BAEL-2914: Immutable @ConfigurationProperties binding (#8623)

spring-boot-modules/spring-boot-properties/src/main/java/com/baeldung/configurationproperties/ImmutableConfigPropertiesApp.java

@@ -0,0 +1,14 @@
+package com.baeldung.configurationproperties;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
+
+@SpringBootApplication
+@ConfigurationPropertiesScan
+public class ImmutableConfigPropertiesApp {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ImmutableConfigPropertiesApp.class, args);
+    }
+}

spring-boot-modules/spring-boot-properties/src/main/java/com/baeldung/configurationproperties/ImmutableCredentials.java

@@ -0,0 +1,31 @@
+package com.baeldung.configurationproperties;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.context.properties.ConstructorBinding;
+
+@ConfigurationProperties(prefix = "mail.credentials")
+@ConstructorBinding
+public class ImmutableCredentials {
+
+    private final String authMethod;
+    private final String username;
+    private final String password;
+
+    public ImmutableCredentials(String authMethod, String username, String password) {
+        this.authMethod = authMethod;
+        this.username = username;
+        this.password = password;
+    }
+
+    public String getAuthMethod() {
+        return authMethod;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+}

spring-boot-modules/spring-boot-properties/src/test/java/com/baeldung/configurationproperties/ImmutableConfigurationPropertiesIntegrationTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.configurationproperties;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.TestPropertySource;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ImmutableConfigPropertiesApp.class)
+@TestPropertySource("classpath:configprops-test.properties")
+public class ImmutableConfigurationPropertiesIntegrationTest {
+
+    @Autowired
+    private ImmutableCredentials immutableCredentials;
+
+    @Test
+    public void whenConstructorBindingUsed_thenPropertiesCorrectlyBound() {
+        assertThat(immutableCredentials.getAuthMethod()).isEqualTo("SHA1");
+        assertThat(immutableCredentials.getUsername()).isEqualTo("john");
+        assertThat(immutableCredentials.getPassword()).isEqualTo("password");
+    }
+}