Hibernate之关于多对多单向关联映射

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【Hibernate】之关于多对多单向关联映射

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，ok！

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