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开闭原则
项目实战
原始 API 接口监控告警类 Alert 类的代码：
public class Alert {
private AlertRule rule;
private Notification notification;
public Alert(AlertRule rule, Notification notification) {
this.rule = rule;
this.notification = notification;
}
public void check(String api, long requestCount, long errorCount, long dur
long tps = requestCount / durationOfSeconds;
if (tps > rule.getMatchedRule(api).getMaxTps()) {
notification.notify(NotificationEmergencyLevel.URGENCY, "...");
}
if (errorCount > rule.getMatchedRule(api).getMaxErrorCount()) {
notification.notify(NotificationEmergencyLevel.SEVERE, "...");
}
}
}
修改方案：
public class Alert {
// ... 省略 AlertRule/Notification 属性和构造函数...
// 改动一：添加参数 timeoutCount
public void check(String api, long requestCount, long errorCount, long tim
long tps = requestCount / durationOfSeconds;
if (tps > rule.getMatchedRule(api).getMaxTps()) {
notification.notify(NotificationEmergencyLevel.URGENCY, "...");
}
if (errorCount > rule.getMatchedRule(api).getMaxErrorCount()) {
notification.notify(NotificationEmergencyLevel.SEVERE, "...");
}
// 改动二：添加接口超时处理逻辑
long timeoutTps = timeoutCount / durationOfSeconds;
if (timeoutTps > rule.getMatchedRule(api).getMaxTimeoutTps()) {
notification.notify(NotificationEmergencyLevel.URGENCY, "...");
}
}
}
扩展方案：
public class Alert {
private List<AlertHandler> alertHandlers = new ArrayList<>();
public void addAlertHandler(AlertHandler alertHandler) {
this.alertHandlers.add(alertHandler);
}
public void check(ApiStatInfo apiStatInfo) {
for (AlertHandler handler : alertHandlers) {
handler.check(apiStatInfo);
}
}
}
public class ApiStatInfo {// 省略 constructor/getter/setter 方法
private String api;
private long requestCount;
private long errorCount;
private long durationOfSeconds;
}
public abstract class AlertHandler {
protected AlertRule rule;
protected Notification notification;
public AlertHandler(AlertRule rule, Notification notification) {
this.rule = rule;
this.notification = notification;
}
public abstract void check(ApiStatInfo apiStatInfo);
}
public class TpsAlertHandler extends AlertHandler {
public TpsAlertHandler(AlertRule rule, Notification notification) {
super(rule, notification);
}
@override
public void check(ApiStatInfo apiStatInfo) {
long tps = apiStatInfo.getRequestCount()/ apiStatInfo.getDurationOfSecon
if (tps > rule.getMatchedRule(apiStatInfo.getApi()).getMaxTps()) {
notification.notify(NotificationEmergencyLevel.URGENCY, "...");
}
}
}
public class ErrorAlertHandler extends AlertHandler {
public ErrorAlertHandler(AlertRule rule, Notification notification){
super(rule, notification);
}
@Override
public void check(ApiStatInfo apiStatInfo) {
if (apiStatInfo.getErrorCount() > rule.getMatchedRule(apiStatInfo.getApi
notification.notify(NotificationEmergencyLevel.SEVERE, "...");
}
}
}
Alert 类的使用方法：ApplicationContext 是一个单例类，负责 Alert 的创建、组装（alertRule 和notification 的依赖注入）、初始化（添加 handlers）工作。
public class ApplicationContext {
private AlertRule alertRule;
private Notification notification;
private Alert alert;
public void inITializeBeans() {
alertRule = new AlertRule(/*. 省略参数.*/); // 省略一些初始化代码
notification = new Notification(/*. 省略参数.*/); // 省略一些初始化代码
alert = new Alert();
alert.addAlertHandler(new TpsAlertHandler(alertRule, notification));
alert.addAlertHandler(new ErrorAlertHandler(alertRule, notification));
}
public Alert getAlert() { return alert; }
// 饿汉式单例
private static final ApplicationContext instance = new ApplicationContext(
private ApplicationContext() {
instance.initializeBeans();
}
public static ApplicationContext getInstance() {
return instance;
}
}
public class Demo {
public static void main(String[] args) {
ApiStatInfo apiStatInfo = new ApiStatInfo();
// ... 省略设置 apiStatInfo 数据值的代码
ApplicationContext.getInstance().getAlert().check(apiStatInfo);
}
}
基于重构之后的代码，如果再添加上面讲到的那个新功能，每秒钟接口超时请求个数超过某个最大阈值就告警，主要的改动有下面四处。
改动之后的代码如下所示：
public class Alert { // 代码未改动... }
public class ApiStatInfo {// 省略 constructor/getter/setter 方法
private String api;
private long requestCount;
private long errorCount;
private long durationOfSeconds;
private long timeoutCount; // 改动一：添加新字段
}
public abstract class AlertHandler { // 代码未改动... }
public class TpsAlertHandler extends AlertHandler {// 代码未改动...}
public class ErrorAlertHandler extends AlertHandler {// 代码未改动...}
// 改动二：添加新的 handler
public class TimeoutAlertHandler extends AlertHandler {// 省略代码...}
public class ApplicationContext {
private AlertRule alertRule;
private Notification notification;
private Alert alert;
public void initializeBeans() {
alertRule = new AlertRule(/*. 省略参数.*/); // 省略一些初始化代码
notification = new Notification(/*. 省略参数.*/); // 省略一些初始化代码
alert = new Alert();
alert.addAlertHandler(new TpsAlertHandler(alertRule, notification));
alert.addAlertHandler(new ErrorAlertHandler(alertRule, notification));
// 改动三：注册 handler
alert.addAlertHandler(new TimeoutAlertHandler(alertRule, notification));
}
//... 省略其他未改动代码...
}
public class Demo {
public static void main(String[] args) {
ApiStatInfo apiStatInfo = new ApiStatInfo();
// ... 省略 apiStatInfo 的 set 字段代码
apiStatInfo.setTimeoutCount(289); // 改动四：设置 tiemoutCount 值
ApplicationContext.getInstance().getAlert().check(apiStatInfo);
}
偏向顶层的指导思想
具体方法论
具体代码：
// 这一部分体现了抽象意识
public interface MessageQueue { //... }
public class KafkamessageQueue implements MessageQueue { //... }
public class RocketMQMessageQueue implements MessageQueue {//...}
public interface MessageFromatter { //... }
public class JsonMessageFromatter implements MessageFromatter {//...}
public class ProtoBufMessageFromatter implements MessageFromatter {//...}
public class Demo {
private MessageQueue msgQueue; // 基于接口而非实现编程
public Demo(MessageQueue msgQueue) { // 依赖注入
this.msgQueue = msgQueue;
}
// msgFormatter：多态、依赖注入
public void sendNotification(Notification notification, MessageFormatter m
//...
}
}
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