Search icon CANCEL
Subscription
0
Cart icon
Your Cart (0 item)
Close icon
You have no products in your basket yet
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Free Learning
Arrow right icon
Scala for Java Developers
Scala for Java Developers

Scala for Java Developers: Build reactive, scalable applications and integrate Java code with the power of Scala.

Arrow left icon
Profile Icon Thomas Alexandre
Arrow right icon
S$66.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3 (16 Ratings)
Paperback Apr 2014 282 pages Edition
eBook
S$36.99 S$52.99
Paperback
S$66.99
Subscription
Free Trial
Arrow left icon
Profile Icon Thomas Alexandre
Arrow right icon
S$66.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3 (16 Ratings)
Paperback Apr 2014 282 pages Edition
eBook
S$36.99 S$52.99
Paperback
S$66.99
Subscription
Free Trial
eBook
S$36.99 S$52.99
Paperback
S$66.99
Subscription
Free Trial

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Table of content icon View table of contents Preview book icon Preview Book

Scala for Java Developers

Chapter 2. Code Integration

Being able to make Java and Scala cooperate on the same code base is a prerequisite to guarantee a smooth transition between the two languages.

In this chapter, we are going to quickly create a small Java web application in which we will show you how to add Scala code to it. Then, we will cover some of the most common integration points between Java and Scala and how programming styles differ so that programmers who want to refactor and extend their Java application can do it according to some guidelines.

To avoid spending too much time on creating, understanding, and documenting a sample Java project, we are going to use a small database that is already available as part of the Oracle's NetBeans IDE distribution and create a JPA persistence layer as well as a REST API from it using the code generation features of the IDE.

Tip

Download the sample Java project

If you are impatient to directly jump into the Scala code integration features of this chapter, you may skip...

Creating a REST API from an existing database


The sample database bundled with the NetBeans IDE can be downloaded from the www.netbeans.org website. Just click on the Download button on this website and pick the JavaEE version of the IDE.

Once you have run the installation wizard, seen the The installation was successful! message, and started the IDE (Version 8.0 in our case), we are ready to create a fully functional web app in five minutes. The first time you use it, just click on the upper-left corner of the NetBeans IDE to close the startup screen and you should see the three tabs: Projects, Files, and Services on the left-hand side of the IDE.

The sample database

Our reference database can be seen from the IDE by clicking on the Services panel. Under the Databases menu that is part of the Services tab, double-click on the jdbc:derby://localhost:1527/sample [app on APP] Database Connection link to connect to the sample database on port 1527 (the default port for Derby databases) with the...

Adding a test in Scala


For now, we have only Java code in the small sample Maven project. We are ready to introduce a few lines of Scala to the same codebase in order to show how both languages seamlessly interoperate. Let's create a src/test/scala directory, next to the existing java/ directory, where we will put our following new CustomerScalaTest.scala class, which is a similar test to the one we already have under src/test/java:

package com.demo.sample

import org.junit._
import Assert._

class CustomerScalaTest {

  @Before
  def setUp: Unit = {
  }

  @After
  def tearDown: Unit = {
  }

  @Test
  def testGetCustomerId = {
    System.out.println("getCustomerId")
    val instance = new Customer()
    val expResult: Integer = null
    val result: Integer = instance.getCustomerId()
    assertEquals(expResult, result)
  }
}

If we run the tests again, that is, type >mvn clean test again, the class will just be ignored as it is not a .java source file.

Setting up Scala within a Java Maven project


In order to be able to start writing a Scala unit test and compile Scala code into our Java project, we need to add a few dependencies and the scala-maven-plugin to the pom.xml file. The dependencies are as follows:

  • Dependency for the core scala-library:

    <dependency>
      <groupId>org.scala-lang</groupId>
      <artifactId>scala-library</artifactId>
      <version>2.10.0</version>
    </dependency>
  • Dependency for scalatest (a framework for testing in Scala that supports JUnit and other styles; we will cover it in detail in Chapter 4, Testing Tools):

    <dependency>
      <groupId>org.scalatest</groupId>
      <artifactId>scalatest_2.10</artifactId>
      <version>2.0/version>
      <scope>test</scope>
    </dependency>
  • Dependency for JUnit to use Java Assert statements in our test case:

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId...

