常用设计模式

单例模式

bean的形式

    @Bean
    public TestService testService(){
        return new TestServiceImpl();
    }

枚举类形式

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
public enum SingletonThreadPool {
 
    INSTANCE;
 
    private ExecutorService threadPool;
 
    SingletonThreadPool() {
        // 创建一个固定大小的线程池
        threadPool = Executors.newFixedThreadPool(5);
    }
 
    public void executeTask(Runnable task) {
        threadPool.execute(task);
    }

 
    //使用案例
    public static void main(String[] args) {
        // 提交任务到线程池
        SingletonThreadPool.INSTANCE.executeTask(() -> {
            System.out.println("任务正在执行...");
        });
    }
}

工厂模式

简单工厂

public class SimplePizzaFactory {
       public Pizza CreatePizza(String ordertype) {
              Pizza pizza = null;
              if (ordertype.equals("cheese")) {
                     pizza = new CheesePizza();
              } else if (ordertype.equals("greek")) {
                     pizza = new GreekPizza();
              } else if (ordertype.equals("pepper")) {
                     pizza = new PepperPizza();
              }
              return pizza;
       }
}

抽象工厂

public interface AbsFactory {
        //创建pizza
       Pizza CreatePizza(String ordertype);

        //创建Cake
       Cake CreateCake(String ordertype);
}


public class LDFactory implements AbsFactory {
       @Override
       public Pizza CreatePizza(String ordertype) {
              Pizza pizza = null;
              if ("cheese".equals(ordertype)) {
                     pizza = new LDCheesePizza();
              } else if ("pepper".equals(ordertype)) {
                     pizza = new LDPepperPizza();
              }
              return pizza;
       }

       @Override
       public Cake CreateCake(String ordertype) {
              Cake cake= null;
              if ("cheese".equals(ordertype)) {
                     cake = new LDCheeseCake();
              } else if ("pepper".equals(ordertype)) {
                     cake = new LDPepperCake();
              }
              return cake;
       }
}

建造者模式

工具类

import lombok.extern.slf4j.Slf4j;

import java.util.ArrayList;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Supplier;

@Slf4j
public class BuilderUtil<T> {

    /**
     * 创建对象的构造方法
     */
    private Supplier<T> createInstance;
    /**
     * 设值的函数方法集合
     */
    private List<Consumer<T>> consumers;

    private BuilderUtil() {
    }

    /**
     * 创建builder实例
     *
     * @param constructor build对象的构造方法
     * @param <T>         build对象的类型
     * @return builder实例
     */
    public static <T> BuilderUtil<T> create(Supplier<T> constructor) {
        BuilderUtil<T> instance = new BuilderUtil<>();
        instance.createInstance = constructor;
        instance.consumers = new ArrayList<>(8);
        return instance;
    }


    /**
     * 设置对象属性
     *
     * @param consumer 对象属性设值方法
     * @param p        参数
     * @param <P>      参数泛型
     * @return 当前builder实例
     */
    public <P> BuilderUtil<T> with(BiConsumer<T, P> consumer, P p) {
        consumers.add(instance -> consumer.accept(instance, p));
        return this;
    }

    /**
     * 生成对象
     *
     * @return 对象实例
     */
    public T build() {
        T t = createInstance.get();
        for (Consumer<T> consumer : consumers) {
            consumer.accept(t);
        }
        return t;
    }

}

使用

     Test user = BuilderUtil.create(Test::new)
                .with(Test::setName, "John")
                .with(Test::setItem1, "Doe")
                .build();

策略模式

抽象类

//父类
public abstract class CustomService {

    public abstract Boolean isDoSharing();

}



//子类
@Service("b_test")
public class TestService extends CustomService {

    @Override
    public Boolean isDoSharing() {
        return null;
    }
}


//使用
    @Autowired
    private Map<String, CustomService> customServiceMap;

    public void test() {
        Boolean bTest = customServiceMap.get("b_test").isDoSharing();
    }

接口

//接口
public interface CustomService {
    
    Boolean isDoSharing();

}



//实现
@Service("b_test")
public class TestService implements CustomService {


    @Override
    public Boolean isDoSharing() {
        return null;
    }
}


//使用
    @Autowired
    private Map<String, CustomService> customServiceMap;

    public void test() {
        Boolean bTest = customServiceMap.get("b_test").isDoSharing();
    }

模板方法模式

//模板类
public abstract class CustomService {

    /***
     * 创建模板
     * @return 结果
     */
    public String make() {
        doSharing();
        createMysqlTable();
        batchInsertMysql();
        return "调用成功！";
    }


    public abstract void doSharing();

    public abstract void createMysqlTable();

    public abstract void batchInsertMysql();

}

//实现类
@Service("b_test")
public class TestService extends CustomService {


    @Override
    public void doSharing() {

    }

    @Override
    public void createMysqlTable() {

    }

    @Override
    public void batchInsertMysql() {

    }
}

//使用
    public void test() {
        TestService testService = new TestService();
        String make = testService.make();
    }

观察者模式

import java.util.ArrayList;
import java.util.List;

// 主题接口
interface Subject {
    void registerObserver(Observer observer);
    void removeObserver(Observer observer);
    void notifyObservers();
}

// 观察者接口
interface Observer {
    void update(String message);
}

// 具体主题实现
class ConcreteSubject implements Subject {
    private List<Observer> observers = new ArrayList<>();

    @Override
    public void registerObserver(Observer observer) {
        observers.add(observer);
    }

    @Override
    public void removeObserver(Observer observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObservers() {
        for (Observer observer : observers) {
            observer.update("Subject's state has changed");
        }
    }

    // 主题状态改变时调用该方法
    public void stateChanged() {
        notifyObservers();
    }
}

// 具体观察者实现
class ConcreteObserver implements Observer {
    private String name;

    public ConcreteObserver(String name) {
        this.name = name;
    }

    @Override
    public void update(String message) {
        System.out.println(name + " received message: " + message);
    }
}

// 测试类
public class ObserverPatternExample {
    public static void main(String[] args) {
        ConcreteSubject subject = new ConcreteSubject();

        ConcreteObserver observer1 = new ConcreteObserver("Observer 1");
        ConcreteObserver observer2 = new ConcreteObserver("Observer 2");

        subject.registerObserver(observer1);
        subject.registerObserver(observer2);

        subject.stateChanged();
    }
}

责任链模式

// 定义处理请求的接口
interface Handler {
    void handleRequest(int request);
    void setNextHandler(Handler nextHandler);
}

// 具体处理请求的类
class ConcreteHandler implements Handler {
    private Handler nextHandler;

    @Override
    public void handleRequest(int request) {
        if (request >= 0 && request < 10) {
            System.out.println("ConcreteHandler 处理请求：" + request);
        } else if (nextHandler != null) {
            nextHandler.handleRequest(request);
        }
    }

    @Override
    public void setNextHandler(Handler nextHandler) {
        this.nextHandler = nextHandler;
    }
}

// 客户端代码
public class Client {
    public static void main(String[] args) {
        Handler handler1 = new ConcreteHandler();
        Handler handler2 = new ConcreteHandler();
        handler1.setNextHandler(handler2);

        handler1.handleRequest(5);
        handler1.handleRequest(15);
    }
}

代理模式

import java.lang.reflect.Proxy;

public class ProxyUtil {
    public static <T> T createProxy(Class<T> interfaceClass, T target) {
        return (T) Proxy.newProxyInstance(target.getClass().getClassLoader(),
                new Class[]{interfaceClass},
                (proxy, method, args) -> {
                    System.out.println("动态代理执行前操作");
                    Object result = method.invoke(target, args);
                    System.out.println("动态代理执行后操作");
                    return result;
                });
    }

    public static void main(String[] args) {
        Subject realSubject = new RealSubject();
        Subject proxy = ProxyUtil.createProxy(Subject.class, realSubject);
        proxy.doSomething();
    }
}