sushant57@gmail.com - Intro to hexagonal archietecture

hexagonal-archietecture/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung.tutorial.hexagonal</groupId>
+    <artifactId>hexagonal-archietecture</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+
+    <dependencies>
+            <dependency>
+                <groupId>org.projectlombok</groupId>
+                <artifactId>lombok</artifactId>
+                <version>1.16.18</version>
+            </dependency>
+    </dependencies>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+</project>

hexagonal-archietecture/src/main/java/com/baeldung/tutorial/hexagonal/application/BankAccountService.java

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+package com.baeldung.tutorial.hexagonal.application;
+
+import java.math.BigDecimal;
+
+public interface BankAccountService {
+
+        void withdraw(String bankAccountId, BigDecimal withdrawalAmount);
+}

hexagonal-archietecture/src/main/java/com/baeldung/tutorial/hexagonal/application/BankAccountServiceImpl.java

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+package com.baeldung.tutorial.hexagonal.application;
+
+import com.baeldung.tutorial.hexagonal.domain.BankAccount;
+import com.baeldung.tutorial.hexagonal.storage.BankAccountRepository;
+
+import java.math.BigDecimal;
+
+import static java.math.BigDecimal.ZERO;
+
+class BankAccountServiceImpl implements BankAccountService {
+
+        private BankAccountRepository repository;
+
+        public void withdraw(String bankAccountId, BigDecimal withdrawalAmount) {
+                BankAccount bankAccount = repository.findByBankAccountId(bankAccountId);
+
+                if (bankAccount == null) {
+                        throw new IllegalArgumentException(String.format("No bank account found with accountId %s", bankAccountId));
+                }
+
+                BigDecimal currentAccountBalance = bankAccount.getAccountBalance();
+                BigDecimal balanceAfterWithdrawal = currentAccountBalance.subtract(withdrawalAmount);
+                if (currentAccountBalance.subtract(withdrawalAmount).compareTo(ZERO) > 0) {
+                        bankAccount.setAccountBalance(balanceAfterWithdrawal);
+                        repository.saveAccount(bankAccount);
+                } else {
+                        throw new IllegalArgumentException(String.format("Balance %d not enough to withdraw %d", currentAccountBalance, withdrawalAmount));
+                }
+        }
+}

hexagonal-archietecture/src/main/java/com/baeldung/tutorial/hexagonal/domain/BankAccount.java

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+package com.baeldung.tutorial.hexagonal.domain;
+
+import lombok.Data;
+
+import java.math.BigDecimal;
+
+@Data
+public class BankAccount {
+        private String accountId;
+        private BigDecimal accountBalance;
+}

hexagonal-archietecture/src/main/java/com/baeldung/tutorial/hexagonal/storage/BankAccountRepository.java

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+package com.baeldung.tutorial.hexagonal.storage;
+
+import com.baeldung.tutorial.hexagonal.domain.BankAccount;
+
+public interface BankAccountRepository {
+
+        BankAccount findByBankAccountId(String bankAccountId);
+
+        void saveAccount(BankAccount bankAccount);
+}

hexagonal-archietecture/src/main/java/com/baeldung/tutorial/hexagonal/storage/InMemoryBankAccountRepository.java

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+package com.baeldung.tutorial.hexagonal.storage;
+
+import com.baeldung.tutorial.hexagonal.domain.BankAccount;
+
+import java.util.Map;
+
+class InMemoryBankAccountRepository implements BankAccountRepository {
+        private Map<String, BankAccount> bankAccounts;
+
+        public BankAccount findByBankAccountId(String bankAccountId) {
+                return bankAccounts.get(bankAccountId);
+        }
+
+        public void saveAccount(BankAccount bankAccount) {
+                bankAccounts.putIfAbsent(bankAccount.getAccountId(), bankAccount);
+        }
+}