SpringBoot與Pulsar整合，實現金融交易場景下的消息有序性保障

作者：Java知識日歷 2025-02-20 18:17:41

開發前端

用戶發起一筆交易請求，系統需要將該請求發送到交易處理系統，并確保請求按順序被處理。而使用Pulsar的獨占訂閱模式確保交易請求按順序被單一消費者處理，避免亂序導致的賬務錯誤。

Apache Pulsar 設計用于大規模實時數據處理，支持多種消息傳遞模型（發布/訂閱、隊列等），并提供了強大的功能來確保消息的可靠性和性能。

優勢

1. 強大的消息模型

發布/訂閱 (Pub/Sub): 支持多個消費者同時從同一個主題接收消息，適合實時數據分析和通知系統。
獨占訂閱 (Exclusive Subscription): 確保只有一個消費者能夠消費某個分區的消息，從而保證消息的嚴格順序。
共享訂閱 (Shared Subscription): 多個消費者可以負載均衡地消費消息，提高吞吐量。
故障域感知路由: 根據地理位置和網絡拓撲優化消息路由，確保高效的數據傳輸。

2. 持久化與存儲

持久化消息: 所有消息都被持久化到磁盤，確保消息不會丟失。
分層存儲: 使用分層存儲策略，結合內存和磁盤存儲，提高讀寫效率。
自動清理: 定期清理過期或不再需要的消息，節省存儲空間。

3. 事務支持

事務消息: 支持事務性的消息發送和確認機制，確保數據一致性。
兩階段提交: 實現ACID特性，保證消息的一致性和可靠性。

4. 死信隊列

死信隊列 (Dead Letter Queue, DLQ): 對于無法成功處理的消息，將其放入死信隊列以便后續排查和處理。
重試機制: 在消息處理失敗時，進行一定次數的重試（默認最多3次），如果仍然失敗，則將消息放入死信隊列。

應用場景

啟動Pulsar：

bin/pulsar standalone

代碼實操

<dependencies>
    <!-- Spring Boot Starter -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- Apache Pulsar Client -->
    <dependency>
        <groupId>org.apache.pulsar</groupId>
        <artifactId>pulsar-client</artifactId>
        <version>2.10.1</version>
    </dependency>

    <!-- Lombok for cleaner Java code -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>

    <!-- JUnit for testing -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

配置文件

在application.properties文件中配置Pulsar的相關屬性：

# Pulsar broker URL
pulsar.service.url=pulsar://localhost:6650

# Topic name
pulsar.topic.name=finance-transaction-topic

# Dead letter topic name
pulsar.dead-letter.topic.name=dead-letter-topic

# Max redelivery count before sending to dead letter queue
pulsar.max.redeliver.count=3

服務類

創建一個服務類來處理生產和消費消息，包括事務消息和死信隊列的處理邏輯。

import lombok.extern.slf4j.Slf4j;
import org.apache.pulsar.client.api.*;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import java.util.concurrent.CompletableFuture;

@Service
@Slf4j
public class FinanceTransactionService {

    @Value("${pulsar.service.url}")
    private String serviceUrl;

    @Value("${pulsar.topic.name}")
    private String topicName;

    @Value("${pulsar.dead-letter.topic.name}")
    private String deadLetterTopicName;

    @Value("${pulsar.max.redeliver.count}")
    private int maxRedeliverCount;

    private PulsarClient client;
    private Producer<String> producer;
    private Consumer<String> consumer;

    /**
     * 初始化Pulsar客戶端、生產者和消費者
     */
    @PostConstruct
    public void init() throws Exception {
        // 初始化Pulsar客戶端
        client = PulsarClient.builder()
                .serviceUrl(serviceUrl)
                .build();

        // 創建生產者
        producer = client.newProducer(Schema.STRING)
                .topic(topicName)
                .sendTimeout(0, java.util.concurrent.TimeUnit.SECONDS)
                .enableBatching(false)
                .create();

        // 創建消費者
        consumer = client.newConsumer(Schema.STRING)
                .topic(topicName)
                .subscriptionName("finance-subscription")
                .subscriptionType(SubscriptionType.Exclusive)
                .negativeAckRedeliveryBackoff(MultiplierRedeliveryBackoff.builder()
                        .maxDelayMs(60_000)
                        .minDelayMs(1_000)
                        .multiplier(2)
                        .build())
                .deadLetterPolicy(DeadLetterPolicy.builder()
                        .maxRedeliverCount(maxRedeliverCount)
                        .deadLetterTopic(deadLetterTopicName)
                        .build())
                .subscribe();

