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1. APP開發(fā)期間的數(shù)據(jù)庫(kù)

在上一篇文章中封裝了GreenDaoManager中有個(gè)構(gòu)造方法如下:

private GreenDaoManager(){
        if (mInstance == null) {
//            DaoMaster.DevOpenHelper devOpenHelper = new
//                    DaoMaster.DevOpenHelper(MyApplication.getContext(), "database_name", null);//此處openhelper為自動(dòng)生成開發(fā)所使用，發(fā)布版本需自定義
            MySQLiteOpenHelper devOpenHelper = new
                    MySQLiteOpenHelper(new GreenDaoContext(), "database_name.db", null);//GreenDaoContext為創(chuàng)建數(shù)據(jù)庫(kù)路徑使用
            mDaoMaster = new DaoMaster(devOpenHelper.getWritableDatabase());
            mDaoSession = mDaoMaster.newSession();
        }
    }

其中注釋掉的兩行代碼中：

DaoMaster.DevOpenHelper devOpenHelper = new
DaoMaster.DevOpenHelper(MyApplication.getContext(), "database_name", null);//此處DevOpenHelper 為自動(dòng)生成開發(fā)所使用，發(fā)布版本需自定義

其中的MyApplication.getContext()上下文表示了數(shù)據(jù)庫(kù)存儲(chǔ)路徑為手機(jī)內(nèi)存。這里的DevOpenHelper即為DaoMaster中自動(dòng)生成代碼，完整代碼如下：

/** * WARNING: Drops all table on Upgrade! Use only during development. */
public static class DevOpenHelper extends OpenHelper {    
  public DevOpenHelper(Context context, String name, CursorFactory factory) {
             super(context, name, factory);    
  }    
  @Override    
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {            
        Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");        
        dropAllTables(db, true);        
        onCreate(db);    
  }
}

注意看第一行注釋：WARNING: Drops all table on Upgrade! Use only during development.
數(shù)據(jù)庫(kù)升級(jí)的話，會(huì)刪除所有表,然后重新創(chuàng)建。這種方式在開發(fā)期間，APP還沒有上線之前是可以的。

當(dāng)APP上線后，我們不能使用這種方式，因?yàn)檫@樣會(huì)導(dǎo)致已經(jīng)存在的數(shù)據(jù)會(huì)被刪除。

2. APP上線后,數(shù)據(jù)庫(kù)升級(jí)

我們需要重寫一個(gè)類MySQLiteOpenHelper實(shí)現(xiàn)OpenHelper.

需要自己實(shí)現(xiàn)了onUpgrade方法來自定義升級(jí)過程。
當(dāng)然升級(jí)過程中也要修改DaoMaster.SCHEMA_VERSION
當(dāng)DaoMaster.SCHEMA_VERSION跟你當(dāng)前數(shù)據(jù)庫(kù)的版本比較后,會(huì)根據(jù)你當(dāng)前數(shù)據(jù)庫(kù)的版本，然后進(jìn)行升級(jí)。
關(guān)鍵代碼onUpgrade方法,會(huì)比較新數(shù)據(jù)庫(kù)和舊數(shù)據(jù)庫(kù)的版本,然后執(zhí)行相應(yīng)的sql升級(jí)：

public class MySQLiteOpenHelper extends DaoMaster.OpenHelper  {
    public MySQLiteOpenHelper(Context context, String name) {
        super(context, name);
    }

    public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
        super(context, name, factory);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //數(shù)據(jù)遷移模塊
        MigrationHelper.migrate(db,
                UserDao.class,
                ProfessionDao.class,
                LTestDao.class);
    }
}

