ManyToMany单向、双向:@JoinTable的使用

ManyToMany单向、双向:@JoinTable的使用

目录ManyToMany单向、双向:@JoinTable使用一、manytomany单向二、manytomany双向@ManyToMany(多对多关系)使用小结

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

**需要用到连接表**@JoinTable(name="t_s",

joinColumns={@JoinColumn(name="teacher_id")},inverseJoinColumns={@JoinColumn(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 s=new HashSet();

@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",

joinColumns={@JoinColumn(name="teacher_id")},inverseJoinColumns={@JoinColumn(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 getS() {

return s;

}

public void setS(Set s) {

this.s = s;

}

}

二、manytomany双向

也可以用@JoinTable对连接表字段名进行修改

@Entity

public class student {

private int id;

private String name;

private Set ts=new HashSet();

@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 getTs() {

return ts;

}

public void setTs(Set ts) {

this.ts = ts;

}

}

@Entity

public class teacher {

private int id;

private String name;

private Set s=new HashSet();

@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 getS() {

return s;

}

public void setS(Set 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 = {@JoinColumn(name = "group_id",referencedColumnName = "groupId")}

,inverseJoinColumns = {@JoinColumn(name = "element_id",referencedColumnName = "neNeid")})

private List elementList;

public List getElementList() {

return elementList;

}

public void setElementList(List 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 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/*@Column(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;

其他关于@ManyToMany(多对多关系)的使用可以去百度再看看，本人就不多说了。

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