JPA多对多持久化

Question

@Entity
@Table(name = "users")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Users.findAll", query = "SELECT u FROM Users u"),
@NamedQuery(name = "Users.findByUserId", query = "SELECT u FROM Users u WHERE u.userId = :userId"),
@NamedQuery(name = "Users.findByUsername", query = "SELECT u FROM Users u WHERE u.username = :username"),
@NamedQuery(name = "Users.findByPassword", query = "SELECT u FROM Users u WHERE u.password = :password")})
public class Users implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 60)
@Column(name = "user_id")
private String userId;
@Basic(optional = false)
@NotNull
@Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?", message="Invalid email")
@Size(min = 1, max = 45)
@Column(name = "username")
private String username;
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 120)
@Column(name = "password")
private String password;
@JoinTable(name = "users_has_roles", joinColumns = {
    @JoinColumn(name = "users_user_id", referencedColumnName = "user_id")}, inverseJoinColumns = {
    @JoinColumn(name = "roles_role_id", referencedColumnName = "role_id")})
@ManyToMany
private Collection<Roles> rolesCollection;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "usersUserId")
private Collection<UserAccount> userAccountCollection;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "usersUserId")
private Collection<UserDetails> userDetailsCollection;

...

All the getter and setter methods etc.

@Entity
@Table(name = "roles")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Roles.findAll", query = "SELECT r FROM Roles r"),
@NamedQuery(name = "Roles.findByRoleId", query = "SELECT r FROM Roles r WHERE r.roleId = :roleId"),
@NamedQuery(name = "Roles.findByRoleName", query = "SELECT r FROM Roles r WHERE r.roleName = :roleName"),
@NamedQuery(name = "Roles.findByRolePermission", query = "SELECT r FROM Roles r WHERE r.rolePermission = :rolePermission"),
@NamedQuery(name = "Roles.findByRoleDescription", query = "SELECT r FROM Roles r WHERE r.roleDescription = :roleDescription")})
public class Roles implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 60)
@Column(name = "role_id")
private String roleId;
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 45)
@Column(name = "role_name")
private String roleName;
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 45)
@Column(name = "role_permission")
private String rolePermission;
@Size(max = 45)
@Column(name = "role_description")
private String roleDescription;
@ManyToMany(mappedBy = "rolesCollection")
private Collection<Users> usersCollection;

...

All the getter and setter methods etc.

谢谢

----更新----

// New Users
Users currentUser = new Users();
currentUser.setUserId(userId);
currentUser.setUsername(email);
currentUser.setPassword(password);
getUsersFacade().create(currentUser);

Answer 1

好的，首先感谢美子带领我找到答案。我只是想贴出一个答案，可能会直接帮助任何人可能在我的位置。此外，这是基于一个尤里卡时刻，所以它可能不是正确的技术，但这是我的看法。

我面临的一个大问题是，在MySQL中，我可以将桥接表视为一个单独的表！（很抱歉，我不能发布我的EER图的图像，但我现在似乎没有足够的特权）所以我假设Java也会将桥接表视为表！其实不是。在Java中，这个桥接表并不是作为常规表存在的，它实际上是由与之关联的相反的表集合类型表示的。

对我来说，最简单的方法就是完全忘记桥接表，而专注于两个“真实”表，并将这些表中的数据关联起来。下面的代码不是最佳实践，因为我只是设置了role_id，但它很好，只是为了表明我的观点。

List<Roles> userRoleList = new ArrayList<Roles>();

Users currentUser = new Users();
currentUser.setUserId(userId);
currentUser.setUsername(email);
currentUser.setPassword(password);

Roles userRole = new Roles();
userRole.setRoleId("2");

userRoleList.add(userRole);
currentUser.setRolesCollection(userRoleList);

getUsersFacade().create(currentUser);