added code examples for @ConfigurationProperties

spring-boot/configuration/src/main/java/io/reflectoring/configuration/ConfigurationApplication.java

@@ -0,0 +1,13 @@
+package io.reflectoring.configuration;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ConfigurationApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(ConfigurationApplication.class, args);
+	}
+
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/mail/MailModuleConfiguration.java

@@ -0,0 +1,18 @@
+package io.reflectoring.configuration.mail;
+
+import org.springframework.boot.context.properties.ConfigurationPropertiesBinding;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@EnableConfigurationProperties(MailModuleProperties.class)
+class MailModuleConfiguration {
+
+	@Bean
+	@ConfigurationPropertiesBinding
+	public WeightConverter weightConverter() {
+		return new WeightConverter();
+	}
+
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/mail/MailModuleProperties.java

@@ -0,0 +1,84 @@
+package io.reflectoring.configuration.mail;
+
+import javax.validation.constraints.NotEmpty;
+import javax.validation.constraints.NotNull;
+
+import java.time.Duration;
+import java.util.List;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
+import org.springframework.util.unit.DataSize;
+import org.springframework.validation.annotation.Validated;
+
+@ConfigurationProperties(prefix = "myapp.mail", ignoreInvalidFields = true, ignoreUnknownFields = false)
+@Validated
+class MailModuleProperties {
+
+  @NotNull
+  private Boolean enabled = Boolean.TRUE;
+
+  @NotEmpty
+  private String defaultSubject;
+
+  @NotNull
+  private Duration pauseBetweenMails;
+
+  @NotNull
+  private DataSize maxAttachmentSize;
+
+  @NotNull
+  private Weight maxAttachmentWeight;
+
+  @NotEmpty
+  private List<String> smtpServers;
+
+  @DeprecatedConfigurationProperty(reason = "not needed anymore", replacement = "none")
+  public String getDefaultSubject() {
+    return defaultSubject;
+  }
+
+  public Boolean getEnabled() {
+    return enabled;
+  }
+
+  public void setEnabled(Boolean enabled) {
+    this.enabled = enabled;
+  }
+
+  public void setDefaultSubject(String defaultSubject) {
+    this.defaultSubject = defaultSubject;
+  }
+
+  public Duration getPauseBetweenMails() {
+    return pauseBetweenMails;
+  }
+
+  public void setPauseBetweenMails(Duration pauseBetweenMails) {
+    this.pauseBetweenMails = pauseBetweenMails;
+  }
+
+  public DataSize getMaxAttachmentSize() {
+    return maxAttachmentSize;
+  }
+
+  public void setMaxAttachmentSize(DataSize maxAttachmentSize) {
+    this.maxAttachmentSize = maxAttachmentSize;
+  }
+
+  public List<String> getSmtpServers() {
+    return smtpServers;
+  }
+
+  public void setSmtpServers(List<String> smtpServers) {
+    this.smtpServers = smtpServers;
+  }
+
+  public Weight getMaxAttachmentWeight() {
+    return maxAttachmentWeight;
+  }
+
+  public void setMaxAttachmentWeight(Weight maxAttachmentWeight) {
+    this.maxAttachmentWeight = maxAttachmentWeight;
+  }
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/mail/Weight.java

@@ -0,0 +1,39 @@
+package io.reflectoring.configuration.mail;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class Weight {
+
+	private static final Pattern PATTERN = Pattern.compile("^([0-9]+)(g|kg|t)$");
+
+	private long grams;
+
+	private Weight(long grams){
+		this.grams = grams;
+	}
+
+	public static Weight fromString(String string) {
+		Matcher matcher = PATTERN.matcher(string);
+		if (matcher.matches()) {
+			Long amount = Long.valueOf(matcher.group(1));
+			String unit = matcher.group(2);
+
+			switch (unit) {
+				case "g":
+					return new Weight(amount);
+				case "kg":
+					return new Weight(amount * 1_000);
+				case "t":
+					return new Weight(amount * 1_000 * 1_000);
+				default:
+					throw new IllegalArgumentException(String.format("invalid weight unit %s", unit));
+			}
+		}
+		throw new IllegalArgumentException(String.format("invalid weight string %s", string));
+	}
+
+	public long getGrams() {
+		return grams;
+	}
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/mail/WeightConverter.java

