I have a situation that is quite similar to the one outlined in this question's diagram: JPA. JoinTable and two JoinColumns, although with different issues.
I have three tables: Function, Group, and Location. Currently, I have a join table set up between Location and Group using #JoinTable. It is #ManyToMany on both sides, and works perfectly fine.
I am attempting to add the constraint that no Location should be associated with more than one Group that has the same Function. So I added a column for Function to my join table in my SQL schema and a uniqueness constraint across the Location and Function columns, like so:
create table function_table (
id varchar(50),
primary key(id)
);
create table group_table (
id varchar(50),
function_id varchar(50) not null,
primary key(id)
);
alter table group_table add constraint FK_TO_FUNCTION foreign key (function_id) references function_table;
create table location_table (
id varchar(50),
primary key(id)
);
create table group_location_join (
location_id varchar(50) not null,
group_id varchar(50) not null,
function_id varchar(50) not null,
primary key(location_id, group_id, function_id),
unique(location_id, function_id)
);
alter table group_location_join add constraint FK_TO_LOCATION foreign key (location_id) references location_table;
alter table group_location_join add constraint FK_TO_GROUP foreign key (group_id) references group_table;
alter table group_location_join add constraint FK_TO_FUNCTION foreign key (function_id) references function_table;
I then attempted to set up the following in my model entities:
#Entity
#Table(name = "function_table")
public class Function {
#Id
#Column(name = "id", length = 50)
private String id;
}
#Entity
#Table(name = "group_table")
public class Group {
#Id
#Column(name = "id", length = 50)
private String id;
#ManyToOne
#JoinColumn(name = "function_id", referencedColumnName = "id", nullable = false)
private Function function;
#ManyToMany
#JoinTable(name = "group_location_join",
joinColumns = {#JoinColumn(name = "group_id", referencedColumnName = "id"),
#JoinColumn(name = "function_id", referencedColumnName = "function_id")},
inverseJoinColumns = #JoinColumn(name="location_id", referencedColumnName = "id"))
private Set<Location> locations;
}
#Entity
#Table(name = "location_table")
public class Location {
#Id
#Column(name = "id", length = 50)
private String id;
#ManyToMany
#JoinTable(name = "group_location_join",
joinColumns = #JoinColumn(name="location_id", referencedColumnName = "id")
inverseJoinColumns = {#JoinColumn(name = "group_id", referencedColumnName = "id"),
#JoinColumn(name = "function_id", referencedColumnName = "function_id")})
private Set<Group> groups;
}
(Obviously, there is more to these entities, but I stripped them down to only the parts relevant to this question.)
This does not work. When I write a simple test to create a Location associated with a Group that is associated with a Function, the minute I try to flush the session to commit the transaction, Hibernate gives me this:
java.lang.ClassCastException: my.package.Group cannot be cast to java.io.Serializable
I think what's happening is that Hibernate is getting confused, throwing up its hands, and saying "I'll just serialize it, send it to the database, and hope it knows what's going on."
When I add implements Serializable and add a serialVersionUID to Group, I then get this:
org.hibernate.exception.SQLGrammarException: user lacks privilege or object not found: FUNCTION_ID
I'm not really sure how to proceed at this point, or if perhaps I have already proceeded too far down the wrong path. Maybe I'm not thinking about the SQL correctly, and there is a much easier way to ensure this constraint that doesn't involve all this ridiculousness.
Edit: In my system, the DAOs for the tables involved have no save capabilities. Which means that as long as my constraint is set up in the database, my application doesn't care; it can't insert things that violate the constraint because it can't insert things at all.
Edit 2: I never originally solved the stated problem, and instead simply added a third column in my database schema without touching the Java code, as stated in my first Edit section above. But I have since experimented with creating an explicit join table object with an #Embedded compound key, and it seems to work.
You are trying to create a composite primary key. In Hibernate you can do it using the #Embeddable annotation. In the example below you can find the way to use a composite key for two entities.
I believe you can move forward with this example and create your own version of primary key.
Mapping ManyToMany with composite Primary key and Annotation:
Related
UPDATE: Changed code to be coherent to db model and changed details of the model itself. Also added code of the section that causes the error.
I am trying to implement a small database consulting system in Hibernate with PostgreSQL and having issues with one specific pair of tables. As you can see, it's a system for car rental services, and the tables store drivers and rentals. A driver is supposed to be able to have multiple rentals (but not the other way around).
