Java jpa insert into

How to construct an insert query in jpa?

JPA (Java Persistence API) is a Java specification for accessing, persisting, and managing data between Java objects/classes and relational databases. One of the most common operations in data persistence is inserting data into the database. The insert operation can be performed using the EntityManager’s persist method or by using JPQL (Java Persistence Query Language) INSERT INTO clause. In this article, we will discuss two methods to construct an insert query in JPA.

Method 1: Using EntityManager’s persist method

To construct an insert query in JPA using EntityManager’s persist method, follow the steps below:

1. Create an instance of the entity you want to insert. For example, if you have an entity called «Person», you would create a new instance like this:

Person person = new Person(); person.setName("John"); person.setAge(30);

1. Get an instance of the EntityManager. This can be done through dependency injection or by creating a new instance using a factory. For example:

EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit"); EntityManager em = emf.createEntityManager();

Here’s the complete code example:

Person person = new Person(); person.setName("John"); person.setAge(30); EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit"); EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); em.persist(person); em.getTransaction().commit(); em.close(); emf.close();

This code creates a new instance of the Person entity, sets its properties, creates an EntityManager, begins a transaction, inserts the entity into the database using the persist method, commits the transaction, and then closes the EntityManager and EntityManagerFactory.

Note that the name of the persistence unit («my-persistence-unit» in this example) should match the name of the persistence unit defined in your persistence.xml file.

This is one of the simplest ways to insert an entity into a database using JPA and the EntityManager’s persist method.

Method 2: Using JPQL INSERT INTO clause

To construct an insert query in JPA using the JPQL INSERT INTO clause, you can follow these steps:

MyEntity entity = new MyEntity(); entity.setName("John"); entity.setAge(25);

String query = "INSERT INTO MyEntity (name, age) VALUES (:name, :age)"; Query q = entityManager.createQuery(query);

q.setParameter("name", entity.getName()); q.setParameter("age", entity.getAge());

int result = q.executeUpdate();

The complete code example will look like this:

MyEntity entity = new MyEntity(); entity.setName("John"); entity.setAge(25); String query = "INSERT INTO MyEntity (name, age) VALUES (:name, :age)"; Query q = entityManager.createQuery(query); q.setParameter("name", entity.getName()); q.setParameter("age", entity.getAge()); int result = q.executeUpdate();

This code will insert a new record into the MyEntity table with the name «John» and age «25».

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INSERT Statement in JPA

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1. Overview

In this quick tutorial, we’ll learn how to perform an INSERT statement on JPA objects.

For more information about Hibernate in general, check out our comprehensive guide to JPA with Spring and introduction to Spring Data with JPA for deep dives into this topic.

2. Persisting Objects in JPA

In JPA, every entity going from a transient to managed state is automatically handled by the EntityManager.

The EntityManager checks whether a given entity already exists and then decides if it should be inserted or updated. Because of this automatic management, the only statements allowed by JPA are SELECT, UPDATE and DELETE.

In the examples below, we’ll look at different ways of managing and bypassing this limitation.

3. Defining a Common Model

Now, let’s start by defining a simple entity that we’ll use throughout this tutorial:

@Entity public class Person < @Id private Long id; private String firstName; private String lastName; // standard getters and setters, default and all-args constructors >

Also, let’s define a repository class that we’ll use for our implementations:

@Repository public class PersonInsertRepository

Additionally, we’ll apply the @Transactional annotation to handle transactions automatically by Spring. This way, we won’t have to worry about creating transactions with our EntityManager, committing our changes, or performing rollback manually in the case of an exception.

4. createNativeQuery

For manually created queries, we can use the EntityManager#createNativeQuery method. It allows us to create any type of SQL query, not only ones supported by JPA. Let’s add a new method to our repository class:

@Transactional public void insertWithQuery(Person person)

With this approach, we need to define a literal query including names of the columns and set their corresponding values.

We can now test our repository:

@Test public void givenPersonEntity_whenInsertedTwiceWithNativeQuery_thenPersistenceExceptionExceptionIsThrown() < Person person = new Person(1L, "firstname", "lastname"); assertThatExceptionOfType(PersistenceException.class).isThrownBy(() ->< personInsertRepository.insertWithQuery(PERSON); personInsertRepository.insertWithQuery(PERSON); >); >

In our test, every operation attempts to insert a new entry into our database. Since we tried to insert two entities with the same id, the second insert operation fails by throwing a PersistenceException.

The principle here is the same if we are using Spring Data’s @Query.

5. persist

In our previous example, we created insert queries, but we had to create literal queries for each entity. This approach is not very efficient and results in a lot of boilerplate code.

Instead, we can make use of the persist method from EntityManager.

As in our previous example, let’s extend our repository class with a custom method:

@Transactional public void insertWithEntityManager(Person person)

Now, we can test our approach again:

@Test public void givenPersonEntity_whenInsertedTwiceWithEntityManager_thenEntityExistsExceptionIsThrown() < assertThatExceptionOfType(EntityExistsException.class).isThrownBy(() ->< personInsertRepository.insertWithEntityManager(new Person(1L, "firstname", "lastname")); personInsertRepository.insertWithEntityManager(new Person(1L, "firstname", "lastname")); >); >

In contrast to using native queries, we don’t have to specify column names and corresponding values. Instead, EntityManager handles that for us.

In the above test, we also expect EntityExistsException to be thrown instead of its superclass PersistenceException which is more specialized and thrown by persist.

On the other hand, in this example, we have to make sure that we call our insert method each time with a new instance of Person. Otherwise, it will be already managed by EntityManager, resulting in an update operation.

6. Conclusion

In this article, we illustrated ways to perform insert operations on JPA objects. We looked at examples of using a native query, as well as using EntityManager#persist to create custom INSERT statements.

As always, the complete code used in this article is available over on GitHub.

Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

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