I'm having an issue with JPA and Hibernate. I have 2 classes (actually more but those are the 2 that are giving me a headache).
They have a OneToMany/ManyToOne relationship, and I have specified on the OneToMany that I want it to cascade every possible change (CascadeType.ALL).
However, when I let HBM2DDL run in "update" mode, it is creating foreign key constraints that are not fitting what I want to achieve. It is creating a constraint in RESTRICT mode, which is absolutely not what I have specified. Perhaps the error is in my code ? I've joined it below.
#Entity
public class Department {
#Id
#Column(name = "id", nullable = false)
private int id;
#Column(name = "name", nullable = false)
private String name;
#OneToMany(mappedBy = "departmentByDepartment", cascade = CascadeType.ALL)
private Collection<Article> productsById;
#OneToMany(mappedBy = "departmentByDepartment", cascade = CascadeType.ALL)
private Collection<User> usersById;
And then :
#Entity
#Table(name = "product", schema = "qlog_project", catalog = "")
public class Article {
#Id
#Column(name = "id", nullable = false)
private int id;
#Column(name = "name", nullable = false)
private String name;
#Column(name = "description", nullable = false)
private String description;
#Column(name = "price", nullable = false)
private double price;
#Column(name = "image", nullable = false)
private String image;
#ManyToOne
#JoinColumn(name = "department", referencedColumnName = "id", nullable = false)
private Department departmentByDepartment;
#OneToMany(mappedBy = "productByProductId", cascade = CascadeType.ALL)
private Collection<Stock> stocksById;
Also, I cannot seem to be able to delete an Article instance with EntityManager.remove(). It's not producing any query and not doing anything. Maybe it is linked ?
Thanks in advance,
Regards
Related
I want to join a single column from another table to one of my #Entity classes:
Currently it works as follows:
#Entity
public class Product {
#Id
private long id; //autogenerated
String type; //used for mapping
#ManyToOne
#JoinColumn(name = "type", insertable = false, updatable = false)
ProductMapping mapping;
}
#Entity
public class ProductMapping {
#Id
String type;
String longname;
}
Question: how could I replace the #ManyToOne mapping to directly map to String longname?
//TODO: how to directly map to 'mapping.longname'?
#JoinColumn(name = "type", insertable = false, updatable = false)
String mapping.longname;
You can use #Formula annotation with a query like this :
#Formula("(select pm.longname from product_mapping pm where pm.COL_NAME = value)")
private String longName;
//give the column name of type from product_mapping table
OR
You can also use the below approach :
#ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
#JoinColumn(name = "type", referencedColumnName = "COL_NAME", insertable = false, updatable = false)
ProductMapping mapping;
The other entity use #NaturalId annotation on the field.
#Entity
public class ProductMapping {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID")
String type;
#NaturalId
#Column(name = "SOME_VALUE")
String longname;
}
Currently I have the following 2 entities with a one to many relationship -
#Data
#Entity
#Table(name = "invoice_line")
#IdClass(InvoiceLinePK.class)
public class InvoiceLineEntity {
#Id
#Column(name = "line_id")
private String lineId;
#Id
#Column(name = "client_id")
private Integer clientId;
#Id
#Column(name = "invoice_id")
private String invoiceId;
#Column(name = "item_id")
private String itemId;
#Column(name = "amount")
private BigDecimal amount;
#ManyToOne
private InvoiceEntity invoice;
}
#Entity
#Table(name = "invoice")
#IdClass(InvoicePK.class)
#Data
public class InvoiceEntity {
#Id
#Column(name = "client_id")
private Integer clientId;
#Id
#Column(name = "invoice_id")
private String invoiceId;
#Column(name = "description")
private String description;
#Column(name = "txn_total_amount")
private BigDecimal txnTotalAmount;
#Column(name = "created_time", updatable = false)
#CreationTimestamp
private Date createdTime;
#Column(name = "updated_time")
#UpdateTimestamp
private Date updatedTime;
#OneToMany(fetch = FetchType.EAGER, orphanRemoval = true, mappedBy = "invoice")
private List<InvoiceLineEntity> invoiceLines;
}
In a case wherein let's say, one of my existing invoice has 3 lines and I receive a request that this particular invoice has been updated and it now has only 1 line instead of the previous 3 (so the other 2 have to be deleted), I would like to create a new Invoice object with this 1 InvoiceLineEntity and then do a invoiceRepository.save(invoice)
I am expecting that the other 2 InvoiceLine records would be automatically deleted because the orphanRemoval flag is enabled.
Can someone tell me how I can achieve this relationship by tweaking the entity relationship structure of the above 2 entities?
Your child entity must be the owner of the relationship, so that the orphans are allowed to be deleted
If you change and add mappedBy to that relation
#OneToMany(fetch = FetchType.EAGER, orphanRemoval = true, mappedBy = "bill")
private List<BillLine> billLines;
Then the BillLine must also hold a reference
public class BillLine {
#Id
#Column(name = "line_id")
private String lineId;
#Id
#Column(name = "company_id")
private Integer companyId;
#Id
#Column(name = "bill_id")
private String billId;
#Column(name = "item_id")
private String itemId;
#Column(name = "amount")
private BigDecimal amount;
#ManyToOne
private Bill bill;
}
Now it will remove the orphans
Also since you have multiple #Id on each entity. Do you know that you have to either declare a composite class or an embeddable class? Without one of those the multiple Ids are not valid.
Edit:
1) My bad mappedBy should be placed inside #OneToMany and not #JoinColumn. I have corrected it in my answer
2) Remove #JoinColumn. It is wrong in your configuration. By default #OneToMany inserts a column in the side of the #ManyToOne which holds the references to the primary table. You can override those default configurations and create a separate table for mappings but then you need the #JoinTable and I don't see any reason for that here.
This here
#JoinColumns(value = { #JoinColumn(name = "company_id", referencedColumnName = "company_id"),
#JoinColumn(name = "bill_id", referencedColumnName = "bill_id") })
definitely does not belong on #OneToMany
The following can be applied to #OneToMany but as said before I don't see any reason to do that and complicate a simple mapping which does not require a separate table.
#JoinTable(joinColumns = #JoinColumn(name = "company_id", referencedColumnName = "company_id"),
inverseJoinColumns = #JoinColumn(name = "bill_id", referencedColumnName = "bill_id") )
Check here for more information Jpa primary key
I have 2 tables project and employee have multiple relationship. Project has many employees, employee can join many projects( many to many). project have one employee whose is team leader, an employee can manager many projects(many to one). So how do I design database, and classes model mapping with database. Some one help me
This is my code
class user
#Entity(name = "USERS")
public class Users {
#Id
#Column(name = "USER_ID", length = 6)
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer userId;
#Column(name = "USER_NAME", length = 50, nullable = false)
private String userName;
#Column(name = "PASS_WORD", length = 50, nullable = false)
private String passWord;
#Column(name = "FULL_NAME", length = 50, nullable = false)
private String fullName;
#Column(name = "EMAIL", length = 50, nullable = false)
private String email;
#Column(name = "PHONE", length = 11, nullable = true)
private String phone;
#Column(name = "STATUS", nullable = true)
private Boolean status;
#ManyToMany(fetch = FetchType.LAZY)
#JsonIgnore
#JoinTable(name = "USERPROJECT", joinColumns = { #JoinColumn(name =
"USER_ID") }, inverseJoinColumns = {
#JoinColumn(name = "PROJECT_ID") })
private List<Project> projects;
#OneToMany(mappedBy = "teamlead")
private List<Project> projectOfTeamLead;
//get set.....
}
class project
#Entity(name = "PROJECTS")
public class Project {
#Id
#Column(name = "PROJECT_ID", length = 6)
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer projectId;
#Column(name = "PROJECT_NAME", length = 50, nullable=false)
private String projectName;
#Column(name = "USER_CREATE_ID", length = 6, nullable=false)
private Integer userCreateId;
// #Column(name = "TEAM_LEAD_ID", length = 6, nullable=false)
// private Integer teamLeadId;
#Column(name = "TIME_START", nullable=true)
private Date timeStart;
#Column(name = "TIME_END", nullable=true)
private Date timeEnd;
#ManyToMany(mappedBy = "projects")
private List<Users> users;
#ManyToOne
#JoinColumn(name = "TEAM_LEAD_ID")
private Users teamlead;
//get set...
}
I think you need to make your database fit into 3nf (third normal form). You are describing a database that uses two tables, but I think you need three at least, that way you can describe what employees are on what project. A "team" table that uses the PK's from the other two tables should be used. Conventionally, you would name it something like "ProjectEmployees" as it is comprised of the PK's from the "Projects" table and the "Employees" table respectively. I hope that answers your question. If you don't understand what I'm talking about, I highly recommend you watch this.
Ok, so I'd like to implement a simple forum example. So, I have threads, messages and users, of course and these are the pojos (I omitted the usually getters and simplicity)
Message
#Entity
#Table(name = "message")
public class Message implements java.io.Serializable, RecognizedServerEntities
{
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "id", unique = true, nullable = false)
private Integer id;
#ManyToOne(fetch = FetchType.LAZY)
#Cascade({ CascadeType.SAVE_UPDATE })
#JoinColumn(name = "thread", nullable = false)
private Thread thread;
#ManyToOne(fetch = FetchType.LAZY)
#Cascade({ CascadeType.SAVE_UPDATE })
#JoinColumn(name = "author", nullable = true)
private User user;
#Column(name = "title", nullable = false, length = 31)
private String title;
#Column(name = "body", nullable = false, columnDefinition = "Text")
private String body;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "last_modified_date", nullable = false, length = 19)
private Date lastModifiedDate;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "created_date", nullable = false, updatable = false, length = 19)
private Date createdDate;
}
User
#Entity
#Table(name = "user", uniqueConstraints =
{ #UniqueConstraint(columnNames = "email"),
#UniqueConstraint(columnNames = "nick") })
public class User implements java.io.Serializable, RecognizedServerEntities
{
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "id", unique = true, nullable = false)
private Integer id;
#Column(name = "email", unique = true, nullable = false, length = 31)
private String email;
#Column(name = "password", nullable = false, length = 31)
private String password;
#Column(name = "nick", unique = true, nullable = false, length = 31)
#NaturalId(mutable = false)
private String nick;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "registered_date", nullable = false, updatable = false, length = 19)
private Date registeredDate;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "user", orphanRemoval = false)
private Set<Thread> threads = new HashSet<Thread>(0);
#OneToMany(fetch = FetchType.LAZY, mappedBy = "user", orphanRemoval = false)
private /**transient /**/ Set<Message> messages = new HashSet<Message>(0);
}
Thread
#Entity
#Table(name = "thread")
public class Thread implements java.io.Serializable, RecognizedServerEntities
{
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "id", unique = true, nullable = false)
private Integer id;
#ManyToOne(fetch = FetchType.LAZY)
#Cascade({CascadeType.SAVE_UPDATE})
#JoinColumn(name = "parent_thread", nullable = true)
private Thread parentThread;
#ManyToOne(fetch = FetchType.LAZY)
#Cascade({CascadeType.SAVE_UPDATE})
#JoinColumn(name = "author", nullable = true)
private User user;
#Column(name = "title", nullable = false, length = 63)
private String title;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "last_modified_date", nullable = false, length = 19)
private Date lastModifiedDate;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "created_date", nullable = false, updatable = false, length = 19)
private Date createdDate;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "thread"/**/, orphanRemoval = true/**/)
#Cascade({ CascadeType.REMOVE })
private /**transient /**/ Set<Message> messages = new HashSet<Message>(0);
#OneToMany(fetch = FetchType.LAZY, mappedBy = "parentThread", orphanRemoval = true)
#Cascade({CascadeType.REMOVE })
private /**transient /**/ Set<Thread> subThreads = new HashSet<Thread>(0);
}
I have many doubts on the annotations of course, but these are the relevant choice.
When I delete an user, I don't want to delete all his threads and messages, so it make sense to don't use orphan-removal or cascade delete on the #OneToMany associations (ie the messages and threads collections).
Also, because the id is automatically generated from the database, I don't think it make sense at all to use the annotation CascadeType.UPDATE (or SAVE_UPDATE) on the collections of all the entity.
A thread are the most problematic entity to manage. When we delete a thread, we want that all its subthreads and all its messages were deleted. So, I use the CascadeType.REMOVE and orphan-removal annotations.
An all the #ManyToOne associations, I use the CascadeType.ALL. The idea is that if we delete a message or a subthread, all the parents will be updated.
All the collections are not transient.
Feel free to propose suggestion on this of course.
Btw, given the whole story, this is the question: suppose I have a thread "mThread" started from the user "mUser" with many messages from different users, how can I safely delete the user?
