一．hibernate多對(duì)多映射（單項(xiàng)），自動(dòng)產(chǎn)生第三張表
User--à Role
user(id,name) role(id,name)
User類：
private int id; private String name; private Set roles;
Role類：
private int id; private String name;
User.hbm.xml中：
<set name=”roles” table=”t_user_role”>
<key column=”userid” />
<many-to-many class=”com.Role” column=”roleid” />
</set>
這樣，hibernate會(huì)自動(dòng)產(chǎn)生中間表t_user_role(userid,roleid) 并且是復(fù)合主鍵，userid為t_user的外鍵，roleid為t_role的外鍵
二．hibernate多對(duì)多的存儲(chǔ)
Role r1 = new Role();
r1.setName(“數(shù)據(jù)錄入人員”);
Role r2 = new Role();
r2.setName(“商務(wù)主管”);
Role r3 = new Role();
r3.setName(“大區(qū)經(jīng)理”);
User u1 = new User();
u1.setName(“10”);
Set u1Roles = new HashSet();
u1Roles.add(r1);
u1Roles.add(r2);
u1.setRoles(u1Roles);
User u2 = new User();
u1.setName(“祖兒”);
Set u2Roles = new HashSet();
u2Roles.add(r2);
u2Roles.add(r3);
u2.setRoles(u2Roles);
User u3 = new User();
u3.setName(“杰倫”);
Set u3Roles = new HashSet();
u3Roles.add(r1);
u3Roles.add(r2);
u3Roles.add(r3);
u3.setRoles(u3Roles);
session.save(r1);
session.save(r2);
session.save(r3);
session.save(u1);
session.save(u2);
session.save(u3);
結(jié)束之后，在第三張表中也有數(shù)據(jù)
三．hibernate多對(duì)多的加載
User user = (User)session.load(User.class,1);
System.out.println(user.getName());
for(Iterator iter = user.getRoles().iterator();iter.hasNext();){
Role role = (Role)iter.next();
System.out.println(role.getName());
}
每次加載都會(huì)發(fā)出sql語(yǔ)句
三．hibernate多對(duì)多的 雙向映射
User ß--.-àRole
user(id,name) role(id,name)
User類：
private int id; private String name; private Set roles;
Role類：
private int id; private String name; private Set users;
User.hbm.xml中：
<set name=”roles” table=”t_user_role”>
<key column=”userid” />
<many-to-many class=”com.Role” column=”roleid” />
</set>
Role.hbm.xml中：
<set name=”roles” table=”t_user_role”> //這里可以設(shè)置order-by=”userid”,根據(jù)userid排序
<key column=”roleid” />
<many-to-many class=”com.User” column=”userid” />
</set>
注意，上面中間表名字是一樣的
這樣，hibernate也會(huì)自動(dòng)產(chǎn)生中間表t_user_role(userid,roleid) 并且是復(fù)合主鍵，userid為t_user的外鍵，roleid為t_role的外鍵