**需要用到連接表**@JoinTable(name="t_s",
joinColumns={@JoinColumn(name="teacher_id")},inverseJoinColumns={@JoinColumn(name="student_id")}
)

@Entity
public class student {
    private int id;
    private String name;
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

@Entity 
public class teacher {
    private int id;
    private String name;
    private Set<student> s=new HashSet<student>();
    @Id //必須加在getId上面
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @ManyToMany
    @JoinTable(name="t_s",
    joinColumns={@JoinColumn(name="teacher_id")},inverseJoinColumns={@JoinColumn(name="student_id")}
    )//將會以上兩個字段為聯(lián)合主鍵
    //定義中間表的名稱，列名：joinColumns，inverseJoinColumns是預防組合主鍵的時候。
    public Set<student> getS() {
        return s;
    }
    public void setS(Set<student> s) {
        this.s = s;
    }   
}

@Entity
public class student {
    private int id;
    private String name;
    private Set<teacher> ts=new HashSet<teacher>();
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToMany
    @JoinTable(name="t_s",
    joinColumns={@JoinColumn(name="teacher_id")},inverseJoinColumns={@JoinColumn(name="student_id")}
    )
    public Set<teacher> getTs() {
        return ts;
    }
    public void setTs(Set<teacher> ts) {
        this.ts = ts;
    }
}

@Entity 
public class teacher {
    private int id;
    private String name;
    private Set<student> s=new HashSet<student>();
    @Id //必須加在getId上面
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToMany(mappedBy="ts")
    //定義中間表的名稱，列名：joinColumns，inverseJoinColumns是預防組合主鍵的時候。
    public Set<student> getS() {
        return s;
    }
    public void setS(Set<student> s) {
        this.s = s;
    }
}

package com.sunwave.grouping.domain;
import javax.persistence.*;
import java.io.Serializable;
import java.util.List;
@Entity
@Table(name = "device_group")
public class DeviceGroup implements Serializable{
    /**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	@Id
    @GeneratedValue(strategy = GenerationType.AUTO)
   /* @Column(name="group_id")*/
    private long groupId;
    @Column(name="group_name")
    private String groupName;
    @Column(name="description")
    private String description;//自動在數(shù)據(jù)庫里生成了group_has_element表，該表包括group_id和element_id兩個字段，該表主要是用于存儲device_group表和ne_element表的對應關系。
    @ManyToMany(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)//表的關聯(lián)，生成一個group_has_element中間表。
    @JoinTable(name = "group_has_element",joinColumns = {@JoinColumn(name = "group_id",referencedColumnName = "groupId")}
    ,inverseJoinColumns = {@JoinColumn(name = "element_id",referencedColumnName = "neNeid")})
    private List<NeElement> elementList;
    
    public List<NeElement> getElementList() {
		return elementList;
	}
	public void setElementList(List<NeElement> elementList) {
		this.elementList = elementList;
	}
	public long getGroupId() {
		return groupId;
	}
	public void setGroupId(long groupId) {
		this.groupId = groupId;
	}
	public String getGroupName() {
		return groupName;
	}
	public void setGroupName(String groupName) {
		this.groupName = groupName;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	@Override
	public String toString() {
		return "DeviceGroup [groupId=" + groupId + ", groupName=" + groupName + ", description=" + description
				+ ", elementList=" + elementList + "]";
	}
	
    
    
}

package com.sunwave.grouping.domain;
import javax.persistence.*;
import java.io.Serializable;
import java.util.Date;
import java.util.List;
/**
 * @author lfw
 * @date   2020年8月3日
 * @time   下午6:44:54
 * 
 */
@Entity
@Table(name = "ne_element")
public class NeElement implements Serializable{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private Long neNeid; //設備唯一標識
	private String coonReqUrl; //設備連接URL
	private String serialNumber; //設備序列號
	private String deviceIp;  //設備IP
	private Long modelId;//modelName對應的id
	private String description;//描述
	private String manufacturer;//制造商
	private String softwareVersion;//軟件版本
	private Date creationTime;//創(chuàng)建時間
	private Date lastBootstrapTime;
	private Date lastConnTime;//最后連接時間
	private Date updateTime;//更新時間
	private String oui;//oui
	private String product;
	private Boolean authRequirement;//是否需要認證
	private String dialectIP;
	private String updateUser;//更新用戶
	private String macAddress;//mac地址
	private Integer onlineStatus;//在線狀態(tài)
	private Integer sessionStatus;//會話狀態(tài)
   @ManyToMany(mappedBy = "elementList")
	private List<DeviceGroup> deviceGroupList;
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public String getManufacturer() {
		return manufacturer;
	}
	public void setManufacturer(String manufacturer) {
		this.manufacturer = manufacturer;
	}
	public String getSoftwareVersion() {
		return softwareVersion;
	}
	public void setSoftwareVersion(String softwareVersion) {
		this.softwareVersion = softwareVersion;
	}
	public Date getLastConnTime() {
		return lastConnTime;
	}
	public void setLastConnTime(Date lastConnTime) {
		this.lastConnTime = lastConnTime;
	}
	public Long getModelId() {
		return modelId;
	}
	public void setModelId(Long modelId) {
		this.modelId = modelId;
	}
	public Long getNeNeid() {
		return neNeid;
	}
	public void setNeNeid(Long neNeid) {
		this.neNeid = neNeid;
	}
	public String getCoonReqUrl() {
		return coonReqUrl;
	}
	public void setCoonReqUrl(String coonReqUrl) {
		this.coonReqUrl = coonReqUrl;
	}
	public String getDeviceIp() {
		return deviceIp;
	}
	public void setDeviceIp(String deviceIp) {
		this.deviceIp = deviceIp;
	}
	public String getSerialNumber() {
		return serialNumber;
	}
	public void setSerialNumber(String serialNumber) {
		this.serialNumber = serialNumber;
	}
	public Date getCreationTime() {
		return creationTime;
	}
	public void setCreationTime(Date creationTime) {
		this.creationTime = creationTime;
	}
	public Date getLastBootstrapTime() {
		return lastBootstrapTime;
	}
	public void setLastBootstrapTime(Date lastBootstrapTime) {
		this.lastBootstrapTime = lastBootstrapTime;
	}
	public Date getUpdateTime() {
		return updateTime;
	}
	public void setUpdateTime(Date updateTime) {
		this.updateTime = updateTime;
	}
	public String getOui() {
		return oui;
	}
	public void setOui(String oui) {
		this.oui = oui;
	}
	public String getProduct() {
		return product;
	}
	public void setProduct(String product) {
		this.product = product;
	}
	public Boolean getAuthRequirement() {
		return authRequirement;
	}
	public void setAuthRequirement(Boolean authRequirement) {
		this.authRequirement = authRequirement;
	}
	public String getDialectIP() {
		return dialectIP;
	}
	public void setDialectIP(String dialectIP) {
		this.dialectIP = dialectIP;
	}
	public String getUpdateUser() {
		return updateUser;
	}
	public void setUpdateUser(String updateUser) {
		this.updateUser = updateUser;
	}
	public String getMacAddress() {
		return macAddress;
	}
	public void setMacAddress(String macAddress) {
		this.macAddress = macAddress;
	}
	public Integer getOnlineStatus() {
		return onlineStatus;
	}
	public void setOnlineStatus(Integer onlineStatus) {
		this.onlineStatus = onlineStatus;
	}
	public Integer getSessionStatus() {
		return sessionStatus;
	}
	public void setSessionStatus(Integer sessionStatus) {
		this.sessionStatus = sessionStatus;
	}
}

/* @Column(name="group_id")*/ private long groupId;