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模版方法

模版方法在 Java 中的实现

模版方法是一种行为设计模式 它在基类中定义了一个算法的框架 允许子类在不修改结构的情况下重写算法的特定步骤

在 Java 中使用模式

复杂度

流行度

使用示例 模版方法模式在 Java 框架中很常见 开发者通常使用它来向框架用户提供通过继承实现的 对标准功能进行扩展的简单方式

这里是一些核心 Java 程序库中模版方法的示例

识别方式 模版方法可以通过行为方法来识别 该方法已有一个在基类中定义的 默认 行为

重写算法的标准步骤

在本例中 模版方法模式定义了一个可与社交网络协作的算法 与特定社交网络相匹配的子类将根据社交网络所提供的 API 来实现这些步骤

networks

networks/Network.java: 基础社交网络类

package refactoring_guru.template_method.example.networks;

/**
 * Base class of social network.
 */
public abstract class Network {
    String userName;
    String password;

    Network() {}

    /**
     * Publish the data to whatever network.
     */
    public boolean post(String message) {
        // Authenticate before posting. Every network uses a different
        // authentication method.
        if (logIn(this.userName, this.password)) {
            // Send the post data.
            boolean result =  sendData(message.getBytes());
            logOut();
            return result;
        }
        return false;
    }

    abstract boolean logIn(String userName, String password);
    abstract boolean sendData(byte[] data);
    abstract void logOut();
}

networks/Facebook.java: 具体社交网络

package refactoring_guru.template_method.example.networks;

/**
 * Class of social network
 */
public class Facebook extends Network {
    public Facebook(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    public boolean logIn(String userName, String password) {
        System.out.println("\nChecking user's parameters");
        System.out.println("Name: " + this.userName);
        System.out.print("Password: ");
        for (int i = 0; i < this.password.length(); i++) {
            System.out.print("*");
        }
        simulateNetworkLatency();
        System.out.println("\n\nLogIn success on Facebook");
        return true;
    }

    public boolean sendData(byte[] data) {
        boolean messagePosted = true;
        if (messagePosted) {
            System.out.println("Message: '" + new String(data) + "' was posted on Facebook");
            return true;
        } else {
            return false;
        }
    }

    public void logOut() {
        System.out.println("User: '" + userName + "' was logged out from Facebook");
    }

    private void simulateNetworkLatency() {
        try {
            int i = 0;
            System.out.println();
            while (i < 10) {
                System.out.print(".");
                Thread.sleep(500);
                i++;
            }
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
    }
}

networks/Twitter.java: 另一个社交网络

package refactoring_guru.template_method.example.networks;

/**
 * Class of social network
 */
public class Twitter extends Network {

    public Twitter(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    public boolean logIn(String userName, String password) {
        System.out.println("\nChecking user's parameters");
        System.out.println("Name: " + this.userName);
        System.out.print("Password: ");
        for (int i = 0; i < this.password.length(); i++) {
            System.out.print("*");
        }
        simulateNetworkLatency();
        System.out.println("\n\nLogIn success on Twitter");
        return true;
    }

    public boolean sendData(byte[] data) {
        boolean messagePosted = true;
        if (messagePosted) {
            System.out.println("Message: '" + new String(data) + "' was posted on Twitter");
            return true;
        } else {
            return false;
        }
    }

    public void logOut() {
        System.out.println("User: '" + userName + "' was logged out from Twitter");
    }

    private void simulateNetworkLatency() {
        try {
            int i = 0;
            System.out.println();
            while (i < 10) {
                System.out.print(".");
                Thread.sleep(500);
                i++;
            }
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
    }
}

Demo.java: 客户端代码

package refactoring_guru.template_method.example;

import refactoring_guru.template_method.example.networks.Facebook;
import refactoring_guru.template_method.example.networks.Network;
import refactoring_guru.template_method.example.networks.Twitter;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Demo class. Everything comes together here.
 */
public class Demo {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        Network network = null;
        System.out.print("Input user name: ");
        String userName = reader.readLine();
        System.out.print("Input password: ");
        String password = reader.readLine();

        // Enter the message.
        System.out.print("Input message: ");
        String message = reader.readLine();

        System.out.println("\nChoose social network for posting message.\n" +
                "1 - Facebook\n" +
                "2 - Twitter");
        int choice = Integer.parseInt(reader.readLine());

        // Create proper network object and send the message.
        if (choice == 1) {
            network = new Facebook(userName, password);
        } else if (choice == 2) {
            network = new Twitter(userName, password);
        }
        network.post(message);
    }
}

OutputDemo.txt: 执行结果

Input user name: Jhonatan
Input password: qswe
Input message: Hello, World!

Choose social network for posting message.
1 - Facebook
2 - Twitter
2

Checking user's parameters
Name: Jhonatan
Password: ****
..........

LogIn success on Twitter
Message: 'Hello, World!' was posted on Twitter
User: 'Jhonatan' was logged out from Twitter

模板方法在其他编程语言中的实现

模板方法在 C# 中的实现 模板方法在 PHP 中的实现 模板方法在 Python 中的实现 模板方法在 Ruby 中的实现 模板方法在 Swift 中的实现 模板方法在 TypeScript 中的实现