Android Hawk数据库的源码解析，Github开源项目，基于SharedPreferences的的存储框架

今天看了朋友一个项目用到了Hawk，然后写了这边文章

一、了解一下概念

Android Hawk数据库github开源项目 Hawk是一个非常便捷的数据库.操作数据库只需一行代码,能存任何数据类型.
相信大家应该很熟悉SharedPreferences。它是一种轻量级的存储简单配置信息的存储机制，以key-value的形式保存数据。本文介绍就是基于SharedPreferences的的存储框架，是由Orhan Obut大神写的，它是Secure，simple key-value storage for Android。安全简单的Android存储工具。

这里附上Orhan Obut大神的Github 地址 https://github.com/orhanobut

二、用法

1.添加依赖

  compile 'com.orhanobut:hawk:2.0.1'

2.初始化

      Hawk.init(this).build();

这两步就可以正常使用了，那就看一下API吧

<T> :Saves any type including any collection, primitive values or custom objects任何数据类型（）
存数据
public static <T> boolean put(String key, T value) {return hawkFacade.put(key, value);}取数据public static <T> T get(String key) {return hawkFacade.get(key);}
总数量public static long count() {return hawkFacade.count();}删除全部数据public static boolean deleteAll() {return hawkFacade.deleteAll();}删除某个数据public static boolean delete(String key) {return hawkFacade.delete(key);}是否包含有某个的数据public static boolean contains(String key) {return hawkFacade.contains(key);}
来验证如果准备使用。如果正确地初始化和建造@return真实。否则错误。public static boolean isBuilt() {return hawkFacade.isBuilt();}public static void destroy() {hawkFacade.destroy();}

下面是在官网图片让我们看看它是怎么工作的

看图片一目了然左边的PUT方法中，是把T value 存储到Disk当中。大致流程是，先将数据进行toString的转换，接下来是加密，然后进行序列化，最后是存储，用的就是SharePreference的存储。获取数据时就正好逆过来啦。

三、源码解析开始啦

先看看初始化的代码

   Hawk.init(this).build();

     /*** This will init the hawk without password protection.** @param context is used to instantiate context based objects.*                ApplicationContext will be used*/public static HawkBuilder init(Context context) {HawkUtils.checkNull("Context", context);hawkFacade = null;return new HawkBuilder(context);}static void build(HawkBuilder hawkBuilder) {hawkFacade = new DefaultHawkFacade(hawkBuilder);}

初始化中创建了HawkBuilder对象，下面如下代码

 public HawkBuilder(Context context) {HawkUtils.checkNull("Context", context);this.context = context.getApplicationContext();}public void build() {Hawk.build(this);}

其中也用到了 HawkUtils，看一下代码
这个工具类就是对数据的判空处理

final class HawkUtils {private HawkUtils() {//no instance}public static void checkNull(String message, Object value) {if (value == null) {throw new NullPointerException(message + " should not be null");}}public static void checkNullOrEmpty(String message, String value) {if (isEmpty(value)) {throw new NullPointerException(message + " should not be null or empty");}}public static boolean isEmpty(String text) {return text == null || text.trim().length() == 0;}
}

上面有个最重的没有看完 DefaultHawkFacade
先看一下源码吧

public DefaultHawkFacade(HawkBuilder builder) {encryption = builder.getEncryption();storage = builder.getStorage();converter = builder.getConverter();serializer = builder.getSerializer();logInterceptor = builder.getLogInterceptor();logInterceptor.onLog("Hawk.init -> Encryption : " + encryption.getClass().getSimpleName());}@Override public <T> boolean put(String key, T value) {// ValidateHawkUtils.checkNull("Key", key);log("Hawk.put -> key: " + key + ", value: " + value);// If the value is null, delete itif (value == null) {log("Hawk.put -> Value is null. Any existing value will be deleted with the given key");return delete(key);}// 1. Convert to textString plainText = converter.toString(value);log("Hawk.put -> Converted to " + plainText);if (plainText == null) {log("Hawk.put -> Converter failed");return false;}// 2. Encrypt the textString cipherText = null;try {cipherText = encryption.encrypt(key, plainText);log("Hawk.put -> Encrypted to  " + cipherText);} catch (Exception e) {e.printStackTrace();}if (cipherText == null) {log("Hawk.put -> Encryption failed");return false;}// 3. Serialize the given object along with the cipher textString serializedText = serializer.serialize(cipherText, value);log("Hawk.put -> Serialized to" + serializedText);if (serializedText == null) {log("Hawk.put -> Serialization failed");return false;}// 4. Save to the storageif (storage.put(key, serializedText)) {log("Hawk.put -> Stored successfully");return true;} else {log("Hawk.put -> Store operation failed");return false;}}@Override public <T> T get(String key) {log("Hawk.get -> key: " + key);if (key == null) {log("Hawk.get -> null key, returning null value ");return null;}// 1. Get serialized text from the storageString serializedText = storage.get(key);log("Hawk.get -> Fetched from storage : " + serializedText);if (serializedText == null) {log("Hawk.get -> Fetching from storage failed");return null;}// 2. DeserializeDataInfo dataInfo = serializer.deserialize(serializedText);log("Hawk.get -> Deserialized");if (dataInfo == null) {log("Hawk.get -> Deserialization failed");return null;}// 3. DecryptString plainText = null;try {plainText = encryption.decrypt(key, dataInfo.cipherText);log("Hawk.get -> Decrypted to : " + plainText);} catch (Exception e) {log("Hawk.get -> Decrypt failed: " + e.getMessage());}if (plainText == null) {log("Hawk.get -> Decrypt failed");return null;}// 4. Convert the text to original data along with original typeT result = null;try {result = converter.fromString(plainText, dataInfo);log("Hawk.get -> Converted to : " + result);} catch (Exception e) {log("Hawk.get -> Converter failed");}return result;}@Override public <T> T get(String key, T defaultValue) {T t = get(key);if (t == null) return defaultValue;return t;}@Override public long count() {return storage.count();}@Override public boolean deleteAll() {return storage.deleteAll();}@Override public boolean delete(String key) {return storage.delete(key);}@Override public boolean contains(String key) {return storage.contains(key);}@Override public boolean isBuilt() {return true;}@Override public void destroy() {}private void log(String message) {logInterceptor.onLog(message);}
}

解析一下DefaultHawkFacade
我们存数据之前应该怎么做？？跟买东西一个道理先检查一下有没有开封，有没有用过。它这也是

验证，如果是空的删除
转换数据转成字符串 HawkConverter看一下源码

/*** Concrete implementation of encoding and decoding.* List types will be encoded/decoded by parser* Serializable types will be encoded/decoded object stream* Not serializable objects will be encoded/decoded by parser*/编码和解码的具体实现。列表类型将被解析器可序列化的编码/解码类型将编码/解码对象流可序列化的对象不会被解析器编码/解码;
final class HawkConverter implements Converter {private final Parser parser;public HawkConverter(Parser parser) {if (parser == null) {throw new NullPointerException("Parser should not be null");}this.parser = parser;}@Override public <T> String toString(T value) {if (value == null) {return null;}return parser.toJson(value);}@SuppressWarnings("unchecked")@Override public <T> T fromString(String value, DataInfo info) throws Exception {if (value == null) {return null;}HawkUtils.checkNull("data info", info);Class<?> keyType = info.keyClazz;Class<?> valueType = info.valueClazz;switch (info.dataType) {case DataInfo.TYPE_OBJECT:return toObject(value, keyType);case DataInfo.TYPE_LIST:return toList(value, keyType);case DataInfo.TYPE_MAP:return toMap(value, keyType, valueType);case DataInfo.TYPE_SET:return toSet(value, keyType);default:return null;}}private <T> T toObject(String json, Class<?> type) throws Exception {return parser.fromJson(json, type);}@SuppressWarnings("unchecked")private <T> T toList(String json, Class<?> type) throws Exception {if (type == null) {return (T) new ArrayList<>();}List<T> list = parser.fromJson(json,new TypeToken<List<T>>() {}.getType());int size = list.size();for (int i = 0; i < size; i++) {list.set(i, (T) parser.fromJson(parser.toJson(list.get(i)), type));}return (T) list;}@SuppressWarnings("unchecked")private <T> T toSet(String json, Class<?> type) throws Exception {Set<T> resultSet = new HashSet<>();if (type == null) {return (T) resultSet;}Set<T> set = parser.fromJson(json, new TypeToken<Set<T>>() {}.getType());for (T t : set) {String valueJson = parser.toJson(t);T value = parser.fromJson(valueJson, type);resultSet.add(value);}return (T) resultSet;}@SuppressWarnings("unchecked")private <K, V, T> T toMap(String json, Class<?> keyType, Class<?> valueType) throws Exception {Map<K, V> resultMap = new HashMap<>();if (keyType == null || valueType == null) {return (T) resultMap;}Map<K, V> map = parser.fromJson(json, new TypeToken<Map<K, V>>() {}.getType());for (Map.Entry<K, V> entry : map.entrySet()) {String keyJson = parser.toJson(entry.getKey());K k = parser.fromJson(keyJson, keyType);String valueJson = parser.toJson(entry.getValue());V v = parser.fromJson(valueJson, valueType);resultMap.put(k, v);}return (T) resultMap;}

加密这里用到的是脸书的加密
先是成是字节数组，然后进行Base64编码得到字符串数据。

       class ConcealEncryption implements Encryption {private final Crypto crypto;public ConcealEncryption(Context context) {SharedPrefsBackedKeyChain keyChain = new SharedPrefsBackedKeyChain(context, CryptoConfig.KEY_256);crypto = AndroidConceal.get().createDefaultCrypto(keyChain);}@Override public boolean init() {return crypto.isAvailable();}@Override public String encrypt(String key, String plainText) throws Exception {Entity entity = Entity.create(key);byte[] bytes = crypto.encrypt(plainText.getBytes(), entity);return Base64.encodeToString(bytes, Base64.NO_WRAP);}@Override public String decrypt(String key, String cipherText) throws Exception {Entity entity = Entity.create(key);byte[] decodedBytes = Base64.decode(cipherText, Base64.NO_WRAP);byte[] bytes = crypto.decrypt(decodedBytes, entity);return new String(bytes);}

4.序列化 HawkSerializer
运用反射获取原数据的数据类型。是List，map，set还是对象，根据不同类型保存不同数据。返回字符串类型的值，这个值是原始key的类型，原始数据的类型，数据类型和密文的拼接，这样就可以存储啦。

class HawkSerializer implements Serializer {private static final char DELIMITER = '@';private static final String INFO_DELIMITER = "#";private static final char NEW_VERSION = 'V';private final LogInterceptor logInterceptor;HawkSerializer(LogInterceptor logInterceptor) {this.logInterceptor = logInterceptor;}@Override public <T> String serialize(String cipherText, T originalGivenValue) {HawkUtils.checkNullOrEmpty("Cipher text", cipherText);HawkUtils.checkNull("Value", originalGivenValue);String keyClassName = "";String valueClassName = "";char dataType;if (List.class.isAssignableFrom(originalGivenValue.getClass())) {List<?> list = (List<?>) originalGivenValue;if (!list.isEmpty()) {keyClassName = list.get(0).getClass().getName();}dataType = DataInfo.TYPE_LIST;} else if (Map.class.isAssignableFrom(originalGivenValue.getClass())) {dataType = DataInfo.TYPE_MAP;Map<?, ?> map = (Map) originalGivenValue;if (!map.isEmpty()) {for (Map.Entry<?, ?> entry : map.entrySet()) {keyClassName = entry.getKey().getClass().getName();valueClassName = entry.getValue().getClass().getName();break;}}} else if (Set.class.isAssignableFrom(originalGivenValue.getClass())) {Set<?> set = (Set<?>) originalGivenValue;if (!set.isEmpty()) {Iterator<?> iterator = set.iterator();if (iterator.hasNext()) {keyClassName = iterator.next().getClass().getName();}}dataType = DataInfo.TYPE_SET;} else {dataType = DataInfo.TYPE_OBJECT;keyClassName = originalGivenValue.getClass().getName();}return keyClassName + INFO_DELIMITER +valueClassName + INFO_DELIMITER +dataType + NEW_VERSION + DELIMITER +cipherText;}@Override public DataInfo deserialize(String serializedText) {String[] infos = serializedText.split(INFO_DELIMITER);char type = infos[2].charAt(0);// if it is collection, no need to create the class objectClass<?> keyClazz = null;String firstElement = infos[0];if (firstElement != null && firstElement.length() != 0) {try {keyClazz = Class.forName(firstElement);} catch (ClassNotFoundException e) {logInterceptor.onLog("HawkSerializer -> " + e.getMessage());}}Class<?> valueClazz = null;String secondElement = infos[1];if (secondElement != null && secondElement.length() != 0) {try {valueClazz = Class.forName(secondElement);} catch (ClassNotFoundException e) {logInterceptor.onLog("HawkSerializer -> " + e.getMessage());}}

终于到最后一步了，那就是存数据了
Hawk给出的默认存储实现是SharedPreferenceStorage。从类名都可以看出，其实就是用SharedPreferences来存储数据。这里就不多说啦。毕竟SharedPreferences用法很简单。

final class SharedPreferencesStorage implements Storage {private final SharedPreferences preferences;SharedPreferencesStorage(Context context, String tag) {preferences = context.getSharedPreferences(tag, Context.MODE_PRIVATE);}SharedPreferencesStorage(SharedPreferences preferences) {this.preferences = preferences;}@Override public <T> boolean put(String key, T value) {HawkUtils.checkNull("key", key);return getEditor().putString(key, String.valueOf(value)).commit();}@SuppressWarnings("unchecked")@Override public <T> T get(String key) {return (T) preferences.getString(key, null);}@Override public boolean delete(String key) {return getEditor().remove(key).commit();}@Override public boolean contains(String key) {return preferences.contains(key);}@Override public boolean deleteAll() {return getEditor().clear().commit();}@Override public long count() {return preferences.getAll().size();}private SharedPreferences.Editor getEditor() {return preferences.edit();}}

  **存储数据put的源码就分析到这里，总结下其实就是开始那幅图显示的，把数据转换成字符串，加密，序列化，存储四个步骤搞定。获取数据get就是put过程反过来，没什么好说的了。至于其他的方法，delete(),deleteAll(),contains(),count()其实都是运用SharedPreferences在打交道。 Hawk存储的源码已经很清晰了。在分析中我们也提到了，有些实现是已经给出的默认实现，其实我们也可以根据需求来定义响应的接口实现。**

Hawk.init(context).setEncryption(new NoEncryption()).setLogInterceptor(new MyLogInterceptor()).setConverter(new MyConverter()).setParser(new MyParser()).setStorage(new MyStorage()).build();

HawkBuilder中还有一些API是供开发者自定义的

public HawkBuilder setStorage(Storage storage) {this.cryptoStorage = storage;return this;}public HawkBuilder setParser(Parser parser) {this.parser = parser;return this;}public HawkBuilder setSerializer(Serializer serializer) {this.serializer = serializer;return this;}public HawkBuilder setLogInterceptor(LogInterceptor logInterceptor) {this.logInterceptor = logInterceptor;return this;}public HawkBuilder setConverter(Converter converter) {this.converter = converter;return this;}public HawkBuilder setEncryption(Encryption encryption) {this.encryption = encryption;return this;}

看完代码也正如Orhan Obut大神说的
Secure, simple key-value storage for android 安全、简单的Android存储工具
有什么写的不好的地方可以在评论区评论