DYNAMIC METHOD INVOCATION 67 | INSIDE JAVA CARD 77 | JAVA QUIZ 91
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JAVA EE 8 WHAT YOU NEED TO KNOW 13 23 43 56 SERVLET 4.0 CDI 2.0 JPA 2.2 MICROPROFILE
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COVER FEATURES 23 43 56 CDI 2.0: MAKING WHAT’S NEW IN JPA 2.2 ECLIPSE MICROPROFILE: DEPENDENCY INJECTION By Josh Juneau THE LIGHT ENTERPRISE A LOT EASIER Streaming results, better date JAVA OPTION By Arjan Tijms conversions, and new annotations By Mert Çalişkan A new spec, new features, are just a few of the many handy Examining a Java EE architecture 13 and new annotations. What’s improvements. designed for microservices and SERVLET 4.0: DOING MORE FASTER not to like? distributed applications
By Alex Theedom A major new release of the Servlet API embraces the HTTP/2 protocol and anticipates resource requirements.
OTHER FEATURES DEPARTMENTS 67 91 05 11 Understanding Java Method Fix This From the Editor Java Proposals of Interest Invocation with Invokedynamic By Simon Roberts Java EE 8 development goes JEP 295: Ahead-of-Time Compilation By Ben Evans Our latest quiz with questions that test open source. to Native Binaries The instruction added in Java 7 makes intermediate and advanced knowledge 07 42 it possible to resolve method calls dynam- of the language ically at runtime. Java Books User Groups Review of Ken Kousen’s Modern The Netherlands JUG 77 Java Recipes 101 An Introduction to Java Card 09 By Nicolas Ponsini and Florian Tournier Contact Us The smallest Java platform is one of the Events Have a comment? Suggestion? Want to most widely distributed. See how pro- Upcoming Java conferences and events submit an article proposal? Here’s how. gramming it is different from developing conventional apps.
COVER ART BY WES ROWELL 02
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Get a Free Trial to Java EE 8 Goes Open Source Oracle Cloud
The new release is moving to the Eclipse Foundation. Experience modern, open cloud development with a free trial to Oracle n an unexpected move, Oracle announced just by companies no longer interested in support- Cloud platform and Ibefore the JavaOne conference this year that it ing them—a phenomenon known as “abandon- infrastructure services. would be turning over control of Java EE 8 to the ware.” Rather, Oracle has pledged to move its open source community. This action, effectively commercial Java EE offering, Oracle WebLogic, to Get your free trial: unthinkable a few years ago, is being realized by conformance with Java EE 8 and to continue con- developer.oracle.com giving control of the technology to the Eclipse tributing to the development and evolution of the Foundation. Included in this transition are the full standards, along with other contributors such as source code and the test suites that ensure confor- Red Hat and IBM as well as the large community mance and compliance with Java EE specificationFPO textof developers. requirements. The latter items are particularly The Eclipse Foundation was chosen in part important because they will enable new imple- due to its experience with enterprise Java tech- mentations of Java EE to be developed and dem- nologies. For example, it currently hosts the com- onstrate their bona fides. plementary MicroProfile project, which is exam- Ceding control of the certification aspect ined in detail on page 56 in this issue. In addition, shows emphatically that Oracle is giving the the foundation has the resources to assist in the developer.oracle.com technology to the community. This move should transition process. Conversations with Eclipse not be confused with the occasional dump- officials revealed that they expected the transi- ing of technologies to open source foundations tion to take roughly a year. Why so long? Not only #developersrule
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do dozens of code repositories, other projects transferred to open numerous change logs, and many source, Java EE benefits from a supporting documents need to be very active community that con- migrated to Eclipse servers, but tinues to push forward the mul- Push a Button a substantial amount of policy tiple constituent technologies. For needs to be formulated. Not only example, in this issue we look at straightforward items will need how those communities, along Move Your Java Apps to be addressed, such as staffing with Oracle, have updated Servlet, the individual projects—who gets CDI, and JPA. We certainly could to the Oracle Cloud to commit, who reviews changes, have included other technologies and who runs the projects?