added example configuration parameter to show how to "cleanly" inject configuration parameters into the application

buckpal-application/src/main/java/io/reflectoring/buckpal/application/service/MoneyTransferProperties.java

@@ -0,0 +1,18 @@
+package io.reflectoring.buckpal.application.service;
+
+import io.reflectoring.buckpal.domain.Money;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+/**
+ * Configuration properties for money transfer use cases.
+ */
+@Data
+@AllArgsConstructor
+@NoArgsConstructor
+public class MoneyTransferProperties {
+
+  private Money maximumTransferThreshold = Money.of(1_000_000L);
+
+}

buckpal-application/src/main/java/io/reflectoring/buckpal/application/service/SendMoneyService.java

@@ -1,9 +1,5 @@
 package io.reflectoring.buckpal.application.service;
 
-import javax.transaction.Transactional;
-
-import java.time.LocalDateTime;
-
 import io.reflectoring.buckpal.application.port.in.SendMoneyUseCase;
 import io.reflectoring.buckpal.application.port.out.AccountLock;
 import io.reflectoring.buckpal.application.port.out.LoadAccountPort;
@@ -12,6 +8,9 @@ import io.reflectoring.buckpal.domain.Account;
 import io.reflectoring.buckpal.testdata.UseCase;
 import lombok.RequiredArgsConstructor;
 
+import javax.transaction.Transactional;
+import java.time.LocalDateTime;
+
 @RequiredArgsConstructor
 @UseCase
 @Transactional
@@ -20,9 +19,15 @@ public class SendMoneyService implements SendMoneyUseCase {
 	private final LoadAccountPort loadAccountPort;
 	private final AccountLock accountLock;
 	private final UpdateAccountStatePort updateAccountStatePort;
+	private final MoneyTransferProperties moneyTransferProperties;
 
 	@Override
 	public boolean sendMoney(SendMoneyCommand command) {
+
+		if(command.getMoney().isGreaterThan(moneyTransferProperties.getMaximumTransferThreshold())){
+			throw new ThresholdExceededException(moneyTransferProperties.getMaximumTransferThreshold(), command.getMoney());
+		}
+
 		LocalDateTime baselineDate = LocalDateTime.now().minusDays(10);
 
 		Account sourceAccount = loadAccountPort.loadAccount(

buckpal-application/src/main/java/io/reflectoring/buckpal/application/service/ThresholdExceededException.java

@@ -0,0 +1,11 @@
+package io.reflectoring.buckpal.application.service;
+
+import io.reflectoring.buckpal.domain.Money;
+
+public class ThresholdExceededException extends RuntimeException {
+
+  public ThresholdExceededException(Money threshold, Money actual) {
+    super(String.format("Maximum threshold for transferring money exceeded: tried to transfer %s but threshold is %s!", actual, threshold));
+  }
+
+}

buckpal-application/src/main/java/io/reflectoring/buckpal/domain/Money.java

@@ -29,6 +29,10 @@ public class Money {
 		return this.amount.compareTo(money.amount) >= 0;
 	}
 
+	public boolean isGreaterThan(Money money){
+		return this.amount.compareTo(money.amount) >= 1;
+	}
+
 	public static Money of(long value) {
 		return new Money(BigInteger.valueOf(value));
 	}

buckpal-application/src/test/java/io/reflectoring/buckpal/application/service/SendMoneyServiceTest.java

@@ -29,7 +29,7 @@ class SendMoneyServiceTest {
 			Mockito.mock(UpdateAccountStatePort.class);
 
 	private final SendMoneyService sendMoneyService =
-			new SendMoneyService(loadAccountPort, accountLock, updateAccountStatePort);
+			new SendMoneyService(loadAccountPort, accountLock, updateAccountStatePort, moneyTransferProperties());
 
 	@Test
 	void givenWithdrawalFails_thenOnlySourceAccountIsLockedAndReleased() {
@@ -138,4 +138,8 @@ class SendMoneyServiceTest {
 		return account;
 	}
 
-}
+	private MoneyTransferProperties moneyTransferProperties(){
+		return new MoneyTransferProperties(Money.of(Long.MAX_VALUE));
+	}
+
+}

buckpal-configuration/build.gradle

@@ -4,6 +4,9 @@ plugins {
 
 dependencies {
 
+    compileOnly 'org.projectlombok:lombok'
+    annotationProcessor 'org.projectlombok:lombok'
+    
     implementation project(':common')
     implementation project(':buckpal-application')
     implementation project(':adapters:buckpal-persistence')

buckpal-configuration/src/main/java/io/reflectoring/buckpal/BuckPalConfiguration.java

@@ -0,0 +1,22 @@
+package io.reflectoring.buckpal;
+
+import io.reflectoring.buckpal.application.service.MoneyTransferProperties;
+import io.reflectoring.buckpal.domain.Money;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@EnableConfigurationProperties(BuckPalConfigurationProperties.class)
+public class BuckPalConfiguration {
+
+  /**
+   * Adds a use-case-specific {@link MoneyTransferProperties} object to the application context. The properties
+   * are read from the Spring-Boot-specific {@link BuckPalConfigurationProperties} object.
+   */
+  @Bean
+  public MoneyTransferProperties moneyTransferProperties(BuckPalConfigurationProperties buckPalConfigurationProperties){
+    return new MoneyTransferProperties(Money.of(buckPalConfigurationProperties.getTransferThreshold()));
+  }
+
+}

buckpal-configuration/src/main/java/io/reflectoring/buckpal/BuckPalConfigurationProperties.java

@@ -0,0 +1,12 @@
+package io.reflectoring.buckpal;
+
+import lombok.Data;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+@Data
+@ConfigurationProperties(prefix = "buckpal")
+public class BuckPalConfigurationProperties {
+
+  private long transferThreshold = Long.MAX_VALUE;
+
+}