关于数据库的三层模式一般见地

数据库的三层模式

关于数据库的封装一般分为三层，即：业务逻辑访问DBManager（顶层业务逻辑直接访问的操作类）→→DBService（操作底层实体类数据，对其进行增删查改（调用DBHelper里面的方法））→→DBHelper（其中DBHelper用于书写增删查改的基本SQL操作方法，DBOpenHelper用于建立相关数据库表、规定相关字段）。

这样分明的层次，能够保证底层数据不易被更改或破坏（数据安全得以保证），且便于后台维护和管理，是各个公司及企业常用的分层模式。

DBManager类

DBService类

DBHelper类

DBManager类

public class HisDbManager {

private static HisDbManager mInstance;
private static Object mSyncLock = new Object();
private final Context mContext;
private static DbServices mDbServices;
private static final String TABLE_HISTORY = DbOpenHelper.TABLE__HISTORY;

public static HisDbManager getInstance(Context context) {
synchronized (mSyncLock) {
if (mInstance == null) {
mInstance = new HisDbManager(context);
}
}
return mInstance;
}

private HisDbManager(Context context) {
mContext = context;
mDbServices = DbServices.getInstance(context);
}

/**
*  删除记录表全部记录
* @return
*/
synchronized public boolean deleteAll(){
return mDbServices.deleteAllHisRec();
}

/**
*  通过Id删除记录表全部记录
*
* @param id 记录表Id
* @return
*/
synchronized public boolean deleteById(int id){
return mDbServices.deleteHisRecById(id);
}

/**
* 批量删除记录表
*
* @param ids
* @return 返回受影响的行数
*/
synchronized public int deleteById(List<Integer> ids) {
return mDbServices.deleteHisRecById(ids,TABLE_HISTORY);
}

/**
* 查询全部记录表记录
*/
public List<HisRecInfo> queryAll(){
return mDbServices.queryAllHisRec();
}

/**
* 查询单条记录表资料
*
* @param id 自增长id
*/
public HisRecInfo queryById(int id){
return mDbServices.queryHisRecById(id);
}

/**
* 模糊查询详历史记录
*/
public List<Info> queryFuzzy(String key){
return mDbServices.queryFuzzyHistory(key);
}

注意：以下这个方法的格式，可套用

public List<Info> queryAllDetails() {
String sql = "SELECT * FROM " + TABLE_DETAILS
+ " WHERE " + DbOpenHelper.DetailsInfo.idCode.name() + " IS NOT NULL"
+ ";";//执行sql语句(注意空格)
Cursor cursor = executeSql(sql, 0);//执行sql语句
List<Info> list = null;
if (cursor != null && cursor.getCount() > 0) {//判断不为空且不为""
list = new ArrayList<Info>();//创建容器
while (cursor.moveToNext()) {
list.add(getInfo(cursor));
}
}
mOpenHelper.closeCursor(cursor);//必须关闭游标，否则内存泄漏
return list;
}

DBService类

public class DbServices {

private static DbServices mInstance;
private static final Object mSyncLock = new Object();
private static DbHelper mDbHelper;
private static final String TABLE__DETAILS = DbOpenHelper.TABLE_DETAILS;
private static final String TABLE_HISTORY = DbOpenHelper.TABLE_HISTORY;

public static DbServices getInstance(Context context) {
synchronized (mSyncLock) {
if (mInstance != null) {
return mInstance;
}
if (context != null) {
mInstance = new DbServices(context);
return mInstance;
}
}

return null;
}

private DbServices(Context context) {
mDbHelper = DbHelper.getInstance(context);
}

public boolean insertDetails(DetailsInfo info) {
if (info == null || TextUtils.isEmpty(info.getInvCode())) {
return false;
}
return mDbHelper.insertDetails(info.getInvCode(), info.getUnitId(),
info.getInvName());
}

public long insertHisRec(HisRecInfo info) {
ContentValues contentValues = getHisContentValues(info);
return mDbHelper.insert(TABLE__HISTORY, contentValues);
}
/**
* 将字段信息的model类转为ContentValues（序列化数据）
*
* @param info
* @return
*/
private ContentValues getDetailsContentValues(DetailsInfo info) {
ContentValues values = new ContentValues();
values.put(DbOpenHelper.Details.invCode.name(), info.getInvCode());
values.put(DbOpenHelper.Details.invName.name(), info.getInvName());
values.put(DbOpenHelper.Details.unitId.name(), info.getUnitId());
return values;
}

public boolean deleteHisRecById(String Id) {
if (TextUtils.isEmpty(Id)) {
return false;
}
return mDbHelper.deleteByCondition(TABLE_HISTORY,
DbOpenHelper.History.invCode.name(),
Id);
}

