Why does @Value work, but not @ConfigurationProperties?

Question

My class:

package com.myCom.test;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties( prefix = "sample.mail")
public class ConfigProperties {

  @Value("${sample.mail.hostName}")
  private String hostName;

  private int port;

  private String from;

  public String getHostName() {
    return hostName;
  }

  public void setHostName(String hostName) {
    this.hostName = hostName;
  }

  public int getPort() {
    return port;
  }

  public void setPort(int port) {
    this.port = port;
  }

  public String getFrom() {
    return from;
  }

  public void setFrom(String from) {
    this.from = from;
  }
}

My test:

package com.myCom.test;

import static org.junit.jupiter.api.Assertions.assertNotNull;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.Bean;
import org.springframework.test.context.ContextConfiguration;

@ContextConfiguration(
    classes = {
        ConfigProperties.class
    })
@SpringBootTest
public class ConfigPropertiesIT {

  @Autowired
  ConfigProperties properties;

  @Test
  public void testProperty() {
    assertNotNull(properties);
    assertNotNull(properties.getHostName());
    assertNotNull(properties.getFrom());
  }
}

My application.yaml

sample:
  mail:
    hostName: www.myCom.com
    port: 8088
    from: aUser

Why the hostName field worked, but not the from field? Adding @Value annotation make a field work, and removing it makes a field not work. It almost seems as if the @ConfigurationProperties annotation is not trying to bind the properties to the fields even though the name is matching. I suspect the @ContextConfiguration may cause this binding to not happen, but I need help from somebody with deeper understanding.

Answer 1

I suspect the @ContextConfiguration may cause this binding to not happen, but I need help from somebody with deeper understanding.

Yes, that's likely the case. With such minimal configuration, nothing will have enabled configuration properties through @EnableConfigurationProperties. As such, configuration property binding will not happen as part of creating your ConfigProperties component.

You need to run your tests with some configuration that is annotated with @EnableConfigurationProperties.