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码库记事本

ManyToMany单向、双向:@JoinTable的使用

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ManyToMany单向、双向:@JoinTable使用

一、manytomany单向

单向是指类层面,在下面例子中老师类可以知道要教哪些学生,学生不知被哪些老师教

[email protected](name="t_s",
[email protected](name="teacher_id")},[email protected](name="student_id")}
)

也可以不用连接表,但是若不用连接表,表名、列名规则:

  • 在student表中没有写外键则会用对方的表名_主键名
  • 在teacher表中有外键,则会s_id(也是student的主键名)
  • 表名是student_teacher

student类

@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;
    }
}

Teacher类

@Entity 
public class teacher {
    private int id;
    private String name;
    private Set<student> s=new HashSet<student>();
    @Id //必须加在getId上面
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @ManyToMany
    @JoinTable(name="t_s",
    [email protected](name="teacher_id")},[email protected](name="student_id")}
    )//将会以上两个字段为联合主键
    //定义中间表的名称,列名:joinColumns,inverseJoinColumns是预防组合主键的时候。
    public Set<student> getS() {
        return s;
    }
    public void setS(Set<student> s) {
        this.s = s;
    }   
}

二、manytomany双向

[email protected]

@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",
    [email protected](name="teacher_id")},[email protected](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 //必须加在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")
    //定义中间表的名称,列名:joinColumns,inverseJoinColumns是预防组合主键的时候。
    public Set<student> getS() {
        return s;
    }
    public void setS(Set<student> s) {
        this.s = s;
    }
}

@ManyToMany(多对多关系)使用小结

DeviceGroup类

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;//自动在数据库里生成了group_has_element表,该表包括group_id和element_id两个字段,该表主要是用于存储device_group表和ne_element表的对应关系。
    @ManyToMany(cascade = CascadeType.PERSIST, fetch = FetchType.LAZY)//表的关联,生成一个group_has_element中间表。
    @JoinTable(name = "group_has_element",joinColumns = [email protected](name = "group_id",referencedColumnName = "groupId")}
    ,inverseJoinColumns = [email protected](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 + "]";
 }
 
    
    
}

NeElement 类

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; //设备唯一标识
 private String coonReqUrl; //设备连接URL
 private String serialNumber; //设备序列号
 private String deviceIp;  //设备IP
 private Long modelId;//modelName对应的id
 private String description;//描述
 private String manufacturer;//制造商
 private String softwareVersion;//软件版本
 private Date creationTime;//创建时间
 private Date lastBootstrapTime;
 private Date lastConnTime;//最后连接时间
 private Date updateTime;//更新时间
 private String oui;//oui
 private String product;
 private Boolean authRequirement;//是否需要认证
 private String dialectIP;
 private String updateUser;//更新用户
 private String macAddress;//mac地址
 private Integer onlineStatus;//在线状态
 private Integer sessionStatus;//会话状态
   @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;
 }
}

以上为多对多关系的使用,大家可以参考,本人在使用过程中遇到以下报错信息:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: Unable to map collection com.sunwave.grouping.domain.DeviceGroup.elementList
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1694) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:573) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1087) ~[spring-context-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:857) ~[spring-context-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:548) ~[spring-context-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) [spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:386) [spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:307) [spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1242) [spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1230) [spring-boot-2.0.8.RELEASE.jar:2.0.8.RELEASE]
 at com.sunwave.Application.main(Application.java:26) [classes/:na]
 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
 at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
 at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
 at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
 at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.0.8.RELEASE.jar:2.0.8.RELEASE]
Caused by: org.hibernate.AnnotationException: Unable to map collection com.sunwave.grouping.domain.DeviceGroup.elementList
 at org.hibernate.cfg.annotations.CollectionBinder.bindCollectionSecondPass(CollectionBinder.java:1621) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.annotations.CollectionBinder.bindManyToManySecondPass(CollectionBinder.java:1352) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:810) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:735) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:54) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1640) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1608) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:278) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:861) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:888) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:57) ~[spring-orm-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:390) ~[spring-orm-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:377) ~[spring-orm-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1753) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1690) ~[spring-beans-5.0.12.RELEASE.jar:5.0.12.RELEASE]
 ... 21 common frames omitted
Caused by: org.hibernate.cfg.RecoverableException: Unable to find column with logical name: groupId in org.hibernate.mapping.Table(device_group) and its related supertables and secondary tables
 at org.hibernate.cfg.Ejb3JoinColumn.checkReferencedColumnsType(Ejb3JoinColumn.java:837) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.BinderHelper.createSyntheticPropertyReference(BinderHelper.java:244) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 at org.hibernate.cfg.annotations.CollectionBinder.bindCollectionSecondPass(CollectionBinder.java:1611) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 ... 37 common frames omitted
Caused by: org.hibernate.MappingException: Unable to find column with logical name: groupId in org.hibernate.mapping.Table(device_group) and its related supertables and secondary tables
 at org.hibernate.cfg.Ejb3JoinColumn.checkReferencedColumnsType(Ejb3JoinColumn.java:832) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
 ... 39 common frames omitted

检查了实体类和数据库发现没有什么错,原来是因为我的实体类里的groupId上用了[email protected](name=“group_id”)注解,如下把该注解注释掉或者删除掉就可以了。

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

[email protected](多对多关系)的使用可以去百度再看看,本人就不多说了。

标签: 使用 ManyToMany JoinTable