本文主要是介绍Java项目之消息队列（手写java模拟实现mq）【五、内存存储数据，方便快速拿到数据对象】✔ ★，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
九. 内存数据结构设计
硬盘上存储数据, 只是为了实现 “持久化” 这样的效果. 但是实际的消息存储/转发, 还是主要靠内存的结
构.
对于 MQ 来说, 内存部分是更关键的, 内存速度更快, 可以达成更⾼的并发
创建 MemoryDataCenter
创建 mqserver.datacenter.MemoryDataCenter
public class MemoryDataCenter {// key 是 exchangeName, value 是 Exchange 对象private ConcurrentHashMap<String, Exchange> exchangeMap = new ConcurrentHashMap<>();// key 是 queueName, value 是 MSGQueue 对象private ConcurrentHashMap<String, MSGQueue> queueMap = new ConcurrentHashMap<>();// 第一个 key 是 exchangeName, 第二个 key 是 queueNameprivate ConcurrentHashMap<String, ConcurrentHashMap<String, Binding>> bindingsMap = new ConcurrentHashMap<>();// key 是 messageId, value 是 Message 对象private ConcurrentHashMap<String, Message> messageMap = new ConcurrentHashMap<>();// key 是 queueName, value 是一个 Message 的链表private ConcurrentHashMap<String, LinkedList<Message>> queueMessageMap = new ConcurrentHashMap<>();// 第一个 key 是 queueName, 第二个 key 是 messageIdprivate ConcurrentHashMap<String, ConcurrentHashMap<String, Message>> queueMessageWaitAckMap = new ConcurrentHashMap<>();
• 使⽤四个哈希表, 管理 Exchange, Queue, Binding, Message.
• 使⽤⼀个哈希表 + 链表管理 队列 -> 消息 之间的关系.
• 使⽤⼀个哈希表 + 哈希表管理所有的未被确认的消息.
为了保证消息被正确消费了, 会使⽤两种⽅式进⾏确认. ⾃动 ACK 和 ⼿动 ACK.
其中⾃动 ACK 是指当消息被消费之后, 就会⽴即被销毁释放.
其中⼿动 ACK 是指当消息被消费之后, 由消费者主动调⽤⼀个 basicAck ⽅法, 进⾏主动确认. 服务器
收到这个确认之后, 才能真正销毁消息.
此处的 “未确认消息” 就是指在⼿动 ACK 模式下, 该消息还没有被调⽤ basicAck. 此时消息不能删除,
但是要和其他未消费的消息区分开. 于是另搞了个结构.
当后续 basicAck 到了, 就可以删除消息了
封装 Exchange ⽅法
public void insertExchange(Exchange exchange) {exchangeMap.put(exchange.getName(), exchange);System.out.println("[MemoryDataCenter] 新交换机添加成功! exchangeName=" + exchange.getName());}public Exchange getExchange(String exchangeName) {return exchangeMap.get(exchangeName);}public void deleteExchange(String exchangeName) {exchangeMap.remove(exchangeName);System.out.println("[MemoryDataCenter] 交换机删除成功! exchangeName=" + exchangeName);}封装 Queue ⽅法
public void insertQueue(MSGQueue queue) {queueMap.put(queue.getName(), queue);System.out.println("[MemoryDataCenter] 新队列添加成功! queueName=" + queue.getName());}public MSGQueue getQueue(String queueName) {return queueMap.get(queueName);}public void deleteQueue(String queueName) {queueMap.remove(queueName);System.out.println("[MemoryDataCenter] 队列删除成功! queueName=" + queueName);}
封装 Binding ⽅法
public void insertBinding(Binding binding) throws MqException {
// ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.get(binding.getExchangeName());
// if (bindingMap == null) {
// bindingMap = new ConcurrentHashMap<>();
// bindingsMap.put(binding.getExchangeName(), bindingMap);
// }// 先使用 exchangeName 查一下, 对应的哈希表是否存在. 不存在就创建一个.ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.computeIfAbsent(binding.getExchangeName(),k -> new ConcurrentHashMap<>());synchronized (bindingMap) {// 再根据 queueName 查一下. 如果已经存在, 就抛出异常. 不存在才能插入.if (bindingMap.get(binding.getQueueName()) != null) {throw new MqException("[MemoryDataCenter] 绑定已经存在! exchangeName=" + binding.getExchangeName() +", queueName=" + binding.getQueueName());}bindingMap.put(binding.getQueueName(), binding);}System.out.println("[MemoryDataCenter] 新绑定添加成功! exchangeName=" + binding.getExchangeName()+ ", queueName=" + binding.getQueueName());}// 获取绑定, 写两个版本:// 1. 