记录一下寄几的greendao数据库升级
之前使用的greendao数据库存储服务器所有的历史推送消息，但是后来消息需要加几个新的字段
举个栗子，比如要新增红色框住的字段到数据库中：
本仙女作为一只思想成熟的菜鸡,当然是加了字段就赶紧重新往里存，然后就一通报错android.database.sqlite.SQLiteException: no such column: T.XXX (code 1): , while compiling...
然后发现，原来是数据库没升级
好的
升级方法：
①.将新增的字段加入需要存储的bean类；
②.数据库版本号上升一个版本（我之前的version是1，升级改为2）
③.修改getDaoMaster()方法，原先是调用greendao里自动生成的
现在改成自己重写的helper类里的方法，是介锅样子的
相关代码了解一下
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; } public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) { generateTempTables(db, daoClasses); DaoMaster.dropAllTables(db, true); DaoMaster.createAllTables(db, false); restoreData(db, daoClasses); } /** * 生成临时列表 * * @param db * @param 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<String> 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(");"); 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(";"); db.execSQL(insertTableStringBuilder.toString()); } } /** * 存储新的数据库表 以及数据 * * @param db * @param daoClasses */ 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<String> properties = 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); } } StringBuilder insertTableStringBuilder = new StringBuilder(); insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" ("); insertTableStringBuilder.append(TextUtils.join(",", properties)); insertTableStringBuilder.append(") SELECT "); insertTableStringBuilder.append(TextUtils.join(",", properties)); insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";"); StringBuilder dropTableStringBuilder = new StringBuilder(); dropTableStringBuilder.append("DROP TABLE ").append(tempTableName); 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)) { return "INTEGER"; } if (type.equals(Boolean.class)) { return "BOOLEAN"; } Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString())); exception.printStackTrace(); throw exception; } private List<String> getColumns(Database db, String tableName) { List<String> 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 class MyOpenHelper extends DaoMaster.OpenHelper { public MyOpenHelper(Context context, String name) { super(context, name); } public MyOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) { super(context, name, factory); } /** * 数据库升级 */ @Override public void onUpgrade(Database db, int oldVersion, int newVersion) { //操作数据库的更新 有几个表升级都可以传入到下面 MigrationHelper.getInstance().migrate(db, MyBeanDao.class); } }
public class DbManager { // 是否加密 public static final boolean ENCRYPTED = true; private static final String DB_NAME = "petssions.db"; private static DbManager mDbManager; private static DaoMaster.DevOpenHelper mDevOpenHelper; private static DaoMaster mDaoMaster; private static DaoSession mDaoSession; private Context mContext; public DbManager(Context context) { this.mContext = context; // 初始化数据库信息 mDevOpenHelper = new DaoMaster.DevOpenHelper(context, DB_NAME); getDaoMaster(context); getDaoSession(context); } public static DbManager getInstance(Context context) { if (null == mDbManager) { synchronized (DbManager.class) { if (null == mDbManager) { mDbManager = new DbManager(context); } } } return mDbManager; } /** * 获取可读数据库 * * @param context * @return */ public static SQLiteDatabase getReadableDatabase(Context context) { if (null == mDevOpenHelper) { getInstance(context); } return mDevOpenHelper.getReadableDatabase(); } /** * 获取可写数据库 * * @param context * @return */ public static SQLiteDatabase getWritableDatabase(Context context) { if (null == mDevOpenHelper) { getInstance(context); } return mDevOpenHelper.getWritableDatabase(); } /** * 获取DaoMaster * * 判断是否存在数据库，如果没有则创建数据库 * @param context * @return */ public static DaoMaster getDaoMaster(Context context) { if (null == mDaoMaster) { synchronized (DbManager.class) { if (null == mDaoMaster) { MyOpenHelper helper = new MyOpenHelper(context,DB_NAME,null); mDaoMaster = new DaoMaster(helper.getWritableDatabase()); } } } return mDaoMaster; } /** * 获取DaoSession * * @param context * @return */ public static DaoSession getDaoSession(Context context) { if (null == mDaoSession) { synchronized (DbManager.class) { mDaoSession = getDaoMaster(context).newSession(); } } return mDaoSession; }
④.可以直接用DBManager里的方法获取dao类了，比如
DbManager.getDaoSession(getApplicationContext()).getBeanDao();
且原数据库中数据依旧保留。
详细代码取自 https://blog.csdn.net/huangxiaoguo1/article/details/54574713
