Spring Boot :Eureka Architecture de Spring Cloud

Building BBank Architecture with Spring Cloud, Gateway & Eureka

Note: This tutorial implements the architecture shown in We'll create 5 microservices: Eureka Server, API Gateway, Account Service, Customer Service, and Transaction Service.

📁 Project Structure

eureka-server - Service registry
api-gateway - Entry point for all requests
account-service - Manages bank accounts
customer-service - Manages customer information
transaction-service - Handles money transfers between accounts

Step 1: Create Eureka Server

The Eureka Server acts as a service registry where all microservices register themselves.

📁 File: `eureka-server/pom.xml`

<?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 
         https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.5</version>
        <relativePath/>
    </parent>

    <groupId>com.bbank</groupId>
    <artifactId>eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-server</name>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

📁 File: `eureka-server/src/main/resources/application.yml`

server:
  port: 8761

eureka:
  client:
    register-with-eureka: false
    fetch-registry: false
  server:
    enable-self-preservation: false

📁 File: `eureka-server/src/main/java/com/bbank/eurekaserver/EurekaServerApplication.java`

package com.bbank.eurekaserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }
}

Step 2: Create API Gateway

The API Gateway routes requests to appropriate microservices and provides a single entry point.

📁 File: `api-gateway/pom.xml`

<?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 
         https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.5</version>
        <relativePath/>
    </parent>

    <groupId>com.bbank</groupId>
    <artifactId>api-gateway</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>api-gateway</name>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

📁 File: `api-gateway/src/main/resources/application.yml`

server:
  port: 8080

spring:
  application:
    name: api-gateway
  cloud:
    gateway:
      routes:
        - id: account-service
          uri: lb://account-service
          predicates:
            - Path=/api/accounts/**
        - id: customer-service
          uri: lb://customer-service
          predicates:
            - Path=/api/customers/**
        - id: transaction-service
          uri: lb://transaction-service
          predicates:
            - Path=/api/transactions/**

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka
    fetch-registry: true
    register-with-eureka: true

📁 File: `api-gateway/src/main/java/com/bbank/apigateway/ApiGatewayApplication.java`

package com.bbank.apigateway;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class ApiGatewayApplication {
    public static void main(String[] args) {
        SpringApplication.run(ApiGatewayApplication.class, args);
    }
}

Step 3: Create Account Service

This service manages bank accounts and their balances.

📁 File: `account-service/pom.xml`

<?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 
         https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.5</version>
        <relativePath/>
    </parent>

    <groupId>com.bbank</groupId>
    <artifactId>account-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>account-service</name>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

📁 File: `account-service/src/main/resources/application.yml`

server:
  port: 8081

spring:
  application:
    name: account-service

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

📁 File: `account-service/src/main/java/com/bbank/accountservice/model/Account.java`

package com.bbank.accountservice.model;

public class Account {
    private Long id;
    private Long customerId;
    private String accountNumber;
    private Double balance;

    // Constructors
    public Account() {}
    public Account(Long id, Long customerId, String accountNumber, Double balance) {
        this.id = id;
        this.customerId = customerId;
        this.accountNumber = accountNumber;
        this.balance = balance;
    }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public Long getCustomerId() { return customerId; }
    public void setCustomerId(Long customerId) { this.customerId = customerId; }
    public String getAccountNumber() { return accountNumber; }
    public void setAccountNumber(String accountNumber) { this.accountNumber = accountNumber; }
    public Double getBalance() { return balance; }
    public void setBalance(Double balance) { this.balance = balance; }
}

📁 File: `account-service/src/main/java/com/bbank/accountservice/repository/AccountRepository.java`

package com.bbank.accountservice.repository;

import com.bbank.accountservice.model.Account;
import org.springframework.stereotype.Repository;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

@Repository
public class AccountRepository {
    private final ConcurrentHashMap<Long, Account> accounts = new ConcurrentHashMap<>();
    private final AtomicLong idGenerator = new AtomicLong(1);

    public Account save(Account account) {
        if (account.getId() == null) {
            account.setId(idGenerator.getAndIncrement());
        }
        accounts.put(account.getId(), account);
        return account;
    }

    public Account findById(Long id) {
        return accounts.get(id);
    }

    public List<Account> findByCustomerId(Long customerId) {
        return accounts.values().stream()
                .filter(acc -> acc.getCustomerId().equals(customerId))
                .toList();
    }

    public List<Account> findAll() {
        return new ArrayList<>(accounts.values());
    }

    public boolean updateBalance(Long id, Double newBalance) {
        Account account = accounts.get(id);
        if (account != null) {
            account.setBalance(newBalance);
            return true;
        }
        return false;
    }
}

