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[英]Java EE - [class <ClassName] uses a non-entity [class <ClassName>] as target entity in the relationship attribute
[英]Java Persistence api: class uses non-entity class as target entity in the relationship attribute
美好的一天。 我尝试使用持久性api具有多对多的依赖关系。 我填写一个新的用户数据并尝试将其添加到数据库,但得到一个例外:
Exception Description: [class main.java.entities.User] uses a non-entity [class main.java.entities.UserAccounts] as target entity in the relationship attribute [field accounts].
我尝试在name
部分使用@ManyToMany注释的差值,例如bank_user_accounts
和userAccounts
。 第二个值是persistence.xml
的单元名称。 但这种麻烦仍然存在。
用户类:
@Entity(name="bank_users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
@ManyToMany
@JoinTable(
name = "bank_user_accounts",
joinColumns = @JoinColumn(name = "user_id"),
inverseJoinColumns = @JoinColumn(name = "account_id")
)
private List<UserAccounts> accounts;
}
UserAccounts类:
@Entity(name="bank_user_accounts")
public class UserAccounts {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
@Column(name = "user_id")
private int userId;
@Column(name = "account_id")
private int accountId;
}
persistence.xml中:
<?xml version="1.0" encoding="UTF-8" ?>
<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_2_0.xsd"
version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="users" transaction-type="RESOURCE_LOCAL">
<class>main.java.entities.User</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="deleted" />
<property name="javax.persistence.jdbc.user" value="deleted" />
<property name="javax.persistence.jdbc.password" value="deleted" />
</properties>
</persistence-unit>
<persistence-unit name="userAccounts" transaction-type="RESOURCE_LOCAL">
<class>main.java.entities.UserAccounts</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="deleted" />
<property name="javax.persistence.jdbc.user" value="deleted" />
<property name="javax.persistence.jdbc.password" value="deleted" />
</properties>
</persistence-unit>
</persistence>
User
和UserAccounts
之间的关系听起来像@OneToMany
或只是一个可嵌入的类。
@ManyToMany
应该在两侧都有注释(双向),并且应该在一侧设置mappedBy
属性,以指向引用该实体作为集合的另一侧的属性名称。
我在你的代码中观察到的一件事是你在User类中使用了很多很多注释,但是你没有在userAccounts类中使用过。 要实现ManyToMany关系,两个实体都应使用ManyToMany进行注释。
问题是(虽然可能已经过时)你有一个从一个持久性单元到另一个持久性单元的引用。 您可以轻松地将两者放在同一个单位:
<?xml version="1.0" encoding="UTF-8" ?>
<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_2_0.xsd"
version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="users" transaction-type="RESOURCE_LOCAL">
<class>main.java.entities.User</class>
<class>main.java.entities.UserAccounts</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="deleted" />
<property name="javax.persistence.jdbc.user" value="deleted" />
<property name="javax.persistence.jdbc.password" value="deleted" />
</properties>
</persistence-unit>
</persistence>
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