Problem Tables
CREATE TABLE Driver(
cod_driver SERIAL PRIMARY KEY,
cod_client INTEGER,
num_license BIGINT UNIQUE,
expiration_license DATE,
ident_driver BIGINT,
FOREIGN KEY (cod_client)
REFERENCES Client(cod_client)
ON UPDATE CASCADE
ON DELETE CASCADE
);
CREATE TABLE Rental(
cod_rental SERIAL PRIMARY KEY,
cod_plate VARCHAR(10),
cod_dest VARCHAR(10),
cod_driver INTEGER,
date_delivery DATE,
FOREIGN KEY (cod_plate)
REFERENCES Vehicle(cod_plate)
ON UPDATE CASCADE
ON DELETE NO ACTION,
FOREIGN KEY (cod_dest)
REFERENCES Location(cod_location)
ON UPDATE CASCADE
ON DELETE NO ACTION,
FOREIGN KEY (cod_driver)
REFERENCES Driver(cod_driver)
ON UPDATE CASCADE
ON DELETE CASCADE
);
I did my implementation using Hibernate as follows (short of getters/setters for brevity):
Driver
#Entity
public class Driver {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer cod_driver;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "cod_client")
private Client client;
private Long num_license;
private Long ident_driver;
private LocalDate expiration_license;
}
Rental
#Entity
public class Rental {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Integer cod_rental;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "cod_plate")
private Vehicle vehicle;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "cod_dest")
private Location location_dest;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "cod_driver")
private Driver driver;
private LocalDate date_delivery;
Context of PSQLException
Persist function call in Main.java (clientGet is obtained through successfull queries, and inserts is just a class for queries):
Driver d = new Driver(clientGet, 3294324792L, 321312931L, LocalDate.of(2030, 10, 01));
inserts.insertEntity(d);
insertEntity function:
public void insertEntity(Object o) // Basic insertion of any persistent object
{
em.getTransaction().begin();
em.persist(o);
em.getTransaction().commit();
}
Error
The error I get is this:
Caused by: org.postgresql.util.PSQLException:
ERROR: insert or update on table "driver" violates foreign key
constraint "fkdfq0qhvpkw1dqguk6dv1dsj0t"
Detail: Key (cod_driver)=(3) is not present in table "rental".
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2497)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2233)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:310)
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:446)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:370)
at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:149)
at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:124)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)
What I've Considered
From my understanding, the relationship didn't need to be bidirectional (though I did try to use mappedBy), given that I don't store rentals in driver table.
I just don't understand what constraint could possibly be violated by this. It's as if it expects the value of cod_driver to be already in the rentals table, but a rental entity depends on the pre-existence of the driver existence. SQL for the database doesn't seem to have any constraint like that.
Can someone help me understand what I'm doing wrong? I tried all things I found, but nothing shed any light on this.
use many to many relationship between rental and driver.the same problem i faced once in my PurchaseOrder and PaymentMethods relationship.
#ManyToMany(cascade = { CascadeType.PERSIST, CascadeType.MERGE })
#JoinTable(name = "rental_driver", joinColumns = #JoinColumn(name = "rental_id"), inverseJoinColumns = #JoinColumn(name = "driver_id"))
private List driver = new List();
I have this Parent class
#Entity
#Table(name = "category")
#NamedQuery(name = "category.findAll", query = "SELECT c FROM Category c")
public class Category implements Serializable {
public Category(){}
#Column(name = "name", nullable = false)
#Id
private String name;
#Column(name = "col2")
private Boolean col2;
}
And i have referenced the parent table in child table as follows:
#ManyToOne(cascade = {CascadeType.ALL})
#JoinColumn(name = "cat_name")
private Category category
when i run this JPQL query
update Category c SET c.name=:newName ,c.termsCanHaveChildren=:canHaveChdrn where c.name=:oldName
it's return with foreign key constraint error while i have put Cascade All in child field
Cannot delete or update a parent row: a foreign key constraint fails (`terms`.`term`, CONSTRAINT `FKaykenypxci167nqioh4xx9p3a` FOREIGN KEY (`cat_name`) REFERENCES `category` (`name`))
The problem lays at the constraint being generated by your persistence provider (hibernate), for the #JoinColumn(name = "cat_name") at the child table (and not with the CascadeType that you're defining)...
