update all fields of an entity in jpa

Question

I have tow entity User and Project that they have "one to many" relationship and I want to find the User then find the specific Project that belong to User and then update it, but I can't. framework 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;
}

and Project entity

@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();

Get The user object , you will get it with the set of projects associated with that user

update the data you want : -

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

Three corrections come in mind, that may make your code behave well:

• Use EntityManager#find() instead of HQL to lookup entity by id;

• Use only one of @Basic or @Column (I'd prefer @Column ), there is no need to use both for a single element;

• If error is " value is too long for column ", maybe it is time to check if some of Project elements are longer than 20 chars defined in columnDefinition ?

Check length of string elements in Project entities, and if there are some longer than 20 characters, say, 500, modify columnDefinition for those elements, eg:

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

I also suggest to drop tables after such modifications (to allow JPA create new according to new definitions) or manually modify their definitions in DB.