—but too—many of which are driven also larger questions, such as by active expert groups donating how will conformance with Java their time and effort to the project. EE standards be validated? What This strong community guar- will the process be for determin- antees the success of this migra- ing a new release? AndFPO so on. As texttion. If all goes well, as I expect it David Delabassée of Oracle points will, the migration should make Same Java Runtime out, there are additional issues it possible to attract even more Same Dev Tools to resolve as well, such as brand- developers to grow and advance ing and the possible integration these technologies. Same Standards of MicroProfile. Same Architecture Branding got off to a bit of Andrew Binstock, Editor in Chief a rocky start at JavaOne, when [email protected] rumor had it that Java EE would be @platypusguy renamed EE4J (Eclipse Enterprise for Java). However, that was the proposed name of the project at the Eclipse Foundation, rather than of the technology itself. To what extent future releases will … or Back to Your Data Center use the Java EE brand has yet to be determined. Reaction to the move by Oracle has been uniformly sup- portive. And there’s good reason for that enthusiasm. Unlike many 06
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MODERN JAVA RECIPES By Ken Kousen
I love recipe books. Judging from knowledgeable developer who is tors; optionals; the java.time pack- the popularity of resources such equally expert at presenting the age; parallelism and concurrency; as StackOverflow, the thirst for information. There are 74 recipes in and a chapter on Java 9’s additions. working chunks of code that cor- 300 pages, which shows the level of A useful addendum is an rectly handle a discrete task is detail and background that accom- 18-page appendix that focuses on nearly insatiable. The big differ- panies every recipe. understanding the complexities of ence between most online sites A common limitation of recipe generics in recent releases of Java. that offer code solutions and a book books is that you don’t remember Surely, they are now as complex as such as Ken Kousen’s Modern Java them when you have a problem function declarations in C and C++. Recipes is the latter’s sustained they cover or, conversely, you con- Consider Listing 1 from Kousen’s quality of the content, the detailed sult them but they don’t address book, which itself is taken from the explanations, and the ability of the question you have. The better Java 8 documentation. one recipe to reference another for books carefully identify the scope This appendix, which saves developers who don’t entirely know of their contents. This is done in Kousen from explaining generics what to ask for. The other benefit this volume in the subtitle, “Simple syntax repeatedly, is a remarkably of a recipe book is that the contents Solutions to Difficult Problems in clear and thoughtful presentation are laid out sequentially, so that Java 8 and 9”—in other words, reci- of a topic that doesn’t get enough variations on a theme are grouped pes for the added features in these attention. For expert developers, it together and you can compare dif- two releases of Java. And in fact, will serve as a good refresher. ferent recipes to obtain a deeper this is what you have: the basics I like Modern Java Recipes a lot understanding of a problem. (lambdas, method references, func- and can find little to fault. Any The success of a recipe book tional interfaces); the java.util developer working through the rests on the knowledge and dili- .function package (consumers, sup- subtleties of the features added in gence of the author. In Kousen, a pliers, predicates, and functions); Java 8 and Java 9 will find this book Java Champion, you have a very streams; comparators and collec- a great help. —Andrew Binstock Listing 1. static
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Available in print and eBook formats. www.OraclePressBooks.com • @OraclePress //events / Javaneiros DevTernity NOVEMBER 18 DECEMBER 1, KEYNOTES CAMPO GRANDE, BRAZIL DECEMBER 2, WORKSHOPS The Javaneiros conference is a RIGA, LATVIA community-organized day of This conference focuses on mod- presentations related to Java ern approaches to coding, archi- programming. (No English tecture, testing, engineering scal- page available.) ability, and operations, with 20 speakers presenting in three par- Voxxed Days Thessaloniki allel tracks. The conference is fol- NOVEMBER 23, WORKSHOPS lowed by a full day of workshops. NOVEMBER 24–25 CONFERENCE THESSALONIKI, GREECE ConFoo Voxxed Days is a community con- DECEMBER 4–6 ference for developers, by devel- VANCOUVER, BRITISH COLUMBIA, opers. Sessions include “Spring CANADA Boot and Kotlin: A Match Made This multitechnology conference in Heaven,” “Stream Puzzlers: for web developers features tar- Traps and Pitfalls in Using geted sessions for Java and JVM Java 8 Streams,” and “Hands-on developers. Sessions include pre- Microservices with OpenShift.” sentations on concurrency models The two-day conference is pre- with Java 9, Angular/TypeScript, Jfokus ceded by a day of free software- and Practical Symfony 4. FEBRUARY 5–7, 2018 development workshops. STOCKHOLM, SWEDEN ArchConf The annual Scandinavian Java developer conference encompasses Java SE JVM-Con DECEMBER 11, WORKSHOPS and Java EE, front-end and web development, mobile, cloud, IoT, and JVM NOVEMBER 28–29 DECEMBER 12–14, CONFERENCE languages such as Scala and