數(shù)據(jù)庫(kù)升級(jí)不外乎兩種情況：
　 1.修改表結(jié)構(gòu)。
　 2.添加新表。

針對(duì)onUpgrade中的實(shí)現(xiàn)方法可以采用兩種不同策略:（稍后都會(huì)提供兩種策略的代碼實(shí)現(xiàn)，下面主要講述第二種數(shù)據(jù)遷移實(shí)現(xiàn)方式）
　1.逐級(jí)版本迭代升級(jí)，比如當(dāng)前版本為1，最新版本為3，此方案就是先從1-->2-->3.
　2.把數(shù)據(jù)庫(kù)中的數(shù)據(jù)備份，然后全刪數(shù)據(jù)庫(kù)，再重新創(chuàng)建新的數(shù)據(jù)庫(kù)，把備份數(shù)據(jù)導(dǎo)入。此方案直接從１-->3。

3. 數(shù)據(jù)遷移（數(shù)據(jù)庫(kù)備份）的具體實(shí)現(xiàn)

android上面對(duì)的數(shù)據(jù)庫(kù)基本上就是輕量級(jí)數(shù)據(jù)庫(kù)sqlite,首先我們需要了解一些后面需要用到的數(shù)據(jù)庫(kù)操作語句：

判斷sqlite表是否存在
SELECT * FROM sqlite_master WHERE type='table' AND name='tempTableName';
sqlite判斷臨時(shí)表是否存在
SELECT * FROM sqlite_temp_master WHERE type='table' AND name='tempTableName';
sqlite創(chuàng)建表tableName的臨時(shí)表
create temporary table tempTableName as select * from tableName;
刪除臨時(shí)表
drop table tempTableName;

sqlite的系統(tǒng)表sqlite_master、臨時(shí)表sqlite_temp_master
SQLite數(shù)據(jù)庫(kù)中一個(gè)特殊的名叫 SQLITE_MASTER上執(zhí)行一個(gè)SELECT查詢以獲得所有表的索引。每一個(gè) SQLite 數(shù)據(jù)庫(kù)都有一個(gè)叫 SQLITE_MASTER的表，它定義數(shù)據(jù)庫(kù)的模式。 SQLITE_MASTER表看起來如下：

CREATE TABLE sqlite_master ( 
type TEXT, 
name TEXT, 
tbl_name TEXT, 
rootpage INTEGER, 
sql TEXT 
);

type 字段永遠(yuǎn)是 ‘table’，name 字段永遠(yuǎn)是對(duì)應(yīng)表的名字。所以，要獲得數(shù)據(jù)庫(kù)中所有表的列表，使用下列SELECT語句：

SELECT name FROM sqlite_master 
WHERE type=’table’ 
ORDER BY name;

對(duì)于索引，type 等于 ‘index’, name 則是索引的名字，tbl_name 是該索引所屬的表的名字。不管是表還是索引，sql 字段是原先用 CREATE TABLE 或 CREATE INDEX 語句創(chuàng)建它們時(shí)的命令文本。對(duì)于自動(dòng)創(chuàng)建的索引（用來實(shí)現(xiàn) PRIMARY KEY 或 UNIQUE 約束），sql字段為NULL。
SQLITE_MASTER 表是只讀的。不能對(duì)它使用 UPDATE、INSERT 或 DELETE。它會(huì)被 CREATE TABLE、CREATE INDEX、DROP TABLE 和 DROP INDEX 命令自動(dòng)更新。
臨時(shí)表及其索引和觸發(fā)器存放在另外一個(gè)叫 SQLITE_TEMP_MASTER 的表中。SQLITE_TEMP_MASTER 跟 SQLITE_MASTER 差不多，但它只是對(duì)于創(chuàng)建那些臨時(shí)表的應(yīng)用可見。如果要獲得所有表的列表，不管是永久的還是臨時(shí)的，可以使用類似下面的命令：

SELECT name FROM 
(SELECT * FROM sqlite_master UNION ALL 
SELECT * FROM sqlite_temp_master) 
WHERE type=’table’ 
ORDER BY name

