Java Magazine 2017 01-02

10.8 MB·English

by  Oracle

LOCAL-VARIABLE TYPE INFERENCE 60 | SCALA 47 | BLOCKCHAIN 36
JANUARY/FEBRUARY 2017
magazine
By and for the Java community
TOOLS
17 22 29
POLYGLOT: INSIDE THE BUILD YOUR OWN
MOVING MAVEN ARCHITECTURE JVM DEBUGGING
PAST XML OF BUILD TOOLS TOOLS
ORACLE.COM/JAVAMAGAZINE
////ttaabbllee ooff ccoonntteennttss //
22 29
THE DESIGN AND CONSTRUCTION CREATING YOUR OWN
OF MODERN BUILD TOOLS DEBUGGING TOOLS
17
By Cédric Beust By Andrei Pangin
A look inside a modern JVM build tool— JDK serviceability technologies allow
POLYGLOT FOR
its architecture and implementation you into the JVM to solve diicult
debugging problems.
MAVEN: MOVING
MAVEN INTO
SCRIPTING
By Jason van Zyl and Manfred Moser
A new tool from the developer of Maven enables POM iles
to be written in Ruby, YAML, Groovy, and other languages.
COVER ART BY I-HUA CHEN
03 13 47 60
From the Editor Java Books JVM Languages Java Proposals of Interest
The Polyglot Future: As the nature of pro- Review of Core Java, Volume II (10th Scala: Deeply Functional, JEP 286: Local-Variable Type Inference
gramming changes, should we add regular Edition), by Cay S. Horstmann Purely Object-Oriented
63
coverage of JavaScript to the magazine?
36 By Adriaan Moors Fix This
A mature, practical, and type-safe
05 Cryptocurrency By Simon Roberts
language for the JVM
Letters to the Editor Blockchain: Using Our latest code quiz
Comments, questions, suggestions, Cryptocurrency with Java 52
21
and kudos Cloud
By Conor Svensson User Groups
Integrating the Ethereum blockchain Java in Containers in the Cloud
08 Chicago JUG
into Java apps using web3j
Events By Harshad Oak
68
Deploy Java apps in Docker containers
Upcoming Java conferences and events.
using Oracle Application Container Contact Us
And introducing Oracle Code, a new series
Cloud Service. Have a comment? Suggestion?
of 20 free one-day events on polyglot pro-
Want to submit an article proposal?
gramming, DevOps, and cloud computing.
Here’s how.
01
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EDITORIAL PUBLISHING
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Stephen Chin
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02
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//from the editor /
Level Up at
Oracle Code
The Polyglot Future
Step up to modern cloud
As the nature of programming changes, should we cover Java and JavaScript? development. At the
Oracle Code roadshow,
expert developers lead
labs and sessions on PaaS,
I
t’s no secret that almost all commercial pro- nontechnical audiences; then the use of both
Java, mobile, and more.
grams today depend on more than one language. languages in web apps, followed by their joint
While Java still stretches from the UI all the way use in mobile; and of course, then the use of
Get on the list
to the back-end work (a true end-to-end proposi- JavaScript as a scripting language for Java, via
for event updates:
tion), its role is frequently complemented by func- Nashorn. In addition, tools such as the Google
go.oracle.com/oraclecoderoadshow
tionality written in other languages. Sometimes, Web Toolkit, which transpiles Java into JavaScript,
those parts are written using scripts or JVM lan- have furthered the connection between the
guages. At other times, a more common scenario two languages.
unfolds: a Java core surrounded by a UI written JavaScript is also seeping into back-end com-
in JavaScript. The multilanguage phenomenon— puting. This trend is most evident with Node (the
referred to as polyglot programming—often implies former node.js), a JavaScript framework that cre-
the use of more than two languages. But if there ates a server-like environment for business logic
is just one other language, that language is over- by providing “an event-driven, non-blocking I/O
whelmingly JavaScript. model that makes it lightweight and eicient.”
