hibernate------对象关系映射

一、一对多(单向)

1.一对多单向关联中的一方

 1 package com.zhidi.entity.one2many;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 /**
 7  * 一对多关单向关联关系中的->一方
 8  * 
 9  * @author lx
10  *
11  */
12 public class Dept {
13 
14     private Integer deptno;
15     private String dname;
16     private String loc;
17     // 需要持有多方的引用
18     private Set<Emp> emps = new HashSet<Emp>();
19 
20     public Integer getDeptno() {
21         return deptno;
22     }
23 
24     public void setDeptno(Integer deptno) {
25         this.deptno = deptno;
26     }
27 
28     public String getDname() {
29         return dname;
30     }
31 
32     public void setDname(String dname) {
33         this.dname = dname;
34     }
35 
36     public String getLoc() {
37         return loc;
38     }
39 
40     public void setLoc(String loc) {
41         this.loc = loc;
42     }
43 
44     public Set<Emp> getEmps() {
45         return emps;
46     }
47 
48     public void setEmps(Set<Emp> emps) {
49         this.emps = emps;
50     }
51 
52 }

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2.一对多单向关联中的多方

 1 package com.zhidi.entity.one2many;
 2 
 3 import java.util.Date;
 4 
 5 /**
 6  * 一对多关单向关联关系中的->多方
 7  * 
 8  * @author lx
 9  *
10  */
11 public class Emp {
12 
13     private Integer empno;
14     private String ename;
15     private String job;
16     private Integer mgr;
17     private Double sal;
18     private Date hiredate;
19 
20     public Integer getEmpno() {
21         return empno;
22     }
23 
24     public void setEmpno(Integer empno) {
25         this.empno = empno;
26     }
27 
28     public String getEname() {
29         return ename;
30     }
31 
32     public void setEname(String ename) {
33         this.ename = ename;
34     }
35 
36     public String getJob() {
37         return job;
38     }
39 
40     public void setJob(String job) {
41         this.job = job;
42     }
43 
44     public Integer getMgr() {
45         return mgr;
46     }
47 
48     public void setMgr(Integer mgr) {
49         this.mgr = mgr;
50     }
51 
52     public Double getSal() {
53         return sal;
54     }
55 
56     public void setSal(Double sal) {
57         this.sal = sal;
58     }
59 
60     public Date getHiredate() {
61         return hiredate;
62     }
63 
64     public void setHiredate(Date hiredate) {
65         this.hiredate = hiredate;
66     }
67 
68 }

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3.文件配置

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC 
 3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4     "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 5 <hibernate-mapping package="com.zhidi.entity.one2many" >
 6     <class name="Dept" table="dept">
 7         <id name="deptno">
 8             <generator class="native"/>
 9         </id>
10         <property name="dname"/>
11         <property name="loc"/>
12         <!-- 配置一对多 -->
13         <!-- cascade：设置级联操作 -->
14         <set name="emps" cascade="save-update,delete,delete-orphan">
15             <!-- 配置外键字段名 -->
16             <key column="deptno"/>
17             <!-- 指定一对多关系的关联对象的类型 -->
18             <one-to-many class="Emp"/>
19         </set>
20     </class>
21 </hibernate-mapping>

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 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC 
 3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4     "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 5 <hibernate-mapping package="com.zhidi.entity.one2many">
 6     <class name="Emp" table="emp">
 7         <id name="empno">
 8             <generator class="native" />
 9         </id>
10         <property name="ename" />
11         <property name="job" />
12         <property name="mgr" />
13         <property name="sal" />
14         <property name="hiredate" type="date" />
15     </class>
16 </hibernate-mapping>

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4.cfg核心配置(一下所有的都不写，包含在这里面)

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC
 3     "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 4     "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
 5 <hibernate-configuration>
 6     <session-factory>
 7         <!-- 为session工厂添加一些基础配置 -->
 8         <!-- 驱动名称 -->
 9         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
10         <!-- url -->
11         <property name="connection.url">jdbc:mysql://localhost:3306/db_hibernate</property>
12         <!-- 用户名 -->
13         <property name="connection.username">root</property>
14         <!-- 密码 -->
15         <property name="connection.password">root</property>
16         
17         <!-- 可以添加一些其他配置 -->
18         <!-- 设置方言 -->
19         <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
20         <property name="pool_size">1</property>
21         <!-- 配置session -->
22         <property name="current_session_context_class">thread</property>
23         <!-- 打印sql语句 -->
24         <property name="show_sql">false</property>
25         <!-- 格式化sql -->
26         <property name="format_sql">true</property>
27         
28         <!-- <mapping resource="com/zhidi/entity/many2one/Emp.hbm.xml"/>
29         <mapping resource="com/zhidi/entity/many2one/Dept.hbm.xml"/> -->
30         
31         <!-- <mapping resource="com/zhidi/entity/one2many/Emp.hbm.xml"/>
32         <mapping resource="com/zhidi/entity/one2many/Dept.hbm.xml"/> -->
33         
34         <mapping resource="com/zhidi/entity/one2many/bothway/Emp.hbm.xml"/>
35         <mapping resource="com/zhidi/entity/one2many/bothway/Dept.hbm.xml"/>
36         
37         <mapping resource="com/zhidi/entity/many2many/Student.hbm.xml"/>
38         <mapping resource="com/zhidi/entity/many2many/Course.hbm.xml"/>
39         
40     </session-factory>
41 </hibernate-configuration>

