public class Emp {    private Integer nid;    private String empname;    Set<Project> pros=new HashSet<Project>();            public Emp() {        super();    }    public Emp(Integer nid, String empname) {        super();        this.nid = nid;        this.empname = empname;    }    public Integer getNid() {        return nid;    }    public void setNid(Integer nid) {        this.nid = nid;    }    public String getEmpname() {        return empname;    }    public void setEmpname(String empname) {        this.empname = empname;    }    public Set<Project> getPros() {        return pros;    }    public void setPros(Set<Project> pros) {        this.pros = pros;    }}

public class Project {    private int pid;    private String pname;    private Set<Emp> emps=new HashSet<Emp>();            public Project() {        super();    }    public Project(int pid, String pname) {        super();        this.pid = pid;        this.pname = pname;    }    public Set<Emp> getEmps() {        return emps;    }    public void setEmps(Set<Emp> emps) {        this.emps = emps;    }    public int getPid() {        return pid;    }    public void setPid(int pid) {        this.pid = pid;    }    public String getPname() {        return pname;    }    public void setPname(String pname) {        this.pname = pname;    }    }

<?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="cn.a.happy">     <class name="Emp" table="EMP">        <id name="nid" column="nid">        <!-- native   数据库方言的可移植性 -->           <generator class="native"></generator>        </id>        <property name="empname" type="string" column="empname"/>                <!-- 多对多 -->        <set name="pros" table="ProEmp" >            <key column="nid"/>    <!-- 在哪个配置，就写配置对应的主键 -->            <many-to-many class="Project" column="pid"/>    <!-- 对应多的一方成员类型 -->        </set>    </class></hibernate-mapping>

<?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="cn.a.happy">     <class name="Project" table="PROJECT">        <id name="pid" column="pid">           <generator class="native"></generator>        </id>        <property name="pname" type="string" column="pname"/>         <!-- 多对多                需要在<set>元素里 加一个table属性               table="生成第三张表的名字"         -->        <set name="emps" table="ProEmp" >            <key column="pid"/>    <!-- 在哪个配置，就写配置对应的主键 -->            <many-to-many class="Emp" column="nid"/>    <!-- 对应多的一方成员类型 -->        </set>            </class></hibernate-mapping>

/**         * 多对多双向关联测试         * 添加操作         */        @Test        public void muchVsMuchTest(){            Emp emp1=new Emp(1,"李睿智");            Emp emp2=new Emp(2,"小明");                                    Project project1=new Project(1,"一号项目");            Project project2=new Project(2,"二号项目");                        project1.getEmps().add(emp1);            project1.getEmps().add(emp2);                        project2.getEmps().add(emp1);                        session.save(project1);            session.save(project2);        }