public boolean deleteHisRecByWorkerId(String workerId) {
if (TextUtils.isEmpty(workerId)) {
return false;
}
return mDbHelper.deleteByCondition(TABLE_HISTORY,
DbOpenHelper.History.userCode.name(),
workerId);
}

public boolean deleteHisRecById(int id) {
return mDbHelper.deleteByCondition(TABLE_HISTORY,
DbOpenHelper.History.id.name(),
id + "");
}

public boolean deleteHisRecByDevice(String deviceName) {
if (TextUtils.isEmpty(deviceName)) {
return false;
}
return mDbHelper.deleteByCondition(TABLE_HISTORY,
DbOpenHelper.History.scaleName.name(),
deviceName + "");
}

public List<DetailsInfo> queryAllDetails() {
return mDbHelper.queryAllDetails();
}

public List<HisRecInfo> queryAllHisRec() {
return mDbHelper.queryAllHisRec();
}

public DetailsInfo queryDetailsById(String Id) {
if (TextUtils.isEmpty(Id)) {
return null;
}
return mDbHelper.queryDetailsByCondition(DbOpenHelper.Details.invCode.name(), Id);
}

public List<HisRecInfo> queryHisRecById(String Id) {
if (TextUtils.isEmpty(Id)) {
return null;
}
return mDbHelper.queryHisRecByCondition(DbOpenHelper.History.invCode.name(), Id);
}

public List<HisRecInfo> queryHisRecByWorkerId(String workerId) {
if (TextUtils.isEmpty(workerId)) {
return null;
}
return mDbHelper.queryHisRecByCondition(DbOpenHelper.History.userCode.name(), workerId);
}

public HisRecInfo queryHisRecById(int id) {
return mDbHelper.queryHisRecById(id);
}

DBHelper类

public boolean insertDetails(String invCode, int unitId, String invName) {
String sql = "REPLACE INTO " + TABLE_DETAILS
+ " ("
+ DbOpenHelper.Details.invCode.name() + ","
+ DbOpenHelper.Details.unitId.name() + ","
+ DbOpenHelper.Details.invName.name()
+ " )"
+ " VALUES ('" + invCode + "','" + unitId + "','" + invName  + "');";
return executeSql(sql);
}

/**
* 批量删除记录表
*
* @param ids
* @return 返回受影响的行数
*/
public int deleteHisRecById(List<Integer> ids, String table) {
String idColName =DbOpenHelper.History.id.name();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < ids.size(); i++) {
sb.append(idColName + "=" + ids.get(i));
if (i + 1 < ids.size()) {
sb.append(" or ");
} else {
sb.append(";");
}
}

String sqlString = "DELETE FROM " + table + " WHERE " + sb.toString();
if (executeSql(sqlString)) {
return ids.size();
}
return -1;
}

/**
* 执行删除操作
*/
public boolean deleteAll(String table) {
String sql = "DELETE FROM " + table;
return executeSql(sql);
}

/**
* 执行单条删除操作
*/
public boolean deleteByCondition(String table, String column, String values) {
String sql = "DELETE FROM " + table + " WHERE " + column + " ='" + values + "';";
return executeSql(sql);
}

/**
* 重置指定表当前id为0
*/
public void revertSeq(String table) {
String sql = "UPDATE sqlite_sequence set seq=0 WHERE name='" + table
+ "'" + ";";
executeSql(sql);
}
/**
* 执行简单SQL语句
*
* @param sqlString
* @return 执行成功返回true，否则返回false
*/
private boolean executeSql(final String sqlString) {
synchronized (mSyncLock) {
Globals.log("数据库测试 sqlString:" + sqlString);
SQLiteDatabase db = null;
try {
db = mOpenHelper.getReadableDatabase();
db.execSQL(sqlString);
return true;
} catch (Exception e) {
e.printStackTrace();
}
return false;
}
}

/**
* 执行插入操作
*
* @param table
* @param values
* @return
*/
public long insert(String table, ContentValues values) {
try {
return executeInsertOrThrow(table, null, values);
} catch (Exception e) {
e.printStackTrace();
return -1;
}
}

/**
* 执行插入操作
*
* @param table
* @param nullColumnHack
* @param values
* @return 返回最后一条插入的rowId，若发生错误则返回-1
*/
private long executeInsertOrThrow(String table, String nullColumnHack, ContentValues values) {
synchronized (mSyncLock) {
SQLiteDatabase db = null;
long rowId = -1;
try {
db = mOpenHelper.getReadableDatabase();
rowId = db.insertOrThrow(table, nullColumnHack, values);
} catch (Exception e) {
e.printStackTrace();
}
return rowId;
}
}

