android GreenDao 数据库升级特殊字段处理

数据库 waitig 496℃ 百度已收录 0评论

greenDao数据库在改变(增加)schemaVersion 版本号后会调用onUpgrade方法,将所有的数据库都删除并重建,这就会丢失数据并影响性能。

GreenDao代码如下

  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);
        }
    }

需求:
修改成保留原始数据,
并处理特殊类型(不能为null)的字段,比如int,float,double等

新建MigrationHelper.java

public final class MigrationHelper {
    private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION = "MigrationHelper - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";

    public static boolean DEBUG = false;
    private static String TAG = "MigrationHelper";
    private static final String SQLITE_MASTER = "sqlite_master";
    private static final String SQLITE_TEMP_MASTER = "sqlite_temp_master";

    private static WeakReference<ReCreateAllTableListener> weakListener;

    public interface ReCreateAllTableListener {
        void onCreateAllTables(Database db, boolean ifNotExists);

        void onDropAllTables(Database db, boolean ifExists);
    }

    public static void migrate(SQLiteDatabase db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        printLog("【The Old Database Version】" + db.getVersion());
        Database database = new StandardDatabase(db);
        migrate(database, daoClasses);
    }

    public static void migrate(SQLiteDatabase db, ReCreateAllTableListener listener, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        weakListener = new WeakReference<>(listener);
        migrate(db, daoClasses);
    }

    public static void migrate(Database database, ReCreateAllTableListener listener, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        weakListener = new WeakReference<>(listener);
        migrate(database, daoClasses);
    }

    public static void migrate(Database database, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        printLog("【Generate temp table】start");
        generateTempTables(database, daoClasses);
        printLog("【Generate temp table】complete");

        ReCreateAllTableListener listener = weakListener.get();
        if (listener != null) {
            listener.onDropAllTables(database, true);
            printLog("【Drop all table by listener】");
            listener.onCreateAllTables(database, false);
            printLog("【Create all table by listener】");
        } else {
            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)) {
                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 by reflect】");
    }

    private static void createAllTables(Database db, boolean ifNotExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {
        reflectMethod(db, "createTable", ifNotExists, daoClasses);
        printLog("【Create all table by reflect】");
    }

    /**
     * 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> columnsTemp = getColumns(db, tempTableName);
                ArrayList<String> propertiesTemp = new ArrayList<>(columnsTemp.size() + 3);
                ArrayList<String> propertiesNew = new ArrayList<>(columnsTemp.size() + 3);
                for (int j = 0; j < daoConfig.properties.length; j++) {
                    String columnName = daoConfig.properties[j].columnName;
                    if (columnsTemp.contains(columnName)) {
                        propertiesTemp.add(columnName);
                        propertiesNew.add(columnName);
                    } else {
                        try {
                            String aClass = getTypeByClass(daoConfig.properties[j].type);
                            if (aClass.equals("INTEGER")) {
                                propertiesTemp.add("0 as " + columnName);
                                propertiesNew.add(columnName);
                            } else if (aClass.equals("DOUBLE")) {
                                propertiesTemp.add("0.00 as " + columnName);
                                propertiesNew.add(columnName);
                            }
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
                if (propertiesTemp.size() > 0) {
                    final String columnSQLTmp = TextUtils.join(",", propertiesTemp);
                    final String columnSQLNew = TextUtils.join(",", propertiesNew);

                    StringBuilder insertTableStringBuilder = new StringBuilder();
                    insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
                    insertTableStringBuilder.append(columnSQLNew);
                    insertTableStringBuilder.append(") SELECT ");
                    insertTableStringBuilder.append(columnSQLTmp);
                    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);
        }
    }

    private static 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";
        }
        if (type.equals(Float.class) || type.equals(Double.class) || type.equals(float.class) || type.equals(double.class)) {
            return "DOUBLE";
        }

        Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
        exception.printStackTrace();
        throw exception;
    }

}

其中特殊字段的处理是第202-221行之间,将int、float等类型字段设置为0或0.00

代码如下


            try {
                // get all columns from tempTable, take careful to use the columns list
                List<String> columnsTemp = getColumns(db, tempTableName);
                ArrayList<String> propertiesTemp = new ArrayList<>(columnsTemp.size() + 3);
                ArrayList<String> propertiesNew = new ArrayList<>(columnsTemp.size() + 3);
                for (int j = 0; j < daoConfig.properties.length; j++) {
                    String columnName = daoConfig.properties[j].columnName;
                    if (columnsTemp.contains(columnName)) {
                        propertiesTemp.add(columnName);
                        propertiesNew.add(columnName);
                    } else {
                        try {
                            String aClass = getTypeByClass(daoConfig.properties[j].type);
                            if (aClass.equals("INTEGER")) {
                                propertiesTemp.add("0 as " + columnName);
                                propertiesNew.add(columnName);
                            } else if (aClass.equals("DOUBLE")) {
                                propertiesTemp.add("0.00 as " + columnName);
                                propertiesNew.add(columnName);
                            }
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
                if (propertiesTemp.size() > 0) {
                    final String columnSQLTmp = TextUtils.join(",", propertiesTemp);
                    final String columnSQLNew = TextUtils.join(",", propertiesNew);

                    StringBuilder insertTableStringBuilder = new StringBuilder();
                    insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
                    insertTableStringBuilder.append(columnSQLNew);
                    insertTableStringBuilder.append(") SELECT ");
                    insertTableStringBuilder.append(columnSQLTmp);
                    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);
            }

新建GreenDaoOpenHelper.java

public class GreenDaoOpenHelper extends DaoMaster.OpenHelper {
    public GreenDaoOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
        super(context, name, factory);
    }
    @Override
    public void onUpgrade(Database db, int oldVersion, int newVersion) {
        MigrationHelper.migrate(db, new MigrationHelper.ReCreateAllTableListener() {
            @Override
            public void onCreateAllTables(Database db, boolean ifNotExists) {
                DaoMaster.createAllTables(db, ifNotExists);
            }
            @Override
            public void onDropAllTables(Database db, boolean ifExists) {
                DaoMaster.dropAllTables(db, ifExists);
            }
        },UserDBeanDao.class,BannerDBeanDao.class);
    }
}

GreenDaoOpenHelper.java中主要是重写onUpgrade,记得将onUpgrade内的super.onUpgrade删除,因为该方法是条用父类的onUpgrade,而父类的onUpgrade会删除所有表和数据。
MigrationHelper.migrate方法的最后一个参数是可变参数,表示传入的数量是随意的。这里表示需要更新并保留原数据的表。
类名是greenDao根据你写的类自动生成的,名称是 你的类名+Dao。
比如我写的用户类是UserDBean.java,则greenDao生成的类是UserDBeanDao.java

参考:
https://github.com/yuweiguocn/GreenDaoUpgradeHelper


本文由【waitig】发表在等英博客
本文固定链接:android GreenDao 数据库升级特殊字段处理
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