@Property annotation is used to inject a value associated with given property name.
Example
@Property(name = "spring.datasource.communicationtimeout")
protected Integer communicationTimeout;
Above statement resolve the value associated with the property "spring.datasource.communicationtimeout" and inject it into the field ‘communicationTimeout’. As a recommendation from Micronaut, fields subject to injection should not be private because expensive reflection must be used.
Can I apply @Property annotation on setter method arguments?
Yes, you can.
@Inject
public void setVersion(@Property(name = "appVersion") String version) {
this.version = version;
}
Resolve submaps using Property annotation
Example application.yml configuration
appName: chat server
appVersion: 1.23.45
spring:
datasource:
communicationtimeout: 6000
jpa:
hibernate:
ddl-auto: none
hikari:
connection-timeout: 3000
idle-timeout: 40000
max-lifetime: 10000
maximum-pool-size: 5
To resolve a flattened map containing only the properties starting with hibernate, use @Property, for example:
@Property(name = "spring.datasource")
@MapFormat(transformation = MapTransformation.FLAT)
protected Map<String, String> datasourceFlatMap;
‘datasourceFlatMap’ contain below information.
communicationtimeout -> 6000 jpa.hibernate.ddl-auto -> none hikari.connection-timeout -> 3000 hikari.idle-timeout -> 40000 hikari.max-lifetime -> 10000 hikari.maximum-pool-size -> 5
If you do not specify any transformation explicitly, then it is NESTED by default.
@Property(name = "spring.datasource")
@MapFormat
protected Map<String, String> datasourceNestedMap;
‘datasourceNestedMap’ contain below information.
communicationtimeout -> 6000
jpa -> {hibernate={ddl-auto=none}}
hikari -> {connection-timeout=3000, idle-timeout=40000, max-lifetime=10000, maximum-pool-size=5}
Find the below working application.
Step 1: Create new maven project ‘micronaut-property-annotation-demo’.
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-property-annotation-demo</artifactId>
<version>1</version>
<properties>
<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
<micronaut.version>3.7.3</micronaut.version>
<slf4j.version>2.0.3</slf4j.version>
<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.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>${micronaut.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>${slf4j.version}</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>${slf4j.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<annotationProcessorPaths>
<path>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-inject-java</artifactId>
<version>${micronaut.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
<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: Create application.yml file under src/main/resources folder.
application.yml
appName: chat server
appVersion: 1.23.45
spring:
datasource:
communicationtimeout: 6000
jpa:
hibernate:
ddl-auto: none
hikari:
connection-timeout: 3000
idle-timeout: 40000
max-lifetime: 10000
maximum-pool-size: 5
Step 4: Define AppConfig class.
AppConfig.java
package com.sample.app.configs;
import java.util.Map;
import io.micronaut.context.annotation.Property;
import io.micronaut.core.convert.format.MapFormat;
import io.micronaut.core.convert.format.MapFormat.MapTransformation;
import jakarta.inject.Inject;
import jakarta.inject.Singleton;
@Singleton
public class AppConfig {
@Property(name = "app-name")
protected String name;
protected String version;
@Property(name = "spring.datasource.communicationtimeout")
protected Integer communicationTimeout;
@Property(name = "spring.datasource")
@MapFormat(transformation = MapTransformation.FLAT)
protected Map<String, String> datasourceFlatMap;
@Property(name = "spring.datasource")
@MapFormat
protected Map<String, String> datasourceNestedMap;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getVersion() {
return version;
}
@Inject
public void setVersion(@Property(name = "appVersion") String version) {
this.version = version;
}
public Integer getCommunicationTimeout() {
return communicationTimeout;
}
public void setCommunicationTimeout(Integer communicationTimeout) {
this.communicationTimeout = communicationTimeout;
}
public Map<String, String> getDatasourceFlatMap() {
return datasourceFlatMap;
}
public void setDatasourceFlatMap(Map<String, String> datasourceFlatMap) {
this.datasourceFlatMap = datasourceFlatMap;
}
public Map<String, String> getDatasourceNestedMap() {
return datasourceNestedMap;
}
public void setDatasourceNestedMap(Map<String, String> datasourceNestedMap) {
this.datasourceNestedMap = datasourceNestedMap;
}
}
Step 5: Define main application class.
App.java
package com.sample.app;
import java.util.Map;
import com.sample.app.configs.AppConfig;
import io.micronaut.context.ApplicationContext;
public class App {
public static void main(String[] args) {
try (ApplicationContext applicationContext = ApplicationContext.run()) {
AppConfig appConfig = applicationContext.getBean(AppConfig.class);
String appName = appConfig.getName();
String version = appConfig.getVersion();
Integer datasourceTimeout = appConfig.getCommunicationTimeout();
System.out.println("appName : " + appName);
System.out.println("version : " + version);
System.out.println("datasourceTimeout : " + datasourceTimeout + "\n");
System.out.println("\nFlat map informaiton");
Map<String, String> datasourceProperties = appConfig.getDatasourceFlatMap();
for (String key : datasourceProperties.keySet()) {
System.out.println(key + " -> " + datasourceProperties.get(key));
}
System.out.println("\nNested map informaiton");
datasourceProperties = appConfig.getDatasourceNestedMap();
for (String key : datasourceProperties.keySet()) {
System.out.println(key + " -> " + datasourceProperties.get(key));
}
}
}
}
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-property-annotation-demo-1-jar-with-dependencies.jar’ in project target folder.
$ls ./target/
archive-tmp
classes
generated-sources
generated-test-sources
maven-archiver
maven-status
micronaut-property-annotation-demo-1-jar-with-dependencies.jar
micronaut-property-annotation-demo-1.jar
test-classes
Execute below command to run the application.
java -jar ./target/micronaut-property-annotation-demo-1-jar-with-dependencies.jar
$java -jar ./target/micronaut-property-annotation-demo-1-jar-with-dependencies.jar
appName : chat server
version : 1.23.45
datasourceTimeout : 6000
Flat map informaiton
communicationtimeout -> 6000
jpa.hibernate.ddl-auto -> none
hikari.connection-timeout -> 3000
hikari.idle-timeout -> 40000
hikari.max-lifetime -> 10000
hikari.maximum-pool-size -> 5
Nested map informaiton
communicationtimeout -> 6000
jpa -> {hibernate={ddl-auto=none}}
hikari -> {connection-timeout=3000, idle-timeout=40000, max-lifetime=10000, maximum-pool-size=5}
You can download this application from this link.
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