根据 exchangeName 和 queueName 确定唯一一个 Binding// 2. 根据 exchangeName 获取到所有的 Bindingpublic Binding getBinding(String exchangeName, String queueName) {ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.get(exchangeName);if (bindingMap == null) {return null;}return bindingMap.get(queueName);}public ConcurrentHashMap<String, Binding> getBindings(String exchangeName) {return bindingsMap.get(exchangeName);}public void deleteBinding(Binding binding) throws MqException {ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.get(binding.getExchangeName());if (bindingMap == null) {// 该交换机没有绑定任何队列. 报错.throw new MqException("[MemoryDataCenter] 绑定不存在! exchangeName=" + binding.getExchangeName()+ ", queueName=" + binding.getQueueName());}bindingMap.remove(binding.getQueueName());System.out.println("[MemoryDataCenter] 绑定删除成功! exchangeName=" + binding.getExchangeName()+ ", queueName=" + binding.getQueueName());}
封装 Message ⽅法
public void addMessage(Message message) {messageMap.put(message.getMessageId(), message);System.out.println("[MemoryDataCenter] 新消息添加成功! messageId=" + message.getMessageId());}// 根据 id 查询消息public Message getMessage(String messageId) {return messageMap.get(messageId);}// 根据 id 删除消息public void removeMessage(String messageId) {messageMap.remove(messageId);System.out.println("[MemoryDataCenter] 消息被移除! messageId=" + messageId);}// 发送消息到指定队列public void sendMessage(MSGQueue queue, Message message) {// 把消息放到对应的队列数据结构中.// 先根据队列的名字, 找到该队列对应的消息链表.LinkedList<Message> messages = queueMessageMap.computeIfAbsent(queue.getName(), k -> new LinkedList<>());// 再把数据加到 messages 里面synchronized (messages) {messages.add(message);}// 在这里把该消息也往消息中心中插入一下. 假设如果 message 已经在消息中心存在, 重复插入也没关系.// 主要就是相同 messageId, 对应的 message 的内容一定是一样的. (服务器代码不会对 Message 内容做修改 basicProperties 和 body)addMessage(message);System.out.println("[MemoryDataCenter] 消息被投递到队列中! messageId=" + message.getMessageId());}// 从队列中取消息public Message pollMessage(String queueName) {// 根据队列名, 查找一下, 对应的队列的消息链表.LinkedList<Message> messages = queueMessageMap.get(queueName);if (messages == null) {return null;}synchronized (messages) {// 如果没找到, 说明队列中没有任何消息.if (messages.size() == 0) {return null;}// 链表中有元素, 就进行头删.Message currentMessage = messages.remove(0);System.out.println("[MemoryDataCenter] 消息从队列中取出! messageId=" + currentMessage.getMessageId());return currentMessage;}}// 获取指定队列中消息的个数public int getMessageCount(String queueName) {LinkedList<Message> messages = queueMessageMap.get(queueName);if (messages == null) {// 队列中没有消息return 0;}synchronized (messages) {return messages.size();}}// 添加未确认的消息public void addMessageWaitAck(String queueName, Message message) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,k -> new ConcurrentHashMap<>());messageHashMap.put(message.getMessageId(), message);System.out.println("[MemoryDataCenter] 消息进入待确认队列! messageId=" + message.getMessageId());}// 删除未确认的消息(消息已经确认了)public void removeMessageWaitAck(String queueName, String messageId) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);if (messageHashMap == null) {return;}messageHashMap.remove(messageId);System.out.println("[MemoryDataCenter] 消息从待确认队列删除! messageId=" + messageId);}// 获取指定的未确认的消息public Message getMessageWaitAck(String queueName, String messageId) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);if (messageHashMap == null) {return null;}return messageHashMap.get(messageId);}