In many ways, JavaScript has been an ever- Its emergence is like Ruby on Rails a decade ago: a
developer.oracle.com
emerging partner to Java: starting with its name, convenient solution to small-scale projects. Node
which Netscape chose to key of of Java’s popu- is likely to expand its presence in that sector due
#developersrule
larity, thereby causing endless confusion for to its reliance on a widely used language.
PHOTOGRAPH BY BOB ADLER/VERBATIM 03
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//from the editor /
I should note that the Java issue of the name for a moment.
community has responded to Node Looking at the last two years, we
with an excellent framework, have regularly covered other JVM
Vert.x, that provides all the for- languages. In this sense, we’ve
mer framework’s capabilities and already had a regular taste of poly-
more and is rapidly gaining adher- glot coverage in our pages. But the
ents. One of its appealing aspects question I’ve been asked involves
is represented by the .x in its a deeper commitment to the poly-
name, which is a direct counter- glot reality, more than just JVM
Register Now
point to the .js in Node’s original languages: Should we add regular
name. While Node is a JavaScript coverage of JavaScript?
Oracle Code
framework, the x in Vert.x signi- As my job is to serve you,
ies support for many languages. I’d like your opinion. Would you
Here again we see the advent of like to see the addition of tutori-
polyglot programming. als, perhaps morphing into regu-
New One-Day, Free Event | 20 Cities Globally
Oracle employs tens of thou- lar coverage, of JavaScript in the
sands of developers and interacts magazine? The guidance I’m spe-
with millions more. The com- ciically looking for is how much
pany’s considered opinion is that JavaScript coverage would help Explore the Latest Developer Trends:
the polyglot trend is real, endur- you in your programming work.
ing, and important. Underlying Feel free to say “absolutely none,”
• DevOps, Containers, Microservices & APIs
this conviction is the belief that or “lots of it,” or anything in
• MySQL, NoSQL, Oracle & Open Source Databases
the cloud will hasten the adop- between. And please include any
tion of multiple languages due to further thoughts as well as any
• Development Tools & Low Code Platforms
the ease of setting up and testing recommendations you have on the
• Open Source Technologies
out diferent stacks and difer- current mix of articles you ind in
ent toolchains in the cloud. With our pages.
• Machine Learning, Chatbots & AI
this in mind, the company has
asked me whether Java Magazine Andrew Binstock, Editor in Chief
should broaden its mission to [e-mail]
Find an event near you:
cover polyglot programming, pri- @platypusguy developer.oracle.com/code
marily via the addition of coverage
of JavaScript.
It might seem odd to consider
this step for a publication with Java
in the name. But let’s put aside the 04
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//letters to the editor /
JUnit 5’s Status Missing Class
NETBEANS’ FATE 03 | DESIGN PATTERNS IN JAVA 8 55 | CLOUD PROGRAMMING 63
Thank you for your multiple articles on JUnit in In the article “Implementing Design Patterns
magazine the November/December 2016 issue. The inal deliv- with Lambdas” in the November/December 2016
By and for the Java community ery of version 5 is now expected to be in the third issue, I think you should explain where the class
quarter of 2017. We intend to introduce as few break- OnlineBankingLambda came from, as it is not included
JUnit 5
ing changes as possible, especially in the program- in the source code.
Arrives!
ming model (Jupiter API) that you covered in —Carlos Carvajal
14 20 25 36 43 your articles. We publish detailed release notes
SPECIAL
WHAT’S NEW RUNNING JUNIT 5 KENT BECK ON MUTATION ISSUE
IN JUNIT 5? TJUESNTITS 4 F RAONMD 5 EXTENSIONS HVIIESW EVSO OLFV ING TESTING in our User Guide for people upgrading from exis- This article was excerpted from the book Java 8 in Action,
TESTING NOVEMBER/DECEMBER 2016
ORACLE.COM/JAVAMAGAZINE ting milestones. whose lead author, Raoul-Gabriel Urma, replies: “For the
We would love to get the remaining work done code example, the learning outcome is really about the
NOVEMBER/DECEMBER 2016
as quickly as possible. However, we are very short method processCustomer itself (the template method
on time at the moment. As you probably know, we pattern) and how it can be parameterized with a behavior.
had some initial funding through a crowdfunding The class OnlineBankingLambda is not important (actu-
campaign, but that was merely a start. If there is a ally, it doesn’t matter what its implementation is as long as
company out there with a strong interest in Java and it declares the processCustomer method).