數(shù)據(jù)遷移的工具類MigrationHelper。
public final class MigrationHelper {
public static boolean DEBUG = true;
private static String TAG = "MigrationHelper";
private static final String SQLITE_MASTER = "sqlite_master";
private static final String SQLITE_TEMP_MASTER = "sqlite_temp_master";
public static void migrate(SQLiteDatabase db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
Database database = new StandardDatabase(db);

   printLog("【The Old Database Version】" + db.getVersion());
   printLog("【Generate temp table】start");
   generateTempTables(database, daoClasses);
   printLog("【Generate temp table】complete");

   dropAllTables(database, true, daoClasses);
   createAllTables(database, false, daoClasses);

   printLog("【Restore data】start");
   restoreData(database, daoClasses);
   printLog("【Restore data】complete");
 }
 private static void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses)   {
   for (int i = 0; i < daoClasses.length; i++) {
     String tempTableName = null;

     DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
     String tableName = daoConfig.tablename;
     if (!isTableExists(db, false, tableName)) {//不存在系統(tǒng)表中，表明是新增表，不需要?jiǎng)?chuàng)建臨時(shí)表
         printLog("【New Table】" + tableName);
         continue;
     }
     try {
         tempTableName = daoConfig.tablename.concat("_TEMP");
         StringBuilder dropTableStringBuilder = new StringBuilder();
         dropTableStringBuilder.append("DROP TABLE IF EXISTS ").append(tempTableName).append(";");
         db.execSQL(dropTableStringBuilder.toString());

         StringBuilder insertTableStringBuilder = new StringBuilder();
         insertTableStringBuilder.append("CREATE TEMPORARY TABLE ").append(tempTableName);
         insertTableStringBuilder.append(" AS SELECT * FROM ").append(tableName).append(";");
         db.execSQL(insertTableStringBuilder.toString());
         printLog("【Table】" + tableName +"\n ---Columns-->"+getColumnsStr(daoConfig));
         printLog("【Generate temp table】" + tempTableName);
     } catch (SQLException e) {
         Log.e(TAG, "【Failed to generate temp table】" + tempTableName, e);
     }
  }
 }

private static boolean isTableExists(Database db, boolean isTemp, String tableName) {
 if (db == null || TextUtils.isEmpty(tableName)) {
     return false;
 }
 String dbName = isTemp ? SQLITE_TEMP_MASTER : SQLITE_MASTER;
 String sql = "SELECT COUNT(*) FROM " + dbName + " WHERE type = ? AND name = ?";
 Cursor cursor=null;
 int count = 0;
 try {
     cursor = db.rawQuery(sql, new String[]{"table", tableName});
     if (cursor == null || !cursor.moveToFirst()) {
         return false;
     }
     count = cursor.getInt(0);
 } catch (Exception e) {
     e.printStackTrace();
 } finally {
     if (cursor != null)
         cursor.close();
 }
 return count > 0;
}
private static String getColumnsStr(DaoConfig daoConfig) {
 if (daoConfig == null) {
     return "no columns";
 }
 StringBuilder builder = new StringBuilder();
 for (int i = 0; i < daoConfig.allColumns.length; i++) {
     builder.append(daoConfig.allColumns[i]);
     builder.append(",");
 }
 if (builder.length() > 0) {
     builder.deleteCharAt(builder.length() - 1);
 }
 return builder.toString();
}
 private static void dropAllTables(Database db, boolean ifExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {
 reflectMethod(db, "dropTable", ifExists, daoClasses);
 printLog("【Drop all table】");
  }
  private static void createAllTables(Database db, boolean ifNotExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {
 reflectMethod(db, "createTable", ifNotExists, daoClasses);
 printLog("【Create all table】");
 }
 /**
  * dao class already define the sql exec method, so just invoke it
  */
 private static void reflectMethod(Database db, String methodName, boolean isExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {
 if (daoClasses.length < 1) {
     return;
 }
 try {
     for (Class cls : daoClasses) {
         Method method = cls.getDeclaredMethod(methodName, Database.class, boolean.class);
         method.invoke(null, db, isExists);
     }
 } catch (NoSuchMethodException e) {
     e.printStackTrace();
 } catch (InvocationTargetException e) {
     e.printStackTrace();
 } catch (IllegalAccessException e) {
     e.printStackTrace();
 }
}
private static void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
 for (int i = 0; i < daoClasses.length; i++) {
     DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
     String tableName = daoConfig.tablename;
     String tempTableName = daoConfig.tablename.concat("_TEMP");

