OkHttp3实现Cookies持续化管理

参考：https://www.zhihu.com/question/19786827
http://www.open-open.com/lib/view/open1453422314105.html

COOKIE和SESSION 是什么？？？

1. 由于HTTP协议是无状态的协议，所以服务端需要记录用户的状态时，就需要用某种机制来识具体的用户，这个机制就是Session.典型的场景比如购物车，当你点击下单按钮时，由于HTTP协议无状态，所以并不知道是哪个用户操作的，所以服务端要为特定的用户创建了特定的Session，用于标识这个用户，并且跟踪用户，这样才知道购物车里面有几本书。这个Session是保存在服务端的，有一个唯一标识。在服务端保存Session的方法很多，内存、数据库、文件都有。集群的时候也要考虑Session的转移，在大型的网站，一般会有专门的Session服务器集群，用来保存用户会话，这个时候 Session 信息都是放在内存的，使用一些缓存服务比如Memcached之类的来放 Session。
2. 思考一下服务端如何识别特定的客户？这个时候Cookie就登场了。每次HTTP请求的时候，客户端都会发送相应的Cookie信息到服务端。实际上大多数的应用都是用 Cookie 来实现Session跟踪的，第一次创建Session的时候，服务端会在HTTP协议中告诉客户端，需要在 Cookie 里面记录一个Session ID，以后每次请求把这个会话ID发送到服务器，我就知道你是谁了。有人问，如果客户端的浏览器禁用了 Cookie 怎么办？一般这种情况下，会使用一种叫做URL重写的技术来进行会话跟踪，即每次HTTP交互，URL后面都会被附加上一个诸如 sid=xxxxx 这样的参数，服务端据此来识别用户。
   

在OkHttp3中，对cookie而言，新增了两个类 Cookiejar 、 Cookie 两个类，在了解这两个类之前，先去看一下 HttpEngine 关于cookie管理的变化

private Request networkRequest(Request request) throws IOException {
Request.Builder result = request.newBuilder();

//例行省略....

List<Cookie> cookies = client.cookieJar().loadForRequest(request.url());
if (!cookies.isEmpty()) {
  result.header("Cookie", cookieHeader(cookies));
}

//例行省略....

return result.build();
}

private String cookieHeader(List<Cookie> cookies) {
StringBuilder cookieHeader = new StringBuilder();
for (int i = 0, size = cookies.size(); i < size; i++) {
  if (i > 0) {
    cookieHeader.append("; ");
  }
  Cookie cookie = cookies.get(i);
  cookieHeader.append(cookie.name()).append('=').append(cookie.value());
}
return cookieHeader.toString();
}

public void receiveHeaders(Headers headers) throws IOException {
if (client.cookieJar() == CookieJar.NO_COOKIES) return;

List<Cookie> cookies = Cookie.parseAll(userRequest.url(), headers);
if (cookies.isEmpty()) return;

client.cookieJar().saveFromResponse(userRequest.url(), cookies);
}

通过以上几个关键方法，可以很明显的感觉到作者的意图了，为了更加自由定制化的cookie管理。其中 loadForRequest() 、 saveFromResponse() 这两个方法最为关键，分别是在发送时向request header中加入cookie，在接收时，读取response header中的

Cookies持久化
对Cookies持久化的方案，与之前版本并无很大区别，还是参考 android-async-http 这个库，主要参考其中两个类:

• PersistentCookieStore

• SerializableHttpCookie 与之前版本的区别是要将对 java.net.HttpCookie 这个类的缓存处理换成对 okhttp3.Cookie 的处理，其他方面几乎一样。

废话不多说了，直接上代码
SerializableOkHttpCookies
主要做两件事：将Cookie对象输出为ObjectStream
将ObjectStream序列化成Cookie对象

public class SerializableOkHttpCookies implements Serializable {

private transient final Cookie cookies;
private transient Cookie clientCookies;

public SerializableOkHttpCookies(Cookie cookies) {
    this.cookies = cookies;
}

public Cookie getCookies() {
    Cookie bestCookies = cookies;
    if (clientCookies != null) {
        bestCookies = clientCookies;
    }
    return bestCookies;
}

private void writeObject(ObjectOutputStream out) throws IOException {
    out.writeObject(cookies.name());
    out.writeObject(cookies.value());
    out.writeLong(cookies.expiresAt());
    out.writeObject(cookies.domain());
    out.writeObject(cookies.path());
    out.writeBoolean(cookies.secure());
    out.writeBoolean(cookies.httpOnly());
    out.writeBoolean(cookies.hostOnly());
    out.writeBoolean(cookies.persistent());
}

private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    String name = (String) in.readObject();
    String value = (String) in.readObject();
    long expiresAt = in.readLong();
    String domain = (String) in.readObject();
    String path = (String) in.readObject();
    boolean secure = in.readBoolean();
    boolean httpOnly = in.readBoolean();
    boolean hostOnly = in.readBoolean();
    boolean persistent = in.readBoolean();
    Cookie.Builder builder = new Cookie.Builder();
    builder = builder.name(name);
    builder = builder.value(value);
    builder = builder.expiresAt(expiresAt);
    builder = hostOnly ? builder.hostOnlyDomain(domain) : builder.domain(domain);
    builder = builder.path(path);
    builder = secure ? builder.secure() : builder;
    builder = httpOnly ? builder.httpOnly() : builder;
    clientCookies =builder.build();
}

}
PersistentCookieStore
根据一定的规则去缓存或者获取Cookie
SharedPreferences 存储

public class PersistentCookieStore {

private static final String LOG_TAG = "PersistentCookieStore";
private static final String COOKIE_PREFS = "Cookies_Prefs";
private final Map<String, ConcurrentHashMap<String, Cookie>> cookies;
private final SharedPreferences cookiePrefs;

public PersistentCookieStore(Context context) {
    cookiePrefs = context.getSharedPreferences(COOKIE_PREFS, 0);
    cookies = new HashMap<>();

    //将持久化的cookies缓存到内存中 即map cookies
    Map<String, ?> prefsMap = cookiePrefs.getAll();
    for (Map.Entry<String, ?> entry : prefsMap.entrySet()) {
        String[] cookieNames = TextUtils.split((String) entry.getValue(), ",");
        for (String name : cookieNames) {
            String encodedCookie = cookiePrefs.getString(name, null);
            if (encodedCookie != null) {
                Cookie decodedCookie = decodeCookie(encodedCookie);
                if (decodedCookie != null) {
                    if (!cookies.containsKey(entry.getKey())) {
                        cookies.put(entry.getKey(), new ConcurrentHashMap<String, Cookie>());
                    }
                    cookies.get(entry.getKey()).put(name, decodedCookie);
                }
            }
        }
    }
}

protected String getCookieToken(Cookie cookie) {
    return cookie.name() + "@" + cookie.domain();
}

public void add(HttpUrl url, Cookie cookie) {
    String name = getCookieToken(cookie);

    //将cookies缓存到内存中 如果缓存过期 就重置此cookie
    if (!cookie.persistent()) {
        if (!cookies.containsKey(url.host())) {
            cookies.put(url.host(), new ConcurrentHashMap<String, Cookie>());
        }
        cookies.get(url.host()).put(name, cookie);
    } else {
        if (cookies.containsKey(url.host())) {
            cookies.get(url.host()).remove(name);
        }
    }

    //讲cookies持久化到本地
    SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
    prefsWriter.putString(url.host(), TextUtils.join(",", cookies.get(url.host()).keySet()));
    prefsWriter.putString(name, encodeCookie(new SerializableOkHttpCookies(cookie)));
    prefsWriter.apply();
}

public List<Cookie> get(HttpUrl url) {
    ArrayList<Cookie> ret = new ArrayList<>();
    if (cookies.containsKey(url.host()))
        ret.addAll(cookies.get(url.host()).values());
    return ret;
}

public boolean removeAll() {
    SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
    prefsWriter.clear();
    prefsWriter.apply();
    cookies.clear();
    return true;
}

public boolean remove(HttpUrl url, Cookie cookie) {
    String name = getCookieToken(cookie);

    if (cookies.containsKey(url.host()) && cookies.get(url.host()).containsKey(name)) {
        cookies.get(url.host()).remove(name);

        SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
        if (cookiePrefs.contains(name)) {
            prefsWriter.remove(name);
        }
        prefsWriter.putString(url.host(), TextUtils.join(",", cookies.get(url.host()).keySet()));
        prefsWriter.apply();

        return true;
    } else {
        return false;
    }
}

public List<Cookie> getCookies() {
    ArrayList<Cookie> ret = new ArrayList<>();
    for (String key : cookies.keySet())
        ret.addAll(cookies.get(key).values());

    return ret;
}

/**
 * cookies 序列化成 string
 *
 * @param cookie 要序列化的cookie
 * @return 序列化之后的string
 */
protected String encodeCookie(SerializableOkHttpCookies cookie) {
    if (cookie == null)
        return null;
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    try {
        ObjectOutputStream outputStream = new ObjectOutputStream(os);
        outputStream.writeObject(cookie);
    } catch (IOException e) {
        Log.d(LOG_TAG, "IOException in encodeCookie", e);
        return null;
    }

    return byteArrayToHexString(os.toByteArray());
}

/**
 * 将字符串反序列化成cookies
 *
 * @param cookieString cookies string
 * @return cookie object
 */
protected Cookie decodeCookie(String cookieString) {
    byte[] bytes = hexStringToByteArray(cookieString);
    ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
    Cookie cookie = null;
    try {
        ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
        cookie = ((SerializableOkHttpCookies) objectInputStream.readObject()).getCookies();
    } catch (IOException e) {
        Log.d(LOG_TAG, "IOException in decodeCookie", e);
    } catch (ClassNotFoundException e) {
        Log.d(LOG_TAG, "ClassNotFoundException in decodeCookie", e);
    }

    return cookie;
}

/**
 * 二进制数组转十六进制字符串
 *
 * @param bytes byte array to be converted
 * @return string containing hex values
 */
protected String byteArrayToHexString(byte[] bytes) {
    StringBuilder sb = new StringBuilder(bytes.length * 2);
    for (byte element : bytes) {
        int v = element & 0xff;
        if (v < 16) {
            sb.append('0');
        }
        sb.append(Integer.toHexString(v));
    }
    return sb.toString().toUpperCase(Locale.US);
}

/**
 * 十六进制字符串转二进制数组
 *
 * @param hexString string of hex-encoded values
 * @return decoded byte array
 */
protected byte[] hexStringToByteArray(String hexString) {
    int len = hexString.length();
    byte[] data = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
        data[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i + 1), 16));
    }
    return data;
}

}
最终效果
完成对Cookie持久化之后，就可以对Cookiejar进行进一步修改了，最终效果：
/** * 自动管理Cookies */

private class CookiesManager implements CookieJar {

    private final PersistentCookieStore cookieStore = new PersistentCookieStore(getApplicationContext());

    @Override
    public void saveFromResponse(HttpUrl url, List<Cookie> cookies) {
        if (cookies != null && cookies.size() > 0) {
            for (Cookie item : cookies) {
                cookieStore.add(url, item);
            }
        }
    }

    @Override
    public List<Cookie> loadForRequest(HttpUrl url) {
        List<Cookie> cookies = cookieStore.get(url);
        return cookies;
    }
}

最后设置OkHttpClient
//持久化管理

Cookiebuilder.cookieJar(new CookiesManager());```