JUnit that would like to help out, we would certainly You’ll ind in the book that its (pre–Java 8) parent
be open to discussing possible options if it reached class is:
out to us.
—Marc Philipp abstract class OnlineBanking {
JUnit 5 team public void processCustomer(int id){
Customer c =
JUnit 5—What Is It?
Database.getCustomerWithId(id);
I want to know a little more about JUnit 5. What does makeCustomerHappy(c);
JUnit 5 actually do? }
—Nikhil Deshmukh abstract void makeCustomerHappy(Customer c);
}
Indeed, we did not provide any basic introduction to JUnit,
in part because it is an almost universal tool in Java devel- After introducing the refactoring with behavior param-
opment. To quote the entry in Wikipedia, “JUnit is a unit eterization, it becomes:
testing framework for the Java programming language.
JUnit has been important in the development of test-driven abstract class OnlineBanking {
development, and is one of a family of unit testing frame- public void processCustomer(
works.” In a nutshell, it’s the primary tool by which Java int id,
developers test their own code before checking it in. Consumer<Customer> makeCustomerHappy){
05
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//letters to the editor /
Customer c = Database.getCustomerWithId(id);
makeCustomerHappy.accept(c);
}
}
and the LambdaOnlineBanking class:
The Best Resource
class LambdaOnlineBanking extends OnlineBanking {
// it's inheriting processCustomer for Modern Cloud Dev
// ... more stuff can come here
}
The Oracle Developer Gateway is the best place
I think it would be simpler if I didn’t declare an abstract
to jump-start modern cloud development. With
class that you have to inherit from. I will change this for the
free trials of PaaS and IaaS, documentation galore,
second edition.”
piles of downloads, and tutorials for leveling up
Back-Issue Downloads your skills, it’s the resource of choice for developers
Although I’m glad to have access to back issues, I’m working in Java, mobile, enterprise apps, and more.
puzzled as to how to download them. Could you explain?
—Several readers
Trials. Downloads. Tutorials.
The content delivery network requires downloads to be done
Start here: developer.oracle.com
from a desktop rather than a mobile device. So, if you go to the
website for this issue from a desktop, you’ll see a panel of icons
on the right. Click the top icon and a new panel will open, show-
ing the contents of the current issue plus the covers of the back
issues from 2015 and 2016. Double-click the back issue you
want to download. A button will pop up on the top of the panel
marked “View.” Click this button and the back issue will load in
the browser. Once it has loaded, go the panel on the right, which
has an icon with a down arrow. Click this icon and a PDF down-
developer.oracle.com
load of the issue will begin immediately. (Note that you can
download a PDF of the current issue using the same technique.)
#developersrule
Contact Us
Write to us at [e-mail]. 06
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//events /
Jfokus SnowCamp 2017
FEBRUARY 6, TUTORIAL FEBRUARY 8, WORKSHOP
FEBRUARY 7–8, CONFERENCE FEBRUARY 9–10, CONFERENCE
STOCKHOLM, SWEDEN FEBRUARY 11, “UNCONFERENCE”
GRENOBLE, FRANCE
Jfokus is the largest annual
Java developer conference This technical conference held
in Sweden. Conference topics in the French Alps focuses on
include Java SE and Java EE, Java, JavaScript, and software
continuous delivery and architecture, with sessions
DevOps, IoT, cloud and big presented in French (primarily)
data, trends, and JVM lan- and English. A workshop day
guages. This year, the irst day precedes the two-day confer-
of the event will include a VM ence. An “Unconference” at
Tech Summit, which is an open the end is for hitting the slopes
technical collaboration among with your fellow attendees.
language designers, compiler
DevNexus
writers, tool builders, runtime
FEBRUARY 22–24
engineers, and VM architects.
