首页 > 代码库 > 【安卓】数据库基于脚本的"增量更新",每次更新时不需修改java代码、!
【安卓】数据库基于脚本的"增量更新",每次更新时不需修改java代码、!
思路:
1.当然是基于SQLiteOpenHelper.onCreate(第一次安装程序时调用)、onUpdate(升级程序时调用)
2.用"脚本"(脚本制作具体方法问度娘)做数据库升级,文件名标识对应版本,java中根据“上一版本、当前版本”选择执行的脚本。
升级时,修改DB_VERSION(当前版本)即可。
DBManager.java:
package com.example.test; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DBManager extends SQLiteOpenHelper { private final static String DBNAME = "mydata.db"; private final static int DB_VERSION = 1; private static DBManager instance; public DBManager(Context context) { // TODO Auto-generated constructor stub super(context, DBNAME, null, DB_VERSION); } public static DBManager getThis() { if (instance == null) instance = new DBManager(MainActivity.getThis()); return instance; } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub initDb(db, 0, DB_VERSION); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub initDb(db, oldVersion, newVersion); } // 初始化db,执行脚本 // 注:1>执行"(oldV,newV]"(全新安装时,oldV=0)间的脚本 // 2>缺失的脚本会直接跳过 private void initDb(SQLiteDatabase db, int oldVersion, int newVersion) { for (int i = oldVersion + 1; i <= newVersion; i++) execDBScript(db, "db/update" + i + ".sql"); } // 执行脚本 private void execDBScript(SQLiteDatabase db, String assetName) { try { InputStream is = MainActivity.getThis().getAssets().open(assetName); String stats = read(is); execSqls(db, stats); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } // 批执行,用";"隔开 private void execSqls(SQLiteDatabase db, String stats) { // onCreate/onUpdate内部已带事务,多层嵌套无影响(最外层起作用) db.beginTransaction(); String[] sqls = stats.split(";"); for (int i = 0; i < sqls.length; i++) { String sqlStatement = sqls[i].trim(); // TODO You may want to parse out comments here if (sqlStatement.length() > 0) { // 捕获错误,防止执行drop时 直接越过 try { db.execSQL(sqlStatement + ";"); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } } db.setTransactionSuccessful(); db.endTransaction(); } public static String read(InputStream instream) throws IOException { ByteArrayOutputStream bos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = 0; while ((len = instream.read(buffer)) != -1) { bos.write(buffer, 0, len); } String ret = new String(bos.toByteArray()); return ret; } }
db脚本:
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