Spring boot H2 DB with mongoDB

Question

I want to save results from a poll when the status is set to "past". I have a H2 db and want to add a mongoDB that only stores the results. How do I go about implementing this with Spring boot?

As of now I have a poll program where you can create poll, edit polls, vote on polls etc.

I have added dependencies for mongodb, spring boot, spring mvc and H2 db etc.

This is my application properties:

spring.datasource.url=jdbc:h2:file:./db;AUTO_RECONNECT=TRUE
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.h2.console.enabled=true
spring.jpa.hibernate.ddl-auto=update

#Mongo Config
spring.main.allow-bean-definition-overriding=true
spring.data.mongodb.database=db-mongo
spring.data.mongodb.port=27017
spring.data.mongodb.host=localhost

I have tried making an interface mongoRepository:

import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.data.repository.PagingAndSortingRepository;
import org.springframework.data.repository.query.Param;
import project.dat250.entity.Poll;
import project.dat250.entity.User;

import java.util.List;

public interface ImongoRepository extends MongoRepository<Poll, Integer>, PagingAndSortingRepository<Poll, Integer> {

    List<Poll> findByNameContainingIgnoreCase(@Param("name") String name);
    List<Poll> findByUser(@Param("user") User user);
    List<Poll> findByIsPublic(@Param("isPublic") boolean isPublic);
    List<Poll> findByStatus(@Param("status") String status);
}

But I am getting hundreds of lines of errors after adding this repository:

Poll class:

@Data
@Entity
public class Poll {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Setter(AccessLevel.PROTECTED)
    private int pollID;
    private String name;
    private String description;
    private boolean isPublic;
    private int voteGreen;
    private int voteRed;
    private String status;
    private int timeLimit;

    @ManyToOne
    private User user;

    @ManyToMany(cascade = CascadeType.PERSIST)
    private List<User> usersVoted = new ArrayList<>();

    public Poll() {
    }

    public Poll(String name, String description, boolean isPublic, int voteGreen, int voteRed, String status,
            int timeLimit, User user) {
        this.name = name;
        this.description = description;
        this.isPublic = isPublic;
        this.voteGreen = voteGreen;
        this.voteRed = voteRed;
        this.status = status;
        this.timeLimit = timeLimit;
        this.user = user;
    }

    public void setUsersVoted(User userVoted) {
        this.usersVoted.add(userVoted);
    }

    public void setUser(User user) {
        this.user = user;
        if (user != null)
            user.setPolls(this);
    }

    public void setVoteRed(int red) {
        this.voteRed += red;
    }

    public void setVoteGreen(int green) {
        this.voteGreen += green;
    }

    public void setPublic(boolean isPublic) {
        this.isPublic = isPublic;
    }

}

Poll is JPA entity class. MongoRepository is not compatible with @Entity. It should be @Document. — gtiwari333
– gtiwari333, Commented Nov 10, 2020 at 22:45
You are reading from a H2 database table and writing it to MongoDB database collection. What is the process that reads and writes? — prasad_
– prasad_, Commented Nov 11, 2020 at 6:31

gtiwari333 · Accepted Answer · 2020-11-10 23:17:56Z

I was not able to reproduce your problem but I believe its because you are trying to create @MongoRepository with class annotated with @Entity.

@MongoRepository requires a plain POJO class or class annotated with @Document.

See this:

package gt.demo64777660;

import lombok.Data;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.mongodb.repository.MongoRepository;

import java.util.List;

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

interface MongoRepo extends MongoRepository<PollMongo, Integer> {
    List<PollMongo> findByIsPublic(boolean isPublic);
}

//A:  doesn't work
//interface MongoRepoFromJpaEntity extends MongoRepository<PollJpa, Integer> {
//    List<PollJpa> findByIsPublic(boolean isPublic);
//}

interface JPARepo extends JpaRepository<PollJpa, Integer> {
    List<PollJpa> findByIsPublic(boolean isPublic);
}

//@org.springframework.data.mongodb.core.mapping.Document(collection = "poll") //B: this is optional
@Data
class PollMongo {
//    @org.springframework.data.annotation.Id //B: this is optional
    int id;
    String name;
    boolean isPublic;
}

@Data
@javax.persistence.Entity
class PollJpa {
    @javax.persistence.Id
    int id;
    String name;
    boolean isPublic;
}

Dependencies (uses H2 and embedded mongo, no config required):

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>gt.mobgo</groupId>
    <artifactId>mongo-h2-spring</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <properties>
        <java.version>11</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-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>

        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

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