Java SPI模块化解耦的技术指南

package com.example.spi;

public interface GreetingService {
    void sayHello(String name);
}

package com.example.spi.impl;

import com.example.spi.GreetingService;

public class EnglishGreetingService implements GreetingService {
    @Override
    public void sayHello(String name) {
        System.out.println("Hello, " + name + "!");
    }
}

package com.example.spi.impl;

import com.example.spi.GreetingService;

public class ChineseGreetingService implements GreetingService {
    @Override
    public void sayHello(String name) {
        System.out.println("你好, " + name + "!");
    }
}

com.example.spi.impl.EnglishGreetingService
com.example.spi.impl.ChineseGreetingService

package com.example.spi;

import java.util.ServiceLoader;

public class SPIDemo {
    public static void main(String[] args) {
        ServiceLoader<GreetingService> services = ServiceLoader.load(GreetingService.class);
        for (GreetingService service : services) {
            service.sayHello("Java Developer");
        }
    }
}

package com.example.spi;

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

public class CustomServiceLoader<T> {

    private Class<T> service;

    public CustomServiceLoader(Class<T> service) {
        this.service = service;
    }

    public List<T> loadServices() {
        List<T> services = new ArrayList<>();
        String serviceFile = "META-INF/services/" + service.getName();
        try {
            // 从 classpath 加载配置文件
            var resources = Thread.currentThread().getContextClassLoader().getResources(serviceFile);
            while (resources.hasMoreElements()) {
                var url = resources.nextElement();
                try (var reader = new java.io.BufferedReader(new java.io.InputStreamReader(url.openStream()))) {
                    String line;
                    while ((line = reader.readLine()) != null) {
                        line = line.trim();
                        if (!line.isEmpty()) {
                            // 动态加载类
                            Class<?> clazz = Class.forName(line);
                            services.add(service.cast(clazz.getDeclaredConstructor().newInstance()));
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return services;
    }
}

package com.example.spi;

public class CustomSPIDemo {
    public static void main(String[] args) {
        CustomServiceLoader<GreetingService> loader = new CustomServiceLoader<>(GreetingService.class);
        var services = loader.loadServices();
        for (GreetingService service : services) {
            service.sayHello("Custom SPI");
        }
    }
}