针对未确认的消息的处理
// 添加未确认的消息
public void addMessageWaitAck(String queueName, Message message) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.computeIfAbsent(queueName,k -> new ConcurrentHashMap<>());messageHashMap.put(message.getMessageId(), message);System.out.println("[MemoryDataCenter] 消息进入待确认队列! messageId=" + message.getMessageId());
}// 删除未确认的消息(消息已经确认了)
public void removeMessageWaitAck(String queueName, String messageId) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);if (messageHashMap == null) {return;}messageHashMap.remove(messageId);System.out.println("[MemoryDataCenter] 消息从待确认队列删除! messageId=" + messageId);
}// 获取指定的未确认的消息
public Message getMessageWaitAck(String queueName, String messageId) {ConcurrentHashMap<String, Message> messageHashMap = queueMessageWaitAckMap.get(queueName);if (messageHashMap == null) {return null;}return messageHashMap.get(messageId);
}
实现重启后恢复内存
// 这个方法就是从硬盘上读取数据, 把硬盘中之前持久化存储的各个维度的数据都恢复到内存中.public void recovery(DiskDataCenter diskDataCenter) throws IOException, MqException, ClassNotFoundException {// 0. 清空之前的所有数据exchangeMap.clear();queueMap.clear();bindingsMap.clear();messageMap.clear();queueMessageMap.clear();// 1. 恢复所有的交换机数据List<Exchange> exchanges = diskDataCenter.selectAllExchanges();for (Exchange exchange : exchanges) {exchangeMap.put(exchange.getName(), exchange);}// 2. 恢复所有的队列数据List<MSGQueue> queues = diskDataCenter.selectAllQueues();for (MSGQueue queue : queues) {queueMap.put(queue.getName(), queue);}// 3. 恢复所有的绑定数据List<Binding> bindings = diskDataCenter.selectAllBindings();for (Binding binding : bindings) {ConcurrentHashMap<String, Binding> bindingMap = bindingsMap.computeIfAbsent(binding.getExchangeName(),k -> new ConcurrentHashMap<>());bindingMap.put(binding.getQueueName(), binding);}// 4. 恢复所有的消息数据// 遍历所有的队列, 根据每个队列的名字, 获取到所有的消息.for (MSGQueue queue : queues) {LinkedList<Message> messages = diskDataCenter.loadAllMessageFromQueue(queue.getName());queueMessageMap.put(queue.getName(), messages);for (Message message : messages) {messageMap.put(message.getMessageId(), message);}}// 注意!! 针对 "未确认的消息" 这部分内存中的数据, 不需要从硬盘恢复. 之前考虑硬盘存储的时候, 也没设定这一块.// 一旦在等待 ack 的过程中, 服务器重启了, 此时这些 "未被确认的消息", 就恢复成 "未被取走的消息" .// 这个消息在硬盘上存储的时候, 就是当做 "未被取走"}
测试 MemoryDataCenter
创建 MemoryDataCenterTests
package com.example.mq;import com.example.mq.common.MqException;
import com.example.mq.mqserver.core.*;
import com.example.mq.mqserver.datacenter.DiskDataCenter;
import com.example.mq.mqserver.datacenter.MemoryDataCenter;
import org.apache.tomcat.util.http.fileupload.FileUtils;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.test.context.SpringBootTest;import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;@SpringBootTest
