GreenDao深入使用
16lz
2021-01-24
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http://blog.csdn.net/u011071427/article/details/54574171
本文出自Allen李的博客
GrenDao的深入使用
在本文中将会讲解一些使用GreenDao的FAQ
混淆
### greenDAO 3-keepclassmembers class * extends org.greenrobot.greendao.AbstractDao {public static java.lang.String TABLENAME;}-keep class **$Properties# If you do not use SQLCipher:-dontwarn org.greenrobot.greendao.database.**# If you do not use RxJava:-dontwarn rx.**### greenDAO 2-keepclassmembers class * extends de.greenrobot.dao.AbstractDao {public static java.lang.String TABLENAME;}-keep class **$PropertiesGreenDao修改生成目录
//目录设置sourceSets { main { java.srcDirs = ['src/main/java', 'src/main/greendao'] jniLibs.srcDirs=['./libs'] }}//GreenDao设置greendao{ targetGenDir 'src/main/greendao' daoPackage 'com.greendao' schemaVersion 1}数据库升级
GreenDao数据库现在唯一不好的可能就是升级数据库了。
1.先看DaoMaster生成的代码。
/** WARNING: Drops all table on Upgrade! Use only during development. */public static class DevOpenHelper extends OpenHelper { public DevOpenHelper(Context context, String name) { super(context, name); } public DevOpenHelper(Context context, String name, CursorFactory factory) { super(context, name, factory); } @Override public void onUpgrade(Database db, int oldVersion, int newVersion) { Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables"); dropAllTables(db, true); onCreate(db); }}2.如果自定义的SqliteOpenHelper是继承自DevOpenHelper，那么在升级数据的时候会把所有表删除掉，然后创建新的表。
这种方式进行升级数据库，会照成原始数据的缺失，所以实际情况中是不运行出现这种升级方式的，这种方式使用于测试期，也就是版本未上线期间。
那么如果我们要进行数据库的保留数据升级，我们应该怎么做呢?
1.首先我们需要重写onUpgrade方法，那么先自定义SqliteOpenHeler.
public class MySqlLiteOpenHelper extends DaoMaster.OpenHelper{ public MySqlLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) { super(context, name, factory); } @Override public void onUpgrade(Database db, int oldVersion, int newVersion) { Log.i("greendao","oldVersion:"+oldVersion+",newVersion"+newVersion); switch (oldVersion){ case 1: db.execSQL("SQL语句"); break; case 2: db.execSQL("SQL语句"); break; case 3: db.execSQL("SQL语句"); break; ………… } }}2.以前确实是这么写的，数据库的升级也的确是这么搞的，但是当项目上线以后，数据库庞大，迭代版本次数多，每一次迭代，都需要升级数据库，Swith语句越来越庞大。我们该怎么办呢？
3.先提供思路给大家参考（PS：不是标准答案）。
（1）首先创建临时表（数据格式和原表一模一样）。
（2）把当前表的数据插入到临时表中去。
（3）删除掉原表，创建新表。
（4）把临时表数据插入到新表中去，然后删除临时表。
在这样基础上，可以保留原数据进行升级数据库。
4.本着拿来主义，因为国外大牛已经有对这些进行封装，所以直接把代码贴出来了
public class MigrationHelper { private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION = "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS"; private static MigrationHelper instance; public static MigrationHelper getInstance() { if (instance == null) { instance = new MigrationHelper(); } return instance; } private static List getColumns(Database db, String tableName) { List columns = new ArrayList<>(); Cursor cursor = null; try { cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null); if (cursor != null) { columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames())); } } catch (Exception e) { Log.v(tableName, e.getMessage(), e); e.printStackTrace(); } finally { if (cursor != null) cursor.close(); } return columns; } public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) { generateTempTables(db, daoClasses); DaoMaster.dropAllTables(db, true); DaoMaster.createAllTables(db, false); restoreData(db, daoClasses); } private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) { for (int i = 0; i < daoClasses.length; i++) { DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]); String divider = ""; String tableName = daoConfig.tablename; String tempTableName = daoConfig.tablename.concat("_TEMP"); ArrayList properties = new ArrayList<>(); StringBuilder createTableStringBuilder = new StringBuilder(); createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" ("); for (int j = 0; j < daoConfig.properties.length; j++) { String columnName = daoConfig.properties[j].columnName; if (getColumns(db, tableName).contains(columnName)) { properties.add(columnName); String type = null; try { type = getTypeByClass(daoConfig.properties[j].type); } catch (Exception exception) { exception.printStackTrace(); } createTableStringBuilder.append(divider).append(columnName).append(" ").append(type); if (daoConfig.properties[j].primaryKey) { createTableStringBuilder.append(" PRIMARY KEY"); } divider = ","; } } createTableStringBuilder.append(");"); Log.i("lxq", "创建临时表的SQL语句： " + createTableStringBuilder.toString()); db.execSQL(createTableStringBuilder.toString()); StringBuilder insertTableStringBuilder = new StringBuilder(); insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" ("); insertTableStringBuilder.append(TextUtils.join(",", properties)); insertTableStringBuilder.append(") SELECT "); insertTableStringBuilder.append(TextUtils.join(",", properties)); insertTableStringBuilder.append(" FROM ").append(tableName).append(";"); Log.i("lxq", "在临时表插入数据的SQL语句：" + insertTableStringBuilder.toString()); db.execSQL(insertTableStringBuilder.toString()); } } private 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"); ArrayList properties = new ArrayList(); ArrayList propertiesQuery = new ArrayList(); for (int j = 0; j < daoConfig.properties.length; j++) { String columnName = daoConfig.properties[j].columnName; if (getColumns(db, tempTableName).contains(columnName)) { properties.add(columnName); propertiesQuery.add(columnName); } else { try { if (getTypeByClass(daoConfig.properties[j].type).equals("INTEGER")) { propertiesQuery.add("0 as " + columnName); properties.add(columnName); } } catch (Exception e) { e.printStackTrace(); } } } StringBuilder insertTableStringBuilder = new StringBuilder(); insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" ("); insertTableStringBuilder.append(TextUtils.join(",", properties)); insertTableStringBuilder.append(") SELECT "); insertTableStringBuilder.append(TextUtils.join(",", propertiesQuery)); insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";"); StringBuilder dropTableStringBuilder = new StringBuilder(); dropTableStringBuilder.append("DROP TABLE ").append(tempTableName); Log.i("lxq", "插入正式表的SQL语句：" + insertTableStringBuilder.toString()); Log.i("lxq", "销毁临时表的SQL语句：" + dropTableStringBuilder.toString()); db.execSQL(insertTableStringBuilder.toString()); db.execSQL(dropTableStringBuilder.toString()); } } private String getTypeByClass(Class<?> type) throws Exception { if (type.equals(String.class)) { return "TEXT"; } if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class) || type.equals(int.class)) { return "INTEGER"; } if (type.equals(Boolean.class) || type.equals(boolean.class)) { return "BOOLEAN"; } Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString())); exception.printStackTrace(); throw exception; }} 5.使用以上工具类的时候，onUpgrade方法就变成以下这么简单了。
public class MySqlLiteOpenHelper extends DaoMaster.OpenHelper{ public MySqlLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) { super(context, name, factory); } @Override public void onUpgrade(Database db, int oldVersion, int newVersion) { Log.i("lxq","oldVersion:"+oldVersion+",newVersion"+newVersion); MigrationHelper.getInstance().migrate(db,UserDao.class); }}6.使用注意：要把为了不忘记某些XXDao.class,最好把所有的XXDao.class丢进去。
GreenDao的封装
GreenDao的简单二次封装
public class DaoManager { private static String DB_NAME = "test.db"; private static DaoManager mDaoManager; private static MySqlLiteOpenHelper mySqlLiteOpenHelper; private static DaoSession mDaoSession; private static Database mDatabase; private DaoManager() {} public static DaoManager getInstance(){ if (mDaoManager == null){ synchronized (DaoManager.class){ if (mDaoManager == null){ mDaoManager = new DaoManager(); } } } return mDaoManager; } public static void init(Context context){ mySqlLiteOpenHelper = new MySqlLiteOpenHelper(context,DB_NAME,null); mDatabase = mySqlLiteOpenHelper.getWritableDb(); mDaoSession = new DaoMaster(mDatabase).newSession(); } public DaoSession getDaoSession(){ return mDaoSession; }}这个管理类中，我把DaoSession给暴漏出来，然后可以通过DaoSession获取XXDao，然后进行操作数据库。下面可以看我的例子：
public class UserDaoManagr implements IDao { private DaoSession mDaoSession = DaoManager.getInstance().getDaoSession(); @Override public boolean insert(User user) { return mDaoSession.getUserDao() .insert(user) > 0 ? true : false; } @Override public boolean delete(User user) { try { mDaoSession.getUserDao() .delete(user); } catch (Exception e) { Log.e("lxq", "删除失败"); return false; } return true; } @Override public boolean update(User user) { try { mDaoSession.getUserDao() .update(user); } catch (Exception e) { Log.e("lxq", "更新失败"); return false; } return true; } @Override public List queryAll() { return mDaoSession.getUserDao() .loadAll(); } @Override public User queryById(long id) { return mDaoSession.getUserDao() .loadByRowId(id); } @Override public List queryByObj(String where, String... params) { return mDaoSession.getUserDao() .queryRaw(where, params); } public User queryByName(String name) { return mDaoSession.getUserDao() .queryBuilder() .where(UserDao.Properties.Name.eq(name)) .build() .unique(); }} 要想使用DaoManager，别忘记在Application中初始化。
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