     if (!isTableExists(db, true, tempTableName)) {
         continue;
     }

     try {
         // get all columns from tempTable, take careful to use the columns list
         List<String> columns = getColumns(db, tempTableName);
         ArrayList<String> properties = new ArrayList<>(columns.size());
         for (int j = 0; j < daoConfig.properties.length; j++) {
             String columnName = daoConfig.properties[j].columnName;
             if (columns.contains(columnName)) {
                 properties.add(columnName);
             }
         }
         if (properties.size() > 0) {
             final String columnSQL = TextUtils.join(",", properties);

             StringBuilder insertTableStringBuilder = new StringBuilder();
             insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
             insertTableStringBuilder.append(columnSQL);
             insertTableStringBuilder.append(") SELECT ");
             insertTableStringBuilder.append(columnSQL);
             insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");
             db.execSQL(insertTableStringBuilder.toString());
             printLog("【Restore data】 to " + tableName);
         }
         StringBuilder dropTableStringBuilder = new StringBuilder();
         dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);
         db.execSQL(dropTableStringBuilder.toString());
         printLog("【Drop temp table】" + tempTableName);
     } catch (SQLException e) {
         Log.e(TAG, "【Failed to restore data from temp table 】" + tempTableName, e);
     }
 }
}
private static List<String> getColumns(Database db, String tableName) {
 List<String> columns = null;
 Cursor cursor = null;
 try {
     cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 0", null);
     if (null != cursor && cursor.getColumnCount() > 0) {
         columns = Arrays.asList(cursor.getColumnNames());
     }
 } catch (Exception e) {
     e.printStackTrace();
 } finally {
     if (cursor != null)
         cursor.close();
     if (null == columns)
         columns = new ArrayList<>();
 }
 return columns;
}
private static void printLog(String info){
 if(DEBUG){
     Log.d(TAG, info);
 }
}
}

4. 設(shè)置數(shù)據(jù)庫(kù)路徑

在第一模塊中有句代碼：
MySQLiteOpenHelper devOpenHelper = new MySQLiteOpenHelper(new GreenDaoContext(), "database_name.db", null);//GreenDaoContext為創(chuàng)建數(shù)據(jù)庫(kù)路徑使用
里面有個(gè)上下文GreenDaoContext繼承了ContextWrapper,里面設(shè)置了數(shù)據(jù)庫(kù)路徑，代碼如下：

public class GreenDaoContext  extends ContextWrapper {

    private String currentUserId = "greendao";//一般用來針對(duì)一個(gè)用戶一個(gè)數(shù)據(jù)庫(kù)，以免數(shù)據(jù)混亂問題
    private Context mContext;

    public GreenDaoContext() {
        super(MyApplication.getContext());
        this.mContext = MyApplication.getContext();
//        this.currentUserId = "greendao";//初始化
    }