@@ -0,0 +1,12 @@
+package io.reflectoring.configuration.mail;
+
+import org.springframework.core.convert.converter.Converter;
+
+class WeightConverter implements Converter<String, Weight> {
+
+	@Override
+	public Weight convert(String source) {
+		return Weight.fromString(source);
+	}
+
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/unknownandinvalidfield/UnkownAndInvalidFieldProperties.java

@@ -0,0 +1,22 @@
+package io.reflectoring.configuration.unknownandinvalidfield;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.stereotype.Component;
+
+@Component
+@ConfigurationProperties(
+        prefix = "myapp.unknown-and-invalid-field-module",
+        ignoreUnknownFields = false,
+        ignoreInvalidFields = true)
+class UnkownAndInvalidFieldProperties {
+
+  private Boolean enabled;
+
+  public Boolean getEnabled() {
+    return enabled;
+  }
+
+  public void setEnabled(Boolean enabled) {
+    this.enabled = enabled;
+  }
+}

spring-boot/configuration/src/main/java/io/reflectoring/configuration/unknownfield/UnkownFieldProperties.java

@@ -0,0 +1,29 @@
+package io.reflectoring.configuration.unknownfield;
+
+import javax.validation.constraints.NotEmpty;
+import javax.validation.constraints.NotNull;
+
+import java.time.Duration;
+import java.util.List;
+
+import io.reflectoring.configuration.mail.Weight;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.DeprecatedConfigurationProperty;
+import org.springframework.stereotype.Component;
+import org.springframework.util.unit.DataSize;
+import org.springframework.validation.annotation.Validated;
+
+@Component
+@ConfigurationProperties(prefix = "myapp.unknownfield", ignoreUnknownFields = false)
+class UnkownFieldProperties {
+
+  private Boolean enabled = Boolean.TRUE;
+
+  public Boolean getEnabled() {
+    return enabled;
+  }
+
+  public void setEnabled(Boolean enabled) {
+    this.enabled = enabled;
+  }
+}

spring-boot/configuration/src/main/resources/application.properties

@@ -0,0 +1,8 @@
+myapp.mail.enabled=true
+myapp.mail.defaultSubject=hello
+myapp.mail.pauseBetweenMails=5s
+myapp.mail.maxAttachmentSize=1MB
+myapp.mail.smtpServers[0]=server1
+myapp.mail.smtpServers[1]=server2
+myapp.mail.maxAttachmentWeight=5kg
+myapp.mail.foo=foo

spring-boot/configuration/src/test/java/io/reflectoring/configuration/ConfigurationApplicationTests.java

@@ -0,0 +1,16 @@
+package io.reflectoring.configuration;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest
+class ConfigurationApplicationTests {
+
+  @Test
+  void contextLoads() {
+  }
+
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/mail/MailModuleTestWithAllProperties.java