        // 開始消費消息
        consumeMessages();
    }

    /**
     * 關閉Pulsar客戶端、生產者和消費者
     */
    @PreDestroy
    public void close() throws Exception {
        if (producer != null) {
            producer.close();
        }
        if (consumer != null) {
            consumer.close();
        }
        if (client != null) {
            client.close();
        }
    }

    /**
     * 發送事務消息
     *
     * @param message 消息內容
     * @return 消息ID的CompletableFuture對象
     */
    public CompletableFuture<MessageId> sendTransactionalMessage(String message) {
        return producer.sendAsync(message);
    }

    /**
     * 消費消息并處理
     */
    private void consumeMessages() {
        new Thread(() -> {
            while (!Thread.currentThread().isInterrupted()) {
                try {
                    Message<String> msg = consumer.receive();
                    log.info("Received message: {}", msg.getValue());

                    // 處理消息
                    boolean processSuccess = processMessage(msg.getValue());

                    if (processSuccess) {
                        // 確認消息
                        consumer.acknowledgeAsync(msg.getMessageId());
                    } else {
                        // 負確認消息，觸發重試機制
                        consumer.negativeAcknowledge(msg.getMessageId(), new CustomException("Processing failed"));
                    }
                } catch (Exception e) {
                    log.error("Error processing message", e);
                }
            }
        }).start();
    }

    /**
     * 模擬消息處理邏輯
     *
     * @param message 消息內容
     * @return 處理是否成功
     */
    private boolean processMessage(String message) {
        // 模擬消息處理邏輯
        // 對于每三條消息中的一條模擬處理失敗
        long messageId = Long.parseLong(message.split(":")[1]);
        return messageId % 3 != 0;
    }

    static class CustomException extends Exception {
        public CustomException(String message) {
            super(message);
        }
    }

    // Getter methods for configuration properties (for testing purposes)
    public String getServiceUrl() {
        return serviceUrl;
    }

    public String getTopicName() {
        return topicName;
    }

    public String getDeadLetterTopicName() {
        return deadLetterTopicName;
    }

    public int getMaxRedeliverCount() {
        return maxRedeliverCount;
    }
}

控制器類

創建一個控制器類來暴露API端點用于發送消息。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.ExecutionException;

@RestController
public class FinanceTransactionController {

    @Autowired
    private FinanceTransactionService financeTransactionService;

    /**
     * 發送消息到Pulsar主題
     *
     * @param message 消息內容
     * @return 發送結果
     */
    @PostMapping("/send-message")
    public String sendMessage(@RequestParam String message) {
        try {
            financeTransactionService.sendTransactionalMessage(message).get();
            return"Message sent successfully";
        } catch (InterruptedException | ExecutionException e) {
            log.error("Failed to send message", e);
            return"Failed to send message";
        }
    }
}

單元測試

為了驗證上述功能是否正常工作，我們寫了一些測試用例。

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.http.ResponseEntity;

import static org.junit.jupiter.api.Assertions.*;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class FinanceTransactionControllerTest {

    @Autowired
    private TestRestTemplate restTemplate;

    @Autowired
    private FinanceTransactionService financeTransactionService;

    /**
     * 清空主題中的消息，確保每次測試前環境干凈
     */
    @BeforeEach
    public void setUp() throws Exception {
        clearTopic(financeTransactionService.getTopicName());
        clearTopic(financeTransactionService.getDeadLetterTopicName());
    }

    /**
     * 關閉資源
     */
    @AfterEach
    public void tearDown() throws Exception {
        financeTransactionService.close();
    }

    /**
     * 測試成功發送的消息是否正確地出現在主主題中，并且沒有出現在死信隊列中
     */
    @Test
    public void testSendMessage_Success() {
        ResponseEntity<String> response = restTemplate.postForEntity("/send-message?message=transaction:1", null, String.class);
        assertEquals("Message sent successfully", response.getBody());

        response = restTemplate.postForEntity("/send-message?message=transaction:2", null, String.class);
        assertEquals("Message sent successfully", response.getBody());

        response = restTemplate.postForEntity("/send-message?message=transaction:4", null, String.class);
        assertEquals("Message sent successfully", response.getBody());

