I am looking for an answer if it is possible or not in hibernate. What I am trying to achieve is that if a field exists in a particular table then only it should insert it. Else just ignore the field in the #Entity class.
I want this as a new field is going to introduce in one of the table we are using and there are many dependent components which right now insert the data into that table. I don't want a big bang release. Want something like it doesn't impact the older version as well as when the upgrade happens and a new column introduced then also it should work.
For example -
#Entity
#Table(name = "EMPLOYEE_RECORDS")
public class Employee
{
#Id
#Column(name = "employee_id")
private Integer employeeId;
#Column(name = "employee_name")
private String employeeName;
#Column(name="address")
private String address;
}
What if I only want to insert address field into DB only when column(address) exists in the table EMPLOYEE_RECORDS. Please forgive me if this is something obvious, as I am not very proficient in Hibernate.
Also let me explain what have I thought of (But not sure if it will also work) -
1. Create 2 different #Entity classes. Try to insert and if the insertion failed then at runtime switch the #Entity and use without address.
2. Check if field exist in the table by simple query if it fails use #Entity without address else use without address.
I'm very confused about the scenario - It seems like there were deeper issues regarding decoupling of components in your system.
Nevertheless, you can add the column in the database, but you don't need to declare the field in the hibernate entity. On the other hand there is no way you can have an optional field in an hibernate entity. Either a field is mapped or it is not mapped.
Related
So I'm new to JPA and just trying to figure out the best practices for what I need. I have code the looks like the following Entity and when I use findAll() in the controller its automatically pulling the data I want from Equipment and Validation. Whats the proper way to just retrieve Equipment though if I dont Validation. The full database is much larger than this with many more joins so there's an ask to be able to just retrieve the data within a single table also.
#Entity
#Table()
public class Equipment{
#Id
#Column(name="eqpmnt_id")
Integer equipmentId;
#Column()
String equipmentName;
#OneToOne()
#JoinColumn(name="eqpmnt_id")
Validation validation;
In a SpringBoot app using Hibernate, I have an entity similar to the following:
#Entity
#Table(...)
public class MyEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id", unique = true, nullable = false)
private Long id;
#Convert(converter = IntegerListConverter.class) //this maps a set of integers to a string, and vice versa when writing to the DB
#Column(name = "types", nullable = false)
private Set<Integer> types;
//other members, getters and setters omitted for brevity
}
I'm doing a search based on several parameters and therefore the query has to be built programmatically to filter based on the variable input. I want to write a query equivalent to the following SQL:
SELECT * FROM my_entity
WHERE id IN (:ids)
AND types LIKE '%:type%';
or equivalent to:
SELECT * FROM my_entity
WHERE id IN (:ids)
AND CONCAT(',', types) LIKE '%,:type%';
When using the first approach the persistence layer complains about types not being a Set.
The second approach works if I write it using a #Query annotation but I can't really use that since, like I mentioned before, the query is built conditionally depending on the user filter.
One additional note, I'm performing the query on a large dataset (i.e. ~100K matching entries) on MySQL, and running separate queries will involve transferring a lot of data which makes it slow (i.e. ~20 seconds).
Note: Please don't ramble about how bad it is to store one-to-many relationships on the same table. There are trade-offs that were considered and the system is designed like that for a reason.
Help appreciated.
Thanks in advance.
Annotate it with #Basic then this should work. IMO you should consider using the JSON type in MySQL instead to avoid the custom "parsing" that you have to do to be able to find individual values. I think you can even index this properly when you switch to JSON.
I want to update an existing entity by handing an "incomplete" instance of that entity to the JpaRepository. By incomplete i mean that only the values i want to change are set and the other values are null. Now if i would do that, all null values would be saved as null too and therefore overwrite the values i want to keep.
I thought about loading the entity from the database first and somehow merge the changes into that loaded object and saving it again, but there must be a better approach.
My entity:
#Entity
#Table
public class Location {
#Id
#NotNull
#Type(type = "uuid-char")
private UUID id = UUID.randomUUID();
#Column
#NotEmpty
private String title;
#Column
#NotEmpty
private String description;
...
My repository:
#Repository
public interface LocationRepository extends JpaRepository<Location, UUID>, LocationFilterFragment, JpaSpecificationExecutor {
Optional<Location> findLocationById(UUID id);
...
I use the standard repo.save(location) method by the way.
Update: One way could be to use a dynamic query / criteria query, but i am looking for something more convenient and less error prone.
It would be enough to show me the right direction, because I do not know exactly what to look for. Thanks in advance!
My first approach would be: don't merge your incomplete object. If you call save on your repository (which translates to a merge on an entityManager) Hibernate treats this as a current state, and will update all values.
I would proceed with the following:
find the entity you want to change by id
set the values you want to change by copying them from your "incomplete object"
Remember that these 2 steps must be performed in one transaction. When exiting the transaction scope, hibernate will rely on its dirty checking mechanism and update the entity (no merge call needed) In this approach your "incomplete object" does not have to be an entity, it is never persisted.