📁 File: `account-service/src/main/java/com/bbank/accountservice/controller/AccountController.java`

package com.bbank.accountservice.controller;

import com.bbank.accountservice.model.Account;
import com.bbank.accountservice.repository.AccountRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/accounts")
public class AccountController {

    @Autowired
    private AccountRepository accountRepository;

    @GetMapping
    public List<Account> getAllAccounts() {
        return accountRepository.findAll();
    }

    @GetMapping("/{id}")
    public Account getAccountById(@PathVariable Long id) {
        return accountRepository.findById(id);
    }

    @GetMapping("/customer/{customerId}")
    public List<Account> getAccountsByCustomerId(@PathVariable Long customerId) {
        return accountRepository.findByCustomerId(customerId);
    }

    @PostMapping
    public Account createAccount(@RequestBody Account account) {
        return accountRepository.save(account);
    }

    @PutMapping("/{id}/balance")
    public boolean updateBalance(@PathVariable Long id, @RequestBody Double newBalance) {
        return accountRepository.updateBalance(id, newBalance);
    }
}

📁 File: `account-service/src/main/java/com/bbank/accountservice/AccountServiceApplication.java`

package com.bbank.accountservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class AccountServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(AccountServiceApplication.class, args);
    }
}

Step 4: Create Customer Service

This service manages customer information.

📁 File: `customer-service/pom.xml`

<?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 
         https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.5</version>
        <relativePath/>
    </parent>

    <groupId>com.bbank</groupId>
    <artifactId>customer-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>customer-service</name>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

📁 File: `customer-service/src/main/resources/application.yml`

server:
  port: 8082

spring:
  application:
    name: customer-service

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

📁 File: `customer-service/src/main/java/com/bbank/customerservice/model/Customer.java`

package com.bbank.customerservice.model;

public class Customer {
    private Long id;
    private String name;
    private String email;
    private String phone;

    public Customer() {}
    public Customer(Long id, String name, String email, String phone) {
        this.id = id;
        this.name = name;
        this.email = email;
        this.phone = phone;
    }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
    public String getPhone() { return phone; }
    public void setPhone(String phone) { this.phone = phone; }
}

📁 File: `customer-service/src/main/java/com/bbank/customerservice/repository/CustomerRepository.java`

package com.bbank.customerservice.repository;

import com.bbank.customerservice.model.Customer;
import org.springframework.stereotype.Repository;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

@Repository
public class CustomerRepository {
    private final ConcurrentHashMap<Long, Customer> customers = new ConcurrentHashMap<>();
    private final AtomicLong idGenerator = new AtomicLong(1);

    public Customer save(Customer customer) {
        if (customer.getId() == null) {
            customer.setId(idGenerator.getAndIncrement());
        }
        customers.put(customer.getId(), customer);
        return customer;
    }

    public Customer findById(Long id) {
        return customers.get(id);
    }

    public List<Customer> findAll() {
        return new ArrayList<>(customers.values());
    }
}

📁 File: `customer-service/src/main/java/com/bbank/customerservice/controller/CustomerController.java`

package com.bbank.customerservice.controller;

import com.bbank.customerservice.model.Customer;
import com.bbank.customerservice.repository.CustomerRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/customers")
public class CustomerController {

    @Autowired
    private CustomerRepository customerRepository;

    @GetMapping
    public List<Customer> getAllCustomers() {
        return customerRepository.findAll();
    }

    @GetMapping("/{id}")
    public Customer getCustomerById(@PathVariable Long id) {
        return customerRepository.findById(id);
    }

    @PostMapping
    public Customer createCustomer(@RequestBody Customer customer) {
        return customerRepository.save(customer);
    }
}

📁 File: `customer-service/src/main/java/com/bbank/customerservice/CustomerServiceApplication.java`

package com.bbank.customerservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
public class CustomerServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(CustomerServiceApplication.class, args);
    }
}

Step 5: Create Transaction Service

This service handles money transfers between accounts using Feign clients to communicate with Account Service.

