eBook – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
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Let's get started with a Microservice Architecture with Spring Cloud:

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eBook – Mockito – NPI EA (tag = Mockito)
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Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.

Get started with mocking and improve your application tests using our Mockito guide:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.

Get started with understanding multi-threaded applications with our Java Concurrency guide:

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eBook – Reactive – NPI EA (cat=Reactive)
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Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:

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eBook – Java Streams – NPI EA (cat=Java Streams)
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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

But these can also be overused and fall into some common pitfalls.

To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

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eBook – Jackson – NPI EA (cat=Jackson)
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Do JSON right with Jackson

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eBook – HTTP Client – NPI EA (cat=Http Client-Side)
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Get the most out of the Apache HTTP Client

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eBook – Maven – NPI EA (cat = Maven)
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Get Started with Apache Maven:

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eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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eBook – RwS – NPI EA (cat=Spring MVC)
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Building a REST API with Spring?

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Course – LS – NPI EA (cat=Jackson)
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Get started with Spring and Spring Boot, through the Learn Spring course:

>> LEARN SPRING
Course – RWSB – NPI EA (cat=REST)
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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

>> The New “REST With Spring Boot”

Course – LSS – NPI EA (cat=Spring Security)
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Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.

I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.

You can explore the course here:

>> Learn Spring Security

Course – LSD – NPI EA (tag=Spring Data JPA)
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Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.

Get started with Spring Data JPA through the guided reference course:

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Partner – Moderne – NPI EA (cat=Spring Boot)
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Refactor Java code safely — and automatically — with OpenRewrite.

Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.

Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.

Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.

Course – LJB – NPI EA (cat = Core Java)
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Code your way through and build up a solid, practical foundation of Java:

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1. Overview

Going out to the database is expensive. We may be able to improve performance and consistency by batching multiple inserts into one.

In this tutorial, we’ll look at how to do this with Spring Data JPA.

2. Spring JPA Repository

First, we’ll need a simple entity. Let’s call it Customer:

@Entity
public class Customer {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;

    // constructor, getters, setters 
}

And then, we need our repository:

public interface CustomerRepository extends CrudRepository<Customer, Long> {
}

This exposes a saveAll method for us, which will batch several inserts into one.

So, let’s leverage that in a controller:

@RestController
public class CustomerController {   
    @Autowired
    CustomerRepository customerRepository;   

    @PostMapping("/customers")
    public ResponseEntity<String> insertCustomers() {        
        Customer c1 = new Customer("James", "Gosling");
        Customer c2 = new Customer("Doug", "Lea");
        Customer c3 = new Customer("Martin", "Fowler");
        Customer c4 = new Customer("Brian", "Goetz");
        List<Customer> customers = Arrays.asList(c1, c2, c3, c4);
        customerRepository.saveAll(customers);
        return ResponseEntity.created("/customers");
    }

    // ... @GetMapping to read customers
}

3. Testing Our Endpoint

Testing our code is simple with MockMvc:

@Autowired
private MockMvc mockMvc;

@Test 
public void whenInsertingCustomers_thenCustomersAreCreated() throws Exception {
    this.mockMvc.perform(post("/customers"))
      .andExpect(status().isCreated()));
}

4. Are We Sure We’re Batching?

So, actually, there is a just a bit more configuration to do – let’s do a quick demo to illustrate the difference.

First, let’s add the following property to application.properties to see some statistics:

spring.jpa.properties.hibernate.generate_statistics=true

At this point, if we run the test, we’ll see stats like the following:

11232586 nanoseconds spent preparing 4 JDBC statements;
4076610 nanoseconds spent executing 4 JDBC statements;
0 nanoseconds spent executing 0 JDBC batches;

So, we created four customers, which is great, but note that none of them were inside a batch.

The reason is that batching isn’t switched on by default in some cases.

In our case, it’s because we are using id auto-generation. So, by default, saveAll does each insert separately.

So, let’s switch it on:

spring.jpa.properties.hibernate.jdbc.batch_size=4
spring.jpa.properties.hibernate.order_inserts=true

The first property tells Hibernate to collect inserts in batches of four. The order_inserts property tells Hibernate to take the time to group inserts by entity, creating larger batches.

So, the second time we run our test, we’ll see the inserts were batched:

16577314 nanoseconds spent preparing 4 JDBC statements;
2207548 nanoseconds spent executing 4 JDBC statements;
2003005 nanoseconds spent executing 1 JDBC batches;

We can apply the same approach to deletes and updates (remembering that Hibernate also has an order_updates property).

5. Conclusion

With the ability to batch inserts, we can see some performance gains.

We, of course, need to be aware that batching is automatically disabled in some cases, and we should check and plan for this before we ship.

The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
Baeldung Pro – NPI EA (cat = Baeldung)
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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

>> Explore a clean Baeldung

Once the early-adopter seats are all used, the price will go up and stay at $33/year.

eBook – HTTP Client – NPI EA (cat=HTTP Client-Side)
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The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:

>> Download the eBook

eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.

Get started with understanding multi-threaded applications with our Java Concurrency guide:

>> Download the eBook

eBook – Java Streams – NPI EA (cat=Java Streams)
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Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.

But these can also be overused and fall into some common pitfalls.

To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:

>> Join Pro and download the eBook

eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

Explore the eBook

Course – LS – NPI EA (cat=REST)

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Get started with Spring Boot and with core Spring, through the Learn Spring course:

>> CHECK OUT THE COURSE

Partner – Moderne – NPI EA (tag=Refactoring)
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Modern Java teams move fast — but codebases don’t always keep up. Frameworks change, dependencies drift, and tech debt builds until it starts to drag on delivery. OpenRewrite was built to fix that: an open-source refactoring engine that automates repetitive code changes while keeping developer intent intact.

The monthly training series, led by the creators and maintainers of OpenRewrite at Moderne, walks through real-world migrations and modernization patterns. Whether you’re new to recipes or ready to write your own, you’ll learn practical ways to refactor safely and at scale.

If you’ve ever wished refactoring felt as natural — and as fast — as writing code, this is a good place to start.

eBook Jackson – NPI EA – 3 (cat = Jackson)