public class MemoryDataCenterTests {private MemoryDataCenter memoryDataCenter = null;@BeforeEachpublic void setUp() {memoryDataCenter = new MemoryDataCenter();}@AfterEachpublic void tearDown() {memoryDataCenter = null;}// 创建一个测试交换机private Exchange createTestExchange(String exchangeName) {Exchange exchange = new Exchange();exchange.setName(exchangeName);exchange.setType(ExchangeType.DIRECT);exchange.setAutoDelete(false);exchange.setDurable(true);return exchange;}// 创建一个测试队列private MSGQueue createTestQueue(String queueName) {MSGQueue queue = new MSGQueue();queue.setName(queueName);queue.setDurable(true);queue.setExclusive(false);queue.setAutoDelete(false);return queue;}// 针对交换机进行测试@Testpublic void testExchange() {// 1. 先构造一个交换机并插入.Exchange expectedExchange = createTestExchange("testExchange");memoryDataCenter.insertExchange(expectedExchange);// 2. 查询出这个交换机, 比较结果是否一致. 此处直接比较这俩引用指向同一个对象.Exchange actualExchange = memoryDataCenter.getExchange("testExchange");Assertions.assertEquals(expectedExchange, actualExchange);// 3. 删除这个交换机memoryDataCenter.deleteExchange("testExchange");// 4. 再查一次, 看是否就查不到了actualExchange = memoryDataCenter.getExchange("testExchange");Assertions.assertNull(actualExchange);}// 针对队列进行测试@Testpublic void testQueue() {// 1. 构造一个队列, 并插入MSGQueue expectedQueue = createTestQueue("testQueue");memoryDataCenter.insertQueue(expectedQueue);// 2. 查询这个队列, 并比较MSGQueue actualQueue = memoryDataCenter.getQueue("testQueue");Assertions.assertEquals(expectedQueue, actualQueue);// 3. 删除这个队列memoryDataCenter.deleteQueue("testQueue");// 4. 再次查询队列, 看是否能查到actualQueue = memoryDataCenter.getQueue("testQueue");Assertions.assertNull(actualQueue);}// 针对绑定进行测试@Testpublic void testBinding() throws MqException {Binding expectedBinding = new Binding();expectedBinding.setExchangeName("testExchange");expectedBinding.setQueueName("testQueue");expectedBinding.setBindingKey("testBindingKey");memoryDataCenter.insertBinding(expectedBinding);Binding actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");Assertions.assertEquals(expectedBinding, actualBinding);ConcurrentHashMap<String, Binding> bindingMap = memoryDataCenter.getBindings("testExchange");Assertions.assertEquals(1, bindingMap.size());Assertions.assertEquals(expectedBinding, bindingMap.get("testQueue"));memoryDataCenter.deleteBinding(expectedBinding);actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");Assertions.assertNull(actualBinding);}private Message createTestMessage(String content) {Message message = Message.createMessageWithId("testRoutingKey", null, content.getBytes());return message;}@Testpublic void testMessage() {Message expectedMessage = createTestMessage("testMessage");memoryDataCenter.addMessage(expectedMessage);Message actualMessage = memoryDataCenter.getMessage(expectedMessage.getMessageId());Assertions.assertEquals(expectedMessage, actualMessage);memoryDataCenter.removeMessage(expectedMessage.getMessageId());actualMessage = memoryDataCenter.getMessage(expectedMessage.getMessageId());Assertions.assertNull(actualMessage);}@Testpublic void testSendMessage() {// 1. 创建一个队列, 创建 10 条消息, 把这些消息都插入队列中.MSGQueue queue = createTestQueue("testQueue");List<Message> expectedMessages = new ArrayList<>();for (int i = 0; i < 10; i++) {Message message = createTestMessage("testMessage" + i);memoryDataCenter.sendMessage(queue, message);expectedMessages.add(message);}// 2. 从队列中取出这些消息.List<Message> actualMessages = new ArrayList<>();while (true) {Message message = memoryDataCenter.pollMessage("testQueue");if (message == null) {break;}actualMessages.add(message);}// 3. 