mrhaki

Spocklight: Use Stub or Mock For Spring Component Using @SpringBean

When we write tests or specifications using Spock for our Spring Boot application, we might want to replace some Spring components with a stub or mock version. With the stub or mock version we can write expected outcomes and behaviour in our specifications. Since Spock 1.2 and the Spock Spring extension we can use the @SpringBean annotation to replace a Spring component with a stub or mock version. (This is quite similar as the @MockBean for Mockito mocks that is supported by Spring Boot). We only have to declare a variable in our...

mrhaki

Java Joy: Transform Elements In Stream Using a Collector

Using the Stream API and the map method we can transform elements in a stream to another object. Instead of using the map method we can also write a custom Collector and transform the elements when we use the collect method as terminal operation of the stream.First we have an example where we transform String value using the map method:package mrhaki; import java.util.List; import java.util.stream.Collectors; public class CollectorString { public static void main(String[] args) { final var items = List.of("JFall",...

mrhaki

Micronaut Mastery: Binding Request Parameters To POJO

Micronaut supports the RFC-6570 URI template specification to define URI variables in a path definition. The path definition can be a value of the @Controller annotation or any of the routing annotations for example @Get or @Post. We can define a path variable as {?binding*} to support binding of request parameters to all properties of an object type that is defined as method argument with the name binding. We can even use the Bean Validation API (JSR380) to validate the values of the request parameters if we add an implementation of this API...

mrhaki

Spring Sweets: Group Loggers With Logical Name

Spring Boot 2.1 introduced log groups. A log group is a logical name for one or more loggers. We can define log groups in our application configuration. Then we can set the log level for a group, so all loggers in the group will get the same log level. This can be very useful to change a log level for multiple loggers that belong together with one setting. Spring Boot already provides two log groups by default: web and sql. In the following list we see which loggers are part of the default log groups: web: org.springframework.core.codec,...

mrhaki

Gradle Goodness: Only Show All Tasks In A Group

To get an overview of all Gradle tasks in our project we need to run the tasks task. Since Gradle 5.1 we can use the --group option followed by a group name. Gradle will then show all tasks belonging to the group and not the other tasks in the project.Suppose we have a Gradle Java project and want to show the tasks that belong to the build group:$ gradle tasks --group build > Task :tasks ------------------------------------------------------------ Tasks runnable from root project -...

mrhaki

Gradle Goodness: Generate Javadoc In HTML5

Since Java 9 we can specify that the Javadoc output must be generated in HTML 5 instead of the default HTML 4. We need to pass the option -html5 to the javadoc tool. To do this in Gradle we must add the option to the javadoc task configuration. We use the addBooleanOption method of the options property that is part of the javadoc task. We set the argument to html5 and the value to true.In the following example we reconfigure the javadoc task to make sure the generated Javadoc output is in HTML 5:// File: build.gradle apply plugin:...

mrhaki

Gradle Goodness: Rerun Incremental Tasks At Specific Intervals

One of the most important features in Gradle is the support for incremental tasks. Incremental tasks have input and output properties that can be checked by Gradle. When the values of the properties haven't changed then the task can be marked as up to date by Gradle and it is not executed. This makes a build much faster. Input and output properties can be files, directories or plain object values. We can set a task input property with a date or date/time value to define when a task is up to date for a specific period. As long as the value of...

mrhaki

Micronaut Mastery: Configuration Property Name Is Lowercased And Hyphen Separated

In Micronaut we can inject configuration properties in different ways into our beans. We can use for example the @Value annotation using a string value with a placeholder for the configuration property name. If we don't want to use a placeholder we can also use the @Property annotation and set the name attribute to the configuration property name. We have to pay attention to the format of the configuration property name we use. If we refer to a configuration property name using @Value or @Property we must use lowercased and hyphen separated...

mrhaki

Micronaut Mastery: Consuming Server-Sent Events (SSE)

Normally we would consume server-sent events (SSE) in a web browser, but we can also consume them in our code on the server. Micronaut has a low-level HTTP client with a SseClient interface that we can use to get server-sent events. The interface has an eventStream method with different arguments that return a Publisher type of the Reactive Streams API. We can use the RxSseClient interface to get back RxJava2 Flowable return type instead of Publisher type. We can also use Micronaut's declarative HTTP client, which we define using the @Client...

mrhaki

Micronaut Mastery: Running Code On Startup

When our Micronaut application starts we can listen for the ServiceStartedEvent event and write code that needs to run when the event is fired. We can write a bean that implements the ApplicationEventListener interface with the type ServiceStartedEvent. Or we can use the @EventListener annotation on our method with code we want to run on startup. If the execution of the code can take a while we can also add the @Async annotation to the method, so Micronaut can execute the code on a separate thread.In our example application we have a reactive...

mrhaki

Spring Sweets: Dockerize Spring Boot Application With Jib

Jib is an open-source Java library from Google for creating Docker images for Java applications. Jib can be used as Maven or Gradle plugin in our Spring Boot project. One of the nice feature of Jib is that it adds layers with our classes, resources and dependency libraries for the Docker image. This means that when only class files have changed, the classes layer is rebuild, but the others remain the same. Therefore the creation of a Docker image with our Spring Boot application is also very fast (after the first creation). Also the Maven and...