KivaKit is an Apache License accessible antecedent Java framework advised for implementing microservices. KivaKit requires a Java 11 basic machine, but is source-compatible with Java 8 and 9 projects. KivaKit is composed of a set of anxiously chip mini-frameworks. Anniversary mini-framework has a constant architecture and its own focus, and can be acclimated in concert with added mini-frameworks or on its own. A simplified annex arrangement of these frameworks provides a acceptable aerial akin appearance of KivaKit:
Each mini-framework addresses a altered affair that is frequently encountered aback developing microservices. This commodity provides a abrupt overview of the mini-frameworks in the diagram above, and a account of how they can be used.
As we can see in the diagram above, messaging is axial to KivaKit. Messaging is advantageous in architecture apparatus whose cachet is observable, which is a accessible affection in a cloud-based world. Abounding altar in KivaKit advertisement or accept to cachet Letters such as Alert, Problem, Warning or Trace. Best are Repeaters, alert for cachet letters from added object(s) and re-broadcasting them to absorbed admirers downstream. This forms a adviser alternation with a terminal Listener:
C -> B -> A
Often, the final adviser in a alternation is some affectionate of Logger, but there can be assorted admirers at the end of the alternation as well, and any article implementing Adviser will work. For example, in the Validation mini-framework, cachet letters are captured by the ValidationIssues class, which is again acclimated to actuate if a validation succeeded or not, as able-bodied as to present specific problems from a validation abortion to a user.
Given the adviser alternation above, C and B apparatus Captive and the final article A accouterments Listener. Within anniversary chic in the chain, the adviser alternation is continued with:
To address a bulletin to absorbed listener(s), accessibility methods are affiliated from Anchorperson for accepted types of messages:
Something has gone amiss and needs to be addressed, but it’s not baleful to the accepted operation.
A accessory botheration has occurred. Unlike a Warning, a Glitch indicates validation abortion or abstracts accident has occurred. Unlike a Problem, a Glitch indicates that the operation will absolutely balance and continue.
A accessory affair has occurred which should be corrected, but does not necessarily crave attention.
A atomic affair has occurred that does not crave correction.
Announces an important appearance of an operation.
A footfall in some operation has started or completed.
Commonly advantageous advice that doesn’t represent any problem
Diagnostic advice for use aback debugging.
Broadcaster additionally provides a apparatus for switching Trace letters on and off from the command band by arrangement analogous adjoin classes and packages.
In KivaKit, there are two agency to apparatus Repeater. The aboriginal is by artlessly extending BaseRepeater. The additional is to use a stateful affection or Mixin. Implementing the RepeaterMixin interface is the aforementioned as extending BaseRepeater, but the captive mixin can be acclimated in a chic that already has a abject class. Note that the aforementioned arrangement is acclimated for the Basic interface discussed below. If it’s not accessible to extend BaseComponent again ComponentMixin can be implemented instead.
The Mixin interface provides a workaround for a missing Java accent feature. It works by delegating accompaniment lookup to a amalgamation clandestine class, MixinState, which uses the this advertence of the chic implementing Mixin to attending up an associated accompaniment article in an character assortment map. The Mixin interface looks like this:
If the accompaniment article for this is not begin by state(), the accustomed branch adjustment will be acclimated to actualize a new accompaniment object, which will again be associated with the mixin in the accompaniment map. For example, our RepeaterMixin interface looks almost like this (without best of the methods for the account of brevity):
Here, the addListener() and removeListener() methods anniversary retrieve their BaseRepeater accompaniment article through repeater() and agent the adjustment alarm to that object. As we can see, it’s not actual complicated to apparatus a mixin in KivaKit.
It should be acclaimed that anniversary alarm to a adjustment in a mixin will crave a lookup in the accompaniment map. An character assortment map should be adequately able in general, but for a few apparatus this could be a achievement problem. As with best achievement problems, it’s best for us to do the simplest affair until our profiler says otherwise.
A KivaKit Basic ability frequently be a key allotment of a microservice. Apparatus accommodate accessible admission to messaging either through addendum of BaseComponent (the best accepted case) or by implementing ComponentMixin. Inheriting from Basic adds no accompaniment at all to an article except for the account of admirers affiliated from Repeater. This makes apparatus actual lightweight. It is not a botheration to instantiate ample numbers of them. Back Apparatus are Repeaters, adviser chains can be created, as declared above.
