我正在嘗試使用此測驗專案第一次設定JPA。遇到以下錯誤。我想建造很多車是一個車主擁有的-有解無憂

主要是我想建立一種多對一的關系。這種關系是許多汽車歸一個車主所有。

這是我的錯誤：

    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: @OneToOne or @ManyToOne on com.javatech.crud.example.entity.Car.owners references an unknown entity: java.util.List
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1154) ~[spring-context-5.3.14.jar:5.3.14]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:908) ~[spring-context-5.3.14.jar:5.3.14]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.14.jar:5.3.14]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.2.jar:2.6.2]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730) ~[spring-boot-2.6.2.jar:2.6.2]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) ~[spring-boot-2.6.2.jar:2.6.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:302) ~[spring-boot-2.6.2.jar:2.6.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) ~[spring-boot-2.6.2.jar:2.6.2]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290) ~[spring-boot-2.6.2.jar:2.6.2]
    at com.javatech.crud.example.SpringBootCrudManyToOneExampleApplication.main(SpringBootCrudManyToOneExampleApplication.java:10) ~[classes/:na]
Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on com.javatech.crud.example.entity.Car.owners references an unknown entity: java.util.List
    at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:100) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processEndOfQueue(InFlightMetadataCollectorImpl.java:1750) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processFkSecondPassesInOrder(InFlightMetadataCollectorImpl.java:1694) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1623) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:295) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:1460) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1494) ~[hibernate-core-5.6.3.Final.jar:5.6.3.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.3.14.jar:5.3.14]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.3.14.jar:5.3.14]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:409) ~[spring-orm-5.3.14.jar:5.3.14]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:396) ~[spring-orm-5.3.14.jar:5.3.14]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1863) ~[spring-beans-5.3.14.jar:5.3.14]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1800) ~[spring-beans-5.3.14.jar:5.3.14]
    ... 16 common frames omitted

這是專案的應用程式類：

package com.javatech.crud.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootCrudManyToOneExampleApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootCrudManyToOneExampleApplication.class, args);
    }

}

這是我的汽車物體類：

    package com.javatech.crud.example.entity;

import java.util.List;

import javax.persistence.CascadeType;  
import javax.persistence.Entity;  
import javax.persistence.GeneratedValue;  
import javax.persistence.GenerationType;  
import javax.persistence.Id;  
import javax.persistence.JoinColumn;  
import javax.persistence.ManyToOne;  
import javax.persistence.Table;  

@Entity  
@Table(name="Car_TBL")  

public class Car {
    

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
    
    private int id;
    private String modelName;
    
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "fk_owner_id")
    private List<Owner> owners;

    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getModelName() {
        return modelName;
    }
    public void setModelName(String modelName) {
        this.modelName = modelName;
    }
    public List<Owner> getOwners() {
        return owners;
    }
    public void setOwners(List<Owner> owners) {
        this.owners = owners;
    }

}

這是我的所有者物體類：

    package com.javatech.crud.example.entity;

    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.GenerationType;
    import javax.persistence.Id;
    import javax.persistence.Table;
    @Entity
@Table(name="Owner_TBL")

    public class Owner {
        
        
        @Id
        @GeneratedValue(strategy=GenerationType.AUTO)
    
    private int id;
    private String name;
    private String location;
    
    
    
    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;
    }
    public String getLocation() {
        return location;
    }
    public void setLocation(String location) {
        this.location = location;
    }
    

}

這是所有者存盤庫介面：

package com.javatech.crud.example.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.javatech.crud.example.entity.Owner;

@Repository
public interface OwnerRepository extends JpaRepository<Owner, Integer> {
    
    public List<Owner> findByName(String name);

}

這是 Car Repository 界面：

package com.javatech.crud.example.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.javatech.crud.example.entity.Car;

@Repository
public interface CarRepository extends JpaRepository<Car, Integer> {
    
    

}

這是所有者控制器類：

package com.javatech.crud.example.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import com.javatech.crud.example.entity.Owner;
import com.javatech.crud.example.service.OwnerService;

@RestController
public class OwnerController {
    
    @Autowired
    private OwnerService service;
    
    @PostMapping("/addcars")
    public void addCars(@RequestBody Owner owner){
        service.save(owner);
        
    }

}

這是所有者服務類：

package com.javatech.crud.example.service;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.javatech.crud.example.entity.Owner;
import com.javatech.crud.example.repository.CarRepository;
import com.javatech.crud.example.repository.OwnerRepository;

@Service
public class OwnerService {
    
    @Autowired
    private CarRepository carrepository;
    @Autowired
    private OwnerRepository ownerrepository;
    
    public void save(Owner owner) {
        
        List<Owner> owners =  ownerrepository.findByName(owner.getName());
        
        if(owners.isEmpty()) {
            
            ownerrepository.save(owner);
        }

        
    }
}

uj5u.com熱心網友回復：

在 List 的一側，你必須使用 @OneToMany 而不是 @ManyToOne

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "fk_owner_id")
private List<Owner> owners;

uj5u.com熱心網友回復：

查看例外：

Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on com.javatech.crud.example.entity.Car.owners references an unknown entity: java.util.List

這意味著，它不會將所有者欄位識別為物體。要更正它，請通過添加以下內容來完成關系：

@JoinColumn(name = "some FK column")
private Car car;

在所有者類中。

此外，在Car類中，

@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "fk_owner_id")
private List<Owner> owners;

這似乎不正確。可能您想模擬“一輛車可以有很多車主”的關系。如果是，請更正為：

@OneToMany(targetEntity = Car.class, cascade = CascadeType.ALL)
@JoinColumn(name = "fk_owner_id")
private List<Owner> owners;

轉載請註明出處，本文鏈接：https://www.uj5u.com/net/400964.html

標籤：爪哇弹簧靴多对一

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