📁 File: `transaction-service/pom.xml`

<?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 
         https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.5</version>
        <relativePath/>
    </parent>

    <groupId>com.bbank</groupId>
    <artifactId>transaction-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>transaction-service</name>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

📁 File: `transaction-service/src/main/resources/application.yml`

server:
  port: 8083

spring:
  application:
    name: transaction-service

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/model/Transaction.java`

package com.bbank.transactionservice.model;

public class Transaction {
    private Long id;
    private Long fromAccountId;
    private Long toAccountId;
    private Double amount;
    private String status; // e.g., "SUCCESS", "FAILED"

    public Transaction() {}
    public Transaction(Long id, Long fromAccountId, Long toAccountId, Double amount, String status) {
        this.id = id;
        this.fromAccountId = fromAccountId;
        this.toAccountId = toAccountId;
        this.amount = amount;
        this.status = status;
    }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public Long getFromAccountId() { return fromAccountId; }
    public void setFromAccountId(Long fromAccountId) { this.fromAccountId = fromAccountId; }
    public Long getToAccountId() { return toAccountId; }
    public void setToAccountId(Long toAccountId) { this.toAccountId = toAccountId; }
    public Double getAmount() { return amount; }
    public void setAmount(Double amount) { this.amount = amount; }
    public String getStatus() { return status; }
    public void setStatus(String status) { this.status = status; }
}

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/client/AccountServiceClient.java`

package com.bbank.transactionservice.client;

import com.bbank.transactionservice.model.Account;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.*;

@FeignClient(name = "account-service")
public interface AccountServiceClient {

    @GetMapping("/api/accounts/{id}")
    Account getAccount(@PathVariable("id") Long id);

    @PutMapping("/api/accounts/{id}/balance")
    Boolean updateBalance(@PathVariable("id") Long id, @RequestBody Double newBalance);
}

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/repository/TransactionRepository.java`

package com.bbank.transactionservice.repository;

import com.bbank.transactionservice.model.Transaction;
import org.springframework.stereotype.Repository;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

@Repository
public class TransactionRepository {
    private final ConcurrentHashMap<Long, Transaction> transactions = new ConcurrentHashMap<>();
    private final AtomicLong idGenerator = new AtomicLong(1);

    public Transaction save(Transaction transaction) {
        if (transaction.getId() == null) {
            transaction.setId(idGenerator.getAndIncrement());
        }
        transactions.put(transaction.getId(), transaction);
        return transaction;
    }

    public List<Transaction> findAll() {
        return new ArrayList<>(transactions.values());
    }

    public List<Transaction> findByAccountId(Long accountId) {
        return transactions.values().stream()
                .filter(t -> t.getFromAccountId().equals(accountId) || t.getToAccountId().equals(accountId))
                .toList();
    }
}

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/service/TransactionService.java`

package com.bbank.transactionservice.service;

import com.bbank.transactionservice.client.AccountServiceClient;
import com.bbank.transactionservice.model.Account;
import com.bbank.transactionservice.model.Transaction;
import com.bbank.transactionservice.repository.TransactionRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class TransactionService {

    @Autowired
    private AccountServiceClient accountServiceClient;

    @Autowired
    private TransactionRepository transactionRepository;

    public Transaction transferMoney(Long fromAccountId, Long toAccountId, Double amount) {
        Account fromAccount = accountServiceClient.getAccount(fromAccountId);
        Account toAccount = accountServiceClient.getAccount(toAccountId);

        if (fromAccount == null || toAccount == null) {
            return new Transaction(null, fromAccountId, toAccountId, amount, "FAILED - Account not found");
        }

        if (fromAccount.getBalance() < amount) {
            return new Transaction(null, fromAccountId, toAccountId, amount, "FAILED - Insufficient balance");
        }

        // Deduct from sender
        boolean fromUpdated = accountServiceClient.updateBalance(fromAccountId, fromAccount.getBalance() - amount);
        if (!fromUpdated) {
            return new Transaction(null, fromAccountId, toAccountId, amount, "FAILED - Could not update sender balance");
        }

        // Add to receiver
        boolean toUpdated = accountServiceClient.updateBalance(toAccountId, toAccount.getBalance() + amount);
        if (!toUpdated) {
            // Rollback sender
            accountServiceClient.updateBalance(fromAccountId, fromAccount.getBalance());
            return new Transaction(null, fromAccountId, toAccountId, amount, "FAILED - Could not update receiver balance");
        }