    /**
     * 獲得數(shù)據(jù)庫(kù)路徑，如果不存在，則創(chuàng)建對(duì)象
     *
     * @param dbName
     */
    @Override
    public File getDatabasePath(String dbName) {
        String dbDir = CommonUtils.getDBPath();
        if (TextUtils.isEmpty(dbDir)){
            Log.e("SD卡管理：", "SD卡不存在，請(qǐng)加載SD卡");
            return null;
        }
        File baseFile = new File(dbDir);
        // 目錄不存在則自動(dòng)創(chuàng)建目錄
        if (!baseFile.exists()){
            baseFile.mkdirs();
        }
        StringBuffer buffer = new StringBuffer();
        buffer.append(baseFile.getPath());
        buffer.append(File.separator);
        buffer.append(currentUserId);
        dbDir = buffer.toString();// 數(shù)據(jù)庫(kù)所在目錄
        buffer.append(File.separator);
//        buffer.append(dbName+"_"+currentUserId);//也可以采用此種方式，將用戶id與表名聯(lián)系到一塊命名
        buffer.append(dbName);
        String dbPath = buffer.toString();// 數(shù)據(jù)庫(kù)路徑
        // 判斷目錄是否存在，不存在則創(chuàng)建該目錄
        File dirFile = new File(dbDir);
        if (!dirFile.exists()){
            dirFile.mkdirs();
        }
        // 數(shù)據(jù)庫(kù)文件是否創(chuàng)建成功
        boolean isFileCreateSuccess = false;
        // 判斷文件是否存在，不存在則創(chuàng)建該文件
        File dbFile = new File(dbPath);
        if (!dbFile.exists()) {
            try {
                isFileCreateSuccess = dbFile.createNewFile();// 創(chuàng)建文件
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else
            isFileCreateSuccess = true;
        // 返回?cái)?shù)據(jù)庫(kù)文件對(duì)象
        if (isFileCreateSuccess)
            return dbFile;
        else
            return super.getDatabasePath(dbName);
    }

    /**
     * 重載這個(gè)方法，是用來打開SD卡上的數(shù)據(jù)庫(kù)的，android 2.3及以下會(huì)調(diào)用這個(gè)方法。
     *
     * @param name
     * @param mode
     * @param factory
     */
    @Override
    public SQLiteDatabase openOrCreateDatabase(String name, int mode,
                                               SQLiteDatabase.CursorFactory factory) {
        SQLiteDatabase result = SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name), factory);
        return result;
    }

    /**
     * Android 4.0會(huì)調(diào)用此方法獲取數(shù)據(jù)庫(kù)。
     *
     * @param name
     * @param mode
     * @param factory
     * @param errorHandler
     * @see android.content.ContextWrapper#openOrCreateDatabase(java.lang.String, int,
     * android.database.sqlite.SQLiteDatabase.CursorFactory,
     * android.database.DatabaseErrorHandler)
     */
    @Override
    public SQLiteDatabase openOrCreateDatabase(String name, int mode, SQLiteDatabase.CursorFactory factory,
                                               DatabaseErrorHandler errorHandler) {
        SQLiteDatabase result = SQLiteDatabase.openOrCreateDatabase(getDatabasePath(name), factory);

        return result;
    }

}

OK，先到這了。。。
源碼奉上，自行參考

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GreenDao設(shè)置數(shù)據(jù)庫(kù)路徑以及數(shù)據(jù)庫(kù)升級(jí)

GreenDao設(shè)置數(shù)據(jù)庫(kù)路徑以及數(shù)據(jù)庫(kù)升級(jí)

1. APP開發(fā)期間的數(shù)據(jù)庫(kù)

2. APP上線后,數(shù)據(jù)庫(kù)升級(jí)

3. 數(shù)據(jù)遷移（數(shù)據(jù)庫(kù)備份）的具體實(shí)現(xiàn)

4. 設(shè)置數(shù)據(jù)庫(kù)路徑

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容

色偷偷精品伊人,欧洲久久精品,欧美综合婷婷骚逼,国产AV主播,国产最新探花在线,九色在线视频一区,伊人大交九 欧美,1769亚洲,黄色成人av

GreenDao設(shè)置數(shù)據(jù)庫(kù)路徑以及數(shù)據(jù)庫(kù)升級(jí)

1. APP開發(fā)期間的數(shù)據(jù)庫(kù)

2. APP上線后,數(shù)據(jù)庫(kù)升級(jí)

3. 數(shù)據(jù)遷移（數(shù)據(jù)庫(kù)備份）的具體實(shí)現(xiàn)

4. 設(shè)置數(shù)據(jù)庫(kù)路徑

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容

色偷偷精品伊人,欧洲久久精品,欧美综合婷婷骚逼,国产AV主播,国产最新探花在线,九色在线视频一区,伊人大交九欧美,1769亚洲,黄色成人av