如何在Entity中的三个表之间建立关系？

Question

我对hibernate和spring非常新，并且无法理解如何在表之间建立关系。我需要存储业务伙伴机器关系数据。即一个业务合作伙伴拥有多台机器，但单台机器只有一个业务合作伙伴。下面我提到了表格信息和我的代码。请帮助我，提前帮助谢谢。

##################业务合作伙伴表####################

 CREATE TABLE `bp_master` (
 `BPId` int(11) NOT NULL,
 `BPName` varchar(100) DEFAULT NULL,
 `BPPrimaryAddress` varchar(45) DEFAULT NULL,
 `BPSecondaryAddress` varchar(45) DEFAULT NULL,
  `BPPrimaryPhoneNum` varchar(45) DEFAULT NULL,
 `BPSecondaryPhoneNum` varchar(45) DEFAULT NULL,
 `BPContactName1` varchar(45) DEFAULT NULL,
 `BPContantName2` varchar(45) DEFAULT NULL,
  `BPContactName3` varchar(45) DEFAULT NULL,
  `BPPrimaryAdminId` varchar(45) NOT NULL,
  `BPStatus` varchar(45) DEFAULT NULL,
   `BPTypeId` int(11) DEFAULT NULL,
   `BPStatusChangeTimeStamp` datetime DEFAULT NULL,
    PRIMARY KEY (`BPId`),
    KEY `BPType_idx` (`BPTypeId`),
    CONSTRAINT `BPType` FOREIGN KEY (`BPTypeId`) REFERENCES `bp_type_master` 
    (`BPTypeId`) ON DELETE NO ACTION ON UPDATE NO ACTION
     ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

###############机床表######################

   CREATE TABLE `machine_master` (
   `MachineId` int(11) NOT NULL,
   `MachineName` varchar(45) DEFAULT NULL,
   `MachineLocation` varchar(45) NOT NULL,
   `MachineAddress` varchar(45) NOT NULL,
   `MachineInstalledDate` datetime DEFAULT NULL,
   `MachineStatus` varchar(45) DEFAULT NULL,
    `MachineStatusChangeTimeStamp` datetime DEFAULT NULL,
   `MachineTypeId` varchar(45) DEFAULT NULL,
    PRIMARY KEY (`MachineId`)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

################## bp_machine_rel table ####################

    CREATE TABLE `bp_machine_rel` (
    `BPId` int(11) DEFAULT NULL,
    `MachineId` int(11) DEFAULT NULL,
    `BPMachineStatus` varchar(45) DEFAULT NULL,
    `BPMachineStatusChangeTimeStamp` datetime DEFAULT NULL,
     UNIQUE KEY `MachineId_UNIQUE` (`MachineId`),
     KEY `BPId_idx` (`BPId`),
      KEY `MachineId_idx` (`MachineId`),
     CONSTRAINT `BPId` FOREIGN KEY (`BPId`) REFERENCES `bp_master` (`BPId`) 
     ON DELETE NO ACTION ON UPDATE NO ACTION,
      CONSTRAINT `MachineId` FOREIGN KEY (`MachineId`) REFERENCES 
     `machine_master` (`MachineId`) ON DELETE NO ACTION ON UPDATE NO ACTION
      ) ENGINE=InnoDB DEFAULT CHARSET=latin1;

   class Machine(){

   @OneToOne
   private BusinessPartner bp;
  }

   class BusinessPartner{
         @OneToMany
        private List<Machine> bpMachines;
    }

Answer 1

正如您所描述的那样：一个业务合作伙伴拥有许多计算机。所以很多拥有一个业务合作伙伴（如果您想要双向关系）。

@Entity
public class BusinessPartner{
    @OneToMany
    @JoinColumn(name="fk_machine") //machine foreign key is the BusinessPartner table
    private List<Machine> bpMachines;
}

@Entity
public class Machine(){
   @ManyToOne
   private BusinessPartner bp;
}