无法演示Hibernate自定义ID生成类型的演示

Question

我对学生实体的主键给出了以下注释-

package com.luv2code.hibernate.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

import org.hibernate.annotations.GenericGenerator;

@Entity
public class Student {

    @Id
    @GenericGenerator(name="my_custom",strategy = "com.luv2code.hibernate.demo.MyGenerator")
    @GeneratedValue(generator="my_custom")
    @Column(name="id")
    private String id;

    @Column(name="first_name")
    private String firstName;


    @Column(name="last_name")
    private String lastName;

    private String email;

    public Student() {

    }


    public Student(String firstName, String lastName, String email) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.email = email;
    }

    public String getId() {
        return id;
    }

    public void setId(String 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 String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email + "]";
    }



}

如果仅将以下硬编码字符串作为自定义生成的返回值，则会收到以下错误-

package com.luv2code.hibernate.demo;

import java.io.Serializable;
import java.sql.Connection;

import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.IdentifierGenerator;

public class MyGeneratorNew implements IdentifierGenerator {

private String prefix="prefix_";

@Override
public Serializable generate(SharedSessionContractImplementor session, Object arg1) throws HibernateException {
Connection conn = session.connection();

/*try {
Statement stm = conn.createStatement();
ResultSet rs = stm.executeQuery("select count(id) as Id from Student");

if(rs.next()) {
//int id = rs.getInt(1);
String generatedID = prefix; // + new Integer(id).toString();
return generatedID;
}
}
catch(Exception e) {
e.printStackTrace();
}
return null;*/

return prefix;
}

}

错误-

ERROR: Incorrect integer value: 'prefix_' for column 'id' at row 1
javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: could not execute statement
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)
at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1364)
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:451)
at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3210)
at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2378)
at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:447)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:183)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$300(JdbcResourceLocalTransactionCoordinatorImpl.java:40)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:281)
at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:101)
at com.luv2code.hibernate.demo.HibernateStudentDemo.main(HibernateStudentDemo.java:23)
Caused by: org.hibernate.exception.GenericJDBCException: could not execute statement
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:47)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:200)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3238)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3763)
at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:107)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:604)
at org.hibernate.engine.spi.ActionQueue.lambda$executeActions$1(ActionQueue.java:478)
at org.hibernate.engine.spi.ActionQueue$$Lambda$66/1791589252.accept(Unknown Source)
at java.util.LinkedHashMap.forEach(LinkedHashMap.java:676)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:475)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:348)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:40)
at org.hibernate.internal.SessionImpl$$Lambda$62/168468389.accept(Unknown Source)
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102)
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1360)
... 9 more
Caused by: java.sql.SQLException: Incorrect integer value: 'prefix_' for column 'id' at row 1
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347)
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:197)
... 22 more

谢谢！