添加两个变量后，BeanCreationException

Question

有人可以告诉我如何摆脱BeanCreationException吗？

在向Owner.java中添加两个变量之后，我得到了BeanCreationException，如下所示：

@OneToMany(cascade = CascadeType.ALL, mappedBy = "owner",  fetch=FetchType.EAGER)
private Set<Pet> pets;

//I added the following two variable declarations
@Transient
private Set<Pet> cats = new HashSet<Pet>();

@Transient
private Set<Pet> dogs = new HashSet<Pet>();

我还添加了用于猫和狗的getter和setter方法，以及将猫和狗作为宠物子集填充的方法，如下所示：

public void parsePets() {
    for (Pet pet : getPetsInternal()) {
    if (pet.getType().getName().equals("cat")) {cats.add(pet);} 
    else if (pet.getType().getName().equals("dog")) {dogs.add(pet);}
  }
}

protected Set<Pet> getPetsInternal() {
    if (this.pets == null) {this.pets = new HashSet<Pet>();}
    return this.pets;
}

当我在Eclipse中在服务器上运行方式为…运行时，应用程序无法初始化，并显示以下错误消息：

org.springframework.beans.factory.BeanCreationException:  
Error creating bean with name  
'org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor#0'  
defined in class path resource [spring/business-config.xml]: Initialization of bean failed;  
nested exception is org.springframework.beans.factory.BeanCreationException:  
Error creating bean with name 'entityManagerFactory' defined in class path resource  
[spring/business-config.xml]: Invocation of init method failed;  
nested exception is javax.persistence.PersistenceException:  
[PersistenceUnit: petclinic] Unable to build EntityManagerFactory

...

Caused by: org.hibernate.MappingException:  
Could not determine type for:  
java.util.Set, at table: owners, for columns:  
[org.hibernate.mapping.Column(cats)]

这是business-config.xml的代码。

我可以消除错误消息，并通过注释掉所做的更改来使应用程序运行，但是当我需要猫和狗各不相同时，我剩下的问题是三个列表（宠物，猫，狗）是相同的宠物的子集。下面的代码消除了错误消息，但创建了三个不相同的相同列表：

@OneToMany(cascade = CascadeType.ALL, mappedBy = "owner",  fetch=FetchType.EAGER)
private Set<Pet> pets;

//I added next two variables
//    @Transient
@OneToMany(cascade = CascadeType.ALL, mappedBy = "owner", fetch=FetchType.EAGER)
private Set<Pet> cats;// = new HashSet<Pet>();

//    @Transient  
@OneToMany(cascade = CascadeType.ALL, mappedBy = "owner", fetch=FetchType.EAGER)  
private Set<Pet> dogs;// = new HashSet<Pet>();

根据公理会的要求，除了添加猫和狗之外，我无法真正注释所有内容，因为宠物，猫和狗是从OwnerController.java中调用的，如下所示：

@RequestMapping(value = "/owners", method = RequestMethod.GET)
public String processFindForm(@RequestParam("ownerID") String ownerId, Owner owner, BindingResult result, Map<String, Object> model) {
    Collection<Owner> results = this.clinicService.findOwnerByLastName("");
    model.put("selections", results);
    int ownrId = Integer.parseInt(ownerId);
    Owner sel_owner = this.clinicService.findOwnerById(ownrId);//jim added this
    sel_owner.parsePets();
    model.put("sel_owner",sel_owner);
    return "owners/ownersList";
}

编辑：

根据Sotirios的请求，这是我的实体类Owner.java：

@Entity
@Table(name = "owners")
public class Owner extends Person {
    @Column(name = "address")
    @NotEmpty
    private String address;

    @Column(name = "city")
    @NotEmpty
    private String city;

    @Column(name = "telephone")
    @NotEmpty
    @Digits(fraction = 0, integer = 10)
    private String telephone;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner",  fetch=FetchType.EAGER)
    private Set<Pet> pets;

    //I added next two variables
    @Transient
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner", fetch=FetchType.EAGER)
    private Set<Pet> cats = new HashSet<Pet>();

    @Transient
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner", fetch=FetchType.EAGER)
    private Set<Pet> dogs = new HashSet<Pet>();
    //end of 2 variables I added

    public String getAddress() {return this.address;}

    public void setAddress(String address) {this.address = address;}

    public String getCity() {return this.city;}

    public void setCity(String city) {this.city = city;}

    public String getTelephone() {return this.telephone;}

    public void setTelephone(String telephone) {this.telephone = telephone;}

    protected void setPetsInternal(Set<Pet> pets) {this.pets = pets;}

    // Call this from OwnerController before returning data to page.
    public void parsePets() {
        for (Pet pet : getPetsInternal()) {
            if (pet.getType().getName().equals("cat")) {
                cats.add(pet);
                System.out.println(pet.getType().getName());
                System.out.println("cats.size() is: "+cats.size());
                System.out.println("added a cat to cats");
            } 
            else if (pet.getType().getName().equals("dog")) {
                  dogs.add(pet);
                System.out.println(pet.getType().getName());
                System.out.println("dogs.size() is: "+dogs.size());
                System.out.println("added a dog to dogs");
            }
            // add as many as you want
    System.out.println("----------------------------------------------");
        }
    }

    public Set<Pet> getCats() {
        System.out.println("about to return cats");
        for (Pet cat : cats) {System.out.println("counting a "+cat.getType()+" in cats.");}
        System.out.println("cats.size() is: "+cats.size());
        return cats;
    }

    public Set<Pet> getDogs() {
        System.out.println("about to return dogs");
        for (Pet dog : dogs) {System.out.println("counting a "+dog.getType()+" in dogs.");}
        System.out.println("dogs.size() is: "+dogs.size());
        return dogs;
    }

    //end section I added

    protected Set<Pet> getPetsInternal() {
        if (this.pets == null) {this.pets = new HashSet<Pet>();}
            return this.pets;
    }


    public List<Pet> getPets() {
        List<Pet> sortedPets = new ArrayList<Pet>(getPetsInternal());
        PropertyComparator.sort(sortedPets, new MutableSortDefinition("name", true, true));
        return Collections.unmodifiableList(sortedPets);
    }

    public void addPet(Pet pet) {
        getPetsInternal().add(pet);
        pet.setOwner(this);
    }

    public Pet getPet(String name) {return getPet(name, false);}

    public Pet getPet(String name, boolean ignoreNew) {
        name = name.toLowerCase();
        for (Pet pet : getPetsInternal()) {
            if (!ignoreNew || !pet.isNew()) {
                String compName = pet.getName();
                compName = compName.toLowerCase();
                if (compName.equals(name)) {
                    return pet;
                }
            }
        }
        return null;
    }

    @Override
    public String toString() {
        return new ToStringCreator(this)

            .append("id", this.getId())
            .append("new", this.isNew())
            .append("lastName", this.getLastName())
            .append("firstName", this.getFirstName())
            .append("address", this.address)
            .append("city", this.city)
            .append("telephone", this.telephone)
            .toString();
    }
}

Answer 1

为什么单独的列表必须是实例变量？！为什么不简单地创建一个getCats方法（和其他方法）并简单地过滤pets集合呢？试图映射所有内容，恕我直言，事情变得过于复杂。

@Entity
@Table(name = "owners")
public class Owner extends Person {

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner",  fetch=FetchType.EAGER)
    private Set<Pet> pets;

    public Set<Pet> getCats() {
        Set<Pet> cats = new HashSet<Pet>();
        for (Pet pet : getPetsInternal()) {
            if (pet.getType().getName().equals("cat")) {
                cats.add(pet);
            }
        }
        return cats;
    }
}

缺点是每次需要时都会重新创建集合。您可以使用Google Guava之类的工具来简化此操作，并创建一个过滤器列表。

@Entity
@Table(name = "owners")
public class Owner extends Person {

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "owner",  fetch=FetchType.EAGER)
    private Set<Pet> pets;

    public Set<Pet> getCats() {
        return Sets.filter(getPetsInternal(), new Predicate<Pet>() {
            public boolean apply(Pet pet) { 
                return pet.getType().getName().equals("cat")
            }
        });         
    }
}

您还可以在parsePets方法内部进行操作并使用它进行注释，@PostLoad以便在所有者从数据库中检索到该方法之后将调用该方法。