Scala and Java collaboration


Going back to the REPL, we are going to experiment further with mixing Scala and Java to explore some common integration needs, and in particular, testing and manipulating the Java REST API that we have built at the beginning of the chapter.

As a reminder on how to restart the REPL from the hello-scala project introduced in Chapter 1, Programming Interactively within Your Project, if you closed it in the meantime, just start a new terminal window, navigate to the root of the hello-scala project, and enter the following command in the command prompt:

> ./activator console

Converting between collection types

Let's start by comparing Java and Scala collection classes and see how we can go from one to the other. For instance, a Scala List (from the scala.collection.immutable package) is different from java.util.List, and sometimes, it can be useful to convert from one to the other. A convenient way in Java to create java.util.List is to use the java.util.Arrays...

Differences in style between Java and Scala code


If you are going to refactor or rewrite Java code into Scala code, there are a number of style differences that are useful to be aware of. Obviously, programming style is largely a matter of taste; however, a few guidelines generally acknowledged by the Scala community can help someone new to Scala to write easier-to-read and more maintainable code. This section is dedicated to showing some of the most common differences.

Writing an algorithm in Java follows an imperative style, that is, a sequence of statements that change a program state. Scala, focusing primarily on functional programming, adopts a more declarative approach, where everything is an expression rather than a statement. Let's illustrate this in an example.

In Java, you would commonly find the following code snippet:

...
String customerLevel = null;
if(amountBought > 3000) {
    customerLevel = "Gold"; 
} else {
    customerLevel = "Silver";
}
...

The Scala equivalent consists...

Summary


In this chapter, we have covered how to start integrating Scala code into a Java codebase as well as how to refactor some of the most common Java constructs into Scala by following some style guidelines. A much more exhaustive list of style recommendations is available at http://docs.scala-lang.org/style/ if you are interested in learning more.

So far we have been mostly addressing the Scala language and syntax. In the next chapter, we are going to introduce the tools that complement it and that are necessary to make our Scala programming both productive and enjoyable.

Left arrow icon Right arrow icon
Estimated delivery fee Deliver to Singapore

Standard delivery 10 - 13 business days

S$11.95

Premium delivery 5 - 8 business days

S$54.95
(Includes tracking information)

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : Apr 25, 2014
Length: 282 pages
Edition :
Language : English
ISBN-13 : 9781783283637
Category :
Languages :

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Estimated delivery fee Deliver to Singapore

Standard delivery 10 - 13 business days

S$11.95

Premium delivery 5 - 8 business days

S$54.95
(Includes tracking information)

Product Details

Publication date : Apr 25, 2014
Length: 282 pages
Edition :
Language : English
ISBN-13 : 9781783283637
Category :
Languages :

Packt Subscriptions

See our plans and pricing
Modal Close icon
$19.99 billed monthly
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Simple pricing, no contract
$199.99 billed annually
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just S$6 each
Feature tick icon Exclusive print discounts
$279.99 billed in 18 months
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just S$6 each
Feature tick icon Exclusive print discounts

Frequently bought together


Stars icon
Total S$ 200.97
Scala for Java Developers
S$66.99
Clojure Reactive Programming
S$66.99
Learning Reactive Programming With Java 8
S$66.99
Total S$ 200.97 Stars icon
Banner background image

