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Services.java
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38 lines (30 loc) · 958 Bytes
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package effectivejava.chapter2;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
//不可实例化的类，用于服务注册和访问
public class Services {
private Services() {
}
// map service name to Service
private static final Map<String, Provider> providers = new ConcurrentHashMap<String, Provider>();
private static final String DEFAULT_PROVIDER_NAME = "<def>";
// provider registration API
public static void registerDefaultProvider(Provider p) {
registerProvider(DEFAULT_PROVIDER_NAME, p);
}
public static void registerProvider(String name, Provider p) {
providers.put(name, p);
}
// Service access API
public Service newInstance() {
return newInstance(DEFAULT_PROVIDER_NAME);
}
public Service newInstance(String name) {
// 通过服务提供者获得服务
Provider p = providers.get(name);
if (p == null)
throw new IllegalArgumentException("No provider registered with "
+ name);
return p.newService();
}
}