In accession to accouterment acceptable admission to messaging, apparatus additionally accommodate functionality to:
Let’s booty a attending at anniversary of these facilities.
KivaKit uses the account locator architecture arrangement instead of annex injection. The use of this arrangement in a Basic is simple. One basic can annals an article with registerObject() and addition basic can attending it up with require():
If assorted instances of a distinct chic charge to be registered, an enum amount can be acclimated to analyze them:
In KivaKit, anywhere we ability accept acclimated annex bang we use annals and crave instead.
Components in KivaKit can additionally readily admission settings advice with the require() method:
As with registered objects, an enum can be acclimated to analyze amid settings altar in the accident that there is added than one of the aforementioned type:
Settings advice can be registered in several ways:
In KivaKit 1.0, settings altar loaded with the registerAllSettingsIn() methods are authentic by .properties files. In the future, an API will be provided to acquiesce backdrop to be loaded from added sources, such as .json files. The name of the settings chic to instantiate is accustomed by the chic property. Individual backdrop of the instantiated article are again retrieved from the actual properties. Anniversary acreage is adapted to an article appliance a KivaKit advocate (described below).
KivaKit provides a ability mini-framework that unifies a array of Ability types:
Resources are Apparatus from which an appliance can apprehend streamed data. WritableResources are assets to which an appliance can address streamed data. Best of the methods accessible to a Book will be accessible in any accustomed Resource, but some ability types may leave some methods unsupported. For example, a ability ability be streamed, so it can’t apparatus sizeInBytes().
KivaKit Book is a appropriate resource. It uses a account provider interface (SPI) to admittance new filesystems to be added. The kivakit-extensions activity provides implementations for the afterward filesystems:
KivaKit apparatus accommodate accessible admission to PackageResources. The appearance of encapsulating assets in KivaKit is agnate to that in Apache Wicket, area a component’s amalgamation will accept a sub-package absolute assets that it requires to function. This allows accessible packaging and use of apparatus from a distinct antecedent tree. Admission to a amalgamation ability about to a Basic looks like this:
Where the amalgamation anatomy looks like this:
A KivaKit Appliance is a adored Component, absolute methods accompanying to startup, initialization and execution. Server is a bracket of Application:
Microservices are the best accepted use for KivaKit applications, but added types of applications can additionally be implemented (desktop, web, utility, etc.). The bald basic cipher for a microservice appliance looks like this:
The main() adjustment actuality creates the appliance and calls the run() adjustment in the Appliance abject chic with the arguments anesthetized from the command line. The architect for the microservice again passes a Activity article to the superclass constructor. This article is acclimated to initialize the activity that contains the application, as able-bodied as any added projects aloft which it depends. Continuing our example, our Activity chic looks like this:
A article instance of MyProject can be retrieved with get(). The dependencies for MyProject are alternate by dependencies(). In this case, MyProject is abased alone on ResourceProject, which is the Activity analogue for the kivakit-resource mini-framework. ResourceProject in about-face has its own dependencies. KivaKit will ensure that all transitive activity dependencies are initialized afore onRun() is called.
KivaKit applications can amount collections of settings altar automatically from an application-relative amalgamation called deployments. This affection is advantageous aback deploying a microservice to a accurate environment. The anatomy of our appliance looks like this:
When the about-face -deployment= is anesthetized to the appliance on the command line, it will amount settings from the called deployment (either development or assembly in this case). It is abnormally nice to use packaged deployment settings for a microservice because use of the appliance is actual simple:
java -jar my-microservice.jar -deployment=development […]
This makes it accessible to run the appliance in a Docker alembic alike if you don’t apperceive abundant about it.
If packaged deployment settings are not desired, an alien binder can be acclimated by ambience the ambiance capricious KIVAKIT_SETTINGS_FOLDERS:
Applications can additionally anatomize command curve by abiding a set of SwitchParsers and/or a account of ArgumentParsers:
Here, the DICTIONARY about-face parser alternate by switchParsers() is acclimated by KivaKit to anatomize the command line. In the onRun() method, the Book altercation anesthetized on the command band is retrieved with get(DICTIONARY). If there is a syntactic botheration with the command band or it doesn’t canyon validation, KivaKit will automatically address the botheration and accord acceptance advice acquired from the description(), and the about-face and altercation parsers:
In our appliance example, we acclimated this cipher to body a SwitchParser:
The File.fileSwitchParser() adjustment allotment a about-face parser architect which can be specialized with several methods afore build() is called:
The accomplishing of File.fileSwitchParser() again looks like this:
All switches and arguments are typed objects, so the builder(Class) adjustment creates a architect with the Book blazon (using the type() method). It is accustomed the name and description anesthetized to fileSwitchParser() and the File.Converter adjustment is acclimated to catechumen amid String and Book objects.
KivaKit provides abounding converters, and converters can be acclimated in abounding places in KivaKit. Converters are reusable altar that transform one blazon into another. They are abnormally accessible to create, and they handle accepted issues like exceptions and absent or abandoned values:
Calling StringConverter.convert(String) will about-face a String into a File. Calling StringConverter.unconvert(File) will about-face a Book aback into a String. Any issues that are encountered during about-face are advertisement to absorbed listener(s), and if about-face fails absent is returned.
As we can see, converters booty a altered admission to adviser chains. Instead of relying on advocate users to alarm listenTo(), all converters crave a adviser as a architect argument. This ensures that all converters are able to address about-face problems to at atomic one listener.
In the command band parsing cipher above, switches and arguments are accurate appliance the kivakit-validation mini-framework. Addition accepted use case is in acceptance the area altar of a web appliance user interface to a microservice.
A Validatable chic implements:
To apparatus this method, a BaseValidator can be subclassed anonymously. BaseValidator provides accessibility methods to analysis accompaniment consistency, and to advertisement problems and warnings. KivaKit captures these letters with a ValidationIssues object. Absence methods in the Validatable interface can again be acclimated to concern this state. Acceptance looks like:
Messages from validation actuality are captured to actuate if the User article is valid. The aforementioned letters are additionally advertisement to admirers of MyComponent, area they ability be logged or displayed in some user interface.
A KivaKit Logger is a bulletin Adviser that logs all of the letters it hears. The abject Appliance chic has a Logger that logs any letters that balloon up from apparatus to the appliance level. This agency that there isn’t any charge to actualize loggers in an appliance or any of its components, provided that the adviser alternation leads from anniversary basic all the way aback to the application.
The simplest logger is ConsoleLogger. Shrinking this architecture to its bald bones, ConsoleLogger and accompanying classes attending almost like this (and see UML diagram below):
The BaseLogger.log(Message) adjustment converts the bulletin it is accustomed into a LogEntry by abacus contextual information. It again passes the log admission to anniversary Log in the account of logs alternate by logs(). In the case of ConsoleLogger, a distinct instance of ConsoleLog is returned. ConsoleLog writes the LogEntry to the console.
KivaKit has an SPI that allows new loggers to be dynamically added and configured from the command line. Some loggers provided with KivaKit include:
The kivakit-extensions activity contains bare-bones abutment for Jetty, Jersey, Swagger and Apache Wicket back these are generally advantageous in implementing microservices. These mini-frameworks are all chip calm so it’s actual accessible to alpha a Jetty server accouterment REST and Web admission for a microservice:
JettyServer actuality allows Jersey, Wicket and Swagger to be accumulated with a constant API, authoritative the cipher bright and concise. Generally this is all that’s needed.
Although KivaKit is aboriginal at adaptation 1.0, it has been in use at Telenav for added than ten years. Ascribe from the accessible antecedent association is actual welcome, including feedback, bug reports, affection ideas, documentation, tests and cipher contributions.
The afterward assets can advice you dive into the details:
Jonathan Locke has been alive with Java back 1996, and he was a affiliate of the Sun Microsystems Java Team. As an accessible antecedent author, he is artist of the Apache Wicket web framework, as able-bodied the Java UML affidavit apparatus Lexakai. Jonathan works as a Principal Software Architect at Telenav.
How To Write Rest Webservices In Java – How To Write Rest Webservices In Java
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