Note that by default, all fields will be sent in the update query (but now unchanged fields are not null, they reflect the previous state of the dB) if you want only dirty fields to be part of your query, learn about #DynamicUpdate
Another note: if you go down your custom jpql or criteria API update, you have the benefit of one select not executed. On the downside, Hibernate isn’t aware of the changes and doesn’t update its caches.
Preliminary Info
I'm currently trying to integrate Hibernate with my team at work. We primarily do Java web development, creating webapps that provide data to clients. Our old approach involves calling stored procedures with JDBC (on top of Oracle boxes) and storing their results in beans. However, I've heard a lot about the benefits of integrating Hibernate into a development environment like ours so I'm attempting to move away from our old habits. Note: I'm using the Hibernate JPA annotation approach due to simplicity for team adoption's sake.
Specific Problem
The specific issue I'm having currently is using Hibernate with normalized tables. We have a lot of schemas structured like so:
StateCodes (integer state_code, varchar state_name)
Businesses (integer business_id, varchar business_name, integer state_code)
I want to be able to have a single #Entity that has all of the "Businesses" fields, except instead of "state_code" it has "state_name". To my understanding, Hibernate treats #Entity classes as tables. The #OneToMany, #OneToOne, #ManyToOne annotations create relationships between entities, but this is a very simplistic, dictionary-like lookup and I feel like it doesn't apply here (or might be overkill).
One approach I've seen is
#Formula("(select state_name from StateCodes where Businesses.state_code = state_code)")
private String stateCode;
But, given Hibernate's perk of "avoiding writing raw SQL", this seems like bad practice. Not to mention, I'm extremely confused about how Hibernate will then treat this field. Does it get saved on a save operation? It's just defined as a query, not a column, after all.
So what is the best way to accomplish this?
I do not see any reason not use the standard JPA mappings in this case. Short of creating a database view and mapping an entity to that (or using the non-JPA compliant #Formula) then you will have to map as below.
Unless you are providing a means for the State to be changed then you do not need to expose the State entity to the outside world: JPA providers do not need getters/setters to be present.. Neither do you need to Map a State to Businesses:
#Entity
#Table(name = "Businesses")
public class Business{
//define id and other fields
#ManyToOne
#JoinColumn(name = "state_code")
private State state;
public String getStateName(){
return state.getName();
}
}
#Entity
#Table(name="StateCodes")
public class State{
//define id and other fields.
#Column(name = "state_name")
private String stateName;
public String getStateName(){
return stateName;
}
}
I'm currently coming (back) up to speed with EJB and while I was away it changed drastically (so far for the better). However, I've come across a concept that I am struggling with and would like to understand better as it seems to be used in our (where I work, not me and all the voices in my head) code quite a bit.
Here's the example I've found in a book. It's part of an example showing how to use the #EmbeddedId annotation:
#Entity
public class Employee implements java.io.Serializable
{
#EmbeddedId
#AttributeOverrides({
#AttributeOverride(name="lastName", column=#Column(name="LAST_NAME"),
#AttributeOverride(name="ssn", column=#Column(name="SSN"))
})
private EmbeddedEmployeePK pk;
...
}
The EmbeddedEmployeePK class is a fairly straightforward #Embeddable class that defines a pair of #Columns: lastName and ssn.
Oh, and I lifted this example from O'Reilly's Enterprise JavaBeans 3.1 by Rubinger & Burke.
Thanks in advance for any help you can give me.
It's saying that the attributes that make up the embedded id may have predefined (through explicit or implicit mappings) column names. By using the #AttributeOverride you're saying "ignore what other information you have with regard to what column it is stored in, and use the one I specify here".
In the UserDetails class, I have overridden homeAddress & officeAddress with Address
This One Address POJO will act for two table in DB.
DB:
Table1 Table2
STREET_NAME HOME_STREET_NAME
CITY_NAME HOME_CITY_NAME
STATE_NAME HOME_STATE_NAME
PIN_CODE HOME_PIN_CODE
The EmbeddedEmployeePK class is a fairly straightforward #Embeddable class that defines a pair of #Columns: lastName and ssn.
Not quite - EmbeddedEmployeePK defines a pair of properties, which are then mapped to columns. The #AttributeOverride annotations allow you to override the columns to which the embedded class's properties are mapped.
The use case for this is when the embeddable class is used in different situations where its column names differ, and some mechanism is required to let you change those column mappings. For example, say you have an entity which contains two separate instances of the same embeddable - they can't both map to the same column names.
JPA tries to map field names to column names in a datasource, so what you're seeing here is the translation between the name of a field variable to the name of a column in a database.
You can override also other column properties (not just names).
Let's assume that you want to change the length of SSN based on who is embedding your component. You can define an #AttributeOverride for the column like this:
#AttributeOverrides({
#AttributeOverride(name = "ssn", column = #Column(name = "SSN", length = 11))
})
private EmbeddedEmployeePK pk;
See "2.2.2.4. Embedded objects (aka components)" in the Hibernate Annotations documentation.
In order to preserve other #Column properties (such as name and nullable) keep them on the overridden column the same as you specified on the original column.