Android中在使用OkHttp这个库的时候。有时候须要持久化Cookie，那么怎么实现呢。OkHttp的内部源代码过于复杂，不进行深究。这里仅仅看当中的HttpEngineer里面的部分源代码，在发起请求以及请求结束都会调用这个类的几个方法。
我们先看networkRequest方法。在里面通过client.getCookieHandler()函数获得了CookieHandler对象。通过该对象拿到cookie并设置到请求头里，请求结束后取得响应后通过networkResponse.headers()函数将请求头获得传入receiveHeaders函数，并将取得的cookie存入getCookieHandler得到的一个CookieHandler对象中去
/**
* Populates request with defaults and cookies.
*
* <p>This client doesn't specify a default {@code Accept} header because it
* doesn't know what content types the application is interested in.
*/
private Request networkRequest(Request request) throws IOException {
Request.Builder result = request.newBuilder();
//此处省略n行代码......
CookieHandler cookieHandler = client.getCookieHandler();
if (cookieHandler != null) {
// Capture the request headers added so far so that they can be offered to the CookieHandler.
// This is mostly to stay close to the RI; it is unlikely any of the headers above would
// affect cookie choice besides "Host".
Map<String, List<String>> headers = OkHeaders.toMultimap(result.build().headers(), null);
Map<String, List<String>> cookies = cookieHandler.get(request.uri(), headers);
// Add any new cookies to the request.
OkHeaders.addCookies(result, cookies);
}
//此处省略n行代码......
return result.build();
}public void readResponse() throws IOException {
//此处省略n行代码......
receiveHeaders(networkResponse.headers());
//此处省略n行代码......
}public void receiveHeaders(Headers headers) throws IOException {
CookieHandler cookieHandler = client.getCookieHandler();
if (cookieHandler != null) {
cookieHandler.put(userRequest.uri(), OkHeaders.toMultimap(headers, null));
}
}而这个CookieHandler对象是OkHttpClient类中的一个属性，提供了getter和setter方法，默认的构造函数OkHttpClient client = new OkHttpClient();不会创建这个CookieHandler对象。如果我们传入了这个对象。那么OkHttp自然会进行cookie的自己主动管理了。
private CookieHandler cookieHandler;
public OkHttpClient setCookieHandler(CookieHandler cookieHandler) {
this.cookieHandler = cookieHandler;
return this;
}
public CookieHandler getCookieHandler() {
return cookieHandler;
}那么如果我们将CookieHandler对象传入
OkHttpClient client = new OkHttpClient();
client.setCookieHandler(CookieHandler cookieHanlder);那么，如今关键是怎样去实现这个CookieHandler 对象。CookieManager是CookieHandler 的一个子类，其构造函数 public CookieManager(CookieStore store, CookiePolicy cookiePolicy)须要传入两个參数，CookieStore 是一个接口，因此我们实现CookieStore接口中的抽象方法。就可以实现这个CookieHandler 对象。
參考android-async-http这个库，它具有cookie的自己主动管理功能。主要我们參考当中的两个类
參考以上两个类并做适当改动，得到了例如以下两个类，他们的功能就是将cookie保持在SharedPreferences中。
package com.kltz88.okhttp.cookie;
/**
* User:lizhangqu(513163535@qq.com)
* Date:2015-07-13
* Time: 17:31
*/
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.net.HttpCookie;
public class SerializableHttpCookie implements Serializable {
private static final long serialVersionUID = 6374381323722046732L;
private transient final HttpCookie cookie;
private transient HttpCookie clientCookie;
public SerializableHttpCookie(HttpCookie cookie) {
this.cookie = cookie;
}
public HttpCookie getCookie() {
HttpCookie bestCookie = cookie;
if (clientCookie != null) {
bestCookie = clientCookie;
}
return bestCookie;
}
private void writeObject(ObjectOutputStream out) throws IOException {
out.writeObject(cookie.getName());
out.writeObject(cookie.getValue());
out.writeObject(cookie.getComment());
out.writeObject(cookie.getCommentURL());
out.writeObject(cookie.getDomain());
out.writeLong(cookie.getMaxAge());
out.writeObject(cookie.getPath());
out.writeObject(cookie.getPortlist());
out.writeInt(cookie.getVersion());
out.writeBoolean(cookie.getSecure());
out.writeBoolean(cookie.getDiscard());
}
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
String name = (String) in.readObject();
String value = (String) in.readObject();
clientCookie = new HttpCookie(name, value);
clientCookie.setComment((String) in.readObject());
clientCookie.setCommentURL((String) in.readObject());
clientCookie.setDomain((String) in.readObject());
clientCookie.setMaxAge(in.readLong());
clientCookie.setPath((String) in.readObject());
clientCookie.setPortlist((String) in.readObject());
clientCookie.setVersion(in.readInt());
clientCookie.setSecure(in.readBoolean());
clientCookie.setDiscard(in.readBoolean());
}
}package com.kltz88.okhttp.cookie;
/**
* User:lizhangqu(513163535@qq.com)
* Date:2015-07-13
* Time: 17:31
*/
import android.content.Context;
import android.content.SharedPreferences;
import android.text.TextUtils;
import android.util.Log;
import java.io.*;
import java.net.CookieStore;
import java.net.HttpCookie;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
/**
* A persistent cookie store which implements the Apache HttpClient CookieStore interface.
* Cookies are stored and will persist on the user's device between application sessions since they
* are serialized and stored in SharedPreferences. Instances of this class are
* designed to be used with AsyncHttpClient#setCookieStore, but can also be used with a
* regular old apache HttpClient/HttpContext if you prefer.
*/
public class PersistentCookieStore implements CookieStore {
private static final String LOG_TAG = "PersistentCookieStore";
private static final String COOKIE_PREFS = "CookiePrefsFile";
private static final String COOKIE_NAME_PREFIX = "cookie_";
private final HashMap<String, ConcurrentHashMap<String, HttpCookie>> cookies;
private final SharedPreferences cookiePrefs;
/**
* Construct a persistent cookie store.
*
* @param context Context to attach cookie store to
*/
public PersistentCookieStore(Context context) {
cookiePrefs = context.getSharedPreferences(COOKIE_PREFS, 0);
cookies = new HashMap<String, ConcurrentHashMap<String, HttpCookie>>();
// Load any previously stored cookies into the store
Map<String, ?> prefsMap = cookiePrefs.getAll();
for(Map.Entry<String, ?> entry : prefsMap.entrySet()) {
if (((String)entry.getValue()) != null && !((String)entry.getValue()).startsWith(COOKIE_NAME_PREFIX)) {
String[] cookieNames = TextUtils.split((String)entry.getValue(), ",");
for (String name : cookieNames) {
String encodedCookie = cookiePrefs.getString(COOKIE_NAME_PREFIX + name, null);
if (encodedCookie != null) {
HttpCookie decodedCookie = decodeCookie(encodedCookie);
if (decodedCookie != null) {
if(!cookies.containsKey(entry.getKey()))
cookies.put(entry.getKey(), new ConcurrentHashMap<String, HttpCookie>());
cookies.get(entry.getKey()).put(name, decodedCookie);
}
}
}
}
}
}
@Override
public void add(URI uri, HttpCookie cookie) {
String name = getCookieToken(uri, cookie);
// Save cookie into local store, or remove if expired
if (!cookie.hasExpired()) {
if(!cookies.containsKey(uri.getHost()))
cookies.put(uri.getHost(), new ConcurrentHashMap<String, HttpCookie>());
cookies.get(uri.getHost()).put(name, cookie);
} else {
if(cookies.containsKey(uri.toString()))
cookies.get(uri.getHost()).remove(name);
}
// Save cookie into persistent store
SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
prefsWriter.putString(uri.getHost(), TextUtils.join(",", cookies.get(uri.getHost()).keySet()));
prefsWriter.putString(COOKIE_NAME_PREFIX + name, encodeCookie(new SerializableHttpCookie(cookie)));
prefsWriter.commit();
}
protected String getCookieToken(URI uri, HttpCookie cookie) {
return cookie.getName() + cookie.getDomain();
}
@Override
public List<HttpCookie> get(URI uri) {
ArrayList<HttpCookie> ret = new ArrayList<HttpCookie>();
if(cookies.containsKey(uri.getHost()))
ret.addAll(cookies.get(uri.getHost()).values());
return ret;
}
@Override
public boolean removeAll() {
SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
prefsWriter.clear();
prefsWriter.commit();
cookies.clear();
return true;
}
@Override
public boolean remove(URI uri, HttpCookie cookie) {
String name = getCookieToken(uri, cookie);
if(cookies.containsKey(uri.getHost()) && cookies.get(uri.getHost()).containsKey(name)) {
cookies.get(uri.getHost()).remove(name);
SharedPreferences.Editor prefsWriter = cookiePrefs.edit();
if(cookiePrefs.contains(COOKIE_NAME_PREFIX + name)) {
prefsWriter.remove(COOKIE_NAME_PREFIX + name);
}
prefsWriter.putString(uri.getHost(), TextUtils.join(",", cookies.get(uri.getHost()).keySet()));
prefsWriter.commit();
return true;
} else {
return false;
}
}
@Override
public List<HttpCookie> getCookies() {
ArrayList<HttpCookie> ret = new ArrayList<HttpCookie>();
for (String key : cookies.keySet())
ret.addAll(cookies.get(key).values());
return ret;
}
@Override
public List<URI> getURIs() {
ArrayList<URI> ret = new ArrayList<URI>();
for (String key : cookies.keySet())
try {
ret.add(new URI(key));
} catch (URISyntaxException e) {
e.printStackTrace();
}
return ret;
}
/**
* Serializes Cookie object into String
*
* @param cookie cookie to be encoded, can be null
* @return cookie encoded as String
*/
protected String encodeCookie(SerializableHttpCookie 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());
}
/**
* Returns cookie decoded from cookie string
*
* @param cookieString string of cookie as returned from http request
* @return decoded cookie or null if exception occured
*/
protected HttpCookie decodeCookie(String cookieString) {
byte[] bytes = hexStringToByteArray(cookieString);
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
HttpCookie cookie = null;
try {
ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
cookie = ((SerializableHttpCookie) objectInputStream.readObject()).getCookie();
} catch (IOException e) {
Log.d(LOG_TAG, "IOException in decodeCookie", e);
} catch (ClassNotFoundException e) {
Log.d(LOG_TAG, "ClassNotFoundException in decodeCookie", e);
}
return cookie;
}
/**
* Using some super basic byte array <-> hex conversions so we don't have to rely on any
* large Base64 libraries. Can be overridden if you like!
*
* @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);
}
/**
* Converts hex values from strings to byte arra
*
* @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;
}
}
使用的时候。在发起请求前对CookieHandler进行设置，兴许的cookie全都是自己主动管理，无需你关心cookie的保存于读取
OkHttpClient client = new OkHttpClient();
client.setCookieHandler(new CookieManager(
new PersistentCookieStore(getApplicationContext()),
CookiePolicy.ACCEPT_ALL));这样，实现模拟登录，抓取一些数据就方便非常多了。再也不用手动处理cookie了。