feat: Java anti-fraud transaction validation system

.gitignore

@@ -102,3 +102,20 @@ dist
 
 # TernJS port file
 .tern-port
+
+# Java / Maven
+target/
+*.class
+*.jar
+*.war
+*.ear
+.settings/
+.project
+.classpath
+.idea/
+*.iml
+.factorypath
+
+# OS
+.DS_Store
+Thumbs.db

antifraud-service/Dockerfile

@@ -0,0 +1,29 @@
+# Stage 1: Build
+FROM maven:3.9-eclipse-temurin-17 AS build
+
+WORKDIR /app
+
+# Copy POM first for dependency caching
+COPY pom.xml .
+RUN mvn dependency:go-offline -B
+
+# Copy source code and build
+COPY src ./src
+RUN mvn clean package -DskipTests -B
+
+# Stage 2: Run
+FROM eclipse-temurin:17-jre-jammy
+
+WORKDIR /app
+
+RUN groupadd -r appgroup && useradd -r -g appgroup appuser
+
+COPY --from=build /app/target/*.jar app.jar
+
+RUN chown -R appuser:appgroup /app
+
+USER appuser
+
+EXPOSE 8081
+
+ENTRYPOINT ["java", "-jar", "app.jar"]

antifraud-service/pom.xml

@@ -0,0 +1,135 @@
+<?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.yape</groupId>
+    <artifactId>antifraud-service</artifactId>
+    <version>1.0.0</version>
+    <name>antifraud-service</name>
+    <description>Anti-fraud microservice for Yape transaction validation</description>
+
+    <properties>
+        <java.version>17</java.version>
+        <testcontainers.version>1.19.7</testcontainers.version>
+    </properties>
+
+    <dependencies>
+        <!-- Spring Boot Core (no web) -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter</artifactId>
+        </dependency>
+
+        <!-- Spring Data JPA -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <!-- Spring Kafka -->
+        <dependency>
+            <groupId>org.springframework.kafka</groupId>
+            <artifactId>spring-kafka</artifactId>
+        </dependency>
+
+        <!-- Flyway -->
+        <dependency>
+            <groupId>org.flywaydb</groupId>
+            <artifactId>flyway-core</artifactId>
+        </dependency>
+
+        <!-- PostgreSQL Driver -->
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+
+        <!-- Lombok -->
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <!-- Jackson Databind -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+
+        <!-- Jackson Java Time module for LocalDateTime serialization -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+        </dependency>
+
+        <!-- Testing -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.kafka</groupId>
+            <artifactId>spring-kafka-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- Testcontainers -->
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>testcontainers</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>postgresql</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>kafka</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <configuration>
+                    <excludes>
+                        <exclude>
+                            <groupId>org.projectlombok</groupId>
+                            <artifactId>lombok</artifactId>
+                        </exclude>
+                    </excludes>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

antifraud-service/src/main/java/com/yape/antifraud/AntifraudServiceApplication.java

@@ -0,0 +1,19 @@
+package com.yape.antifraud;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * Main entry point for the Anti-fraud microservice.
+ * This service consumes transaction events from Kafka, evaluates them
+ * against anti-fraud rules, and publishes the evaluation result.
+ *
+ * No REST endpoints are exposed - communication is event-driven via Kafka.
+ */
+@SpringBootApplication
+public class AntifraudServiceApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AntifraudServiceApplication.class, args);
+    }
+}

antifraud-service/src/main/java/com/yape/antifraud/application/usecase/EvaluateTransactionUseCaseImpl.java

@@ -0,0 +1,31 @@
+package com.yape.antifraud.application.usecase;
+
+import com.yape.antifraud.domain.port.in.EvaluateTransactionUseCase;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.math.BigDecimal;
+import java.util.UUID;
+
+@Service
+@Slf4j
+public class EvaluateTransactionUseCaseImpl implements EvaluateTransactionUseCase {
+
+    private static final BigDecimal FRAUD_THRESHOLD = new BigDecimal("1000");
+
+    @Override
+    public String evaluate(UUID transactionId, BigDecimal value) {
+        log.info("Evaluating transaction {} with value {}", transactionId, value);
+
+        String status;
+        if (value.compareTo(FRAUD_THRESHOLD) > 0) {
+            status = "REJECTED";
+            log.warn("Transaction {} REJECTED - value {} exceeds threshold {}", transactionId, value, FRAUD_THRESHOLD);
+        } else {
+            status = "APPROVED";
+            log.info("Transaction {} APPROVED - value {} within threshold {}", transactionId, value, FRAUD_THRESHOLD);
+        }
+
+        return status;
+    }
+}

antifraud-service/src/main/java/com/yape/antifraud/domain/model/EvaluatedTransaction.java

@@ -0,0 +1,24 @@
+package com.yape.antifraud.domain.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDateTime;
+import java.util.UUID;
+
+/**
+ * Pure domain entity representing an evaluated transaction.
+ * No JPA or infrastructure annotations - this belongs to the domain layer.
+ */
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class EvaluatedTransaction {
+
+    private UUID transactionId;
+    private String status;
+    private LocalDateTime evaluatedAt;
+}

antifraud-service/src/main/java/com/yape/antifraud/domain/port/in/EvaluateTransactionUseCase.java

@@ -0,0 +1,20 @@
+package com.yape.antifraud.domain.port.in;
+
+import java.math.BigDecimal;
+import java.util.UUID;
+
+/**
+ * Input port for evaluating a transaction against anti-fraud rules.
+ * Returns "APPROVED" if the transaction passes validation, or "REJECTED" otherwise.
+ */
+public interface EvaluateTransactionUseCase {
+
+    /**
+     * Evaluates a transaction based on its value.
+     *
+     * @param transactionId the unique identifier of the transaction
+     * @param value         the monetary value of the transaction
+     * @return "APPROVED" if value <= 1000, "REJECTED" if value > 1000
+     */
+    String evaluate(UUID transactionId, BigDecimal value);
+}

antifraud-service/src/main/java/com/yape/antifraud/domain/port/out/EvaluatedTransactionRepository.java

@@ -0,0 +1,36 @@
+package com.yape.antifraud.domain.port.out;
+
+import com.yape.antifraud.domain.model.EvaluatedTransaction;
+
+import java.util.Optional;
+import java.util.UUID;
+
+/**
+ * Output port for persisting evaluated transactions.
+ * This interface is defined in the domain layer and implemented by the infrastructure layer.
+ */
+public interface EvaluatedTransactionRepository {
+
+    /**
+     * Checks if a transaction has already been evaluated (idempotency check).
+     *
+     * @param transactionId the transaction identifier
+     * @return true if the transaction has already been evaluated
+     */
+    boolean existsByTransactionId(UUID transactionId);
+
+    /**
+     * Persists an evaluated transaction.
+     *
+     * @param evaluatedTransaction the evaluated transaction to save
+     */
+    void save(EvaluatedTransaction evaluatedTransaction);
+
+    /**
+     * Finds an evaluated transaction by its transaction ID.
+     *
+     * @param transactionId the transaction identifier
+     * @return the evaluated transaction if found
+     */
+    Optional<EvaluatedTransaction> findByTransactionId(UUID transactionId);
+}

antifraud-service/src/main/java/com/yape/antifraud/domain/port/out/TransactionStatusPublisher.java

@@ -0,0 +1,18 @@
+package com.yape.antifraud.domain.port.out;
+
+import java.util.UUID;
+
+/**
+ * Output port for publishing transaction status updates.
+ * Implemented by the Kafka producer in the infrastructure layer.
+ */
+public interface TransactionStatusPublisher {
+
+    /**
+     * Publishes a status update for a given transaction.
+     *
+     * @param transactionId the transaction identifier
+     * @param status        the evaluation status ("APPROVED" or "REJECTED")
+     */
+    void publishStatusUpdate(UUID transactionId, String status);
+}

antifraud-service/src/main/java/com/yape/antifraud/infrastructure/config/JacksonConfig.java

@@ -0,0 +1,19 @@
+package com.yape.antifraud.infrastructure.config;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class JacksonConfig {
+
+    @Bean
+    public ObjectMapper objectMapper() {
+        ObjectMapper mapper = new ObjectMapper();
+        mapper.registerModule(new JavaTimeModule());
+        mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
+        return mapper;
+    }
+}

antifraud-service/src/main/java/com/yape/antifraud/infrastructure/kafka/KafkaConfig.java

@@ -0,0 +1,30 @@
+package com.yape.antifraud.infrastructure.kafka;
+
+import org.apache.kafka.clients.admin.NewTopic;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.kafka.config.TopicBuilder;
+
+/**
+ * Kafka topic configuration.
+ * Ensures required topics are created on application startup.
+ */
+@Configuration
+public class KafkaConfig {
+
+    @Bean
+    public NewTopic transactionCreatedTopic() {
+        return TopicBuilder.name("transaction.created")
+                .partitions(3)
+                .replicas(1)
+                .build();
+    }
+
+    @Bean
+    public NewTopic transactionStatusUpdatedTopic() {
+        return TopicBuilder.name("transaction.status.updated")
+                .partitions(3)
+                .replicas(1)
+                .build();
+    }
+}