Micronaut: How to make a request parameter optional in Micronaut?

You can define query parameter in Micronaut as optional by io.micronaut.core.annotation.Nullable annotation.

 

Example

@Get(value = "/even-numbers", produces = MediaType.TEXT_PLAIN)
public String evenNumbers(@Nullable @QueryValue("from") Integer from, @Nullable @QueryValue("to") Integer to) {

	if (from == null || from < 0) {
		from = 0;
	}

	if (to == null || to < 0) {
		to = from + 10;
	}

	final StringJoiner stringJoiner = new StringJoiner(",");

	for (int i = from; i < to; i += 2) {
		stringJoiner.add("" + i);
	}

	return stringJoiner.toString();
}

Find the below working application.

 

Step 1: Create new maven project ‘micronaut-rest-bind-request-query-param’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.sample.app</groupId>
	<artifactId>micronaut-rest-bind-request-query-param</artifactId>
	<version>0.1</version>
	<packaging>jar</packaging>

	<parent>
		<groupId>io.micronaut</groupId>
		<artifactId>micronaut-parent</artifactId>
		<version>3.7.4</version>
	</parent>

	<properties>
		<packaging>jar</packaging>
		<jdk.version>11</jdk.version>
		<release.version>11</release.version>
		<micronaut.version>3.7.3</micronaut.version>
		<micronaut.runtime>netty</micronaut.runtime>
		<exec.mainClass>com.sample.app.App</exec.mainClass>
	</properties>

	<repositories>
		<repository>
			<id>central</id>
			<url>https://repo.maven.apache.org/maven2</url>
		</repository>
	</repositories>

	<dependencies>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-inject</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-validation</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-http-client</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-http-server-netty</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-jackson-databind</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>jakarta.annotation</groupId>
			<artifactId>jakarta.annotation-api</artifactId>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>ch.qos.logback</groupId>
			<artifactId>logback-classic</artifactId>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>io.micronaut.test</groupId>
			<artifactId>micronaut-test-junit5</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-api</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-engine</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>io.micronaut.build</groupId>
				<artifactId>micronaut-maven-plugin</artifactId>
			</plugin>

			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<!-- Uncomment to enable incremental compilation -->
					<!-- <useIncrementalCompilation>false</useIncrementalCompilation> -->

					<annotationProcessorPaths
						combine.children="append">
						<path>
							<groupId>io.micronaut</groupId>
							<artifactId>micronaut-http-validation</artifactId>
							<version>${micronaut.version}</version>
						</path>
					</annotationProcessorPaths>

				</configuration>
			</plugin>
		</plugins>
	</build>

</project>

Step 3: Define HelloController class.

 

HelloController.java

package com.sample.app.controller;

import java.util.StringJoiner;

import io.micronaut.core.annotation.Nullable;
import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.QueryValue;

@Controller("/hello")
public class HelloController {

	@Get(value = "/even-numbers", produces = MediaType.TEXT_PLAIN)
	public String evenNumbers(@Nullable @QueryValue("from") Integer from, @Nullable @QueryValue("to") Integer to) {

		if (from == null || from < 0) {
			from = 0;
		}

		if (to == null || to < 0) {
			to = from + 10;
		}

		final StringJoiner stringJoiner = new StringJoiner(",");

		for (int i = from; i < to; i += 2) {
			stringJoiner.add("" + i);
		}

		return stringJoiner.toString();
	}
}

Step 4: Define main application class.

 

App.java

package com.sample.app;

import io.micronaut.runtime.Micronaut;

public class App {

	public static void main(String[] args) {
		Micronaut.run(App.class);

		// Use this if you want the beans to be initialized eagerly
		/*
		 * Micronaut.build(args) .eagerInitSingletons(true) .mainClass(App.class)
		 * .start();
		 */
	}
}

Total project structure looks like below.

Build the project using mvn package command.

Navigate to the folder where pom.xml is located and execute the command ‘mvn package’.

 

Upon command successful execution, you can see the jar file ‘micronaut-rest-bind-request-query-param-0.1.jar’ in project target folder.

$ls ./target/
classes
generated-sources
generated-test-sources
maven-archiver
maven-status
micronaut-rest-bind-request-query-param-0.1.jar
original-micronaut-rest-bind-request-query-param-0.1.jar
test-classes

Execute below command to run the application.

java -jar ./target/micronaut-rest-bind-request-query-param-0.1.jar

 

Run below command to test the application.

curl --location --request GET 'http://localhost:8080/hello/even-numbers/?from=2&to=20'

$curl --location --request GET 'http://localhost:8080/hello/even-numbers/?from=2&to=20'
2,4,6,8,10,12,14,16,18

You can download this application from this link.

 

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