Table of Contents

10 Chapters
Programming Interactively within Your Project Chevron down icon Chevron up icon
Code Integration Chevron down icon Chevron up icon
Understanding the Scala Ecosystem Chevron down icon Chevron up icon
Testing Tools Chevron down icon Chevron up icon
Getting Started with the Play Framework Chevron down icon Chevron up icon
Database Access and the Future of ORM Chevron down icon Chevron up icon
Working with Integration and Web Services Chevron down icon Chevron up icon
Essential Properties of Modern Applications – Asynchrony and Concurrency Chevron down icon Chevron up icon
Building Reactive Web Applications Chevron down icon Chevron up icon
Scala Goodies Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3
(16 Ratings)
5 star 62.5%
4 star 18.8%
3 star 6.3%
2 star 12.5%
1 star 0%
Filter icon Filter
Top Reviews

Filter reviews by




MK Oct 07, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Meets expectations of Java developer
Amazon Verified review Amazon
Jens Richnow May 29, 2014
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Book ReviewI enjoyed reading the book 'Scala for Java Developers'! It covers so many topics a developer is faced with every day and across the entire development stack (testing, DB interaction, UI, Web Services, etc. - the table of contents says it all). Despite of approaching such a wide range of topics each gives one gives a gentle introduction with hands-on examples that are easy to understand and follow. Also, there are always many pointers on where to go next and references for further reading.Especially now with Java 8 introducing streams and lambdas it will be a compelling cross-over as Java developers get to know functional programming which makes using both languages and/or migration from Java Scala easier.Another goog point is the advice to pick small(ish) projects/features to get into Scala, to get to run Scala alongside an existing Java project. Once a certain confidence is achieved new projects, features or modules can be written entirely in Scala to complement existing Java projects.As a disclaimer: I have been a Java developer for 15+ years and actively looking at Scala for more than a year now. I implemented a few small projects using the Typesafe stack, did read a few books about Scala and followed the courses at Coursera. I wished that this book had been available at the beginning of my journey as it really eases the introduction into Scala as an alternative/complement to Java and highlights the advantages of Scala. Nevertheless, the book provided so many new tricks and ways of implementing certain solution that it was invaluable. I applied quite a number of the nuggads straight to existing applications.In summary, the book is well written, rather pragmatic, no-nonsense in approach and easy to follow. I will certainly keep it as reference handy at all times. I can recommend the book not only to any Java developer looking into getting a new tool under the toolbelt but also developers who are new(ish) to Scala as they will pick up many tricks and tips.
Amazon Verified review Amazon
Prashanth Jul 22, 2014
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Scala for Java Developers takes your journey through what is scala? How Scala integrates with Java.The book covers all the components of scala ecosystem. Scala, Play Framework, Akka and Reactive applications topics can have their own book. This book will be helpful for beginners and as well some one who are adopting and want to take quick overlook of what each technology does.The only thing I didnt like is the author used Netbeans in one chapter and eclipse in another chapter? The book should ideally have used one IDE.Note: I got the book as part of the reviewers program by Packtpub.
Amazon Verified review Amazon
Eric Le Goff May 05, 2014
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I wish this book had existed when I fitst started learning Scala . Coming from the Java (object-oriented / imperative) school, all I could do is just some trial and error attempts (this is where the Scala REPL helped a lot).While other books are targetting readers from different backgrounds, this one is essentially written for those coming from the Java (object-oriented / imperative)The most interesting aspects in my opinion of this books are :- Introduction to scala collections- Overview of the interoperability with Java- Scala tools and ecosystem (SBT, ScalaTest...)- XML and JSON manipulation- Concurrency programming and how to deal with asynchronous actionsMost of all, the book is full of real life examples which take advantage of technologies such as Play / Akka / NoSql... Those are easy to test in your local environment.It should provide the reader a pragmactic guide to scala adoption.
Amazon Verified review Amazon
Priyadharshini N. Dec 07, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I read this book after reading the Scala Cookbook and I found it extremely useful. It's more of "what" rather than "how".
Amazon Verified review Amazon
Get free access to Packt library with over 7500+ books and video courses for 7 days!
Start Free Trial

FAQs

What is the delivery time and cost of print book? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela
What is custom duty/charge? Chevron down icon Chevron up icon

Customs duty are charges levied on goods when they cross international borders. It is a tax that is imposed on imported goods. These duties are charged by special authorities and bodies created by local governments and are meant to protect local industries, economies, and businesses.