Clojure. COLOGNE, GERMANY CLEARWATER, FLORIDA On February 5, the conference will hold the Jfokus VM Tech Summit, Among the topics slated for this ArchConf is an educational event which is an open technical collaboration among language designers, conference devoted to JVM lan- for software architects, techni- compiler writers, tool builders, runtime engineers, and VM architects. guages are Java 9, Java EE, Scala, cal leaders, and senior develop- The schedule for the Summit will be divided e.qually between traditional Jython, Kotlin, Clojure, FreePascal, ers. Topics include agile design, presentations of 45 minutes and workshops. Groovy, JRuby, cloud native devel- microservices, web application opment, microservices, and secu- security, cloud architectures, and rity. (No English page available.) modular Java. PHOTOGRAPH BY THOMAS FABIAN/FLICKR 09
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ture, with a mix of sessions in chain, APIs and microservices, French and English. The last day, and JavaScript. dubbed “unconference,” offers a unique opportunity to socialize Devnexus with peers and speakers on the FEBRUARY 21–23 ski slopes. ATLANTA, GEORGIA Devnexus is an international DevConf.cz open source developer confer- JANUARY 26–28 ence. Its stated goal is to con- BRNO, CZECH REPUBLIC nect developers from all over the DevConf.cz is a free three- world, provide affordable educa- day open source developer and tion, and promote open source DevOps conference. All talks, values. Past presenters have presentations, and workshops will included Venkat Subramaniam, be conducted in English. Several author of Pragmatic’s Functional tracks are devoted specifically to Programming in Java: Harnessing the Java EE, and the conference can be Power of Java 8 Lambda Expressions. attended online. QCon London CodeMash featuring two days of sessions fol- DeveloperWeek MARCH 5–7: CONFERENCE JANUARY 9–12, 2018 lowed by two days of skiing. Day 3 FEBRUARY 3–4: HACKATHON MARCH 8–9: WORKSHOPS SANDUSKY, OHIO also has a mini-conference for FEBRUARY 5: WORKSHOPS LONDON, ENGLAND CodeMash is a unique event that kids, jSpirit4Kids. Specific topics FEBRUARY 5–7: CONFERENCE Although the content has not yet educates developers on current other than programming in Java FEBRUARY 6–7: EXPO been announced, past QCon con- practices, methodologies, and are not known in advance. OAKLAND, CALIFORNIA ferences have offered several Java technology trends in a variety of DeveloperWeek is the world’s tracks along with tracks related to platforms and development lan- SnowCamp largest developer expo and con- web development, DevOps, cloud guages such as Java, .NET, Ruby, JANUARY 24: WORKSHOPS ference series, gathering 8,000 computing, and more. Last year’s Python, and PHP. JANUARY 25–26: CONFERENCE participants for a week-long session topics included perfor- JANUARY 27: UNCONFERENCE technology-neutral programming mance and low-latency Java. jSpirit GRENOBLE, FRANCE conference and associated events. JANUARY 12–16 SnowCamp is a developer con- The theme for 2018 is “Industrial Voxxed Days Zürich HAUSHAM, GERMANY ference held in the French Alps Revolution of Code,” and tracks MARCH 8 This is an “unconference”-style that focuses on Java, web, cloud, include artificial intelligence, ZÜRICH, SWITZERLAND event organized by JUG Oberland DevOps, and software architec- serverless development, block- Voxxed Days Zürich shares the
PHOTOGRAPH BY DOUGLAS SACHA/GETTY IMAGES 10
ORACLE.COM/JAVAMAGAZINE //////////////////////////////// NOVEMBER/DECEMBER 2017 //events / //java proposals of interest /
Devoxx philosophy that content from around the world to talk comes first and draws inter- about all aspects of Java and JVM JEP 295: Ahead-of-Time nationally renowned and local languages, development tools, and speakers. While the schedule trends in programming. Tutorials Compilation to Native Binaries of speakers has not yet been on numerous related Java and JVM As most Java developers know, Java code is executed by announced, last year’s event fea- topics will be offered. the JVM using one of two primary mechanisms: initially tured presentations on using interpretation, and then for code that is used exten- Java 8 lambdas and StampedLock JavaOne 2017 Recap sively, just-in-time (JIT) compilation. Java does not have to manage thread safety, extract- The JavaOne conference in October ahead-of-time (AOT) compilation in which code is com- ing knowledge from crypto was headlined by the release of piled to native executable binaries a priori as is done by curren cies, and a preview Java SE 9 and the news that Oracle C or C++. of Java EE 8. was migrating Java EE to the JDK Enhancement Proposal (JEP) 295 proposes that Eclipse Foundation. These links Java provide an AOT option. Its primary goal is to reduce Voxxed Days Melbourne provide access to some of the pop- the amount of time Java applications spend starting up. MAY 2–3 ular sessions from the conference: Specifically, during the initial parts of a Java program’s MELBOURNE, AUSTRALIA ■■ “JDK 9 