Java 无法确定关系属性的目标实体
我想不出是什么问题,请帮忙。我找了很多,但没有找到任何有用的建议。也许你能帮我。非常感谢 有两个类使用eclipselink作为jpa提供者:Java 无法确定关系属性的目标实体,java,jpa,eclipselink,Java,Jpa,Eclipselink,我想不出是什么问题,请帮忙。我找了很多,但没有找到任何有用的建议。也许你能帮我。非常感谢 有两个类使用eclipselink作为jpa提供者: @Entity @Table(name = "USER") public class User { @Id @GeneratedValue(strategy = GenerationType.TABLE) private Long id; private String login; private Long
@Entity
@Table(name = "USER")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private Long id;
private String login;
private Long groupId;
private String email;
@ManyToMany(mappedBy = "users")
private List polls;
@OneToMany(mappedBy = "user")
private List votes;
public List getVotes() {
return votes;
}
public void setVotes(List votes) {
this.votes = votes;
}
public User() {
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getLogin() {
return login;
}
public void setLogin(String login) {
this.login = login;
}
public Long getGroupId() {
return groupId;
}
public void setGroupId(Long groupId) {
this.groupId = groupId;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public List getPolls() {
return polls;
}
public void setPolls(List polls) {
this.polls = polls;
}
}
及
当我试图编译此文件时,收到错误:
Exception [EclipseLink-7214] (Eclipse Persistence Services - 2.4.0.v20120608-r11652): org.eclipse.persistence.exceptions.ValidationException
Exception Description: The target entity of the relationship attribute [votes] on the class [class logic.User] cannot be determined. When not using generics, ensure the target entity is defined on the relationship mapping.
这是我的persistence.xml文件:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="pollsPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>logic.Option</class>
<class>logic.Poll</class>
<class>logic.User</class>
<class>logic.Vote</class>
<class>logic.Greeting</class>
<properties>
<property name="eclipselink.jdbc.password" value="" />
<property name="eclipselink.jdbc.user" value="" />
<property name="eclipselink.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="eclipselink.jdbc.url"
value="jdbc:mysql://localhost:3306/core_polls" />
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.logging.level" value="INFO" />
<property name="eclipselink.ddl-generation.output-mode"
value="database" />
</properties>
</persistence-unit>
</persistence>
org.eclipse.persistence.jpa.PersistenceProvider
逻辑。选项
逻辑民意测验
逻辑用户
逻辑,投票
逻辑。问候语
如
如果使用泛型定义集合以指定元素
类型,则不需要指定关联的目标实体类型;
否则,必须指定目标实体类
所以,你可以做任何一件事
@OneToMany(mappedBy = "user")
private List<Vote> votes;
但是我更喜欢第一种。如果多对一和一对多被混淆了,这种情况也会发生(不是你的情况,而是对从搜索引擎到达这里的人有用)。
@OneToMany(mappedBy = "user")
private List<Vote> votes;
@OneToMany(targetEntity=logic.Vote.class, mappedBy = "user")
private List votes;