我有一个 hibernate 实体类
public class MyComplexClass implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
String name;
int number;
@ElementCollection
Map<String,String> myMap;
@ManyToOne
Simple simple;
public MyComplexClass(String name, int number, Map<String,String> myMap) {
this.name = name;
this.port = number;
this.myMap = myMap;
}
public MyComplexClass() {
// TODO Auto-generated constructor stub
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setNumber(int number) {
this.port = number;
}
public int getPort() {
return port;
}
public void setMyMap(Map<String,String> myMap) {
this.myMap = myMap;
}
public Map<String,String> getMyMap() {
return this.myMap;
}
public Simple getSimple() {
return this.simple;
}
在 simple 类中，我有一个表单的映射
@Entity
@Table(name = "Simple")
public class Simple implements Comparable<Simple>, Serializable {
@JsonProperty
@OneToMany(mappedBy="simple",fetch = FetchType.EAGER,cascade = CascadeType.ALL)
Set<MyComplexClass> myComplexClass;
public void setMyComplexClass(List<MyComplexClass> myComplexClass) {
this.myComplexClass = myComplexClass;
}
public List<MyComplexClass> getMyComplexClass() {
return this.myComplexClass;
}
在系统中的某个位置我将值设置为
Map<String, String> myMap = new HashMap<String,String>();
myMap.put("value","value");
MyComplexClass myComplexClass = new MyComplexclass("a", 123, myMap)
Set<MyComplexClass> myComplexClassList = new HashSet<MyComplexClass>();
myComplexClassList.add(myComplexClassList)
simple.setMyComplexClass(myComplexClassList);
myComplexClass.setSimple(simple);
// save to the database
dao.save(simple);
这会持久保存在数据库中，其中复杂类的多行与简单类的外键相同
Table: MyComplexClass
id name number simple_id
1 abc 234 1
2 abc 234 1
3 abc 234 1
4 abc 234 1
5 abc 234 1
6 xyz 432 2
7 xyz 432 2
8 xyz 432 2
我错过了什么？所有这些行的 id 都是不同的，这让我认为它们在代码中已被初始化多次。但他们不是。他们有不同的条目有什么原因吗？我正在使用 AKKA Actor ，这可能是一个原因吗？
基于各种类似的问题。我已将 Collection 更改为 Set，并添加了一个 CompareTo 方法，如下所示
public int compareTo(MyComplexClass o) {
if (o == null) {
return 1;
}
if (this.getName().equals(o.getName()) && this.getNumber() == o.getPort()) {
return 0;
}
return (int) (id - o.id);
}
最佳答案
如果可以的话，我会投票关闭这个无法编译且不完整的示例，但由于它有赏金，所以我不能。您引用了一个不包含源代码的 dao 对象。你调用doa.save，这是一个Spring问题吗？否则，您的实体没有任何问题，这对我来说一切都很好。
public class JPAExample {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("persistence");
EntityManager em = emf.createEntityManager();
try {
EntityTransaction tx = em.getTransaction();
tx.begin();
Simple simple = new Simple();
Map<String, String> myMap = new HashMap<String,String>();
myMap.put("value","value");
MyComplexClass myComplexClass = new MyComplexClass("a", 123, myMap);
Set<MyComplexClass> myComplexClassList = new HashSet<MyComplexClass>();
myComplexClassList.add(myComplexClass);
simple.setMyComplexClass(myComplexClassList);
myComplexClass.setSimple(simple);
// save to the database
em.persist(simple);
tx.commit();
} finally {
emf.close();
}
}
}
简单类
@Entity
@Table(name = "Simple")
public class Simple implements Serializable {
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy = GenerationType.IDENTITY) Long id;
// @JsonProperty
@OneToMany(mappedBy = "simple", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
Set<MyComplexClass> myComplexClass;
public void setMyComplexClass(Set<MyComplexClass> myComplexClass) {
this.myComplexClass = myComplexClass;
}
public Set<MyComplexClass> getMyComplexClass() {
return this.myComplexClass;
}
}
我的复杂类
@Entity
@Table(name="MyComplexClass")
public class MyComplexClass implements Serializable {
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy = GenerationType.IDENTITY) Long id;
String name;
int number;
@ElementCollection
Map<String,String> myMap;
@ManyToOne
Simple simple;
public MyComplexClass(String name, int number, Map<String,String> myMap) {
this.name = name;
this.myMap = myMap;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setMyMap(Map<String,String> myMap) {
this.myMap = myMap;
}
public Map<String,String> getMyMap() {
return this.myMap;
}
public Simple getSimple() {
return this.simple;
}
public void setSimple(Simple simple ) {
this.simple = simple;
}
}
产生以下输出...
Hibernate: create table MyComplexClass (id bigint generated by default as identity (start with 1), name varchar(255), number integer not null, simple_id bigint, primary key (id))
Hibernate: create table MyComplexClass_myMap (MyComplexClass_id bigint not null, myMap varchar(255), myMap_KEY varchar(255), primary key (MyComplexClass_id, myMap_KEY))
Hibernate: create table Simple (id bigint generated by default as identity (start with 1), primary key (id))
Hibernate: alter table MyComplexClass add constraint FK_qlkwvh7xyrn3udhnrn40fl6f8 foreign key (simple_id) references Simple
Hibernate: alter table MyComplexClass_myMap add constraint FK_qp5xa90y7pk94lb64kvt62589 foreign key (MyComplexClass_id) references MyComplexClass
Jun 12, 2017 10:06:56 AM org.hibernate.tool.hbm2ddl.SchemaExport execute
INFO: HHH000230: Schema export complete
Hibernate: insert into Simple (id) values (default)
Hibernate: insert into MyComplexClass (id, name, number, simple_id) values (default, ?, ?, ?)
Hibernate: insert into MyComplexClass_myMap (MyComplexClass_id, myMap_KEY, myMap) values (?, ?, ?)
Jun 12, 2017 10:06:56 AM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:hsqldb:mem:standalone]
这仅显示插入到 MyComplexClass 表中的一行。
您可以复制此代码并使用它来找出代码的问题所在。
关于hibernate - 为什么 OneToMany 关系会保存在数据库的多行中，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44461194/