I tried different things, but I'm not sure of anything and in most cases I only have exceptions.
EDIT
I also have another class, StorageManager<T>, that is used to encapsulate the common code between entities. Basically, it implements the "one session per transaction" pattern. So each methodX() basically:
invoke sessionFactory.openSession() and session.beginTransaction()
invoke session.methodX()
invoke transaction.commit()
invoke session.clear() and session.close
Example with code
for (Thread t : mUser.getThreads())
{
t.setUser(null);
storageManagerThread.update(t);
}
for (Message m : mUser.getMessages())
{
m.setUser(null);
storageManagerMessage.update(t);
}
storageManagerUser.delete(mUser);
Until this point, all the table in the database have the right values. However, I don't know if it is the right way to proceed, because it leaves dirty collections.
Indeed, when at later point I try to execute some other options (e.g. update(mThread) or delete a message from mThread) a NullPointerException was thrown. Why is this? .
[using JPA, MySQL, MVC, Servlets, JSP]
If I read some data from database LEFT JOIN-ing three tables (inside method of DAO object) how should I format that result, so i can set it as request attribute (in servlet) and forwards to JSP page?
Entities(tables in db):
Post:
#Entity
#Table(name = "post")
public class Post implements Serializable {
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "post_id", unique = true, nullable = false)
private Integer id;
#Column(name = "post_title", length=300, unique = false, nullable = false)
private String title;
#Column(name = "post_date", unique = false, nullable = false)
private Date date;
#Column(name = "post_summary", length=1000, unique = false, nullable = true)
private String summary;
#Column(name = "post_content", length=50000, unique = false, nullable = false)
private String content;
#Column(name = "post_visitors", unique = false, nullable = false)
private Integer visitors;
#ManyToOne
#JoinColumn (name = "user_id", referencedColumnName="user_id", nullable = false)
private User user;
#ManyToOne
#JoinColumn (name = "category_id", referencedColumnName="category_id", nullable = false)
private Category category;
#OneToMany(cascade = { ALL }, fetch = LAZY, mappedBy = "post")
private Set<Comment> comments = new HashSet<Comment>();
...
Entity Comment:
#Entity
#Table(name = "comment")
public class Comment implements Serializable {
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "comment_id", unique = true, nullable = false)
private Integer id;
#Column(name = "comment_title", length=300, unique = false, nullable = false)
private String title;
#Column(name = "comment_date", unique = false, nullable = false)
private Date date;
#Column(name = "comment_content", length=600, unique = false, nullable = false)
private String content;
#ManyToOne
#JoinColumn (name = "user_id", referencedColumnName="user_id", nullable = false)
private User user;
#ManyToOne
#JoinColumn (name = "post_id", referencedColumnName="post_id", nullable = false)
private Post post;
...
Entity User:
#Entity
#Table(name = "user")
public class User implements Serializable {
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "user_id", unique = true, nullable = false)
private Integer id;
#Column(name = "user_name", length=45, unique = false, nullable = false)
private String name; // "first_name" + ' ' + "last_name"
//URL address to user's image
#Column(name = "user_image", length=500, unique = false, nullable = true)
private String image;
#Column(name = "user_username", length=45, unique = false, nullable = false)
private String username;
#Column(name = "user_password", length=45, unique = false, nullable = false)
private String password;
...
So, I would like to make a method, probably inside PostDAO object that will look something like this:
public <SomeDataTypeFormat???> getPostsSummaries(){
Query q = em.createNativeQuery("SELECT
post_title,
post_summary,
post_date,
COUNT(comment_id) AS comment_cnt,
user.user_name
FROM
post
LEFT JOIN user USING(user_id)
LEFT JOIN comment USING(post_id)
GROUP BY
post_id
ORDER BY
comment_cnt DESC");
...
}
Method returns some fields from all three tables in database.
Do I need to make separate class and store those data in objects of that class? Or JSON (although I haven't worked with it yet)?
What is the practice? What is easiest data format to use and forward from servlet to JSP, for some fields gotten as a result of joining couple tables?
It depends on your objective; to get the data to the browser, JSON and AJAX isn't a bad choice. To get the data to the JSP (from the Servlet), you'll probably want a Data Transfer Object (or possibly an immutable Value Object).