Micronaut: Introspect public and package protected fields

There are situations, where you have a class that has public and package protected fields without accessor (getter, setter) methods. You can introspect these fields using accessKind attribute of @Introspected annotation.

 

Step 1: Create new maven project ‘micronaut-bean-introspect-bean-fields’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.sample.app</groupId>
	<artifactId>micronaut-bean-introspect-bean-fields</artifactId>
	<version>1</version>

	<properties>
		<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
		<micronaut.version>3.7.2</micronaut.version>
		<slf4j.version>2.0.3</slf4j.version>

		<maven.compiler.target>15</maven.compiler.target>
		<maven.compiler.source>15</maven.compiler.source>
	</properties>

	<dependencies>

		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-inject-java</artifactId>
			<version>${micronaut.version}</version>
		</dependency>
		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-runtime</artifactId>
			<version>${micronaut.version}</version>
		</dependency>


		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>${slf4j.version}</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-simple</artifactId>
			<version>${slf4j.version}</version>
		</dependency>
	</dependencies>

	<build>
		<plugins>

			<plugin>
				<artifactId>maven-assembly-plugin</artifactId>
				<configuration>
					<archive>
						<manifest>
							<mainClass>com.sample.app.App</mainClass>
						</manifest>
					</archive>
					<descriptorRefs>
						<descriptorRef>jar-with-dependencies</descriptorRef>
					</descriptorRefs>
				</configuration>

				<executions>
					<execution>
						<id>make-assembly</id>
						<phase>package</phase>
						<goals>
							<goal>single</goal>
						</goals>
					</execution>
				</executions>
			</plugin>

		</plugins>
	</build>
</project>

Step 3: Define Person class.

 

Person.java

package com.sample.app.model;

import io.micronaut.core.annotation.Introspected;

@Introspected(accessKind = Introspected.AccessKind.FIELD)
public class Person {

	public Integer id;

	public String name;

	public Person(Integer id, String name) {
		this.id = id;
		this.name = name;
	}

}

Step 4: Define main application class.

 

App.java

package com.sample.app;

import com.sample.app.model.Person;

import io.micronaut.context.ApplicationContext;
import io.micronaut.core.beans.BeanIntrospection;
import io.micronaut.core.beans.BeanProperty;

public class App {

	public static void main(String[] args) {
		try (ApplicationContext applicationContext = ApplicationContext.run()) {
			final BeanIntrospection<Person> introspection = BeanIntrospection.getIntrospection(Person.class);
			Person person = introspection.instantiate(1, "Krishna");
			
			System.out.println("id : " + person.id);
			System.out.println("name : " + person.name);

			final BeanProperty<Person, String> property = introspection.getRequiredProperty("name", String.class); 
			property.set(person, "Ram");
			String name = property.get(person);
		
			System.out.println("\nname : " + name);	
			System.out.println("id : " + person.id);
			System.out.println("name : " + person.name);

		}

	}
}

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-bean-introspect-bean-fields-1-jar-with-dependencies.jar’ in project target folder.

$ ls ./target/
archive-tmp
classes
generated-sources
maven-archiver
maven-status
micronaut-bean-introspect-bean-fields-1-jar-with-dependencies.jar
micronaut-bean-introspect-bean-fields-1.jar
test-classes

Execute below command to run the application.

$ java -jar ./target/micronaut-bean-introspect-bean-fields-1-jar-with-dependencies.jar
id : 1
name : Krishna

name : Ram
id : 1
name : Ram

You can download this application from this link.

 

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