The generated constraint should indicated that when the PK of Category is Updated, any reference to such column should be updated also...
I believe this configuration should work (but you need to test it first, because I always generated my database model using scripts and not using hibernate features):
#ManyToOne
#JoinColumn(
name = "cat_name",
foreignKey = #ForeingKey(
name = "fk_child_category",
foreignKeyDefinition = "FOREIGN KEY (cat_name) REFERENCES category ON UPDATE CASCADE"
)
)
private Category category;
Also you need to check if your database supports "ON UPDATE CASCADE"... According to this link, oracle does not... (What database are you using?)
If this does not work, try the suggestion of Michelle...
That's expected: you are changing the Primary Key (#Id), that's used in a Foreign Key (#JoinColumn).
Use a surrogated immutable primary key.
I'm relatively new to JPA and Hibernate and am trying to see how the #OneTo One annotation works, let's say I have an entity "Task" with the following relation:
#OneToOne
#JoinColumn(name = "manager_id")
private Manager manager;
And there's the entity "Manager":
#Entity
#Table(name = "manager")
public class Manager {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
private String name;
public Manager() {
}
When I run the test file along with the "hibernate.hbm2ddl.auto" set to "update" I get a Many to One relation in the database (as you can see, there is no unique constraint of any kind that'd make it a one to one relation):
CREATE TABLE IF NOT EXISTS `timesheet`.`task` (
`id` BIGINT(20) NOT NULL AUTO_INCREMENT,
`completed` BIT(1) NOT NULL,
`description` VARCHAR(255) NULL DEFAULT NULL,
`manager_id` BIGINT(20) NULL DEFAULT NULL,
PRIMARY KEY (`id`),
INDEX `FK3635851B178516` (`manager_id` ASC),
CONSTRAINT `FK3635851B178516`
FOREIGN KEY (`manager_id`)
REFERENCES `timesheet`.`manager` (`id`))
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;
To be sure of this I tried adding two records with the same manager id and were indeed added, I also tried setting the unique constraint like "#Table(name = "Task",uniqueConstraints = #UniqueConstraint(columnNames =..." but no luck.
So Why is this happening and what's exactly the pros of using #OneToOne annotaion if no application logic is applied to validate this?
Also, Is there any chance that Hibernate is not able to do the DDL generation properly?
(I know that generation of schemas through hibernate is only meant for testing)
In a unidirectional relationship you will get the expected unique constraint if you mark it as "optional=false". You also get it if you set the join column explicitly as unique, of course.
So either
#OneToOne(optional=false)
#JoinColumn(name = "manager_id")
private Manager manager;
or
#OneToOne
#JoinColumn(name = "manager_id", unique=true)
private Manager manager;
So why do you need to mark it as not optional?
My guess is that, when a value is optional, the column can contain many null values, but in many databases this can not be done when a unique constraint is present. You can do it in MySQL though, so maybe the Hibernate generator is not taking the database into account in this case (a bug?).
See a discussion about MySQL handling of nulls here.
I had this issue too and I just needed to add the referenced column so I can get a generated table:
#Entity(name = "news")
public class News extends BaseEntity {
#Column(length = 500)
private String title;
#Column(length = 2000)
private String description;
#OneToOne(optional = false, fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#JoinColumn(name = "file_id", referencedColumnName = "id", unique = true)
private Picture picture;
}
I am using java and hibernate annotations to define the database schema and want to specify the foreign key in one table as the primary key.
I am getting an error when I set this up and think it could be down to how I am setting up the foreign key as the primary key because when I use a normal primary key I don't get an error.
What is the correct way to set up a foreign key as the primary key?
My current code set up is :
#Table(name="BATCH_STEP_EXECUTION_CONTEXT")
public class BatchStepExecutionContext implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#JoinColumn(name = "STEP_EXECUTION_ID" , columnDefinition="BIGINT NOT NULL", referencedColumnName="STEP_EXECUTION_ID")
#ForeignKey(name="STEP_EXEC_CTX_FK ")
#IndexColumn(name="IDX_STEP_EXEC_CTX")
private BatchStepExecution batchStepExecution;
and is referenced by the Batch Step Execution table as:
// bi-directional many-to-one association to Batch Step Execution Context
#OneToMany(mappedBy = "batchStepExecution", cascade = {CascadeType.ALL})
private List<BatchStepExecutionContext> batchStepExecutionContext;
the error I'm getting when I try to run the code is:
Unable to read the mapped by attribute for batchStepExecutionContext in com.ccs.nbook.domain.model.BatchStepExecutionContext!