/**
* 执行简单查询SQL语句
* 不可用于执行delete update
*
* @param sqlString
* @param flag      任意数值,无实际作用
* @return
*/
private Cursor executeSql(final String sqlString, int flag) {
synchronized (mSyncLock) {
Globals.log("数据库测试 sqlString:" + sqlString);
SQLiteDatabase db = null;
Cursor cursor = null;
try {
db = mOpenHelper.getReadableDatabase();
cursor = db.rawQuery(sqlString, null);
} catch (Exception e) {
e.printStackTrace();
}
return cursor;
}
}

public long replace(final String table, final String nullColumnhack, final List<ContentValues> valuesList) {
synchronized (mSyncLock) {
long affected = 0;
SQLiteDatabase db = null;
try {
db = mOpenHelper.getWritableDatabase();
db.beginTransaction();
for (ContentValues values : valuesList) {
for (String key : values.keySet()) {
Globals.log("", "replace order pCode List:"
+ key + ":" + values.get(key));
}
db.replace(table, nullColumnhack, values);
affected++;
}
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (db != null) {
db.endTransaction();
}
}
return affected;
}
}

/**
* 模糊查询的一般书写步骤
* 筛选累计记录
* 若不筛选传入null
* @param groupByFlag  标记哪个列需要groupBy ( 1：Id, 2：Name 3: area 4:worker)
* @return
*/
public List<HisRecInfo> queryHistoryRecAll(String id,String name, String area, String worker,
String scaleName, String startTime, String endTime,
int groupByFlag) {
String idArg = " AND " + DbOpenHelper.History.invCode.name() + "='" + Id + "'";
String nameArg = " AND " + DbOpenHelper.History.invName.name() + "='" + Name + "'";
String areaArg = " AND " + DbOpenHelper.History.area.name() + "='" + area + "'";
String workerNameArg = " AND " + DbOpenHelper.History.userName.name() + "='" + worker + "'";
String scaleNameArg = " AND " + DbOpenHelper.History.scaleName.name() + "='" + scaleName + "'";
String dateTimeArg = " AND " + DbOpenHelper.History.date.name() + " >= '" + startTime + "'"
+ " AND " + DbOpenHelper.History.date.name() + " <= '" + endTime + "'";

String idGroupByArg = " GROUP BY " + DbOpenHelper.History.invCode.name();
String nameGroupByArg = " GROUP BY " + DbOpenHelper.History.invName.name();
String areaGroupByArg = " GROUP BY " + DbOpenHelper.History.area.name();
String workerNameGroupByArg = " GROUP BY " + DbOpenHelper.History.userName.name();

StringBuffer sb = new StringBuffer();
if (!TextUtils.isEmpty(Id)) {
sb.append(idArg);
}
if (!TextUtils.isEmpty(name)) {
sb.append(nameArg);
}
if (!TextUtils.isEmpty(area)) {
sb.append(areaArg);
}
if (!TextUtils.isEmpty(worker)) {
sb.append(workerNameArg);
}
if (!TextUtils.isEmpty(scaleName)) {
sb.append(scaleNameArg);
}
if (!TextUtils.isEmpty(startTime) && !TextUtils.isEmpty(endTime)) {
sb.append(dateTimeArg);
}

if (1 == groupByFlag) {
sb.append(idGroupByArg);
} else if (2 == groupByFlag) {
sb.append(nameGroupByArg);
} else if (3 == groupByFlag) {
sb.append(areaGroupByArg);
} else if (4 == groupByFlag) {
sb.append(workerNameGroupByArg);
}

String sql = "SELECT * FROM " + TABLE_HISTORY
+ " WHERE " + DbOpenHelper.History.invCode.name() + " IS NOT NULL "
+ sb.toString() + " "
+ "ORDER BY " + DbOpenHelper.History.id.name() + " DESC"
+ ";";
Cursor cursor = executeSql(sql, 0);
List<Info> list = null;
if (cursor != null && cursor.getCount() > 0) {
list = new ArrayList<Info>();
while (cursor.moveToNext()) {
list.add(getHisRecInfo(cursor));
}
}
mOpenHelper.closeCursor(cursor);
return list;
}

private DetailsInfo getDetailsInfo(Cursor cursor) {
DetailsInfo info = new DetailsInfo();
info.setInvCode(cursor.getString(cursor.getColumnIndex(DbOpenHelper.Details.invCode.name())));
info.setInvName(cursor.getString(cursor.getColumnIndex(DbOpenHelper.Details.invName.name())));
info.setUnitId(cursor.getInt(cursor.getColumnIndex(DbOpenHelper.Details.unitId.name())));
return info;
}

先介绍到这了，如有需要改进的，还望各位大神指导，谢谢！

附上一些学习教程的地址
http://www.runoob.com/sqlite/sqlite-tutorial.html“SQLite学习”

http://download.csdn.net/download/disanxiaoyao/9744470“sql语句学习pdf文件下载，免费的”