JPA坚持多对多 [英] JPA persist many to many
问题描述
我有一个非常标准的方案，其中有一个以user_id为PK的Users表和一个以role_id为PK的Roles表.这两个表通过多对多关系关联(即，用户可以具有多个角色，并且一个角色可以应用于许多用户)，随后，我有了一个名为users_has_roles的联接表. users_has_roles中仅有的两列是users_user_id和Roles_role_id.
我已经生成了实体类(请参见下文)，并且可以将数据持久保存到用户表和角色表中没有问题，但是我失败了将任何内容持久地保存到users_has_roles联接表中，因此目前没有为我的用户分配任何角色.在发疯之前，有人可以让我摆脱困境，向我展示如何将具有相应role_role_id的users_user_id添加到users_has_roles表中，以便我的用户可以拥有角色吗?
我的Users.java实体类:
@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.
我的Roles.java实体类:
@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);
首先，感谢Mikko带领我回答了这个问题.我只想发布一个可能对我所处位置的其他人有直接帮助的答案.这也是基于尤里卡的时刻，因此在技术上可能并不正确，但这就是我的看法.
我面临的最大问题是在MySQL中，我可以将桥接表视为一个单独的表！ (对不起，我无法发布EER图的图像，但目前看来我没有足够的特权)，所以我假设Java还将桥接表视为表！嗯，事实并非如此.该桥接表实际上不是Java中的常规表，实际上由与之关联的相反表集合类型表示.
对我来说，最简单的方法是完全忘记桥接表，而专注于两个实际"表，并将其中的数据关联起来.下面的代码不是最佳实践，因为我只是设置了role_id，但为了表明我的观点也很好.
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);
希望能帮助其他在多对多关系中挣扎的人.
(注意.为了方便起见，我已经编辑了原始的问题代码以使用列表而不是集合，但是您也可以使用其他任何适合您需要的类型.)
I have a pretty standard scenario whereby I have a table of Users with user_id as the PK and a table of Roles with role_id as the PK. The two tables are related via a many to many relationship (ie. Users can have many roles and a role can be applied to many users) and subsequently I have a joining table called users_has_roles. The only two columns in users_has_roles are users_user_id and roles_role_id.
I have generated the entity classes (see below) and I have no problem persisting data to the users and roles tables but I have failed miserably persist anything to the users_has_roles joining table so currently none of my users are being assigned a role. Before I go crazy could somebody put me out of my misery and show me how I should go about adding a users_user_id with a corresponding roles_role_id to the users_has_roles table so my users can have roles?
My Users.java entity class:
@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.
My Roles.java entity class:
@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.
Thanks
---- UPDATE ----
// New Users
Users currentUser = new Users();
currentUser.setUserId(userId);
currentUser.setUsername(email);
currentUser.setPassword(password);
getUsersFacade().create(currentUser);
Ok first off thanks to Mikko for leading me to the answer. I just wanted to post an answer that might be directly helpful to anybody else that might be in the position I was in. Also this is based on a Eureka moment so it might not be technically correct but this is how I see it.
The big issue that I faces was that in MySQL I could see the bridging table as an individual table! (sorry I can't post an image of my EER diagram but I don't seem to have enough privileges at the moment) So I assumed that Java would also see the bridging table as a table! Well it doesn't. That bridging table doesn't really exist in Java as a conventional table it is in fact represented by the opposing tables collection type that you associate with it.
The easiest way to see it for me was to completely forget the bridging table and concentrate on the two 'real' tables and associating the data in those. The following code is NOT best practice as I'm simply setting the role_id but it's fine just to show my point.
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);
Hope that helps anybody else that is struggling with many to many relationships.
(NB. I've edited the original question code to use a List instead of a Collection for ease but you can just as well use any other type that fits your needs.)
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