The tables I'm trying to model in the java code are:
CREATE TABLE BATCH_STEP_EXECUTION
(
STEP_EXECUTION_ID BIGINT NOT NULL GENERATED BY DEFAULT AS IDENTITY (MAXVALUE 9223372036854775807),
VERSION BIGINT NOT NULL,
STEP_NAME VARCHAR (100) NOT NULL,
JOB_EXECUTION_ID BIGINT NOT NULL,
STATUS VARCHAR (10),
COUNT BIGINT,
CONSTRAINT JOB_EXEC_STEP_FK FOREIGN KEY (JOB_EXECUTION_ID) REFERENCES BATCH_JOB_EXECUTION (JOB_EXECUTION_ID),
PRIMARY KEY (STEP_EXECUTION_ID)
)
;
CREATE TABLE BATCH_STEP_EXECUTION_CONTEXT
(
STEP_EXECUTION_ID BIGINT NOT NULL,
SHORT_CONTEXT VARCHAR (2500) NOT NULL,
SERIALIZED_CONTEXT LONG VARCHAR,
PRIMARY KEY (STEP_EXECUTION_ID),
CONSTRAINT STEP_EXEC_CTX_FK FOREIGN KEY (STEP_EXECUTION_ID) REFERENCES BATCH_STEP_EXECUTION (STEP_EXECUTION_ID)
)
;
So I am trying to model the relationship of STEP_EXECUTION_ID between both tables where it is a primary key in BATCH_STEP_EXECUTION and is a primary key and foreign key in BATCH_STEP_EXECUTION_CONTEXT
Not pretty sure you mean with
want to specify the foreign key in one table as the primary key.
Don't get exactly what you mean... this foreign key is already primary key, right?
Anyway, to know what's going on (and not only in this case), read the Exception:
Caused by: org.hibernate.MappingException: Unable to read the mapped by attribute for batchJobExecutionContext in com.domain.model.BatchJobExecutionContext!
It says: There's a missing mappedby in BatchJobExecutionContext!
How to fix it? Reading this answer with a simple example:
#Entity
public class Company {
#OneToMany(fetch = FetchType.LAZY, mappedBy = "company")
private List<Branch> branches;
}
#Entity
public class Branch {
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "companyId")
private Company company;
}
I can see you are missing the #ManyToOne side of the relation #OneToMany and it's mappedby attribute. As long you used: #OneToMany(mappedBy = "batchStepExecution", cascade = {CascadeType.ALL}) you must add #ManyToOne anottation in the other side. So your code need to be like this:
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "STEP_EXECUTION_ID" , columnDefinition="BIGINT NOT NULL", referencedColumnName="STEP_EXECUTION_ID")
#ForeignKey(name="STEP_EXEC_CTX_FK ")
#IndexColumn(name="IDX_STEP_EXEC_CTX")
private BatchStepExecution batchStepExecution;
NOTES:
Check this tutorial for further info
I'm using Hibernate 3.5.2-FINAL with annotations to specify my persistence mappings. I'm struggling with modelling a relationship between an Application and a set of Platforms. Each application is available for a set of platforms.
From all the reading and searching I've done, I think I need to have the platform enum class be persisted as an Entity, and to have a join table to represent the many-to-many relationship. I want the relationship to be unidirectional at the object level, that is, I want to be able to get the list of platforms for a given application, but I don't need to find out the list of applications for a given platform.
Here are my simplified model classes:
#Entity
#Table(name = "TBL_PLATFORM")
public enum Platform {
Windows,
Mac,
Linux,
Other;
#Id
#GeneratedValue
#Column(name = "ID")
private Long id = null;
#Column(name = "NAME")
private String name;
private DevicePlatform() {
this.name = toString();
}
// Setters and getters for id and name...
