代理模式

public interface IDBQuery {
    String request();
}

public class DBQuery implements IDBQuery {
    public DBQuery() {
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    @Override
    public String request() {
        return "request string";
    }
}

/**
 * 代理模式用于实现延时加载，有效提升系统的启动速度
 */
public class DBQueryProxy implements IDBQuery {
    private DBQuery query = null;
    @Override
    public String request() {
        if (query==null){
            query = new DBQuery();
        }
        return query.request();
    }

    public static void main(String[] args){
        IDBQuery proxy = new DBQueryProxy();
        String request = proxy.request();//使用时才创建真实对象
        System.out.println(request);
    }
}

转载于:https://www.cnblogs.com/fly-book/p/11413022.html