更新jpa中实体的所有字段

Question

我必须拖曳实体User和Project，它们具有“一对多”关系，我想找到User，然后找到属于User的特定Project，然后更新它，但是我不能。 框架Struts2 + Hibernate。

@Entity (name = "User")
@Table (name = "users")
public class User implements Serializable{
@Id
@Column (name = "user_id", columnDefinition = "number")
@SequenceGenerator(name = "seq", sequenceName = "gen")
@GeneratedValue(strategy = GenerationType.AUTO, generator = "seq")
private int id;

@Basic
@Column(name = "user_name", columnDefinition = "nvarchar2(20)")
private String userName;

@Basic
@Column(name = "password", columnDefinition ="nvarchar2(20)")
private String password;

@Basic
@Column(name = "create_date",columnDefinition = "date")
private Date creation_date;

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "user_id")
private List<Project> projectses;

public List<Project> getProjectses() {
    return projectses;
}

public void setProjectses(List<Project> projectses) {
    this.projectses = projectses;
}

和项目实体

@Entity(name = "Project")
@Table(name = "project")
public class Project implements Serializable {
@Id
@Column(name = "project_id" , columnDefinition = "number")
@SequenceGenerator(name = "projectSeq", sequenceName = "projectGen")
@GeneratedValue(strategy = GenerationType.AUTO,generator = "projectSeq")
private int projectId;

@Basic
@Column(name = "project_name" , columnDefinition = "nvarchar2(20)")
private String projectName;

@Basic
@Column(name = "project_description" , columnDefinition = nvarchar2(20)")
private String projectDescription;

@Basic
@Column(name = "start_date",columnDefinition = "date")
private Date startDate;

@Basic
@Column(name = "due_date",columnDefinition = "date")
private Date dueDate;

@Basic
@Column(name = "project_status",columnDefinition = "nvarchar2(20)")
private String projectStatus;

@Basic
@Column(name = "project_amount",columnDefinition = "number(8)")
private int projectAmount;

Answer 1

User u = (User)entityManager.createQuery(SELECT u FROM User u JOIN FETCH u.Project where u.id = :id).setParameter("id",your_userId).uniqueResult();

获取用户对象，您将通过与该用户关联的项目集来获取它

更新您想要的数据：-

List<Project> userProjects = u.getProjectses();   
for(int i = 0 ; i < userProjects.size() ; i++){
   Project p = userProjects.get(i);
   entityManager.getTransaction().begin();
   p.setProjectName("test"); 
   entityManager.merge(p); 
   entityManager.getTransaction().commit(); 
}

Answer 2

请记住三个更正，它们可能会使您的代码表现良好：

• 使用EntityManager#find()代替HQL通过id查找实体；

• 仅使用@Basic或@Column （我希望使用@Column ），一个元素无需同时使用两者；

• 如果错误是“ 列的值太长 ”，也许是时候检查一些Project元素是否长于columnDefinition定义的20个字符了？

检查Project实体中字符串元素的长度，如果长度超过20个字符（例如500个），请为这些元素修改columnDefinition ，例如：

@Column(name = "project_description", columnDefinition = "nvarchar2(500)")
private String projectDescription;

我还建议修改后删除表（以允许JPA根据新定义创建新表）或在DB中手动修改其定义。