java - Hibernate 无法正确从数据库读取对象

Question

我在 Hibernate 方面遇到了一些问题。

我有一个或多或少复杂的对象结构，我想使用 Hibernate EntityManager(版本 4.3.5.Final)保存/加载。我设法保存它，但如果我尝试读取该对象，则只会读取 PK。即使 PK 正确，EntityManager 的 find 方法也会返回 null，因此我使用其 getReference 方法。

我仍然无法使用正确的关系(ManyToOne 等)，所以我很可能在那里犯了一个错误，我猜这就是导致问题的原因。无论如何。

我的问题是:如何使用 Hibernate 持久保存这样的对象结构？

这是我正在使用的 POJO:

编辑:更新了代码

计算列表:

@Entity(name = "calculation")
public class CalculationList implements EntityList {

@Id
private Date created;

@OneToMany(mappedBy = "", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<Product> products;

public CalculationList(Date created) {
    this.created = created;
    this.products = new LinkedList<>();
}

public CalculationList(Date created, List<Product> products) {
    this.created = created;
    this.products = products;
}

public CalculationList() {
}

public Date getCreated() {
    return created;
}

public void setCreated(Date created) {
    this.created = created;
}

public List<Product> getProducts() {
    return products;
}

public void setProducts(List<Product> entities) {
    this.products = entities;
}

@Override
public String toString() {
    return "CalculationList{" +
            "created=" + created +
            ", products=" + products +
            '}';
}
}

计算器实体:

@Entity(name = "calculator_entity")
public class CalculatorEntity implements Serializable {

@Id
private int id;

private CalculatorEntityType type;

private String name;

private int number;

@ManyToOne(cascade = CascadeType.ALL)
private Product product;

public CalculatorEntity(CalculatorEntityType type) {
    this.type = type;
}

protected CalculatorEntity() {
}

public int getNumber() {
    return number;
}

public void setNumber(int number) {
    this.number = number;
}

public Product getProduct() {
    return product;
}

public void setProduct(Product product) {
    this.product = product;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public CalculatorEntityType getType() {
    return type;
}

public void setType(CalculatorEntityType type) {
    this.type = type;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public enum CalculatorEntityType {
    GAS_PUMP, DELIVERY_BILL;
}

@Override
public String toString() {
    return "CalculatorEntity{" +
            "id=" + id +
            ", type=" + type +
            ", name='" + name + '\'' +
            ", product=" + product +
            ", number=" + number +
            '}';
}
}

产品:

@Entity(name = "product")
public class Product implements Serializable {

@Id
private int id;

private String name;

private ProductType type;

@OneToMany(mappedBy = "product", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<CalculatorEntity> entities;

public Product(String name, ProductType type) {
    this.name = name;
    this.type = type;
    this.entities = new LinkedList<>();
}

/**
 * JPA - Konstruktor
 */
public Product() {
}

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 ProductType getType() {
    return type;
}

public void setType(ProductType type) {
    this.type = type;
}

public List<CalculatorEntity> getEntities() {
    return entities;
}

public void setEntities(List<CalculatorEntity> entities) {
    this.entities = entities;
}

@Override
public String toString() {
    return "Product{" +
            "id=" + id +
            ", name='" + name + '\'' +
            ", type=" + type +
            ", entities=" + entities +
            '}';
}

public enum ProductType {

    FUEL("Treibstoff"), OIL("Öl"), OTHER("Verschiedenes");

    private String name;

    private ProductType(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }
}
}

Answer 1

您正在使用带有错误实体的 @OneToMany 映射，而不是映射 Product 类，而是映射 CalculationList 类，请移动以下内容配置:

@OneToMany(mappedBy = "product", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<CalculatorEntity> entities;

到 Product 类。