Greendao 3.X 数据库升级，新增int、long数据类型字段NOT NULL 解决方案

      项目使用到Greendao当做数据库，升级的时候遇到个问题，但新添加int类型字段的时候，数据迁移报错了，查看到是因为新增int、long类型字段的时候，给的是NOT NULL，就是说不能为空。
   数据库升级方案使用的是外国某个大神写的代码，大概思路是：
1、新建一张跟原先表一样的临时表，同时把数据也复制进去。
2、删除原先表
3、新建最新的表，将临时表数据复制进去
4、删除临时表
问题就出在第三不，如果临时表有1个字段。新表有2个字段，而且新多的字段为int类型，那么复制数据的时候，字段二（新增）是存NULL，但是其属性是不能为NULL，这就异常了，这里有个解决思路：在临时表上也给多加一个一样的字段，然后给默认值，因为有了默认值，所有当复制数据的时候就不会是NULL，亲测，可行。
代码：
    openHelper:
public class ReleaseOpenHelper extends DaoMaster.OpenHelper {
Class<? extends AbstractDao<?,?>>[] daoClasses;

public ReleaseOpenHelper(Context context, String name,Class<? extends AbstractDao<?, ?>>... daoClasses) {
super(context, name);
this.daoClasses = daoClasses;
}

public ReleaseOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,Class<? extends AbstractDao<?, ?>>... daoClasses) {
super(context, name, factory);
this.daoClasses = daoClasses;
}

@Override
public void onCreate(Database db) {
super.onCreate(db);
}

@Override
public void onUpgrade(Database db, int oldVersion, int newVersion) {
// super.onUpgrade(db, oldVersion, newVersion);
if(oldVersion < newVersion){
MigrationHelper.migrate(db,daoClasses);
}
}
}

   Manager：
public class DatabaseManager {
public static final String mDBName = "xxx.db";
private DaoSession mDaoSession = null;
private NavModelDao favModelDao = null;
private VideoModelDao videoModelDao = null;
private VideoStatusModelDao videoStatusModelDao = null;
private PlayListDao playListDao = null;
private PlaylistDetailListDao playlistDetailListDao;

private DatabaseManager() {
}

public DatabaseManager init(Context context,Class<? extends AbstractDao<?, ?>>... daoClasses) {
initDao(context,daoClasses);
return this;
}

private static final class Holder {
private static final DatabaseManager INSTANCE = new DatabaseManager();
}

public static DatabaseManager getInstance() {
return Holder.INSTANCE;
}

private void initDao(Context context,Class<? extends AbstractDao<?, ?>>... daoClasses) {
final ReleaseOpenHelper helper = new ReleaseOpenHelper(context, mDBName,daoClasses);
final Database db = helper.getWritableDb();
mDaoSession = new DaoMaster(db).newSession();
favModelDao = mDaoSession.getNavModelDao();
videoModelDao = mDaoSession.getVideoModelDao();
videoStatusModelDao = mDaoSession.getVideoStatusModelDao();
playListDao = mDaoSession.getPlayListDao();
playlistDetailListDao = mDaoSession.getPlaylistDetailListDao();

}

public final NavModelDao getNavDao() {
return favModelDao;
}
public final VideoModelDao getVideoModelDao() {
return videoModelDao;
}
public final VideoStatusModelDao getVideoStatusModelDao() {
return videoStatusModelDao;
}
public final PlayListDao getVideoPlayListDao() {
return playListDao;
}
public final PlaylistDetailListDao getVideoPlayListDetailDao() {
return playlistDetailListDao;
}
}import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.support.annotation.NonNull;
import android.text.TextUtils;

import org.greenrobot.greendao.AbstractDao;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.database.StandardDatabase;
import org.greenrobot.greendao.internal.DaoConfig;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MigrationHelper {
public static boolean DEBUG = true;
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);
migrate(database, daoClasses);
}

public static void migrate(Database database, Class<? extends AbstractDao<?, ?>>... daoClasses) {
generateTempTables(database, daoClasses);
dropAllTables(database, true, daoClasses);
createAllTables(database, false, daoClasses);
restoreData(database, daoClasses);
}

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)) {
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());
} catch (SQLException 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);
}

private static void createAllTables(Database db, boolean ifNotExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {
reflectMethod(db, "createTable", ifNotExists, daoClasses);
}

/**
* 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)) {
StringBuilder insertTableStringBuilder = new StringBuilder();
insertTableStringBuilder.append("ALTER TABLE "+tempTableName +" ADD COLUMN "+columnName+
getTableType(daoConfig.properties[j].type));
db.execSQL(insertTableStringBuilder.toString());
}
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);
insertTableStringBuilder.append(";");
db.execSQL(insertTableStringBuilder.toString());
}
StringBuilder dropTableStringBuilder = new StringBuilder();
dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);
db.execSQL(dropTableStringBuilder.toString());
} catch (SQLException 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 Object getTableType(Class<?> type){
if(type.equals(int.class)){
return " INTEGER DEFAULT 0";
}
if(type.equals(long.class)){
return " Long DEFAULT 0";
}
if(type.equals(String.class)){
return " TEXT ";
}
if(type.equals(boolean.class)){
return " NUMERIC DEFAULT 0";
}
return " TEXT";
}
}    Application ：
public class MyApplication extends Application {
@Override
public void onCreate() {
super.onCreate();

DatabaseManager.getInstance().init(
this,
NavModelDao.class,
PlayListDao.class,
PlaylistDetailListDao.class,
VideoModelDao.class,
VideoStatusModelDao.class);

}