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字段设置为自动生成的，对此有什么解决方案?我没有使用jpa jar.so我不能使用@Generatedvalue注释.所以我们在这里如何显示此字段是自动生成的. 代码在下面.

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附带了所有复杂的ObjectId生成功能，但是通常您只是从关系数据库中跳了出来，并且您仍然希望易于阅读/交流数字标识符字段每次插入新记录时都会自动递增.

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教程的一个简洁建议是使用带有计数器名称"作为其ID的计数器集合以及一个"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.

使用Spring Data MongoDB进行开发时，可以将这种巧妙的技巧写成一个简单的服务.在这里，我使用集合名称作为计数器名称，这样很容易猜测/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只是表示集合的简单类.请注意int数据类型的使用，最多将限制为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)，只需在保存之前像这样设置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，则需要使用MongoDBEvents并使用onBeforeConvert来使用与上述相同的方法来生成自动值.

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

这篇关于我们如何使用Spring Boot为MongoDB创建自动生成的字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！