比较取出的消息和之前的消息是否一致.Assertions.assertEquals(expectedMessages.size(), actualMessages.size());for (int i = 0; i < expectedMessages.size(); i++) {Assertions.assertEquals(expectedMessages.get(i), actualMessages.get(i));}}@Testpublic void testMessageWaitAck() {Message expectedMessage = createTestMessage("expectedMessage");memoryDataCenter.addMessageWaitAck("testQueue", expectedMessage);Message actualMessage = memoryDataCenter.getMessageWaitAck("testQueue", expectedMessage.getMessageId());Assertions.assertEquals(expectedMessage, actualMessage);memoryDataCenter.removeMessageWaitAck("testQueue", expectedMessage.getMessageId());actualMessage = memoryDataCenter.getMessageWaitAck("testQueue", expectedMessage.getMessageId());Assertions.assertNull(actualMessage);}@Testpublic void testRecovery() throws IOException, MqException, ClassNotFoundException {// 由于后续需要进行数据库操作, 依赖 MyBatis. 就需要先启动 SpringApplication, 这样才能进行后续的数据库操作.MqApplication.context = SpringApplication.run(MqApplication.class);// 1. 在硬盘上构造好数据DiskDataCenter diskDataCenter = new DiskDataCenter();diskDataCenter.init();// 构造交换机Exchange expectedExchange = createTestExchange("testExchange");diskDataCenter.insertExchange(expectedExchange);// 构造队列MSGQueue expectedQueue = createTestQueue("testQueue");diskDataCenter.insertQueue(expectedQueue);// 构造绑定Binding expectedBinding = new Binding();expectedBinding.setExchangeName("testExchange");expectedBinding.setQueueName("testQueue");expectedBinding.setBindingKey("testBindingKey");diskDataCenter.insertBinding(expectedBinding);// 构造消息Message expectedMessage = createTestMessage("testContent");diskDataCenter.sendMessage(expectedQueue, expectedMessage);// 2. 执行恢复操作memoryDataCenter.recovery(diskDataCenter);// 3. 对比结果Exchange actualExchange = memoryDataCenter.getExchange("testExchange");Assertions.assertEquals(expectedExchange.getName(), actualExchange.getName());Assertions.assertEquals(expectedExchange.getType(), actualExchange.getType());Assertions.assertEquals(expectedExchange.isDurable(), actualExchange.isDurable());Assertions.assertEquals(expectedExchange.isAutoDelete(), actualExchange.isAutoDelete());MSGQueue actualQueue = memoryDataCenter.getQueue("testQueue");Assertions.assertEquals(expectedQueue.getName(), actualQueue.getName());Assertions.assertEquals(expectedQueue.isDurable(), actualQueue.isDurable());Assertions.assertEquals(expectedQueue.isAutoDelete(), actualQueue.isAutoDelete());Assertions.assertEquals(expectedQueue.isExclusive(), actualQueue.isExclusive());Binding actualBinding = memoryDataCenter.getBinding("testExchange", "testQueue");Assertions.assertEquals(expectedBinding.getExchangeName(), actualBinding.getExchangeName());Assertions.assertEquals(expectedBinding.getQueueName(), actualBinding.getQueueName());Assertions.assertEquals(expectedBinding.getBindingKey(), actualBinding.getBindingKey());Message actualMessage = memoryDataCenter.pollMessage("testQueue");Assertions.assertEquals(expectedMessage.getMessageId(), actualMessage.getMessageId());Assertions.assertEquals(expectedMessage.getRoutingKey(), actualMessage.getRoutingKey());Assertions.assertEquals(expectedMessage.getDeliverMode(), actualMessage.getDeliverMode());Assertions.assertArrayEquals(expectedMessage.getBody(), actualMessage.getBody());// 4. 清理硬盘的数据, 把整个 data 目录里的内容都删掉(包含了 meta.db 和 队列的目录).MqApplication.context.close();File dataDir = new File("./data");FileUtils.deleteDirectory(dataDir);}
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