如何在Java中制作实体[重复]

Question

我需要创建一个名为 EventEvent 的 Entityan 实体，该实体将有几个字段，如名称、描述、所有者和其他。我在这里搜索并添加了一些依赖项，但它不起作用。这是我的代码：

package com.example.app.entity;

import javax.persistence.*;
import java.util.List;

@Entity
@Table (name = "events")
public class Event {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;

private String name;
private List<String> games;
private List<User> players;
private double latitude;
private double longitude;
private String description;
private User owner;

public User getOwner(){
    return owner;
}
public void setOwner(User owner){
    this.owner = owner;
}

public String getDescription(){
    return description;
}
public void setDescription(String description){
    this.description = description;
}

public double getLatitude(){
    return latitude;
}
public void setLatitude(double latitude){
    this.latitude = latitude;
}

public double getLongitude(){
    return longitude;
}
public void setLongitude( double longitude){
    this.longitude = longitude;
}

public String getName(){
    return name;
}
public void setName( String name){
    this.name = name;
}

public long getId() {
    return id;
}

public void setId(long id) {
    this.id = id;
}

public List<String> getGames() {
    return games;
}

public void setGames(List<String> games) {
    this.games = games;
}

public List<User> getPlayers() {
    return players;
}

public void setPlayers(List<User> players) {
    this.players = players;
}

}

Here is an image of my folders and resources if helps to resolve the problem:

这是我的错误信息：

    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
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1710) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:583) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:502) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:312) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1085) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:858) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:752) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:388) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234) [spring-boot-2.0.0.RELEASE.jar:2.0.0.RELEASE]
at com.example.app.AppApplication.main(AppApplication.java:12) [classes/:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:970) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:895) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:57) ~[spring-orm-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:388) ~[spring-orm-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:377) ~[spring-orm-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1769) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1706) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
... 16 common frames omitted
Caused by: org.hibernate.MappingException: Could not determine type for: java.util.List, at table: events, for columns: [org.hibernate.mapping.Column(games)]
at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:455) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:422) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.mapping.Property.isValid(Property.java:226) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:597) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.mapping.RootClass.validate(RootClass.java:265) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.boot.internal.MetadataImpl.validate(MetadataImpl.java:329) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:459) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:892) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
... 23 common frames omitted


Process finished with exit code 1

Answer 1

Hibernate 不能映射对象列表。在表形式中，它必须是另一个表的外键。 Hibernate 可以使用延迟加载模式来初始化 Collection。看到那个帖子 Hibernate, List<String>.

Answer 2

问题其实是the org.hibernate.MappingException: Could not determine type for: java.util.List引起的。所以，需要打上Mapping注解（比如：OneToMany,ManyToMany等）

@OneToMany(targetEntity="your target enity", mappedBy="", fetch="Fetch Type")
private List<String> games;

或者对于基本实体（整数、字符串）

@Column
@ElementCollection(targetClass=String.class)
private List<String> games;

你需要为private List<User> players;做同样的事情

欲了解更多信息，请访问link。