Here I used the collection name as the counter name so it’s easy to guess / remember.

import static org.springframework.data.mongodb.core.FindAndModifyOptions.options;
import static org.springframework.data.mongodb.core.query.Criteria.where;
import static org.springframework.data.mongodb.core.query.Query.query;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.data.mongodb.core.query.Update;
import org.springframework.stereotype.Service;

import com.model.CustomSequences;


@Service
public class NextSequenceService {
    @Autowired private MongoOperations mongo;

    public int getNextSequence(String seqName)
    {
        CustomSequences counter = mongo.findAndModify(
            query(where("_id").is(seqName)),
            new Update().inc("seq",1),
            options().returnNew(true).upsert(true),
            CustomSequences.class);
        return counter.getSeq();
    }
}

CustomSequences 只是一个表示集合的简单类.请注意 int 数据类型的使用，这将限制为最多 2^31 个条目.

CustomSequences is just a simple class representing the collection. Please beware the usage of int data type, this will limit to 2^31 entries maximum.

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

@Document(collection = "customSequences")
public class CustomSequences {
    @Id
    private String id;
    private int seq;

// getters and setters
}

然后在插入新条目时(借助 Spring MongoDB Repository 支持)，在保存之前只需像这样设置 id 字段

Then when inserting a new entry (with help of Spring MongoDB Repository support), just set the id field like this before you save it

BaseQuestion baseQuestion = new BaseQuestion();
baseQuestion.setQuestionId(nextSequenceService.getNextSequence("customSequences"));
/* Rest all values */

baseQuestionRepository.save(baseQuestion);

如果您不喜欢这种方式，那么您需要使用 MongoDBEvents 并使用 onBeforeConvert 使用上述相同的方法生成自动值.

If you don't like this way then you need to use MongoDBEvents and use onBeforeConvert to generate automated value using same above approach.

上述方法也是线程安全的，因为 findAndModify() 是线程安全的原子方法

Also above approach is threadsafe as findAndModify() is a thread safe atomic method

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