}
#Entity
#Table(name = "TBL_APP")
public class Application extends AbstractEntity implements Serializable {
private static final long serialVersionUID = 1L;
#Column(name = "NAME")
protected String _name;
#ManyToMany(cascade = javax.persistence.CascadeType.ALL)
#Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE})
#JoinTable(name = "TBL_APP_PLATFORM",
joinColumns = #JoinColumn(name = "APP_ID"),
inverseJoinColumns = #JoinColumn(name = "PLATFORM_ID"))
#ElementCollection(targetClass=Platform.class)
protected Set<Platform> _platforms;
// Setters and getters...
}
When I run the Hibernate hbm2ddl tool, I see the following (I'm using MySQL):
create table TBL_APP_PLATFORM (
APP_ID bigint not null,
PLATFORM_ID bigint not null,
primary key (APP_ID, PLATFORM_ID)
);
The appropriate foreign keys are also created from this table to the application table and platform table. So far so good.
One problem I'm running into is when I try to persist an application object:
Application newApp = new Application();
newApp.setName("The Test Application");
Set<DevicePlatform> platforms = EnumSet.of(Platform.Windows, Platform.Linux);
newApp.setPlatforms(platforms);
applicationDao.addApplication(newApp);
What I would like to happen is for the appropriate rows in the Platform table to created, i.e. create a row for Windows and Linux, if they don't already exist. Then, a row for the new application should be created, and then the mapping between the new application and the two platforms in the join table.
One issue I'm running into is getting the following runtime exception:
2010-06-30 13:18:09,382 6613126-0 ERROR FlushingEventListener Could not synchronize database state with session org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.example.model.Platform
Somehow, the platform set is not being persisted when I try to persist the application. The cascade annotations are supposed to take care of that, but I don't know what's wrong.
So my questions are:
Is there a better way to model what I want to do, e.g. is using an Enum appropriate?
If my model is alright, how do I properly persist all of the objects?
I've been struggling with this for hours, and I've tried to recreate all of the code above, but it might not be complete and/or accurate. I'm hoping someone will point out something obvious!
You should decide whether your Platform is an entity or not.
If it's an entity, it can't be an enum, because list of possible platforms is stored in the database, not in the application. It should be a regular class with #Entity annotation and you will have a normal many-to-many relation.
If it isn't an entity, then you don't need TBL_PLATFORM table, and you don't have a many-to-many relation. In this case you can represent a set of Platforms either as an integer field with bit flags, or as a simple one-to-many relation. JPA 2.0 makes the latter case simple with #ElementCollection:
#ElementCollection(targetClass = Platform.class)
#CollectionTable(name = "TBL_APP_PLATFORM",
joinColumns = #JoinColumn(name = "APP_ID"))
#Column(name = "PLATFORM_ID")
protected Set<Platform> _platforms;
-
create table TBL_APP_PLATFORM (
APP_ID bigint not null,
PLATFORM_ID bigint not null, -- the ordinal number of enum value
primary key (APP_ID, PLATFORM_ID)
);
and enum Platform without annotations.
Simple use below mapping on your entity. Suppose that we have:
public enum TestEnum { A, B }
Then in your Entity class:
#ElementCollection(targetClass = TestEnum.class)
#CollectionTable(
name = "yourJoinTable",
joinColumns = #JoinColumn(name = "YourEntityId")
)
#Column(name = "EnumId")
private final Set<TestEnum> enumSet= new HashSet<>();
The following example shows what the situation is when Module is an entity and Langue is an enum.
#Entity
public class Module {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String libelle;
#ElementCollection(targetClass = Langue.class, fetch = FetchType.EAGER)
#CollectionTable(name = "link_module_langue",
joinColumns = #JoinColumn(name = "module_id", referencedColumnName = "id"))
#Enumerated(EnumType.STRING)
#Column(name = "langue")
private Set<Langue> langues;
}
public enum Langue {
FRANCAIS, ANGLAIS, ESPAGNOLE
}
You should create link_module_langue table, please see the following sql code :
CREATE TABLE `link_module_langue` (
`module_id` BIGINT(20) NOT NULL,
`langue` VARCHAR(45) NOT NULL,
PRIMARY KEY (`module_id`, `langue`),
CONSTRAINT `module_fk`
FOREIGN KEY (`module_id`)
REFERENCES `module` (`id`)
ON DELETE CASCADE
ON UPDATE CASCADE);
NB: Langue is not an entity and would not have its own table.