Hibernate之关于多对多单向关联映射

【Hibernate】之关于多对多的单向关联映射

老师和学生，最典型的多对多关联，

Teacher和Student，所谓单向意思就是说，老师知道自己的教的是哪些学生而学生不知道是哪些老师教。也可以这么说，在查询的时候，通过老师可以级联查询出学生，但是通过学生不可以级联查询出老师！

而多对多最麻烦的是怎么自定义我们中间表的，表名和列名，这个是重要的！

Annotations配置

@Entity
@Table(name="t_teacher")
publicclass Teacher {
private Integer id;
private String name;
private Set<Student> students=new HashSet<Student>();//set不允许重复，最适合数据库模型
@Id
@GeneratedValue
public Integer getId() {
returnid;
}
publicvoid setId(Integerid) {
this.id = id;
}
@Column(name="t_name")
public String getName() {
returnname;
}
publicvoid setName(Stringname) {
this.name = name;
}
@ManyToMany
@JoinTable(name="t_s_two",//自定义表名
joinColumns={@JoinColumn(name="teacher_id")},//自定义列名
inverseJoinColumns={@JoinColumn(name="student_id")})//反转，和Teacher对应的那个表的列名，也是自定义
public Set<Student>getStudents() {
returnstudents;
}
publicvoidsetStudents(Set<Student> students) {
this.students = students;
}
}

@Entity
@Table(name="t_student")
publicclass Student {
private Integer id;
private String name;
private Integer age;
@Id
@GeneratedValue
public Integer getId() {
returnid;
}
publicvoid setId(Integerid) {
this.id = id;
}
@Column(name="s_name")
public String getName() {
returnname;
}
publicvoid setName(Stringname) {
this.name = name;
}
@Column(name="s_age")
public Integer getAge() {
returnage;
}
publicvoid setAge(Integerage) {
this.age = age;
}
}

XML配置

publicclass Teacher {
private Integer id;
private String name;
private Set<Student> students=newHashSet<Student>();//set不允许重复，最适合数据库模型
public Integer getId() {
returnid;
}
publicvoid setId(Integerid) {
this.id = id;
}
public String getName() {
returnname;
}
publicvoid setName(Stringname) {
this.name = name;
}
public Set<Student>getStudents() {
returnstudents;
}
publicvoidsetStudents(Set<Student> students) {
this.students = students;
}
}

publicclass Student {
private Integer id;
private String name;
private Integer age;
public Integer getId() {
returnid;
}
publicvoid setId(Integerid) {
this.id = id;
}
public String getName() {
returnname;
}
publicvoid setName(Stringname) {
this.name = name;
}
public Integer getAge() {
returnage;
}
publicvoid setAge(Integerage) {
this.age = age;
}
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="csg.hibernate.entity">
<class name="Teacher" table="t_teacher">
<id name="id">
<column name="id"/>
<generator class="native" />
</id>
<property name="name" />
<set name="students" table="t_s_two"><!—-自定义表名-->
<key column="teacher_id"/><!—自定义列名-->
<many-to-many class="csg.hibernate.entity.Student" column="student_id"/><!—自定义列名-->
</set>
</class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="csg.hibernate.entity">
<class name="Student" table="t_student">
<id name="id">
<column name="id"/>
<generator class="native" />
</id>
<property name="name" />
<property name="age" />
</class>
</hibernate-mapping>

以上就是XML的many-to-many(单向)的配置方法