优秀代码记录

最新推荐文章于 2025-11-24 15:26:36 发布

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优秀代码都遵循的六大原则

Java六大设计原则（SOLID +1）是面向对象设计的核心准则：

‌单一职责原则 (SRP)‌

一个类只负责一个功能领域
示例：用户管理类不应同时处理登录和支付逻辑

‌开闭原则 (OCP)‌

对扩展开放，对修改关闭
通过抽象层（接口/抽象类）实现功能扩展

‌里氏替换原则 (LSP)‌

子类必须能替换父类且不影响程序正确性
典型违反：子类重写父类方法抛出更宽泛异常

‌接口隔离原则 (ISP)‌

客户端不应依赖不需要的接口方法
解决方案：将大接口拆分为多个小接口

‌依赖倒置原则 (DIP)‌

高层模块不应依赖低层模块，二者都应依赖抽象
通过依赖注入实现（如Spring IoC）

‌迪米特法则 (LoD)‌

最少知识原则，对象只与直接朋友通信
避免链式调用：a.getB().getC().doSomething()

‌扩展原则‌：组合优于继承（非SOLID但重要）

优先使用对象组合而非类继承实现代码复用
示例：策略模式通过组合不同算法对象实现行为变化

这些原则共同作用可提升代码的可维护性、扩展性和复用性，是设计模式的理论基础。实际开发中需根据场景灵活运用而非教条执行。

责任链


import org.jetbrains.annotations.NotNull;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class AuditManagementFilterChain implements InitializingBean, ApplicationContextAware {

    private IAuditManagementFilter[] filters = new IAuditManagementFilter[0];

    private int pos = 0;

    private int n = 0;

    private ApplicationContext appContext;

    private void addFilter(IAuditManagementFilter newFilter) {
        IAuditManagementFilter[] newFilters = this.filters;

        for (IAuditManagementFilter filter : newFilters) {
            if (filter == newFilter) {
                return;
            }
        }

        if (this.n == this.filters.length) {
            newFilters = new IAuditManagementFilter[this.n + 10];
            System.arraycopy(this.filters, 0, newFilters, 0, this.n);
            this.filters = newFilters;
        }

        this.filters[this.n++] = newFilter;
    }

    public void doFilter(Object obj) {
        if (this.pos < this.n) {
            IAuditManagementFilter filter = this.filters[this.pos++];
            filter.doFilter(obj, this);
        }
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        this.appContext
                .getBeansOfType(IAuditManagementFilter.class)
                .values()
                .forEach(this::addFilter);
    }

    @Override
    public void setApplicationContext(@NotNull ApplicationContext applicationContext) throws BeansException {
        this.appContext = applicationContext;
    }
}

工厂


import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import java.util.HashMap;
import java.util.Map;


@Component
public class BankPayNotifyFactory implements InitializingBean, ApplicationContextAware {

    private static final Map<String, BankPayNotifyStrategy> NOTIFY_MAP = new HashMap<>(8);

    private ApplicationContext appContext;

    /**
     * 根据银行编码获取对应的处理器
     *
     * @param bankChannelCode 银行渠道编码
     * @return
     */
    public BankPayNotifyStrategy getHandler(String bankChannelCode) {
        return NOTIFY_MAP.get(bankChannelCode);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        this.appContext.getBeansOfType(BankPayNotifyStrategy.class)
                .values()
                .forEach(handler -> NOTIFY_MAP.put(handler.getBankChannelCode(), handler));
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.appContext = applicationContext;
    }
}


import lombok.extern.slf4j.Slf4j;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Slf4j
public class TagHandlerStrategyFactory {

    private static final Map<String, TagHandlerStrategy> strategyMap = new HashMap<>();

    public static TagHandlerStrategy addStrategy(TagHandlerStrategy strategy) {
        log.info("Register a policy class[{}]", strategy.getClass().getName());
        return strategyMap.put(strategy.getClass().getSimpleName(), strategy);
    }

    public static TagHandlerStrategy getStrategy(String name) {
        return strategyMap.get(name);
    }

}

门面

// 子系统
class CPU { void start() { /* ... */ } }
class Memory { void load() { /* ... */ } }

// 外观类
class ComputerFacade {
    private CPU cpu;
    private Memory memory;
    public void startComputer() {
        cpu.start();
        memory.load();
    }
}
// 客户端调用
facade.startComputer(); // 隐藏了CPU和Memory的细节


// 子系统：DVD播放器
class DvdPlayer {
    public void on() { System.out.println("DVD启动"); }
    public void play(String movie) { System.out.println("播放电影：" + movie); }
}

// 子系统：投影仪
class Projector {
    public void on() { System.out.println("投影仪开启"); }
}

// 外观类
class HomeTheaterFacade {
    private DvdPlayer dvd;
    private Projector projector;

    public HomeTheaterFacade() {
        this.dvd = new DvdPlayer();
        this.projector = new Projector();
    }

    public void watchMovie(String movie) {
        projector.on();
        dvd.on();
        dvd.play(movie);
    }
}

