Spring boot Kotlin SpringBoot和JPA-一对一的关系问题

我试图在两个实体之间创建一个关系OneToMany，但在创建名为“entityManagerFactory”的bean时总是会出错：

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-11-23 12:17:20.082 ERROR 17130 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.moises.kotlinstoreapi.model.Customer.purchases, com.moises.kotlinstoreapi.model.Purchase.purchasesLines]
...

我已经与其他两个实体（购买客户）创建了相同类型的关系，但在这种情况下，它不会运行

产品代码： 包com.moises.kotlinstoreapi.model

import com.fasterxml.jackson.annotation.JsonManagedReference
import java.time.LocalDateTime
import javax.persistence.*
import javax.validation.constraints.NotBlank
import javax.validation.constraints.NotEmpty
import javax.validation.constraints.NotNull

@Entity
@Table(name="products")
data class Product (
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    val id: Long = 0,
    @NotBlank
    val title: String = "",
    @NotEmpty
    val price: Double = 999.99,
    @NotNull
    val created_at: LocalDateTime = LocalDateTime.now(),
    val update_at: LocalDateTime? = null,

    /**
    * Relations
    *
    */
    @OneToOne(mappedBy="product")
    val purchaseLine: PurchaseLine? = null
)

购买代码：

package com.moises.kotlinstoreapi.model

import com.fasterxml.jackson.annotation.JsonBackReference
import com.fasterxml.jackson.annotation.JsonManagedReference
import com.sun.istack.NotNull
import java.time.LocalDateTime
import javax.persistence.*
import javax.validation.constraints.NotEmpty

@Entity
@Table(name="purchases")
data class Purchase(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private val id: Long=0,
    @Column(name="notes", columnDefinition="TEXT")
    val notes: String = "",
    @NotNull
    val created_at: LocalDateTime = LocalDateTime.now(),
    val update_at: LocalDateTime? = null,

    /**
    * Relations
    *
    */
    //@ManyToOne(cascade = arrayOf(CascadeType.ALL),fetch= FetchType.EAGER)
    //@JoinColumn(name="customer_id")
    //@JsonBackReference
    //val customer: Customer? = null,

    @OneToMany(mappedBy="purchase", cascade=arrayOf(CascadeType.ALL), fetch=FetchType.EAGER)
    @JsonManagedReference
    var purchasesLines: List<PurchaseLine> = emptyList()
)

我在Ubuntu中使用IntelliJ和Maven以及OpenJDK 11

My pow.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 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>2.2.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.moises</groupId>
    <artifactId>kotlin-store-api</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>kotlin-store-api</name>
    <description>API store with Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <kotlin.version>1.3.50</kotlin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                        <plugin>jpa</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>

4.0.0
org.springframework.boot
spring启动程序父级
2.2.1.发布
com.moises
kotlin商店api
0.0.1-快照
kotlin商店api
带Spring引导的API存储
1.8
1.3.50
org.springframework.boot
spring引导启动器数据jpa
org.springframework.boot
弹簧启动启动器数据rest
org.springframework.boot
SpringBootStarterWeb
com.fasterxml.jackson.module
杰克逊模块科特林
org.jetbrains.kotlin
科特林反射
org.jetbrains.kotlin
kotlin-stdlib-jdk8
org.springframework.boot
弹簧靴开发工具
运行时
真的
mysql
mysql连接器java
运行时
org.springframework.boot
弹簧起动试验
测试
org.junit.vintage
朱尼特老式发动机
${project.basedir}/src/main/kotlin
${project.basedir}/src/test/kotlin
org.springframework.boot
springbootmaven插件
org.jetbrains.kotlin
kotlin maven插件
-Xjsr305=严格
春天
jpa
org.jetbrains.kotlin
科特林·马文·阿洛彭
${kotlin.version}
org.jetbrains.kotlin
科特林·马文·诺格
${kotlin.version}

我的猜测是，错误消息中列出的两个OneToMany关联是急切的（为什么？）。让你的toMany关联保持懒惰：这将避免破坏你应用程序的性能。这也可以避免这个问题。我不知道我该怎么做。这是我的第一个Kotlin/Java、Spring和JPA项目。当我从“购买”中的关系中清除

fetch=FetchType.EAGER

时，它运行正常。它在列表中，但我想用Set检查，使用它更有意义。

<?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>2.2.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.moises</groupId>
    <artifactId>kotlin-store-api</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>kotlin-store-api</name>
    <description>API store with Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <kotlin.version>1.3.50</kotlin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                        <plugin>jpa</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>