Do I have to pay customs charges for the print book order? Chevron down icon Chevron up icon

The orders shipped to the countries that are listed under EU27 will not bear custom charges. They are paid by Packt as part of the order.

List of EU27 countries: www.gov.uk/eu-eea:

A custom duty or localized taxes may be applicable on the shipment and would be charged by the recipient country outside of the EU27 which should be paid by the customer and these duties are not included in the shipping charges been charged on the order.

How do I know my custom duty charges? Chevron down icon Chevron up icon

The amount of duty payable varies greatly depending on the imported goods, the country of origin and several other factors like the total invoice amount or dimensions like weight, and other such criteria applicable in your country.

For example:

  • If you live in Mexico, and the declared value of your ordered items is over $ 50, for you to receive a package, you will have to pay additional import tax of 19% which will be $ 9.50 to the courier service.
  • Whereas if you live in Turkey, and the declared value of your ordered items is over € 22, for you to receive a package, you will have to pay additional import tax of 18% which will be € 3.96 to the courier service.
How can I cancel my order? Chevron down icon Chevron up icon

Cancellation Policy for Published Printed Books:

You can cancel any order within 1 hour of placing the order. Simply contact [email protected] with your order details or payment transaction id. If your order has already started the shipment process, we will do our best to stop it. However, if it is already on the way to you then when you receive it, you can contact us at [email protected] using the returns and refund process.

Please understand that Packt Publishing cannot provide refunds or cancel any order except for the cases described in our Return Policy (i.e. Packt Publishing agrees to replace your printed book because it arrives damaged or material defect in book), Packt Publishing will not accept returns.

What is your returns and refunds policy? Chevron down icon Chevron up icon

Return Policy:

We want you to be happy with your purchase from Packtpub.com. We will not hassle you with returning print books to us. If the print book you receive from us is incorrect, damaged, doesn't work or is unacceptably late, please contact Customer Relations Team on [email protected] with the order number and issue details as explained below:

  1. If you ordered (eBook, Video or Print Book) incorrectly or accidentally, please contact Customer Relations Team on [email protected] within one hour of placing the order and we will replace/refund you the item cost.
  2. Sadly, if your eBook or Video file is faulty or a fault occurs during the eBook or Video being made available to you, i.e. during download then you should contact Customer Relations Team within 14 days of purchase on [email protected] who will be able to resolve this issue for you.
  3. You will have a choice of replacement or refund of the problem items.(damaged, defective or incorrect)
  4. Once Customer Care Team confirms that you will be refunded, you should receive the refund within 10 to 12 working days.
  5. If you are only requesting a refund of one book from a multiple order, then we will refund you the appropriate single item.
  6. Where the items were shipped under a free shipping offer, there will be no shipping costs to refund.

On the off chance your printed book arrives damaged, with book material defect, contact our Customer Relation Team on [email protected] within 14 days of receipt of the book with appropriate evidence of damage and we will work with you to secure a replacement copy, if necessary. Please note that each printed book you order from us is individually made by Packt's professional book-printing partner which is on a print-on-demand basis.

What tax is charged? Chevron down icon Chevron up icon

Currently, no tax is charged on the purchase of any print book (subject to change based on the laws and regulations). A localized VAT fee is charged only to our European and UK customers on eBooks, Video and subscriptions that they buy. GST is charged to Indian customers for eBooks and video purchases.

What payment methods can I use? Chevron down icon Chevron up icon

You can pay with the following card types:

  1. Visa Debit
  2. Visa Credit
  3. MasterCard
  4. PayPal
What is the delivery time and cost of print books? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela