Question

我的应用程序有两个实体产品和类别。添加产品时，用户选择产品所属的类别。但是当我将产品保存到数据库时，我遇到了错误

org.springframework.web.util.NestedServletException：请求处理失败;嵌套异常是java.lang.IllegalStateException：org.hibernate.TransientPropertyValueException：非null属性引用瞬态值 - 必须在当前操作之前保存瞬态实例

实体的内容是 Category.java

@Entity
@Table(name="category")
public class Category {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@Column(name="category_name")
private String categoryName;

@Column(name="description")
private String description;

@OneToMany(mappedBy = "category", fetch=FetchType.LAZY)
private Set<Product> products;

//getter and setter method
}

Product.java

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

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

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

@Column(name="description")
private String description;

@Column(name="manufacture")
private String manufacture;

@Column(name="price")
private long price;

@Column(name="image_name")
private String imageName;

@ManyToOne
@JoinColumn(name = "category_id", referencedColumnName = "id", nullable = false)
Category category;

//getter and setter method
}

ProductDAO.java

@Repository("ProductDAO")
@Transactional
public class ProductDAO {

@PersistenceContext
private EntityManager entityManager;

public EntityManager getEntityManager() {
    return entityManager;
}

public void setEntityManager(EntityManager entityManager) {
    this.entityManager = entityManager;
}

public void create(Product product) {
    entityManager.merge(product.getCategory());
    entityManager.persist(product);
}
//other method
}

我的jsp文件

<form:form method="post" commandName="product" action="add.html" enctype="multipart/form-data">
    Productname <form:input path="name"/>
                <form:errors path="name" class ="error"/><br>
    description    <form:input   path="description"/><br>
    price    <form:input   path="price"/><br>
    manufacture <form:input path="manufacture"/><br>
    Category
    <form:select path="category">
    <form:options items="${categories}" itemValue="id" itemLabel="categoryName" />
    </form:select>
    <form:errors path="category" class ="error"/><br>
    <br/>
    Product image<input type="file" name="file" />
    <form:errors path="imageName" class ="error"/><br>
    <input type="submit" class="register" value="Save">
</form:form>

我的转换器

public class CategoryConverter implements Converter<String, Category>{

    @Autowired
    private CategoryService categoryService;

    public Category convert(String id) {
        return categoryService.findById(Long.valueOf(id));
    }
}

感谢您的帮助

Answer 1

请将（cascade = CascadeType.ALL）添加到Product

的类别字段映射中

@ManyToOne(cascade=CascadeType.ALL)
@JoinColumn(name = "category_id", referencedColumnName = "id", nullable = false)
Category category;

并在ProductDAO中删除此行：

entityManager.merge(product.getCategory());

注意：如果您的产品类别是现有产品，则应首先加载它，然后将其设置为您的产品，这是正常流程。不要重复新的Category对象。

Answer 2

这是我的固定代码

@Transactional
public void create(Product product) {
    Category category=categoryDAO.findById(product.getCategory().getId());
    category.getProducts().add(product);
    categoryDAO.edit(category);
    product.setCategory(category);
    this.productDAO.create(product);
}

java.lang.IllegalStateException：org.hibernate.TransientPropertyValueException

2 个答案: