Java泛型軟件工程設計

Question

我有一個RabbitQueue類，它基本上像一個隊列，並實現了我的Pollable接口。

我還有一個類SaveToDatabaseStrategy ，它實現了我的DataProcessingStrategy接口。 這是根據策略模式設計的。

現在，實現我的接口InputListener的類InputHandler包含Pollable接口的一個實例和DataProcessingStrategy接口之一。

但是，在聲明這兩個字段時，我不想設置通用類型（String），因為通用類型取決於此接口的實現，這將在以后給出。

您將如何設計？

public interface Pollable<T> {
    T poll();
}

public class RabbitQueue implements Pollable<String> {
    // code..
}

public interface DataProcessingStrategy<T> {
    void processData(T t);
}

public class SaveToDatabaseStrategy<T> implements DataProcessingStrategy<T> {

    private Repository<T, ?> repo;

    public SaveToDatabaseStrategy(Repository<T, ?> repo) {
        this.repo = repo;
    }

    @Override
    public void processData(T data) {
        repo.create(data);
        System.out.printf("Received data of type %s: %s\n", data.getClass().getSimpleName(), data);
    }
}

public interface InputListener<T> {
    void inputReceived();
    void inputReceived(T t);
}

public class InputHandler implements InputListener<String> {

    private Pollable<String> queue;
    private DataProcessingStrategy<String> strategy;

    public InputHandler(String host, String queueName) throws IOException, TimeoutException {
        queue = new RabbitQueue(host, queueName, this);
    }

    public void setStrategy(DataProcessingStrategy strategy) {
        this.strategy = strategy;
    }

    @Override
    public void inputReceived() {
        System.out.println("Input received!");
        strategy.processData(queue.poll());
    }

    @Override
    public void inputReceived(String s) {
        System.out.println("Input received: " + s + "!");
        System.out.println("> " + queue.poll());
    }
}

Answer 1

您可以將類型參數添加到InputHandler類。

public class InputHandler<T> implements InputListener<T> {

private Pollable<T> queue;
private DataProcessingStrategy<T> strategy;

public InputHandler(String host, String queueName) throws IOException, TimeoutException {
    queue = new RabbitQueue(host, queueName, this);
}

public void setStrategy(DataProcessingStrategy strategy) {
    this.strategy = strategy;
}

@Override
public void inputReceived() {
    System.out.println("Input received!");
    strategy.processData(queue.poll());
}

@Override
public void inputReceived(String s) {
    System.out.println("Input received: " + s + "!");
    System.out.println("> " + queue.poll().toString());
}
}

然后創建一個新的對象，如

new InputHandler<String>(host, queueName)