@@ -0,0 +1,38 @@
+package io.reflectoring.configuration.mail;
+
+import java.time.Duration;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.util.unit.DataSize;
+import static org.assertj.core.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(properties = {
+		"myapp.mail.enabled=asd",
+		"myapp.mail.defaultSubject=hello",
+		"myapp.mail.pauseBetweenMails=5s",
+		"myapp.mail.maxAttachmentSize=1MB",
+		"myapp.mail.smtpServers[0]=server1",
+		"myapp.mail.smtpServers[1]=server2",
+		"myapp.mail.maxAttachmentWeight=5kg"
+})
+class MailModuleTestWithAllProperties {
+
+  @Autowired(required = false)
+  private MailModuleProperties mailModuleProperties;
+
+  @Test
+  void propertiesAreLoaded() {
+	assertThat(mailModuleProperties).isNotNull();
+	assertThat(mailModuleProperties.getDefaultSubject()).isEqualTo("hello");
+	assertThat(mailModuleProperties.getEnabled()).isTrue();
+	assertThat(mailModuleProperties.getPauseBetweenMails()).isEqualByComparingTo(Duration.ofSeconds(5));
+	assertThat(mailModuleProperties.getMaxAttachmentSize()).isEqualByComparingTo(DataSize.ofMegabytes(1));
+	assertThat(mailModuleProperties.getSmtpServers()).hasSize(2);
+	assertThat(mailModuleProperties.getMaxAttachmentWeight().getGrams()).isEqualTo(5000L);
+  }
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/mail/MailModuleTestWithInvalidProperties.java

@@ -0,0 +1,25 @@
+package io.reflectoring.configuration.mail;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import static org.assertj.core.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(properties = {
+		"myapp.mail.defaultSubject="
+})
+@Disabled("this test will fail due to invalid properties")
+class MailModuleTestWithInvalidProperties {
+
+  @Autowired(required = false)
+  private MailModuleProperties mailModuleProperties;
+
+  @Test
+  void propertiesAreLoaded() {
+	assertThat(mailModuleProperties).isNotNull();
+  }
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/mail/MailModuleTestWithUnknownField.java

@@ -0,0 +1,22 @@
+package io.reflectoring.configuration.mail;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import static org.assertj.core.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest
+class MailModuleTestWithUnknownField {
+
+  @Autowired(required = false)
+  private MailModuleProperties mailModuleProperties;
+
+  @Test
+  void propertiesAreLoaded() {
+	assertThat(mailModuleProperties).isNotNull();
+  }
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/unknownandinvalidfield/UnknownAndInvalidFieldModule.java

@@ -0,0 +1,9 @@
+package io.reflectoring.configuration.unknownandinvalidfield;
+
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+
+@SpringBootConfiguration
+@EnableConfigurationProperties(UnkownAndInvalidFieldProperties.class)
+class UnknownAndInvalidFieldModule {
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/unknownandinvalidfield/UnkownFieldPropertiesTest.java

@@ -0,0 +1,28 @@
+package io.reflectoring.configuration.unknownandinvalidfield;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import static org.assertj.core.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(properties = {
+		"myapp.unknown-and-invalid-field-module.unknown-property=foo"
+})
+class UnkownFieldPropertiesTest {
+
+	@Autowired(required = false)
+	private UnkownAndInvalidFieldProperties properties;
+
+	@Test
+	@Disabled("disabled due to unexpected behavior")
+	void loadsApplicationContext() {
+		// This test passes.
+		// However, I would expect this test to fail application context startup due to the unknown property.
+		// If we set ignoreInvalidFields to true, it works as expected.
+		assertThat(properties).isNotNull();
+	}
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/unknownfield/UnknownFieldModule.java

@@ -0,0 +1,10 @@
+package io.reflectoring.configuration.unknownfield;
+
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Configuration;
+
+@SpringBootConfiguration
+@EnableConfigurationProperties(UnkownFieldProperties.class)
+class UnknownFieldModule {
+}

spring-boot/configuration/src/test/java/io/reflectoring/configuration/unknownfield/UnkownFieldPropertiesTest.java

@@ -0,0 +1,25 @@
+package io.reflectoring.configuration.unknownfield;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import static org.assertj.core.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(properties = {
+		"myapp.unknownfield.unknown-property=foo"
+})
+@Disabled("this test is expected to fail due an unknown property")
+class UnkownFieldPropertiesTest {
+
+	@Autowired(required = false)
+	private UnkownFieldProperties properties;
+
+	@Test
+	void propertiesAreLoaded() {
+		assertThat(properties).isNotNull();
+	}
+}