Notes Of A Web Developer Learning Kotlin And Android Development

Generally, you should finalize all configuration changes before interacting with the database. It is important that your transaction does Kotlin developer job not have side effects as it may be executed multiple times. Both optionally allow you to specify the transaction isolation level.

Kotlin developer guide

Kotlin for Android utilizes JVM and combines the features of OOPs and functional-oriented programming. In this blog post, I shared my initial feelings and thoughts from learning about Kotlin and Android development. It’s been fun , and I’m looking forward to the following units.

What Is The Index Of An Array In Kotlin?

If you like the sound of supporting chat bubbles, then you’ll want to stick with the most recent version. You can learn more about the two options here by reading our guide to Kotlin vs Java for Android. Kotlin, on the other hand, has become Google’s preferred choice for Android development. This is the default when starting a new app, and it is likely to become more common going forward.

  • Data types are set of relatable values and describe the operations that can be operated on them.
  • A ColumnMapper converts a single column’s value into a Java object.
  • However this is not a requirement—​some annotations may choose to apply configuration differently depending on whether the annotation is placed on the type or the method.
  • An Array is the homogenous set of data types and is one of the most fundamental data types which is used to store the same types of data in the contiguous memory location.
  • Method decorating annotations are used to enhance a SQL Object method with additional behavior.
  • By default, the Java compiler does not write parameter names of constructors and methods to class files.

TransactionConsumer and TransactionCallback only take a Handle now—​theTransactionStatus argument is removed. Jdbi tries to be defensive and fail eagerly when you hold it wrong. Most users will not need to implement the ResultProducer interface. Jdbi also provides StringTemplateEngine, which renders templates using the StringTemplate library. Jdbi uses a TemplateEngineimplementation to render templates into SQL.

1 Jdbi

If you load all Jdbi plugins via Jdbi.installPlugins() this plugin will be discovered and registered automatically. Otherwise, you can attach it usingJdbi.installPlugin(KotlinPlugin()). The Jdbi element bound with the SpecialDatabase annotation will have the SpecialDatabaseModule loaded and can use the CustomColumnMapper.

Okay, I have to admit that I’m not a complete newbie in Android development. When I was learning to code about 6-7 years ago, one of the learning paths I was following was Android development. I was working through Google’s Android courses in Udacity back then but never finished them. We have provided Kotlin Online Compiler which helps you to Edit and Execute the code directly from your browser.

Kotlin developer guide

As mentioned at the beginning of the post, I was learning about Android Development years ago. Because of that, it was relatively easy to jump back to the world of Android Studio and other things. And as the first unit concentrates on fundamental things, it felt familiar and easy.


A “Basic Activity” on the other hand will create a starting screen for your app and will add a button in the bottom and a hamburger menu at the top. These are common elements in many Android apps, so this can save you some time. First, you need to create your development environment so that your desktop is ready to support your Android development goals. For that, you will need Android Studio and the Android SDK. Thankfully, these both come packaged together in a single download that you can find here. In addition to the required configuration parameters, you can define a number of optional configuration parameters if relevant. AbstractArgumentFactory is a generic implementation of ArgumentFactoryfor factories that handle a single argument type.

Updates may return Generated Keys instead of a result count. Alternatively, theResultBearing.reduceRowsvariant accepts a RowReducer and returns a stream of reduced elements. Jdbi provides a few different APIs for dealing with joined data. Note that we’ve given aliases (e.g. c_id, p_id) to distinguish columns of the same name from different tables. Any @Nullable annotation from any package may be used.javax.annotation.Nullable is a good choice.

To address this issue, implement ArgumentFactory.Preparable which promises to handle all values of a given Type. Most built in argument factories now implement the Preparable interface. Fortunately, Jdbi can be configured to bind custom data types as arguments, by implementing a few simple interfaces. Jdbi3-kotlin-sqlobjectEnhance the SQL Object extension to support Kotlin default methods and method default parameters. Kotlin is a modern programming language that many developers are migrating to and loving and is Google’s recommended programming language for Android development.

Jdbi 3 Developer Guide

There are two types of increment and decrement that are pre-increment ++a, post-increment a++, pre decrement –b, post decrement b–. With these simple steps, it is easy downloading Eclipse and Kotlin on your system and write your first Kotlin program right away. Now, you have to define a name for the project, and you are ready to work with Kotlin. Once, you have verified the Kotlin installation, let us create the first Kotlin program in the next step. Please restart the Eclipse IDE, once the installation is complete.

Likewise for r_idand r_name into id and name parameters of the Role constructor, respectively. SeeBuiltInCollectorFactoryfor the complete list of collection types supported out of the box. Certain Jdbi plugins (e.g. GuavaPlugin) register additional collection types. Some support only one generated key column per statement, and some can return the entire row. You should check your database vendor’s documentation before relying on this behavior. At runtime, you can request an instance of your interface, and Jdbi synthesizes an implementation based on the annotations and methods you declared.

It uses the mapping registry to determine how to map each given type, and presents you with a JoinRow that holds all of the resulting values. You may be wondering about the getRow() and getColumn() calls to rowView. When you call rowView.getRow(SomeType.class), RowView looks up the registered row mapper for SomeType, and uses it to map the current row to aSomeType object.

Kotlin Functions

Consult the JdbiCollectors registry to obtain aCollectorFactory which supports the given container type. Otherwise, throw an exception that Jdbi doesn’t know which constructor to use. To instruct Jdbi to ignore an otherwise mappable method, annotate it as @Unmappable. This ColumnMapper is equivalent to the lambda mapper above, but more explicit.

Kotlin Null Safety

After the last row has been processed,reducedRows() returns the last value returned from the lambda. returns the only row in the result set. If zero or multiple rows are encountered, it will throw IllegalStateException.

The Jdbi object is exposed to Guice using the annotation passed on the module constructor . The AbstractJdbiDefinitionModule supports both annotation instances and classes, similar to Guice itself. The parameters to the method are used as arguments to the statement, and the SQL statement result mapped into the method return type. By using the TypeResolvingCodecFactory from the guava module, it is possible to use codecs that are registered for subclasses or interface types for concrete classes.

Stream integration allows you to use a RowMapper to adapt a ResultSet into the new Java 8 Streams framework. As long as your database supports streaming results , the stream will lazily fetch rows from the database as necessary. ResultIterable.first() returns the first row in the result set.

Written for experienced Java developers, this example-rich book goes further than most language books, covering interesting topics like building DSLs with natural language syntax. Kotlin is very easy to learn, especially for Java developers. You can use Kotlin for developing not only Android but also iOS, backend, and web applications. Enjoy the benefits of sharing the common code among the platforms.

Unlike argument binding, the rendering of attributes performed by TemplateEngines is not SQL-aware. Since they perform generic String manipulations, TemplateEngines can easily produce horribly mangled or subtly defective queries if you don’t use them carefully. Parameters annotated @Nullable may be omitted from the result set, in whichConstructorMapper will pass null to the constructor for that parameter. Next we call ColumnMappers.findFor() to get the column mapper for the embedded type. It is possible to register more than one mapper for any given type. When this happens, the last-registered mapper for a given type takes precedence.