Language, Tooling, and execution, the JVM has not yet determined what meth- Voxxed Days is heading down Library Features” ods to run through the JIT compiler, so the performance under to Melbourne, Australia. ■■ “Migrating to Modules” does not immediately get the benefit of this step. With The event will feature insights ■■ “JDK 9 Hidden Gems” the proposed AOT compilation, Java programs would into cloud, containers and infra- ■■ “JUnit 5: New Opportunities for execute binary code from the start. Note that the goal structure, real-world architec- Testing on the JVM” is specifically to reduce that initial delay, rather than tures, data and machine learning, ■■ “Streams in JDK 8: The Good, achieving higher performance throughout the pro- the modern web, and program- The Bad, and The Ugly” gram’s entire run. ming languages. ■■ “Exploring Java 9 with REPL” The compiler referenced in this JEP uses Graal as the code-generating back end. At present, the AOT JavaOne 2018 Are you hosting an upcoming option is being targeted exclusively at 64-bit Linux. OCTOBER 28–NOVEMBER 1 Java conference that you would Third-party AOT compilers exist for Java—most SAN FRANCISCO, CALIFORNIA like to see included in this cal- notably, Excelsior JET, which delivers binaries for Whether you are a seasoned endar? Please send us a link Windows, Linux, macOS, and ARM. Excelsior notes that coder or a new Java programmer, and a description of your event while the AOT compilation improves startup times, one JavaOne is for you. It’s the ulti- at least 90 days in advance at of the key reasons customers purchase its product is mate source of technical informa- [email protected]. Other IP protection, as native binaries are more difficult to tion and learning about Java. For ways to reach us appear on the reverse-engineer than Java bytecode. five days, Java developers gather last page of this issue. 11
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SERVLET 4.0 13 CDI 2.0 23 Java EE 8: JPA 2.2 43 MICROPROFILE 56 What You Need to Know
hile the Java SE community has been focused on the release of Java 9, the Java EE community now has its turn in the spotlight. The editorial at the front of this issue (page 5) examines Oracle’s recent announcement that Java EE development is being moved to the Eclipse Foundation. The articles in this section focus on the many technical advances in WJava EE 8. For some technologies, the new release brings significant upgrades and welcome enhancements. These include Servlet 4.0’s embrace of HTTP/2 and its new server push capabili- ties (page 13); CDI 2.0’s improved dependency injection (page 23); and JPA 2.2’s streaming results, upgraded date conversions, and new annotations (page 43). We also examine MicroProfile, the new lightweight implementation of Java EE intended for microservices and distributed computing (page 56). If a single lightweight vehicle isn’t enough for you, we look at Java Card, a super-lightweight Java SE implementation that thrives on smartcards (page 77). It’s interesting to find out how the JVM is activated, how objects’ lifetimes are managed, and of course how security is enforced. None of this is easy or trivial in tiny environments. In addition, we have the final installment of Ben Evans’ two-part series on how the JVM executes dynamic method invocations (page 67). Throw in our book review (page 7) and the usual quiz (page 91) with its deep look into the operations of the language, and you have an issue of Java Magazine that tops 100 pages. Enjoy! We’ll have more coming after this!
ART BY WES ROWELL 12
ORACLE.COM/JAVAMAGAZINE //////////////////////////////// NOVEMBER/DECEMBER 2017 //java ee 8 / Servlet 4.0: Doing More Faster A major new release of the Servlet API embraces the HTTP/2 protocol and anticipates resource requirements.
he long-awaited update to Java EE 8 includes updates to existing APIs—JAX-RS 2.1, Bean ALEX THEEDOM TValidation 2.0, JavaServer Faces (JSF) 2.3, Contexts and Dependency Injection (CDI) 2.0, JSON with Padding (JSONP) 1.1, and Servlet 4.0—and two brand-new APIs: JSON-Binding (JSON-B) and Java EE Security. Among these APIs, Servlet 4.0 represents a major update, its first since 2009. The impetus that prompted this major release (rather than a point release) is the worldwide rollout of the HTTP/2 protocol and the many new capabilities it brings. This update to HTTP is the first in nearly 20 years and addresses many of the shortcomings of HTTP 1.x. The new capa- bilities are numerous (request/response multiplexing, header compression, stream prioritiza- tion, and server push), but the most visible feature to users of the Servlet API is Server Push, which I will discuss in this article. Server Push is not the only noteworthy addition to Servlet 4.0. This release also introduces a feature refinement in the form of the Servlet Mapping API, which permits the runtime dis- covery of mappings by refining the way referrer paths are obtained. This article discusses these features and how Server Push has been integrated into the JavaServer Faces 2.3 API.