// 客户端调用
public class Client {
    public static void main(String[] args) {
        HomeTheaterFacade facade = new HomeTheaterFacade();
        facade.watchMovie("星际穿越");
    }
}

适配器


// 目标接口（客户端期望的接口）
interface MediaPlayer {
    void play(String audioType, String fileName);
}

// 被适配者：现有实现类（不兼容接口）
class AdvancedMediaPlayer {
    public void playMp4(String fileName) {
        System.out.println("Playing MP4 file: " + fileName);
    }
    
    public void playVlc(String fileName) {
        System.out.println("Playing VLC file: " + fileName);
    }
}

// 适配器类（实现目标接口并封装被适配者）
class MediaAdapter implements MediaPlayer {
    private AdvancedMediaPlayer advancedPlayer;

    public MediaAdapter(String audioType) {
        if(audioType.equalsIgnoreCase("vlc")) {
            advancedPlayer = new AdvancedMediaPlayer();
        } else if(audioType.equalsIgnoreCase("mp4")) {
            advancedPlayer = new AdvancedMediaPlayer();
        }
    }

    @Override
    public void play(String audioType, String fileName) {
        if(audioType.equalsIgnoreCase("vlc")) {
            advancedPlayer.playVlc(fileName);
        } else if(audioType.equalsIgnoreCase("mp4")) {
            advancedPlayer.playMp4(fileName);
        }
    }
}

// 客户端代码
public class AdapterDemo {
    public static void main(String[] args) {
        MediaPlayer player = new MediaAdapter("mp4");
        player.play("mp4", "movie.mp4");
        
        player = new MediaAdapter("vlc");
        player.play("vlc", "song.vlc");
    }
}

事件

@Component
public class BankWithholdRecordEventUtil {

    @Autowired
    private ApplicationEventPublisher publisher;

    /**
     * 发布监听
     *
     * @param bankWithholdRecord
     */
    public void publishBankWithholdRecordEvent(BankWithholdRecord bankWithholdRecord) {
        publisher.publishEvent(new BankWithholdRecordEvent(bankWithholdRecord));
    }
}

public class BankWithholdRecordEvent extends ApplicationEvent {

    /**
     * 事件
     *
     * @param source
     */
    public BankWithholdRecordEvent(BankWithholdRecord source) {
        super(source);
    }
}


@Component
@Slf4j
public class BankWithholdRecordListener {
    @Autowired
    private IBankWithholdRecordService bankWithholdRecordService;

    /**
     * 代扣流水监听
     *
     * @param event
     */
    @Async
    @EventListener({BankWithholdRecordEvent.class})
    public void saveWithholdRecord(BankWithholdRecordEvent event) {
        BankWithholdRecord bankWithholdRecord = (BankWithholdRecord) event.getSource();
        log.info("进入代扣流水监听方法：{}", bankWithholdRecord);
        bankWithholdRecordService.insertBankWithholdRecord(bankWithholdRecord);
    }
}

监听


import java.util.*;
public class Button {
    private List<ClickListener> listeners = new ArrayList<>();
    
    public void addListener(ClickListener listener) {
        listeners.add(listener);
    }
    
    public void click() {
        listeners.forEach(ClickListener::onClick);
    }
}


public interface ClickListener {
    void onClick();
}



public class Main {
    public static void main(String[] args) {
        Button button = new Button();
        button.addListener(() -> System.out.println("Button clicked!"));
        button.click();
    }
}

发布订阅


import java.util.*;
public class EventBroker {
    private Map<String, List<Subscriber>> topics = new HashMap<>();
    
    public void subscribe(String topic, Subscriber subscriber) {
        topics.computeIfAbsent(topic, k -> new ArrayList<>()).add(subscriber);
    }
    
    public void publish(String topic, String message) {
        topics.getOrDefault(topic, Collections.emptyList())
              .forEach(sub -> sub.onEvent(message));
    }
}


public interface Subscriber {
    void onEvent(String message);
}


public class Main {
    public static void main(String[] args) {
        EventBroker broker = new EventBroker();
        broker.subscribe("news", message -> System.out.println("Sub1 received: " + message));
        broker.publish("news", "Java 21 released!");
    }
}

单例

最好的单例就是枚举！！！


public class Singleton {
    // 方式1：双重检查锁定（适用于JDK5+）
    private static volatile Singleton instance;
    
    private Singleton() {}
    
    public static Singleton getInstance() {
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }

    // 方式2：枚举单例（推荐写法）
    public enum EnumSingleton {
        INSTANCE;
        public void doSomething() {
            System.out.println("Enum singleton working");
        }
    }
    
    public static void main(String[] args) {
        Singleton s1 = Singleton.getInstance();
        Singleton s2 = Singleton.getInstance();
        System.out.println(s1 == s2); // true
        
        EnumSingleton.INSTANCE.doSomething();
    }
}