ChainDnsServer.java

package com.cheng.zenofdesignpatterns.patternpk.behavioral.observer_vs_chain.chain;

import java.util.Random;

/**
 * 抽象域名服务器
 */
public abstract class ChainDnsServer {

    // 上级DNS是谁
    private ChainDnsServer upperServer;

    // 解析域名
    public final Recorder resolve(String domain) {
        Recorder recorder = null;
        if (isLocal(domain)) { // 是本服能解析的域名
            recorder = echo(domain);
        } else { // 本服不能解析
            // 提交上级DNS进行解析
            recorder = upperServer.resolve(domain);
        }
        return recorder;
    }

    // 指向上级DNS
    public void setUpperServer(ChainDnsServer _upperServer) {
        this.upperServer = _upperServer;
    }

    // 每个DNS都有一个DNS的数据处理区（ZONE）,检查域名是否在本zone中
    protected abstract boolean isLocal(String domain);

    // 每个DNS服务器都必须实现解析任务
    protected Recorder echo(String domain) {
        Recorder recorder = new Recorder();
        //获得IP地址
        recorder.setIp(genIpAddress());
        recorder.setDomain(domain);
        return recorder;
    }

    // 随机产生一个IP地址，工具类
    protected String genIpAddress() {
        Random rand = new Random();
        String address = rand.nextInt(255) + "." + rand.nextInt(255) + "." + rand.nextInt(255) + "." + rand.nextInt(255);
        return address;
    }
}