        Transaction transaction = new Transaction();
        transaction.setFromAccountId(fromAccountId);
        transaction.setToAccountId(toAccountId);
        transaction.setAmount(amount);
        transaction.setStatus("SUCCESS");

        return transactionRepository.save(transaction);
    }

    public Iterable<Transaction> getAllTransactions() {
        return transactionRepository.findAll();
    }

    public Iterable<Transaction> getTransactionsByAccountId(Long accountId) {
        return transactionRepository.findByAccountId(accountId);
    }
}

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/controller/TransactionController.java`

package com.bbank.transactionservice.controller;

import com.bbank.transactionservice.model.Transaction;
import com.bbank.transactionservice.service.TransactionService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/transactions")
public class TransactionController {

    @Autowired
    private TransactionService transactionService;

    @PostMapping("/transfer")
    public Transaction transferMoney(@RequestParam Long fromAccountId,
                                     @RequestParam Long toAccountId,
                                     @RequestParam Double amount) {
        return transactionService.transferMoney(fromAccountId, toAccountId, amount);
    }

    @GetMapping
    public Iterable<Transaction> getAllTransactions() {
        return transactionService.getAllTransactions();
    }

    @GetMapping("/account/{accountId}")
    public Iterable<Transaction> getTransactionsByAccountId(@PathVariable Long accountId) {
        return transactionService.getTransactionsByAccountId(accountId);
    }
}

📁 File: `transaction-service/src/main/java/com/bbank/transactionservice/TransactionServiceApplication.java`

package com.bbank.transactionservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class TransactionServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(TransactionServiceApplication.class, args);
    }
}

✅ Final Step: Run All Services

Start services in this order:

Eureka Server → http://localhost:8761
Account Service
Customer Service
Transaction Service
API Gateway → http://localhost:8080

🧪 Test Endpoints via Gateway

Get all accounts: GET http://localhost:8080/api/accounts
Create customer: POST http://localhost:8080/api/customers
Transfer money: POST http://localhost:8080/api/transactions/transfer?fromAccountId=1&toAccountId=2&amount=100

🎉 Congratulations! You now have a fully working Spring Cloud Microservices system with:

Service Discovery (Eureka)
API Gateway (Spring Cloud Gateway)
Inter-service communication (Feign Client)
REST APIs for Account, Customer, Transaction

Rappel

Cloud computing

Architecture de Spring Cloud

Spring Boot (BackEnd) TPs

Produit Rest API

Angular (FrontEnd)

Spring Security

CRUD

To be Continued...

Middlewares Orientés Messages

Communication Synchrone vs. Asynchrone API JMS : Java Message Service JMS avec ActiveMQ et HornetQ KAFKA

Spring Batch

Spring Batch

Stream Processing

Kafka Streams

Architectures Serverless

Architectures Serverless Résumé

Building BBank Architecture with Spring Cloud, Gateway & Eureka

📁 Project Structure

Step 1: Create Eureka Server

📁 File: eureka-server/pom.xml

📁 File: eureka-server/src/main/resources/application.yml

📁 File: eureka-server/src/main/java/com/bbank/eurekaserver/EurekaServerApplication.java

Step 2: Create API Gateway

📁 File: api-gateway/pom.xml

📁 File: api-gateway/src/main/resources/application.yml

📁 File: api-gateway/src/main/java/com/bbank/apigateway/ApiGatewayApplication.java

Step 3: Create Account Service

📁 File: account-service/pom.xml

📁 File: account-service/src/main/resources/application.yml

📁 File: account-service/src/main/java/com/bbank/accountservice/model/Account.java

📁 File: account-service/src/main/java/com/bbank/accountservice/repository/AccountRepository.java

📁 File: account-service/src/main/java/com/bbank/accountservice/controller/AccountController.java

📁 File: account-service/src/main/java/com/bbank/accountservice/AccountServiceApplication.java

Step 4: Create Customer Service

📁 File: customer-service/pom.xml

📁 File: customer-service/src/main/resources/application.yml

📁 File: customer-service/src/main/java/com/bbank/customerservice/model/Customer.java

📁 File: customer-service/src/main/java/com/bbank/customerservice/repository/CustomerRepository.java

📁 File: customer-service/src/main/java/com/bbank/customerservice/controller/CustomerController.java

📁 File: customer-service/src/main/java/com/bbank/customerservice/CustomerServiceApplication.java