Hibernate实战——继承映射之每个具体类对应一个表的映射策略

Love The Way You Lie 2021-07-24 12:27 302阅读 0赞

**一 配置文件**

<?xml version="1.0" encoding="GBK"?>
    
    <!DOCTYPE hibernate-configuration PUBLIC
         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
         <session-factory>
               
               <property  name="connection.driver_class">com.mysql.jdbc.Driver</property>
               
               <property  name="connection.url">jdbc:mysql://localhost/hibernate</property>
               
               <property name="connection.username">root</property>
               
               <property name="connection.password">32147</property>
               
               <property  name="hibernate.c3p0.max_size">20</property>
               
               <property name="hibernate.c3p0.min_size">1</property>
               
               <property  name="hibernate.c3p0.timeout">5000</property>
               
               <property  name="hibernate.c3p0.max_statements">100</property>
               <property  name="hibernate.c3p0.idle_test_period">3000</property>
               <property  name="hibernate.c3p0.acquire_increment">2</property>
               <property  name="hibernate.c3p0.validate">true</property>
               
               <property  name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
               
               <property name="hbm2ddl.auto">update</property>
               
               <property name="show_sql">true</property>
               
               <property name="hibernate.format_sql">true</property>
               
               <mapping class="org.crazyit.app.domain.Person"/>
               <mapping class="org.crazyit.app.domain.Customer"/>
               <mapping class="org.crazyit.app.domain.Employee"/>
               <mapping class="org.crazyit.app.domain.Manager"/>
         </session-factory>
    </hibernate-configuration>

**二 PO**

1 Address

package org.crazyit.app.domain;
    
    public class Address
    {
         // 定义代表该Address详细信息的成员变量
         private String detail;
         // 定义代表该Address邮编信息的成员变量
         private String zip;
         // 定义代表该Address国家信息的成员变量
         private String country;
         // 无参数的构造器
         public Address()
         {
         }
         // 初始化全部成员变量的构造器
         public Address(String detail , String zip , String  country)
         {
               this.detail = detail;
               this.zip = zip;
               this.country = country;
         }
         // detail的setter和getter方法
         public void setDetail(String detail)
         {
               this.detail = detail;
         }
         public String getDetail()
         {
               return this.detail;
         }
         // zip的setter和getter方法
         public void setZip(String zip)
         {
               this.zip = zip;
         }
         public String getZip()
         {
               return this.zip;
         }
         // country的setter和getter方法
         public void setCountry(String country)
         {
               this.country = country;
         }
         public String getCountry()
         {
               return this.country;
         }
    }

2 Person

package org.crazyit.app.domain;
    
    import javax.persistence.*;
    import org.hibernate.annotations.GenericGenerator;
    
    @Entity
    // 指定使用每个具体类对应一张表的映射策略
    @Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
    @Table(name="person_inf")
    public class Person
    {
        // 标识属性
        @Id @Column(name="person_id")
        // 由于不能使用identity主键生成策略，故此处采用hilo主键生成策略
        @GenericGenerator(name="person_hilo" , strategy="hilo")
        @GeneratedValue(generator="person_hilo")
        private Integer id;
        private String name;
        private char gender;
        // 定义该Person实体的组件属性：address
        @Embedded
        @AttributeOverrides({
            @AttributeOverride(name="detail",
            column=@Column(name="address_detail")),
            @AttributeOverride(name="zip",
            column=@Column(name="address_zip")),
            @AttributeOverride(name="country",
            column=@Column(name="address_country"))
        })
        private Address address;
        // 无参数的构造器
        public Person(){}
        // 初始化全部成员变量的构造器
        public Person(Integer id , String name , char gender)
        {
            this.id = id;
            this.name = name;
            this.gender = gender;
        }
    
        // id的setter和getter方法
        public void setId(Integer id)
        {
            this.id = id;
        }
        public Integer getId()
        {
            return this.id;
        }
    
        // name的setter和getter方法
        public void setName(String name)
        {
            this.name = name;
        }
        public String getName()
        {
            return this.name;
        }
    
        // gender的setter和getter方法
        public void setGender(char gender)
        {
            this.gender = gender;
        }
        public char getGender()
        {
            return this.gender;
        }
    
        // address的setter和getter方法
        public void setAddress(Address address)
        {
            this.address = address;
        }
        public Address getAddress()
        {
            return this.address;
        }
    }

3 Employee

package org.crazyit.app.domain;
    
    import java.util.*;
    
    import javax.persistence.*;
    
