hibernate多对多查询

下面用最简单的Role和User来展现一个简单的hibernate多对多查询:

User:
public class User implements Serializable{
	private Long id;
	private String name;
	public Long getId() {
		return id;
	}
	public void setId(Long id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

 

Role:
public class Role implements Serializable{
	private Long id;
	private String roleName;
	private String descri;
	public String getDescri() {
		return descri;
	}
	public void setDescri(String descri) {
		this.descri = descri;
	}
	public Long getId() {
		return id;
	}
	public void setId(Long id) {
		this.id = id;
	}
	public String getRoleName() {
		return roleName;
	}
	public void setRoleName(String roleName) {
		this.roleName = roleName;
	}
}

  

关系表:

public class UserRoleTemp implements Serializable{
	private Long id;
	private User user;
	private Role role;
	public Long getId() {
		return id;
	}
	public void setId(Long id) {
		this.id = id;
	}
	public Role getRole() {
		return role;
	}
	public void setRole(Role role) {
		this.role = role;
	}
	public User getUser() {
		return user;
	}
	public void setUser(User user) {
		this.user = user;
	}
}

 查询:

String hql = "select ut.role from UserRoleTemp  ut where ut.user.id = 2";
		Session session = this.getSession();
		Query q = session.createQuery(hql);
		List<Role> list = q.list();
		for(Role r :list){
			System.out.println(r.getRoleName());
		}

 

查询结果:

yang
gao

 说明：中间省略了hbm映射及向表中添加信息的代码:

主要是想记录一下“select ut.role from UserRoleTemp  ut where ut.user.id = 2”这条查询语句。

通过中间表的user的id,查询出了对应的role中的信息！由此可见，通过这种映射关系，查询起相应的信息来还是很方便的!