Server Push Designed to anticipate the resource requirements of a web page, the Server Push feature pushes images, CSS, and JavaScript files, and other resources to the client before request processing has been completed. Therefore, by the time the browser receives the response to its request for the web page, the resources it needs are already in its cache and ready to use.
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Gone is the need to shard resources across domains to get around browser TCP connection limitations. Simply specify the resources and let the server handle delivery. This is the way it should always have been. With the resources already in the browser’s cache, the browser can render the page much more quickly. With a typical web page requiring more than 100 resources, it’s easy to see how much of an opportunity this represents for performance enhancements.
Server Push in Action Servlets are the backbone technology behind the Java EE web application tier. They provide the server capabilities that form the basis of many frameworks. JavaServer Faces (JSF) relies on the FacesServlet to manage the request processing lifecycle for web applications, and JSP pages are translated into servlets upon the first client request; so it should be no wonder that servlets are the natural place to expose the HTTP/2 Server Push abstraction. That abstraction is represented as a PushBuilder object and is created by calling the newPushBuilder() method from the HttpServletRequest instance passed to all overridden request handling methods. With a PushBuilder instance, you can start pushing the resources required by the requested web page. The resource is set on the PushBuilder instance by passing its location to the path() method. The resource is pushed to the client by invoking the push() method. It can be reused to send as many resources as required. Listing 1 and Listing 2 show the simplest example that uses Server Push. Listing 1 shows an HTTP servlet that responds to a GET request to the URI /simplestexample:
Listing 1. @WebServlet("/simplestexample") public class SimplestExample extends HttpServlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 14
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request.newPushBuilder() .path("images/coffee-cup.jpg") .push(); getServletContext() .getRequestDispatcher("/coffee-cup.jsp") .forward(request, response); }}
Listing 2 shows the JSP web page:
Listing 2.
In Listing 1, I have a servlet called SimplestExample and a JSP to which the servlet dispatches. As you can see, the JSP page requires only one resource, the coffee-cup.jpg image. When the doGet() request handling method is invoked, it creates a new PushBuilder instance, sets the image’s location, and calls the push() method to send the resource to the client. As the image is making its way to the client, the servlet is forwarding the request to the JSP that requires the coffee-cup.jpg resource. By the time the browser has received the rendered HTML, it already has the image in its cache and can display the page without needing to make another request. To see Server Push in action, you can use the developer’s tools provided by Google’s Chrome browser. Select More Tools>Developer Tools and then click the Network tab, and make a request to the SimplestExample servlet. You should see a result similar to that shown in Figure 1. You can 15
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Figure 1: Resource request satisfied by Server Push
clearly see that the protocol it uses is h2 (short for “HTTP/2”) and the image was initiated via Push. This confirms that Server Push was used to satisfy the resource request.
TLS Required for HTTP/2 You might have noticed in Figure 1 that the scheme of the request is HTTPS. This is because all major browser vendors have chosen to implement HTTP/2 over Transport Layer Security (TLS) only. However, the specification does not mandate that a secure connection is required for suc- cessful HTTP/2 communication. Browser vendors have made that decision on our behalf. Care must be taken when using a new PushBuilder object. A call to newPushBuilder() will return null if the connection is not secure, if the client does not support Server Push, or if the client has requested to disable Server Push via the SETTINGS_ENABLE_PUSH parameter of a SETTINGS frame. If you want to try this example for yourself, you can clone the code from the GitHub repository.
Anatomy of a PushBuilder Each new instance of PushBuilder created by calling newPushBuilder() is based upon the cur- rent HttpServletRequest instance. It is initiated with the HTTP GET method, and all headers are stripped out except for conditional, range, expect, authorization, and referrer headers. PushBuilder implements the builder pattern where chained method calls are used to mutate the instance before calling the push() method. The resource path is the only configuration 16
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required before pushing. The push action initiates an asynchronous Especially welcome is Server Push’s seamless nonblocking request, and when it integration into the JSF API, which makes the adoption returns, the path and conditional of performance-enhancing HTTP/2 features possible headers are cleared in preparation without any code changes. for the builder’s reuse. You might be wondering how useful it is to use PushBuilder in this way in a real-world application, and you would be right to question this. The example was a little artificial and is for demonstration purposes only. A more likely scenario is that your application will use JSF or JSP. So let’s look at JSF integration and how you might use the Server Push feature w it h JSP.
JSF Integration The JSF API takes full advantage of Server Push. It has full knowledge of all the resource requirements of the requested web page and is well placed to push resources to the client. Listing 3 shows a simple example of a JSF page that relies on three resources:
Listing 3.
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