Question

我正在尝试使用Hibernate更新表中的记录，但是记录没有更新，并且在下次执行时需要花费很多时间并引发以下错误：Exception in thread "main" org.hibernate.exception.LockAcquisitionException: could not execute statement

员工：

    import javax.persistence.CascadeType;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.OneToOne;
    import javax.persistence.Table;

    import org.hibernate.annotations.*;

    @Entity
    @Table(name = "Emp_Table")
    public class Employee {
        @Id
        @GeneratedValue
        private int id;
        private String name;
        private double salary;

        @OneToOne(mappedBy = "emp")
        @Cascade(value = org.hibernate.annotations.CascadeType.ALL)
        private Address addr;

        /* Getter-Setter methods */
    }

地址：

    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import javax.persistence.OneToOne;
    import javax.persistence.PrimaryKeyJoinColumn;
    import javax.persistence.Table;

    import org.hibernate.annotations.GenericGenerator;
    import org.hibernate.annotations.Parameter;

    @Entity
    @Table(name = "Addr_Table")
    public class Address {

        @Id
        @Column(name = "eid")
        @GeneratedValue(generator = "gen")
        @GenericGenerator(name = "gen", strategy = "foreign", parameters = {@Parameter(name = "property", value = "emp")})
        private int id;
        private String state;
        private String country;

        @OneToOne
        @PrimaryKeyJoinColumn
        private Employee emp;

        /* Getter-Setter methods */
    }

HQLExample 包含CRUD操作。

package com.Hibernate.Main;

import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.Hibernate.Model.Employee;
import com.Hibernate.Util.HibernateUtil;

public class HQLExample {

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {

        SessionFactory factory = new Configuration().configure().buildSessionFactory();
        Session session = factory.openSession();

        Transaction tx = session.beginTransaction();
        Query query = session.createQuery("from Employee");
        List<Employee> emp = query.list();
        for (Employee empList : emp) {
            System.out.println("\nID:\t" + empList.getId() + "\nName:\t" + empList.getName() + "\nSalary:\t"
                    + empList.getSalary());
        }

        Query query1 = session.createQuery("from Employee where id = :id");
        query1.setInteger("id", 2);
        Employee empList = (Employee) query1.uniqueResult();
        System.out.println(
                "\nID:\t" + empList.getId() + "\nName:\t" + empList.getName() + "\nSalary:\t" + empList.getSalary());


        Query query2 = session.createQuery("from Employee");
        query2.setFirstResult(1);
        query2.setFetchSize(1);
        emp = query2.list();
        for (Employee empList1 : emp) {
            System.out.println("\nID:\t" + empList1.getId() + "\nName:\t" + empList1.getName() + "\nSalary:\t"
                    + empList1.getSalary());
        }

        query = session.createQuery("update Employee set name = :name where id = :id");
        query.setParameter("name", "Gaurav");
        query.setInteger("id", 2);
        int result = query.executeUpdate();
        System.out.println("\n\nEmployee updated successfully: "+result);



        query = session.createQuery("delete from Employee where id: eid");
        query.setInteger("eid", 4);
        result = query.executeUpdate();
        System.out.println("Employee deleted successfully "+ result);*/
    }
}

我能够检索记录，但在更新记录期间，它要么不更新记录，要么花费很长时间并抛出错误：线程“main”中的异常org.hibernate.exception.LockAcquisitionException：无法执行语句。

使用命令 show processlist ，我试图在睡眠模式下杀死进程。在杀死这些进程后，我能够执行更新语句，但它不会反映到数据库中。当试图再次执行代码时，将进行长时间运行并失败。

hibernate.cfg.xml中：

<?xml version="1.0" encoding="utf-8"?>
 <!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root.123</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/Hibernate</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.current_session_context_class">thread</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <property name="hibernate.show_sql">true</property>
        <mapping class="com.Hibernate.Model.Address"></mapping>
        <mapping class="com.Hibernate.Model.Employee"></mapping>
    </session-factory>
</hibernate-configuration>

Answer 1

您必须提交事务以将修改保存到数据库。您还必须关闭会话和会话工厂。如果您没有关闭资源，则意味着代码将锁定数据库中的记录。

我还在删除查询中发现了语法错误。以下是您可以执行的更改，以使代码正常工作。

{
    $group: {
        _id: "$month",
        total: { $sum: 1 },
        total_canceled: { $sum: { $cond: [{ $eq: ['cancelled_flights', true] }, 1, 0] } }
        total_non_canceled: { $sum: { $cond: [{ $eq: ['cancelled_flights', false] }, 1, 0] } }
    }
},

线程“main”中的异常org.hibernate.exception.LockAcquisitionException：无法执行语句

1 个答案: