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需求
使用GreenDao数据库进行数据的存储。
介绍
GreenDao 是一个轻量级的对象关系映射（ORM）库，用于简化 Android 应用中的数据库操作。它提供了以下主要功能：
简化数据库操作：通过注解定义实体类，GreenDao 自动生成 DAO（数据访问对象）类，简化了数据库的增、删、改、查操作。
高性能：GreenDao 设计目标之一是高效地执行数据库操作，尤其在处理大量数据时表现出色。
自动生成代码：通过编译时生成代码，减少了手动编写 SQL 和数据处理逻辑的需要。
事务支持：支持数据库事务，确保数据操作的原子性和一致性。
灵活性：可以通过自定义查询和批量操作，满足复杂的数据处理需求。
小巧：库体积小，适合需要轻量级 ORM 的应用。
集成
在 build.gradle 文件中添加 GreenDao 依赖：
implementation 'org.greenrobot:greendao:3.3.0'
配置 build.gradle 以生成 DAO 类。添加插件和配置：
apply plugin: 'org.greenrobot.greendao'greendao {schemaVersion 1 //定义数据库的版本号，用于处理数据库升级。daoPackage 'com.example.dao' //指定生成的 DAO 类包名。targetGenDir 'src/main/java' //指定生成的实体类包名。
}
使用
创建实体类：
使用 GreenDao 提供的注解定义实体类。举例：
@Entity
public class UpdateBean{@Id(autoincrement = true)private Long id;private String name;// getters and setters
}创建实体类之后，使用Build重新构建一下项目，然后会自动生成相关文件
【DaoMaster】【DaoSession】【UpdateBeanDao】
创建一个帮助类 【UpdateOpenHelper】
public class UpdateOpenHelper extends DaoMaster.OpenHelper {public UpdateOpenHelper(Context context, String name) {super(context, name);}public UpdateOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {super(context, name, factory);}@Overridepublic void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {DaoMaster.dropAllTables(wrap(db), true);}@Overridepublic void onUpgrade(Database db, int oldVersion, int newVersion) {super.onUpgrade(db, oldVersion, newVersion);}
}
创建一个管理类【UpdateManager 】
public class UpdateManager {private Context mContext;private static UpdateManager manager = new UpdateManager();private static ConcurrentHashMap<String, DaoMaster> masterMap = new ConcurrentHashMap<>();private static ConcurrentHashMap<String, DaoSession> daoSessionMap = new ConcurrentHashMap<>();private static ConcurrentHashMap<String, UpdateOpenHelper> helperMap = new ConcurrentHashMap<>();public static UpdateManager getInstance() {return manager;}public void init(Context context) {this.mContext = context;}private DaoMaster getDaoMaster(String dbName) {if (!masterMap.containsKey(dbName)) {UpdateOpenHelper openHelper = helperMap.get(dbName);if (openHelper == null) {UGDaoContext daoContext = new UGDaoContext(mContext);openHelper = new UpdateOpenHelper(daoContext, dbName, null);helperMap.put(dbName, openHelper);}DaoMaster master;try {master = new DaoMaster(openHelper.getWritableDatabase());masterMap.put(dbName, master);} catch (Exception e) {e.printStackTrace();}}return masterMap.get(dbName);}public DaoSession getDaoSession(String dbName) {if (!daoSessionMap.containsKey(dbName)) {DaoMaster master = getDaoMaster(dbName);if (master != null) {DaoSession session = master.newSession();daoSessionMap.put(dbName, session);}}return daoSessionMap.get(dbName);}/*** 关闭指定数据库连接** @param dbName 数据库名字*/public void closeConnection(String dbName) {DaoSession session = daoSessionMap.get(dbName);if (session != null) {session.clear();daoSessionMap.remove(dbName);}DaoMaster master = masterMap.get(dbName);if (master != null) {master = null;masterMap.remove(dbName);}UpdateOpenHelper helper = helperMap.get(dbName);if (helper != null) {helper.close();helperMap.remove(dbName);}}/*** 关闭所有数据库连接*/public void closeAllConnection() {// 关闭所有DaoSessionssynchronized (this) {for (String dbName : daoSessionMap.keySet()) {closeConnection(dbName); // 关闭每一个连接}// 额外步骤：清理所有映射daoSessionMap.clear();masterMap.clear();helperMap.clear();}}}
还有需要修改数据库的文件的存储路径，GreenDao数据库默认的存储路径是在应用内部私有存储，所以如果删除了应用之后，数据文件也会被删除，同时也不利于外部查找数据库文件。
创建【UGDaoContext】修改数据库文件地址
public class UGDaoContext extends ContextWrapper {public UGDaoContext(Context base) {super(base);}@Overridepublic File getDatabasePath(String name) {String dbDir;boolean isExistSDCar = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);if (isExistSDCar) {dbDir = Environment.getExternalStorageDirectory().getAbsolutePath();} else {dbDir = Environment.getDataDirectory().getAbsolutePath();}String dbDirPath = dbDir + File.separator + "app_dao" + File.separator + "data_update";Log.d("TAG", "数据库的文件夹地址：" + dbDirPath);File dbDirFile = new File(dbDirPath);if (!dbDirFile.exists()) {dbDirFile.mkdirs();}String dbNamePath = dbDirPath + File.separator + name;File dbNameFile = new File(dbNamePath);boolean isSuccess = false;if (!dbNameFile.exists()) {try {isSuccess = dbNameFile.createNewFile();} catch (IOException e) {e.printStackTrace();}} else {isSuccess = true;}if (isSuccess) {Log.d("TAG", "数据库的文件地址：" + dbNamePath);return dbNameFile;} else {return super.getDatabasePath(name);}}@Overridepublic SQLiteDatabase openOrCreateDatabase(String name, int mode, SQLiteDatabase.CursorFactory factory) {return SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name), null);}@Overridepublic SQLiteDatabase openOrCreateDatabase(String name, int mode, SQLiteDatabase.CursorFactory factory, DatabaseErrorHandler errorHandler) {return SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name), null);}
}
接下里再创建一个工具类实现对数据库的操作【UpdateDaoUtil】
public class UpdateDaoUtil {private UpdateManager manager;public UpdateDaoUtil(Context context) {manager = UpdateManager.getInstance();manager.init(context);}/*** 完成UpdateBean记录的插入*/public synchronized boolean insertUpdate(UpdateBean updateBean, String dbName) {boolean flag = false;if (manager.getDaoSession(dbName).getUpdateBeanDao().insert(updateBean) != -1) {flag = true;}return flag;}/*** 完成UpdateBean记录的插入*/public synchronized boolean insertUpdate(UpdateBean updateBean) {boolean flag = false;if (manager.getDaoSession(getCurrentDBName()).getUpdateBeanDao().insert(updateBean) != -1) {flag = true;}return flag;}/*** 完成UpdateBean列表记录的插入*/public synchronized boolean insertUpdate(List<UpdateBean> list) {int frequency = 0;UpdateBeanDao dao = manager.getDaoSession(getCurrentDBName()).getUpdateBeanDao();for (UpdateBean updateBean : list) {if (dao.insert(updateBean) == -1) {frequency++;}}return frequency == 0;}/*** 删除单条记录*/public synchronized boolean deleteUpdateBean(UpdateBean updateBean, String dbName) {boolean flag = false;try {manager.getDaoSession(dbName).delete(updateBean);flag = true;} catch (Exception e) {e.printStackTrace();}return flag;}/*** 删除单条记录*/public synchronized boolean deleteUpdateBean(UpdateBean updateBean) {boolean flag = false;try {manager.getDaoSession(getCurrentDBName()).delete(updateBean);flag = true;} catch (Exception e) {e.printStackTrace();}return flag;}/*** 删除所有记录*/public synchronized boolean deleteAll(String dbname) {boolean flag = false;try {manager.getDaoSession(dbname).deleteAll(UpdateBean.class);flag = true;} catch (Exception e) {e.printStackTrace();}return flag;}/*** 删除所有记录*/public synchronized boolean deleteAll() {boolean flag = false;try {manager.getDaoSession(getCurrentDBName()).deleteAll(UpdateBean.class);flag = true;} catch (Exception e) {e.printStackTrace();}return flag;}/*** 查询数据库前 number 条数据*/public synchronized List<UpdateBean> queryDataNumber(int number, String dbname) {QueryBuilder<UpdateBean> queryBuilder = manager.getDaoSession(dbname).queryBuilder(UpdateBean.class);return queryBuilder.limit(number).list();}/*** 查询数据库前 number 条数据*/public synchronized List<UpdateBean> queryDataNumber(int number) {QueryBuilder<UpdateBean> queryBuilder = manager.getDaoSession(getCurrentDBName()).queryBuilder(UpdateBean.class);return queryBuilder.limit(number).list();}/*** 删除数据库前 number 条数据*/public synchronized void deleteDataNumber(int number, String dbname) {UpdateBeanDao dao = manager.getDaoSession(dbname).getUpdateBeanDao();List<UpdateBean> lists = dao.queryBuilder().limit(number).list();dao.deleteInTx(lists);}/*** 删除数据库前 number 条数据*/public synchronized void deleteDataNumber(int number) {UpdateBeanDao dao = manager.getDaoSession(getCurrentDBName()).getUpdateBeanDao();List<UpdateBean> lists = dao.queryBuilder().limit(number).list();dao.deleteInTx(lists);}/*** 查询所有记录*/public synchronized List<UpdateBean> queryAll(String dbName) {return manager.getDaoSession(dbName).loadAll(UpdateBean.class);}/*** 查询所有记录*/public synchronized List<UpdateBean> queryAll() {return manager.getDaoSession(getCurrentDBName()).loadAll(UpdateBean.class);}/*** 使用指定名称的数据库,每次查询200条未上传的数据** @param dbname 数据库表名称*/public synchronized List<UpdateBean> queryListUpdate(String dbname) {QueryBuilder<UpdateBean> queryBuilder = manager.getDaoSession(dbname).queryBuilder(UpdateBean.class);return queryBuilder.where(UpdateBeanDao.Properties.IsUpdate.eq(0)).limit(200).list();}/*** 更新是否上传状态** @param list 上传数据的ID的list*/public synchronized void updateStatus(List<Long> list) {DaoSession daoSession = manager.getDaoSession(getCurrentDBName());UpdateBeanDao updateBeanDao = daoSession.getUpdateBeanDao();try {daoSession.runInTx(() -> {for (Long id : list) {UpdateBean bean = updateBeanDao.load(id);if (bean != null) {bean.setIsUpdate(1);updateBeanDao.update(bean);}}});} catch (Exception e) {e.printStackTrace();}}/*** 更新是否上传状态** @param dbName 数据库表名字* @param list 上传数据的ID的list*/public synchronized void updateStatus(String dbName, List<Long> list) {DaoSession daoSession = manager.getDaoSession(dbName);UpdateBeanDao updateBeanDao = daoSession.getUpdateBeanDao();try {daoSession.runInTx(() -> {for (Long id : list) {UpdateBean bean = updateBeanDao.load(id);if (bean != null) {bean.setIsUpdate(1);updateBeanDao.update(bean);}}});} catch (Exception e) {e.printStackTrace();}}/*** 使用queryBuilder进行查询未上传的数据*/public synchronized List<UpdateBean> queryItemByQueryBuilder(int isUpdate) {QueryBuilder<UpdateBean> queryBuilder = manager.getDaoSession(getCurrentDBName()).queryBuilder(UpdateBean.class);return queryBuilder.where(UpdateBeanDao.Properties.IsUpdate.eq(isUpdate)).limit(100).list();}/*** 关闭当前日期资源*/public synchronized void close() {manager.closeConnection(getCurrentDBName());}/*** 关闭特定名字的数据资源*/public synchronized void close(String dbName) {manager.closeConnection(dbName);}/*** 关闭所有连接*/public synchronized void closeAll() {manager.closeAllConnection();}/*** 数据表的名称是当天的日期** @return 当天日期*/private static String getCurrentDateFormatted() {long currentTimeMillis = System.currentTimeMillis();Date date = new Date(currentTimeMillis);SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd", Locale.getDefault());return sdf.format(date);}/*** 获取当天数据库表的名称*/private static String getCurrentDBName() {return getCurrentDateFormatted() + "_db";}/*** 组装数据库名字** @param dateTime 日期时间 例如 20240814*/public static String setDBName(String dateTime) {return dateTime + "_db";}
}
这样基本上一个数据库就创建了，剩下就是如何使用了。
UpdateDaoUtil updateDaoUtil;
updateDaoUtil = new UpdateDaoUtil(this);
if (updateDaoUtil != null) {Log.i("TAG", "将List数据存入本地数据库,存入条数 " + updateBeanList.size());List<UpdateBean> list = new ArrayList<>(updateBeanList);boolean update = updateDaoUtil.insertUpdate(list);if (update) {Log.i("TAG", "数据存入数据库正常");}}
记得销毁
@Overrideprotected void onDestroy() {super.onDestroy();if (updateDaoUtil != null) {updateDaoUtil.closeAll();}}GreenDao数据库的基本使用方式就是这样了。