        // 驗證消息在主主題中
        assertMessageInTopic("transaction:1");
        assertMessageInTopic("transaction:2");
        assertMessageInTopic("transaction:4");

        // 驗證死信隊列中沒有消息
        assertNoMessagesInTopic(financeTransactionService.getDeadLetterTopicName());
    }

    /**
     * 測試失敗發送的消息是否在達到最大重試次數后進入死信隊列
     */
    @Test
    public void testSendMessage_Failure() {
        ResponseEntity<String> response = restTemplate.postForEntity("/send-message?message=transaction:3", null, String.class);
        assertEquals("Message sent successfully", response.getBody());

        // 驗證消息在死信隊列中（經過多次重試）
        assertMessageInTopicWithRetries("transaction:3", financeTransactionService.getMaxRedeliverCount());
    }

    /**
     * 清空指定主題中的所有消息
     *
     * @param topicName 主題名稱
     */
    private void clearTopic(String topicName) throws Exception {
        PulsarClient client = PulsarClient.builder()
                .serviceUrl(financeTransactionService.getServiceUrl())
                .build();

        Reader<String> reader = client.newReader(Schema.STRING)
                .topic(topicName)
                .startMessageId(MessageId.earliest)
                .create();

        while (reader.hasMessageAvailable()) {
            reader.readNext();
        }

        reader.close();
        client.close();
    }

    /**
     * 驗證指定主題中是否存在特定消息
     *
     * @param expectedMessage 預期消息內容
     */
    private void assertMessageInTopic(String expectedMessage) {
        try (PulsarClient client = PulsarClient.builder()
                .serviceUrl(financeTransactionService.getServiceUrl())
                .build();

             Reader<String> reader = client.newReader(Schema.STRING)
                     .topic(financeTransactionService.getTopicName())
                     .startMessageId(MessageId.earliest)
                     .create()) {

            while (reader.hasMessageAvailable()) {
                Message<String> msg = reader.readNext();
                if (msg.getValue().equals(expectedMessage)) {
                    return;
                }
            }
            fail("Expected message not found in topic: " + expectedMessage);
        } catch (Exception e) {
            fail("Failed to read from topic: " + e.getMessage());
        }
    }

    /**
     * 驗證指定主題中沒有消息
     *
     * @param topicName 主題名稱
     */
    private void assertNoMessagesInTopic(String topicName) {
        try (PulsarClient client = PulsarClient.builder()
                .serviceUrl(financeTransactionService.getServiceUrl())
                .build();

             Reader<String> reader = client.newReader(Schema.STRING)
                     .topic(topicName)
                     .startMessageId(MessageId.earliest)
                     .create()) {

            assertFalse(reader.hasMessageAvailable(), "Unexpected messages found in topic: " + topicName);
        } catch (Exception e) {
            fail("Failed to read from topic: " + e.getMessage());
        }
    }

    /**
     * 驗證指定主題中是否存在特定消息（帶有重試機制）
     *
     * @param expectedMessage 預期消息內容
     * @param maxRetries      最大重試次數
     */
    private void assertMessageInTopicWithRetries(String expectedMessage, int maxRetries) {
        try (PulsarClient client = PulsarClient.builder()
                .serviceUrl(financeTransactionService.getServiceUrl())
                .build();

             Reader<String> reader = client.newReader(Schema.STRING)
                     .topic(financeTransactionService.getDeadLetterTopicName())
                     .startMessageId(MessageId.earliest)
                     .create()) {

            int retryCount = 0;
            while (retryCount < maxRetries) {
                if (reader.hasMessageAvailable()) {
                    Message<String> msg = reader.readNext();
                    if (msg.getValue().equals(expectedMessage)) {
                        return;
                    }
                }
                retryCount++;
                Thread.sleep(1000); // 等待1秒后重試
            }
            fail("Expected message not found in dead letter topic after retries: " + expectedMessage);
        } catch (Exception e) {
            fail("Failed to read from dead letter topic: " + e.getMessage());
        }
    }
}

測試結果

發送消息：

curl -X POST http://localhost:8080/send-message\?message\=transaction\:1
curl -X POST http://localhost:8080/send-message\?message\=transaction\:2
curl -X POST http://localhost:8080/send-message\?message\=transaction\:3
curl -X POST http://localhost:8080/send-message\?message\=transaction\:4

日志：

Received message: transaction:1
Received message: transaction:2
Received message: transaction:3
Received message: transaction:4

責任編輯：武曉燕來源： Java知識日歷

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