我有两张桌子 - 学生和地址。他们有一对多的关系。学生实体正在收集地址实体。当我更新学生的地址集合时。它没有更新数据并给出此错误。当我使用子集合更新父实体时，它接下来是增量键，而不在数据库中。 -
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not execute statement
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:129)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:124)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:109)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:189)
at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:59)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3079)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3521)
at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:88)
at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:395)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:387)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:303)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:349)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:56)
at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1195)
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:404)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175)
at com.HibernateExample.test.HibernateTest.main(HibernateTest.java:51)
Caused by: org.postgresql.util.PSQLException: ERROR: insert or update on table "address" violates foreign key constraint "student_fk"
Detail: Key (id)=(5) is not present in table "student".
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2476)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2189)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:300)
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:428)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:354)
at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:169)
at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:136)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:186)
... 14 more
Student.java
public class Student {
public int id;
public String firstName;
public String lastName;
public int age;
public Set<Address> address = new HashSet<>(0);
public Set<Address> getAddress() {
return address;
}
public void setAddress(Set<Address> address) {
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Address.java
public class Address {
public int id;
public String streetName;
public String cityName;
public String stateName;
public String plotNo;
public Student student;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getStreetName() {
return streetName;
}
public void setStreetName(String streetName) {
this.streetName = streetName;
}
public String getCityName() {
return cityName;
}
public void setCityName(String cityName) {
this.cityName = cityName;
}
public String getStateName() {
return stateName;
}
public void setStateName(String stateName) {
this.stateName = stateName;
}
public String getPlotNo() {
return plotNo;
}
public void setPlotNo(String plotNo) {
this.plotNo = plotNo;
}
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
}
HibernateTest.java
public class HibernateTest {
public static void main(String[] args) {
Configuration configuration = new Configuration();
configuration.configure("hibernate-cfg.xml");
@SuppressWarnings("deprecation")
SessionFactory sessionFactory = configuration.buildSessionFactory();
Session session = sessionFactory.openSession();
session.setFlushMode(FlushMode.COMMIT);
System.out.println(session.getFlushMode().name());
Transaction transaction = session.beginTransaction();
Student student = (Student) session.get(Student.class, 3);
Address address = new Address();
address.setStateName("Kerala");
address.setCityName("Old Delhi");
address.setStreetName("Uttaam Nagar");
address.setPlotNo("158A");
address.setStudent(student);
student.getAddress().add(address);
session.update(student);
transaction.commit();
session.close();
sessionFactory.close();
}
}
address.hbm.xml
<hibernate-mapping>
<class name="com.HibernateExample.entity.Address" table="address">
<meta attribute="class-description">
This class contains the address detail.
</meta>
<id name="id" type="int" column="id">
<generator class="increment" />
</id>
<property name="streetName" column="street_name" type="string"/>
<property name="cityName" column="city_name" type="string"/>
<property name="stateName" column="state_name" type="string"/>
<property name="plotNo" column="plot_no" type="string"/>
<many-to-one name="student" class="com.HibernateExample.entity.Student" >
<column name="student_id" not-null="true"></column>
</many-to-one>
</class>
</hibernate-mapping>
student.hbm.xml
<hibernate-mapping>
<class name="com.HibernateExample.entity.Student" table="student">
<meta attribute="class-description">
This class contains the student detail.
</meta>
<id name="id" type="int" column="id">
<generator class="increment" />
</id>
<property name="firstName" column="first_name" type="string" length="40" />
<property name="lastName" column="last_name" type="string" length="40" />
<property name="age" column="age" type="int"/>
<set name="address" cascade="all">
<key column="student_id"/>
<one-to-many class="com.HibernateExample.entity.Address"/>
</set>
</class>
</hibernate-mapping>
答案 0 :(得分：2)
从Session javadoc开始，Session.update()被指定用于分离的实体实例。 “如果存在具有相同标识符的持久化实例，则抛出异常。”确切地说，未指定哪个异常，并且级联可能会将其发送到复杂的代码路径，这可能会导致此错误。
您修改的Student对象不是分离，而是持久，因为您是通过从Session加载并且没有关闭了Session或做了任何会分离它的事情。这意味着对它的所有修改都会自动保存到数据库中，而无需在Session上进行任何手动调用。这在Session的类javadoc中指定，其句子“在刷新时检测到对持久化实例的更改，并导致SQL更新。”
只需删除行session.update(student);，我认为您的代码将开始工作，包括在提交事务时通过级联关系保存新地址。
自从我使用级联以来已经有一段时间了，所以我不完全确定，但你可能还需要在关系的另一端设置级联。
答案 1 :(得分：0)
“student_id”与您的任何主键都没有关联。如果学生和地址表中都存在“student_id”，则将学生映射文件中的此行从“id”更改为“student_id”：
<id name="id" type="int" column="student_id">
答案 2 :(得分：0)
使用数据库表查看器/浏览器仔细检查数据库表。 您似乎尝试插入数据库中已存在的ID（5）