ATLANTA, GEORGIA
The schedule will be divided
equally between traditional DevNexus is devoted to con-
presentations of 45 minutes necting developers from all
and informal, facilitated deep- over the world, providing
Devoxx US dive discussion groups among afordable education, and pro-
MARCH 21–23 smaller, self-selected partici- moting open source values.
SAN JOSE, CALIFORNIA pants. Space is limited, as this The 2017 conference will take
Devoxx US focuses on Java, web, mobile, and JVM languages. The con- summit is organized around a place at the Georgia World
ference includes more than 100 sessions in total, with tracks devoted to single classroom-style room to Congress Center in down-
server-side Java, architecture and security, cloud and containers, big data, support direct communication town Atlanta. Presenters
Internet of Things (IoT), and more. between participants. will include Josh Long,
author of O’Reilly’s upcom-
ing Cloud Native Java: Designing
08
PHOTOGRAPH BY THINKSTOCK/GETTY IMAGES
ORACLE.COM/JAVAMAGAZINE ////////////////////////////////// JANUARY/FEBRUARY 2017
//events /
Of,” and “Spring Framework 5: presentations by popular inter-
Reactive Microservices on JDK 9.” national speakers. Past ConFoo
topics have included how to write
QCon London 2017
better streams with Java 8 and an
MARCH 6–8, CONFERENCE
introduction to Java 9.
MARCH 9–10, WORKSHOPS
LONDON, ENGLAND Embedded World
MARCH 14–16
For more than a decade, QCon
NUREMBERG, GERMANY
London has empowered software
development by facilitating the The theme for the 15th annual
spread of knowledge and innova- gathering of embedded system
tion in the developer community. developers is Securely Connecting
Scheduled tracks this year include the Embedded World. Topics
“Performance Mythbusting” and include IoT, connectivity, soft-
“Every Last Nanosecond: Low ware engineering, and safety
Latency Java.” and security.
jDays JavaLand
MARCH 7–8 MARCH 28–30
Resilient Systems with Spring Boot, formance of Structs to Java
GOTHENBURG, SWEDEN BRÜHL, GERMANY
Spring Cloud, and Cloud Foundry, (Sort Of),” by Simon Ritter, and
and Venkat Subramaniam, “Java Security Architecture jDays brings together software This annual conference features
author of Pragmatic’s Functional Demystiied,” by Martin Toshev. engineers from around the world more than 100 lectures on sub-
Programming in Java: Harnessing the to share their experiences in dif- jects such as core Java and JVM
Topconf Linz 2017
Power of Java 8 Lambda Expressions. ferent areas such as Java, software languages, enterprise Java and
FEBRUARY 28, WORKSHOPS engineering, IoT, digital trends, cloud technologies, IoT, front-end
Voxxed Days Zürich MARCH 1–2, CONFERENCE testing, agile methodologies, and mobile computing, and much
FEBRUARY 23 LINZ, AUSTRIA and security. more. Scheduled presentations
ZÜRICH, SWITZERLAND Topconf covers Java and JVM, include “Multiplexing and Server
ConFoo Montreal 2017
Sharing the Devoxx philosophy DevOps, reactive architecture, Push: HTTP/2 in Java 9,” “The
MARCH 8–10
that content comes irst, Voxxed innovative languages, UX/UI, and Dark and Light Side of JavaFX,”
MONTREAL, QUEBEC, CANADA
Days events see both internation- agile development. Presentations “JDK 8 Lambdas: Cool Code that
ally renowned and local speakers this year include “Java Libraries ConFoo Montreal is a multi- Doesn’t Use Streams,” “Migrating
converge. Past presentations You Can’t Aford to Miss,” “8 Akka technology conference for web to Java 9 Modules,” and “Java EE 8:
have included “Bringing the Per- Antipatterns You’d Better Be Aware developers that promises 155 Java EE Security API.”
09
PHOTOGRAPH BY JAN REMUND/FLICKR
ORACLE.COM/JAVAMAGAZINE ////////////////////////////////// JANUARY/FEBRUARY 2017