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二、一对多(双向)

1.一对多关双向关联关系中的->一方

 1 package com.zhidi.entity.one2many.bothway;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 /**
 7  * 一对多关双向关联关系中的->一方
 8  * 
 9  * @author lx
10  *
11  */
12 public class Dept {
13 
14     private Integer deptno;
15     private String dname;
16     private String loc;
17     // 需要持有多方的引用
18     private Set<Emp> emps = new HashSet<Emp>();
19 
20     public Integer getDeptno() {
21         return deptno;
22     }
23 
24     public void setDeptno(Integer deptno) {
25         this.deptno = deptno;
26     }
27 
28     public String getDname() {
29         return dname;
30     }
31 
32     public void setDname(String dname) {
33         this.dname = dname;
34     }
35 
36     public String getLoc() {
37         return loc;
38     }
39 
40     public void setLoc(String loc) {
41         this.loc = loc;
42     }
43 
44     public Set<Emp> getEmps() {
45         return emps;
46     }
47 
48     public void setEmps(Set<Emp> emps) {
49         this.emps = emps;
50     }
51 
52 }

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2.一对多关单向关联关系中的->多方

 1 package com.zhidi.entity.one2many.bothway;
 2 
 3 import java.util.Date;
 4 
 5 /**
 6  * 一对多关单向关联关系中的->多方
 7  * 
 8  * @author lx
 9  *
10  */
11 public class Emp {
12 
13     private Integer empno;
14     private String ename;
15     private String job;
16     private Integer mgr;
17     private Double sal;
18     private Date hiredate;
19     private Dept dept;
20 
21     public Integer getEmpno() {
22         return empno;
23     }
24 
25     public void setEmpno(Integer empno) {
26         this.empno = empno;
27     }
28 
29     public String getEname() {
30         return ename;
31     }
32 
33     public void setEname(String ename) {
34         this.ename = ename;
35     }
36 
37     public String getJob() {
38         return job;
39     }
40 
41     public void setJob(String job) {
42         this.job = job;
43     }
44 
45     public Integer getMgr() {
46         return mgr;
47     }
48 
49     public void setMgr(Integer mgr) {
50         this.mgr = mgr;
51     }
52 
53     public Double getSal() {
54         return sal;
55     }
56 
57     public void setSal(Double sal) {
58         this.sal = sal;
59     }
60 
61     public Date getHiredate() {
62         return hiredate;
63     }
64 
65     public void setHiredate(Date hiredate) {
66         this.hiredate = hiredate;
67     }
68 
69     public Dept getDept() {
70         return dept;
71     }
72 
73     public void setDept(Dept dept) {
74         this.dept = dept;
75     }
76 
77 }

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3.文件配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.one2many.bothway" >
    <class name="Dept" table="dept">
        <id name="deptno">
            <generator class="native"/>
        </id>
        <property name="dname"/>
        <property name="loc"/>
        <!-- 配置一对多 -->
        <!-- inverse：代表由谁来维护两者之间的关系，为false时，由当前实体维护对应关系
            inverse=true，代表有对方来维护关系
         -->
        <set name="emps" inverse="true">
            <!-- 配置外键字段名 -->
            <key column="deptno"/>
            <!-- 指定一对多关系的关联对象的类型 -->
            <one-to-many class="Emp"/>
        </set>
    </class>
</hibernate-mapping>

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.one2many.bothway">
    <class name="Emp" table="emp">
        <id name="empno">
            <generator class="native"/>
        </id>
        <property name="ename"/>
        <property name="job"/>
        <property name="mgr"/>
        <property name="sal"/>
        <!-- 当java中的类型对一数据库中的类型有多个时，需要明确指定其hibernate类型是什么 -->
        <property name="hiredate" type="date"/>
        <!-- 多对一 -->
        <many-to-one name="dept" column="deptno" class="Dept" cascade="save-update"/>
    </class>
</hibernate-mapping>

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三、多对一

1.多对一关单向关联关系中的->一方

package com.zhidi.entity.many2one;

public class Dept {

    private Integer deptno;
    private String dname;
    private String loc;

    public Integer getDeptno() {
        return deptno;
    }

    public void setDeptno(Integer deptno) {
        this.deptno = deptno;
    }

    public String getDname() {
        return dname;
    }

    public void setDname(String dname) {
        this.dname = dname;
    }

    public String getLoc() {
        return loc;
    }

    public void setLoc(String loc) {
        this.loc = loc;
    }

}

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2.多对一关单向关联关系中的->多方

package com.zhidi.entity.many2one;

import java.util.Date;

/**
 * 多对一关单向关联关系中的->多方
 * 
 * @author lx
 *
 */
public class Emp {

    private Integer empno;
    private String ename;
    private String job;
    private Integer mgr;
    private Double sal;
    private Date hiredate;

    // 提供类型为Dept的成员变量
    private Dept dept;

    public Integer getEmpno() {
        return empno;
    }

    public void setEmpno(Integer empno) {
        this.empno = empno;
    }

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }

    public Integer getMgr() {
        return mgr;
    }

    public void setMgr(Integer mgr) {
        this.mgr = mgr;
    }

    public Double getSal() {
        return sal;
    }

    public void setSal(Double sal) {
        this.sal = sal;
    }

    public Date getHiredate() {
        return hiredate;
    }

    public void setHiredate(Date hiredate) {
        this.hiredate = hiredate;
    }

    public Dept getDept() {
        return dept;
    }

    public void setDept(Dept dept) {
        this.dept = dept;
    }

}

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3.文件配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.many2one" >
    <class name="Dept" table="dept">
        <id name="deptno">
            <generator class="native"/>
        </id>
        <property name="dname"/>
        <property name="loc"/>
    </class>
</hibernate-mapping>

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.many2one">
    <class name="Emp" table="emp">
        <id name="empno">
            <generator class="native"/>
        </id>
        <property name="ename"/>
        <property name="job"/>
        <property name="mgr"/>
        <property name="sal"/>
        <property name="hiredate" type="date"/>
        
        <!-- 维护关系 -->
        <!-- cascade="save-update":设置级联保存 -->
        <many-to-one name="dept" column="deptno" class="Dept" cascade="save-update"/>
    </class>
</hibernate-mapping>

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4.测试

package com.zhidi.entity.many2one;

import java.util.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;

public class Test {

    public static void main(String[] args) {
        Configuration cfg = new Configuration().configure();
        SessionFactory sessionFactory = cfg
                .buildSessionFactory(new StandardServiceRegistryBuilder().applySettings(cfg.getProperties()).build());
        
        //获取session
        Session session = sessionFactory.getCurrentSession();
        //开启事务
        session.beginTransaction();
        
        Emp emp = new Emp();
        emp.setEname("肖");
        emp.setJob("主播");
        emp.setSal(10000.0);
        emp.setHiredate(new Date());
        
        Dept dept = new Dept();
        dept.setDname("斗鱼");
        dept.setLoc("武汉");
        
        //添加关联
        emp.setDept(dept);
        
        //执行保存操作
        //没有设置级联保存的情况下，要注意保存顺序，否则会出现多余的sql语句用来维护关联关系
        //设置了级联保存，就只需要保存维护关系的一方
        session.save(emp);
//        session.save(dept);
        
        session.getTransaction().commit();
    }

}

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四、多对多

1.多对多的多方

package com.zhidi.entity.many2many;

import java.util.HashSet;
import java.util.Set;

public class Course {

    private Integer id;
    private String name;

    // 学生集合
    private Set<Student> students = new HashSet<Student>();

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<Student> getStudents() {
        return students;
    }

    public void setStudents(Set<Student> students) {
        this.students = students;
    }

}

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2.多对多的多方

package com.zhidi.entity.many2many;

import java.util.HashSet;
import java.util.Set;

public class Student {
    
    private Integer id;
    private String name;
    private String sex;
    
    //课程
    private Set<Course> courses = new HashSet<Course>();

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Set<Course> getCourses() {
        return courses;
    }

    public void setCourses(Set<Course> courses) {
        this.courses = courses;
    }
    
    

}

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3.文件配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.many2many">
    <class name="Course" table="tb_courses">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <!-- 当指定set元素的table属性时，会将关系维护到指定表中 -->
        <set name="students" table="tb_students_courses">
            <!-- 指定当前表在中间表的外键 -->
            <key column="cou_id"/>
            <!-- 指定关系表中的外键，以及关系表的类型 -->
            <many-to-many column="stu_id" class="Student"/>
        </set>
    </class>
</hibernate-mapping>

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zhidi.entity.many2many">
    <class name="Student" table="tb_students">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <property name="sex"/>
        <!-- 关系 -->
        <set name="courses" table="tb_students_courses">
            <key column="stu_id"/>
            <many-to-many column="cou_id" class="Course"/>
        </set>
    </class>
</hibernate-mapping>

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test

 1 package com.zhidi.test.base;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.SessionFactory;
 5 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 6 import org.hibernate.cfg.Configuration;
 7 import org.junit.After;
 8 import org.junit.AfterClass;
 9 import org.junit.Before;
10 import org.junit.BeforeClass;
11 
12 public class BaseTest {
13 
14     protected static SessionFactory sessionFactory;
15     protected Session session;
16 
17     @BeforeClass
18     public static void beforeClass() {
19         Configuration cfg = new Configuration().configure();
20         //初始化会话工厂
21         sessionFactory = cfg
22                 .buildSessionFactory(new StandardServiceRegistryBuilder().applySettings(cfg.getProperties()).build());
23     }
24     
25     @AfterClass
26     public static void afterClass() {
27         //如果会话工厂不为空，就关闭
28         if (sessionFactory != null) {
29             sessionFactory.close();
30         }
31     }
32     
33     @Before
34     public void beforeMethod() {
35         //获取session
36         session = sessionFactory.getCurrentSession();
37         session.beginTransaction();
38     }
39     
40     @After
41     public void afterMethod() {
42         //有存活的事务就提交
43         if (session.getTransaction().isActive()) {
44             session.getTransaction().commit();
45         }
46     }
47     
48     
49 }

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以上的测试

 1 package com.zhidi.test.retention;
 2 
 3 import org.junit.Test;
 4 
 5 import com.zhidi.entity.many2many.Course;
 6 import com.zhidi.entity.many2many.Student;
 7 import com.zhidi.test.base.BaseTest;
 8 
 9 public class TestMany2Many extends BaseTest{
10     
11     @Test
12     public void testSave() {
13         Student stu = new Student();
14         stu.setName("赵日天");
15         stu.setSex("男");
16         
17         Course course = new Course();
18         course.setName("马克思理论");
19         
20         course.getStudents().add(stu);
21 //        stu.getCourses().add(course);
22         
23         session.save(stu);
24         session.save(course);
25     }
26     
27     @Test
28     public void test() {
29         Student stu = (Student) session.get(Student.class, 2);
30         System.out.println(stu.getCourses());
31     }
32 
33 }

View Code

 1 package com.zhidi.test.retention;
 2 
 3 import org.junit.Test;
 4 
 5 import com.zhidi.entity.many2one.Emp;
 6 import com.zhidi.test.base.BaseTest;
 7 
 8 public class TestMany2One extends BaseTest {
 9     
10     @Test
11     public void test() {
12         //延迟加载
13         //查询员工
14         Emp emp = (Emp) session.get(Emp.class, 7958);
15         //在使用关联实体的非主键字段时，会发送sql语句查询出关联实体,关联属性要使用的时候才会去查询
16         System.out.println(emp.getDept().getDeptno());
17         
18         session.close();
19         
20         //延迟加载只能在session的生命周期之内
21         System.out.println(emp.getDept().getDname());
22         
23     }
24 
25 }

View Code

  1 package com.zhidi.test.retention;
  2 
  3 import java.util.Date;
  4 import java.util.Set;
  5 
  6 import org.junit.Test;
  7 
  8 import com.zhidi.entity.one2many.Dept;
  9 import com.zhidi.entity.one2many.Emp;
 10 import com.zhidi.test.base.BaseTest;
 11 
 12 public class TestOne2Many extends BaseTest {
 13 
 14     /**
 15      * 没有设置级联保存，会有3条sql
 16      * insert emp ...
 17      * insert dept ...
 18      * update emp set deptno=? where empno=?
 19      */
 20     @Test
 21     public void testSave() {
 22         Emp emp = new Emp();
 23         emp.setEname("王尼玛");
 24         emp.setJob("逗比");
 25         emp.setSal(2000d);
 26         emp.setHiredate(new Date());
 27 
 28         Dept dept = new Dept();
 29         dept.setDname("暴漫");
 30         dept.setLoc("杭州");
 31         
 32         //关系由部门维护
 33         dept.getEmps().add(emp);
 34         
 35         session.save(dept);
 36         session.save(emp);
 37     }
 38     
 39     /**
 40      * cascade=save-update,只需要保存关系维护方
 41      */
 42     @Test
 43     public void testSave2() {
 44         Emp emp = new Emp();
 45         emp.setEname("张全蛋");
 46         emp.setJob("富土康员工");
 47         emp.setSal(800d);
 48         emp.setHiredate(new Date());
 49 
 50         Dept dept = new Dept();
 51         dept.setDname("暴漫");
 52         dept.setLoc("杭州");
 53         
 54         //关系由部门维护
 55         dept.getEmps().add(emp);
 56         
 57         session.save(dept);
 58     }
 59     
 60     /**
 61      * 在没有cascade=delete时，删除主表数据会执行以下操作
 62      * 1.update emp set deptno=null where ename=?
 63      * 2.delete from dept where deptno=?
 64      */
 65     @Test
 66     public void testDelete() {
 67         Dept dept = (Dept) session.get(Dept.class, 91);
 68         session.delete(dept);
 69     }
 70     
 71     /**
 72      * 设置cascade=delete
 73      * 设置了级联删除
 74      */
 75     @Test
 76     public void testDelete2() {
 77         Dept dept = (Dept) session.get(Dept.class, 90);
 78         session.delete(dept);
 79     }
 80     
 81     /**
 82      * 没有设置cascade=delete-orphan，
 83      * 直接解除关系，但是不会删除数据
 84      */
 85     @Test
 86     public void testRemove() {
 87         Dept dept = (Dept) session.get(Dept.class, 89);
 88         Set<Emp> emps = dept.getEmps();
 89         for (Emp emp : emps) {
 90             dept.getEmps().remove(emp);
 91         }
 92     }
 93     
 94     /**
 95      * 设置cascade=delete-orphan，
 96      * 直接将解除关系的关联数据给删除掉
 97      */
 98     @Test
 99     public void testRemove2() {
100         Dept dept = (Dept) session.get(Dept.class, 82);
101         Set<Emp> emps = dept.getEmps();
102         for (Emp emp : emps) {
103             dept.getEmps().remove(emp);
104         }
105     }
106 }

View Code

 1 package com.zhidi.test.retention;
 2 
 3 import java.util.Calendar;
 4 
 5 import org.junit.Test;
 6 
 7 import com.zhidi.entity.one2many.bothway.Dept;
 8 import com.zhidi.entity.one2many.bothway.Emp;
 9 import com.zhidi.test.base.BaseTest;
10 
11 public class TestOne2ManyBothway extends BaseTest {
12 
13     /**
14      * inverse=false
15      */
16     @Test
17     public void testSave() {
18         Dept dept = new Dept();
19         dept.setDname("阿里妈妈");
20         dept.setLoc("杭州");
21         
22         Emp emp = new Emp();
23         emp.setEname("马云爸爸");
24         Calendar calendar = Calendar.getInstance();
25         calendar.set(1999, 0, 01);
26         emp.setHiredate(calendar.getTime());
27         emp.setSal(1234d);
28         
29         //添加依赖关系
30         emp.setDept(dept);
31         dept.getEmps().add(emp);
32         
33         //当inverse=false或不设置时，会有多余sql语句来维护两者之间的关系
34         session.save(dept);
35         session.save(emp);
36     }
37     
38     /**
39      * inverse=true,就不会产生多余的sql语句来维护对应关系
40      */
41     @Test
42     public void testSave2() {
43         Dept dept = new Dept();
44         dept.setDname("阿里妈妈");
45         dept.setLoc("杭州");
46         
47         Emp emp = new Emp();
48         emp.setEname("马云爸爸");
49         Calendar calendar = Calendar.getInstance();
50         calendar.set(1999, 0, 01);
51         emp.setHiredate(calendar.getTime());
52         emp.setSal(1234d);
53         
54         //添加依赖关系
55         emp.setDept(dept);
56 //        dept.getEmps().add(emp);
57         
58 //        session.save(dept);
59         session.save(emp);
60     }
61     
62     /**
63      * 现在关系是由员工来维护，所有部门解除依赖关系没有卵用
64      */
65     @Test
66     public void testRemove() {
67         Dept dept = (Dept) session.get(Dept.class, 103);
68         dept.getEmps().clear();
69     }
70     
71     @Test
72     public void testRemove2() {
73         Emp emp = (Emp) session.get(Emp.class, 7983);
74         //解除关系会保存到数据库
75         emp.setDept(null);
76     }
77 }

View Code

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原文地址：https://www.cnblogs.com/zclqian/p/7416761.html