Close

Spring Framework - @Value Examples

Spring Framework 

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import jakarta.annotation.PostConstruct;

@Component
public class MyBean {
    @Value("${java.io.tmpdir:/temp}")
    private String tempDir;
    @Value("${contact-person:Joe}")
    private String contactPerson;

    @PostConstruct
    public void postInit() {
        System.out.println("System tempDir: " + tempDir);
        System.out.println("contact-person: " + contactPerson);
    }
}
Original Post




Using Spring Expression Language with @Value annotation. 

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import jakarta.annotation.PostConstruct;

@Component
public class MyBean {
    @Value("#{systemProperties['user.home']}")
    private String userHome;

    @Value("#{T(java.lang.Math).random()*1000}")
    private int randomNumber;

    @PostConstruct
    public void postInit() {
        System.out.println("System userHome: " + userHome);
        System.out.println("Random number: " + randomNumber);
    }
}
Original Post




In this example, @Value param 'theCurrency' value is auto converted to Currency object. Spring does this implicit conversion using property editors. In this example CurrencyEditor is used behind the scene. 

package com.logicbig.example;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import java.util.Currency;

public class ValueAnnotationExample {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context =
                            new AnnotationConfigApplicationContext(Config.class);
        ClientBean bean = context.getBean(ClientBean.class);
        bean.doSomething();
    }

    @Configuration
    @PropertySource("classpath:app.properties")
    public static class Config {
        @Bean
        public ClientBean clientBean () {
            return new ClientBean();
        }
    }

    public static class ClientBean {
        @Value("${theCurrency}")
        private Currency currency;

        public void doSomething () {
            System.out.printf("The currency from prop file is %s%n", currency);
            System.out.printf("The currency name is %s%n", currency.getDisplayName());
        }
    }
}

Output

The currency from prop file is PLN
The currency name is Polish Zloty

src/main/resources/app.properties:

theCurrency=PLN
thePrice=12,323.7654
theTradeDate=2016-9-14
Original Post




This JavaConfig example shows how to use PropertyEditorRegistrar implementation to register a custom editor. Here we use PropertyEditor to convert text from a property file to a Java object. 

package com.logicbig.example;

import org.springframework.beans.PropertyEditorRegistrar;
import org.springframework.beans.PropertyEditorRegistry;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.beans.factory.config.CustomEditorConfigurer;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import java.text.SimpleDateFormat;
import java.util.Date;

public class ValueAnnotationExample2 {

    public static void main (String[] args) {
        AnnotationConfigApplicationContext context =
                            new AnnotationConfigApplicationContext(Config.class);
        ClientBean bean = context.getBean(ClientBean.class);
        bean.doSomething();
    }

    @Configuration
    @PropertySource("classpath:app.properties")
    public static class Config {

        @Bean
        public ClientBean clientBean () {
            return new ClientBean();
        }

        @Bean
        public static CustomEditorConfigurer customEditorConfigurer () {
            CustomEditorConfigurer cec = new CustomEditorConfigurer();
            cec.setPropertyEditorRegistrars(
                                new PropertyEditorRegistrar[]{
                                                    new MyCustomBeanRegistrar()});
            return cec;
        }
    }

    public static class ClientBean {
        @Value("${theTradeDate}")
        private Date tradeDate;

        public void doSomething () {
            System.out.printf("The trade date from prop file is %s%n", tradeDate);
        }
    }

    public static class MyCustomBeanRegistrar implements PropertyEditorRegistrar {
        @Override
        public void registerCustomEditors (PropertyEditorRegistry registry) {
            SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd");
            dateFormatter.setLenient(false);
            registry.registerCustomEditor(Date.class,
                                          new CustomDateEditor(dateFormatter, true));
        }
    }
}

src/main/resources/app.properties:

theCurrency=PLN
thePrice=12,323.7654
theTradeDate=2016-9-14
Original Post

See Also