    
    // 员工类继承了Person类
    @Entity
    @Table(name="employee_inf")
    public class Employee extends Person
    {
        // 定义该员工职位的成员变量
        private String title;
        // 定义该员工工资的成员变量
        private double salary;
        // 定义和该员工保持关联的Customer关联实体
        @OneToMany(cascade=CascadeType.ALL
            , mappedBy="employee" , targetEntity=Customer.class)
        private Set<Customer> customers
            = new HashSet<>();
        // 定义和该员工保持关联的Manager关联实体
        @ManyToOne(cascade=CascadeType.ALL
            ,targetEntity=Manager.class)
        @JoinColumn(name="manager_id", nullable=true)
        private Manager manager;
    
        // 无参数的构造器
        public Employee()
        {
        }
        // 初始化全部成员变量的构造器
        public Employee(String title , double salary)
        {
            this.title = title;
            this.salary = salary;
        }
    
        // title的setter和getter方法
        public void setTitle(String title)
        {
            this.title = title;
        }
        public String getTitle()
        {
            return this.title;
        }
    
        // salary的setter和getter方法
        public void setSalary(double salary)
        {
            this.salary = salary;
        }
        public double getSalary()
        {
            return this.salary;
        }
    
        // customers的setter和getter方法
        public void setCustomers(Set<Customer> customers)
        {
            this.customers = customers;
        }
        public Set<Customer> getCustomers()
        {
            return this.customers;
        }
    
        // manager的setter和getter方法
        public void setManager(Manager manager)
        {
            this.manager = manager;
        }
        public Manager getManager()
        {
            return this.manager;
        }
    }

4 Customer

package org.crazyit.app.domain;
    import javax.persistence.*;
    
    // 顾客类继承了Person类
    @Entity
    @Table(name="customer_inf")
    public class Customer extends Person
    {
         // 顾客的评论信息
         private String comments;
         // 定义和该顾客保持关联的Employee关联实体
         @ManyToOne(cascade=CascadeType.ALL
               ,targetEntity=Employee.class)
         @JoinColumn(name="employee_id", nullable=true)
         private Employee employee;
         // 无参数的构造器
         public Customer()
         {
         }
         // 初始化comments成员变量的构造器
         public Customer(String comments)
         {
               this.comments = comments;
         }
         // comments的setter和getter方法
         public void setComments(String comments)
         {
               this.comments = comments;
         }
         public String getComments()
         {
               return this.comments;
         }
         // employee的setter和getter方法
         public void setEmployee(Employee employee)
         {
               this.employee = employee;
         }
         public Employee getEmployee()
         {
               return this.employee;
         }
    }

5 Manager

package org.crazyit.app.domain;
    
    import javax.persistence.*;
    
    import java.util.Set;
    import java.util.HashSet;
    
    // 经理类继承员工类
    @Entity
    @Table(name="manager_inf")
    public class  Manager extends Employee
    {
        // 定义经理管辖部门的属性
        private String department;
        // 定义和该经理保持关联的Employee关联实体
        @OneToMany(cascade=CascadeType.ALL
            , mappedBy="manager" , targetEntity=Employee.class)
        private Set<Employee> employees
            = new HashSet<>();
        // 无参数的构造器
        public Manager()
        {
        }
        // 初始化全部成员变量的构造器
        public Manager(String department)
        {
            this.department = department;
        }
    
        // department的setter和getter方法
        public void setDepartment(String department)
        {
            this.department = department;
        }
        public String getDepartment()
        {
            return this.department;
        }
    
        // employees的setter和getter方法
        public void setEmployees(Set<Employee> employees)
        {
            this.employees = employees;
        }
        public Set<Employee> getEmployees()
        {
            return this.employees;
        }
    }

**三 测试**

1 工具类

package lee;
    
    import org.hibernate.*;
    import org.hibernate.cfg.*;
    import org.hibernate.service.*;
    import org.hibernate.boot.registry.*;
    
    public class HibernateUtil
    {
        public static final SessionFactory sessionFactory;
    
        static
        {
            try
            {
                // 使用默认的hibernate.cfg.xml配置文件创建Configuration实例
                Configuration cfg = new Configuration()
                    .configure();
                // 以Configuration实例来创建SessionFactory实例
                ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                    .applySettings(cfg.getProperties()).build();
                sessionFactory = cfg.buildSessionFactory(serviceRegistry);
            }
            catch (Throwable ex)
            {
                System.err.println("Initial SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }
        }
    
        // ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
        public static final ThreadLocal<Session> session
            = new ThreadLocal<Session>();
    
        public static Session currentSession()
            throws HibernateException
        {
            Session s = session.get();
            // 如果该线程还没有Session,则创建一个新的Session
            if (s == null)
            {
                s = sessionFactory.openSession();
                // 将获得的Session变量存储在ThreadLocal变量session里
                session.set(s);
            }
            return s;
        }
    
        public static void closeSession()
            throws HibernateException
        {
            Session s = session.get();
            if (s != null)
                s.close();
            session.set(null);
        }
    }

2 测试类

package lee;
    
    import org.hibernate.Transaction;
    import org.hibernate.Session;
    
    import java.util.*;
    
    import org.crazyit.app.domain.*;
    
    
    public class PersonManager
    {
        public static void main(String[] args)
        {
            PersonManager mgr = new PersonManager();
            mgr.createAndStorePerson();
            HibernateUtil.sessionFactory.close();
        }
    
        private void createAndStorePerson()
        {
            Session session = HibernateUtil.currentSession();
            Transaction tx = session.beginTransaction();
            // 创建一个普通员工
            Employee zhu = new Employee();
            // 设置员工的基本属性
            zhu.setName("老朱");
            zhu.setTitle("项目组长");
            zhu.setGender('男');
            zhu.setSalary(4500);
            // 设置员工的组件属性
            zhu.setAddress(new Address("广州","523034","中国"));
            // 创建第二个员工
            Employee zhang = new Employee();
            // 设置该员工的基本属性
            zhang.setName("张美丽");
            zhang.setTitle("项目分析");
            zhang.setGender('女');
            zhang.setSalary(5500);
            // 设置该员工的组件属性
            zhang.setAddress(new Address("广州","523034","中国"));
            // 创建一个经理对象
            Manager grace = new Manager();
            // 设置经理对象的基本属性
            grace.setName("Grace");
            grace.setTitle("项目经理");
            grace.setGender('女');
            grace.setSalary(12000);
            // 设置经理的组件属性
            grace.setAddress(new Address("加州" , "523034" , "美国"));
            // 设置经理的管辖部门属性
            grace.setDepartment("研发部");
            // 设置第二个员工和grace之间的关联关系
            zhang.setManager(grace);
            // 创建一个Customer对象
            Customer he = new Customer();
            // 设置Customer对象的基本属性
            he.setName("小贺");
            he.setGender('男');
            // 设置Customer对象的组件属性
            he.setAddress(new Address("湖南" , "233034" , "中国"));
            he.setComments("喜欢购物");
            // 建立Customer对象和grace对象的关联关系
            he.setEmployee(grace);
            // 创建一个普通Person对象
            Person lee = new Person();
            // 设置Person对象的基本属性
            lee.setName("crazyit.org");
            lee.setGender('男');
            // 设置Person对象的组件属性
            lee.setAddress(new Address("天河" , "434333" , "中国"));
            // 持久化所有实体。
            session.save(lee);
            session.save(grace);
            session.persist(zhu);
            session.persist(zhang);
            session.save(he);
            tx.commit();
            HibernateUtil.closeSession();
        }
    }

**四 运行**

Hibernate:
        select
            next_hi
        from
            hibernate_unique_key for update
                
    Hibernate:
        update
            hibernate_unique_key
        set
            next_hi = ?
        where
            next_hi = ?
    Hibernate:
        insert
        into
            person_inf
            (address_country, address_detail, address_zip, gender,  name, person_id)
        values
            (?, ?, ?, ?, ?, ?)
    Hibernate:
        insert
        into
            manager_inf
            (address_country, address_detail, address_zip, gender,  name, manager_id, salary, title, department, person_id)
        values
            (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
    Hibernate:
        insert
        into
            employee_inf
            (address_country, address_detail, address_zip, gender,  name, manager_id, salary, title, person_id)
        values
            (?, ?, ?, ?, ?, ?, ?, ?, ?)
    Hibernate:
        insert
        into
            employee_inf
            (address_country, address_detail, address_zip, gender,  name, manager_id, salary, title, person_id)
        values
            (?, ?, ?, ?, ?, ?, ?, ?, ?)
    Hibernate:
        insert
        into
            customer_inf
            (address_country, address_detail, address_zip, gender,  name, comments, employee_id, person_id)
        values
            (?, ?, ?, ?, ?, ?, ?, ?)

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