Service Provider Interface

  • 在classpath下创建META-INF/services/
  • 在services文件夹下创建接口名字的文件，并在文件中添加实现的类列表
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    ServiceLoader<DriverService> serviceLoader = ServiceLoader.load(DriverService.class);
    for (DriverService ds : serviceLoader) {
        System.out.println(ds.getClass().getName());
        ds.onStartUp();
    }

源码解读

PREFIX就是定义好的文件

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public final class ServiceLoader<S>
    implements Iterable<S>
{

    private static final String PREFIX = "META-INF/services/";

configs是Enumeration<URL>类型，可以迭代

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private boolean hasNextService() {
    if (nextName != null) {
        return true;
    }
    if (configs == null) {
        try {
            String fullName = PREFIX + service.getName();
            if (loader == null)
                configs = ClassLoader.getSystemResources(fullName);
            else
                configs = loader.getResources(fullName);
        } catch (IOException x) {
            fail(service, "Error locating configuration files", x);
        }
    }
    while ((pending == null) || !pending.hasNext()) {
        if (!configs.hasMoreElements()) {
            return false;
        }
        pending = parse(service, configs.nextElement());
    }
    nextName = pending.next();
    return true;
}