Error creating bean with name 'entityManagerFactory': Property 'com.example.shopping.models.Account.orders' is not a collection

Question

Hello everyone I am a beginner with Springboot and I need some help with the setup, somehow when I start the spring application it throws the following error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name
'entityManagerFactory' defined in class path resource 
[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]:
Property 'com.example.shopping.models.Account.orders' is not a collection and
may not be a '@OneToMany', '@ManyToMany', or '@ElementCollection'

The Account model is as follows:

package com.example.shopping.models;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.OneToMany;

@Entity
public class Account {
    
    @Id
    @GeneratedValue(strategy= GenerationType.SEQUENCE, generator="account_id")
    private Long id;

    public String name;

    public String email;

    @OneToMany()
    public Iterable<Order> orders;

}

I also have the Order model as follows:

package com.example.shopping.models;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.ManyToOne;
import jakarta.persistence.OneToMany;

@Entity
public class Order {
    @Id
    @GeneratedValue(strategy= GenerationType.SEQUENCE, generator="order_id")
    private Long id;
    
    @Id
    public Long accountId;
    
    @ManyToOne
    public Account account;

    @OneToMany()
    public Iterable<ProductOrder> products;
}

This is the application.properties file:

## default connection pool
spring.datasource.hikari.connectionTimeout=20000
spring.datasource.hikari.maximumPoolSize=5

## PostgreSQL
spring.datasource.url=jdbc:postgresql://localhost:5432/shopping?createDatabaseIfNotExist=true&useUnicode=true&characterEncoding=utf-8&autoReconnect=true
spring.datasource.username=postgres
spring.datasource.password=test

# create and drop table, good for testing, production set to none or comment it
spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.generate-ddl=true
app.db.init.enabled=true
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect

And this is the pom.xml file:

<?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>3.2.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>shopping</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>shopping</name>
    <description>Shopping project for Spring Boot</description>
    <properties>
        <java.version>21</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-boot-starter</artifactId>
            <version>3.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>3.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

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

</project>

I didn't create the database, I think it should be automatically created by Spring with the tables as well correct?

Answer 1

The error that you get tells you what you have to change.

Property 'com.example.shopping.models.Account.orders' is not a collection and may not be a '@OneToMany', '@ManyToMany', or '@ElementCollection'

To fix it you have to replace

    @OneToMany
    public Iterable<Order> orders;

To:

@OneToMany
public List<Order> orders;

And also

    @OneToMany
    public Iterable<ProductOrder> products;

To use List instead of Iterable