前面博客中有介紹輕量級的數(shù)據(jù)庫GreenDao的整合。本文介紹如何對GreenDao數(shù)據(jù)庫進行升級。
為什么要進行數(shù)據(jù)庫升級呢？
在項目建立之初，數(shù)據(jù)庫的表結(jié)構(gòu)基本上以滿足現(xiàn)階段的業(yè)務(wù)而建立，隨著后面業(yè)務(wù)的增加需要更多的column，或者廢棄掉表中的某些column,此時如果直接去修改表結(jié)構(gòu)，就會與之前已有的表沖突，導(dǎo)致Crash，此時我們就需要升級數(shù)據(jù)庫中的表。
數(shù)據(jù)庫升級的思路
刪除重建
這種方法是最簡單直接的。直接將之前的數(shù)據(jù)庫刪除后，再重新建立數(shù)據(jù)庫。這樣會使得之前保存的數(shù)據(jù)丟失。不需要持久化的保存數(shù)據(jù)，可以采用這種方式。
逐級版本迭代升級
比如當前版本為1，最新版本為3，此方案就是先從1–>2–>3. 這種方法實際應(yīng)用中用起來相當?shù)姆爆崳S護每個版本，所以不做過多介紹。
備份數(shù)據(jù)庫，建立新數(shù)據(jù)庫，然后將備份導(dǎo)入
如題，，獎原來的表刪除，之后再將臨時表插入到新建的表之中，然后再將臨時表給刪除了。以此完成數(shù)據(jù)遷移。
在原表基礎(chǔ)上直接添加新的column
對比原表，增加或者刪除column
代碼實現(xiàn)
首先創(chuàng)建一個數(shù)據(jù)庫幫助類
/**
* description: GreenDao幫助類
* author: bear .
* Created date: 2017/5/17.
*/
public class MyOpenHelper extends DaoMaster.DevOpenHelper {
public MyOpenHelper(Context context, String name) {
super(context, name);
}
public MyOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
super(context, name, factory);
}
@Override
public void onUpgrade(Database db, int oldVersion, int newVersion) {
/*此處不用super，因為父類中包含了
dropAllTables(db, true);
onCreate(db);
需要自己定制升級
*/
}
}
修改greenDao的版本號，在內(nèi)層的gradle中的buildTypes節(jié)點下添加
greendao{
schemaVersion 1
// 這個地方是自動生成的配置文件存放在哪個位置的
targetGenDir 'src/main/java'
}
以下是更新方式：
- 刪除再新建
/**
* 刪除原表重新再建立一個表
* @param db
*/
public void dropAndCreate(Database db){
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
}
- 備份數(shù)據(jù)庫，建立新數(shù)據(jù)庫，然后將備份導(dǎo)入
/**
* 備份還原
* @param db
* @param daoClasses
*/
public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
generateTempTables(db, daoClasses);
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
restoreData(db, daoClasses);
}
/**
* 數(shù)據(jù)庫備份
* @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) {
}
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());
}
}
/**
* 數(shù)據(jù)庫恢復(fù)
* @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()));
throw exception;
}
private static 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;
}
- 對比表差異，向原表中直接插入
column
/**
* 對比差異，在原表中直接添加column,贊不做刪除操作
* @param db
* @param daoClasses
*/
public void contrastDiff(Database db,ArrayList<String>properties, Class<? extends AbstractDao<?, ?>>... daoClasses){
for(int i=0;i<daoClasses.length;i++){
DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
String tableName=daoConfig.tablename;
if(properties!=null&&properties.size()>0){
ArrayList<String>tem=new ArrayList<>();
StringBuilder sqlBuilder=new StringBuilder();
for(int j=0;j<properties.size();j++){
if(getColumns(db,tableName).contains(properties.get(j))){
continue;
}
tem.add(properties.get(j));
}
sqlBuilder.append("INSERT INTO ").append(tableName).append(" (");
sqlBuilder.append(TextUtils.join(",", tem));
sqlBuilder.append(") SELECT ");
sqlBuilder.append(TextUtils.join(",", tem));
sqlBuilder.append(" FROM ").append(tableName).append(";");
db.execSQL(sqlBuilder.toString());
}
}
}
下面貼出，完整的數(shù)據(jù)庫升級幫助類
/**
* description: greenDao升級幫助
* author: bear .
* Created date: 2017/5/17.
*/
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;
}
/**
* 備份還原
* @param db
* @param daoClasses
*/
public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
generateTempTables(db, daoClasses);
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
restoreData(db, daoClasses);
}
/**
* 對比差異，在原表中直接添加column,贊不做刪除操作
* @param db
* @param daoClasses
*/
public void contrastDiff(Database db,ArrayList<String>properties, Class<? extends AbstractDao<?, ?>>... daoClasses){
for(int i=0;i<daoClasses.length;i++){
DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
String tableName=daoConfig.tablename;
if(properties!=null&&properties.size()>0){
ArrayList<String>tem=new ArrayList<>();
StringBuilder sqlBuilder=new StringBuilder();
for(int j=0;j<properties.size();j++){
if(getColumns(db,tableName).contains(properties.get(j))){
continue;
}
tem.add(properties.get(j));
}
sqlBuilder.append("INSERT INTO ").append(tableName).append(" (");
sqlBuilder.append(TextUtils.join(",", tem));
sqlBuilder.append(") SELECT ");
sqlBuilder.append(TextUtils.join(",", tem));
sqlBuilder.append(" FROM ").append(tableName).append(";");
db.execSQL(sqlBuilder.toString());
}
}
}
/**
* 刪除原表重新再建立一個表
* @param db
*/
public void dropAndCreate(Database db){
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
}
/**
* 數(shù)據(jù)庫備份
* @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) {
}
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());
}
}
/**
* 數(shù)據(jù)庫恢復(fù)
* @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()));
throw exception;
}
private static 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;
}
}
以上是本人自己整理的一些升級方法，請大家批評指正。
