Sqlite教程(2) Data Access Object

因为这个项目的业务层很薄，因此想在架构上尽量保持着「轻」，不会把创建DbHelper的interface。

而是直接用DAO创建DbHelper对象。

DAO和DbHelper也是同样使用懒汉模式。

1. UserDAO懒汉模式。

public class UserDAO {

    private Configuration config = new Configuration();
    protected SQLiteDatabase db;
    private DbHelper dbHelper;

    public UserDAO(Context context) {
        this.dbHelper = DbHelper.getInstance(context);
        this.db = this.dbHelper.getWritableDatabase();
    }
    
}

2. DAO负责处理Query SQlite的业务。这里分别有6个方法。

1. boolean setUser()
2. UserDTO getUser()
3. int getUserCount()
4. boolean setUserPortrait(Bitmap)
5. Bitmap getUserPortrait()
6. byte[] getUserPortraitBYTE()

3. 完整的DAO代码如下。

package com.paradise.electronic.eparadise2.dao;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

import com.paradise.electronic.eparadise2.dto.UserDTO;
import com.paradise.electronic.eparadise2.sqlite.DbHelper;
import com.paradise.electronic.eparadise2.util.Configuration;

import java.io.ByteArrayOutputStream;

/**
 * Created by Administrator on 17-11-17.
 */
public class UserDAO {

    private Configuration config = new Configuration();
    protected SQLiteDatabase db;
    private DbHelper dbHelper;

    public UserDAO(Context context) {
        this.dbHelper = DbHelper.getInstance(context);
        this.db = this.dbHelper.getWritableDatabase();
    }

    /*
    *   @return 1: Successful   0: Failed
    */
    public boolean setUser (UserDTO user) {
        ContentValues values = new ContentValues();
        boolean result = true;

        values.put(config.USER_USERID, user.getId());
        values.put(config.USER_NAME, user.getName());
        values.put(config.USER_PASSWORD, user.getPassword());
        values.put(config.USER_EMAIL, user.getEmail());
        values.put(config.USER_DESCRIPTION, user.getDescription());
        values.put(config.USER_TEAM, user.getTeam());
        values.put(config.USER_ACADEMIC, user.getAcademic());
        values.put(config.USER_PORTRAIT, user.getPortrait());
        values.put(config.USER_REGISTER_DATE, user.getRegisterDate());

        try {
            db.insert(config.DB_USER, null, values);
        } catch (SQLException e) {
            result = false;
        }
        return result;
    }

    /*
    *   @return UserDTO
    */
    public UserDTO getUser() {
        String query = " SELECT "+config.USER_USERID+
                ", "+config.USER_NAME+
                ", "+config.USER_PASSWORD+
                ", "+config.USER_EMAIL+
                ", "+config.USER_DESCRIPTION+
                ", "+config.USER_TEAM+
                ", "+config.USER_ACADEMIC+
                ", "+config.USER_PORTRAIT+
                ", "+config.USER_REGISTER_DATE+
                " FROM "+config.DB_USER+
                " ORDER BY "+config.USER_ID+" DESC LIMIT 1 ";
        Cursor cursor = db.rawQuery(query, null);

        if (cursor != null) {
            cursor.moveToFirst();
        }

        UserDTO user = new UserDTO(cursor.getInt(0), cursor.getString(1), cursor.getString(2),
                cursor.getString(3), cursor.getString(4), cursor.getString(5), cursor.getString(6), cursor.getString(7),
                cursor.getString(8));
        return user;
    }

    public void updateUser() {

    }

    public void deleteUser() {

    }

    public int getUserCount() {
        String query = " SELECT * FROM "+config.DB_USER;
        Cursor cursor = db.rawQuery(query, null);
        int count = cursor.getCount();
        return count;
    }

    /*
    *   @param [Bitmap]portrait
    *   @return 1: Successful   0: Failed
     */
    public boolean setUserPortrait(Bitmap portrait) {
        ContentValues values = new ContentValues();
        boolean result = true;

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        portrait.compress(Bitmap.CompressFormat.JPEG, 0, stream);

        values.put(config.USER_PORTRAIT_DATA, stream.toByteArray());
        try {
            db.insert(config.DB_USER, null, values);
        } catch (SQLException e) {
            result = false;
        }
        return result;
    }

    /*
    *   @return [Bitmap]portrait
     */
    public Bitmap getUserPortrait() {
        String query = " SELECT "+config.USER_USERID+
                ", "+config.USER_PORTRAIT_DATA+
                " FROM "+config.DB_USER+
                " ORDER BY "+config.USER_ID+" DESC LIMIT 1 ";
        Cursor cursor = db.rawQuery(query, null);
        if (cursor != null) {
            cursor.moveToFirst();
        }

        byte[] bytePortrait = cursor.getBlob(0);
        Bitmap portrait = BitmapFactory.decodeByteArray(bytePortrait, 0, bytePortrait.length);
        return portrait;
    }

    /*
    *   @reyurn [byte]protrait
     */
    public byte[] getUserPortraitBYTE() {
        String query = " SELECT "+config.USER_USERID+
                ", "+config.USER_PORTRAIT_DATA+
                " FROM "+config.DB_USER+
                " ORDER BY "+config.USER_ID+" DESC LIMIT 1 ";
        Cursor cursor = db.rawQuery(query, null);
        if (cursor != null) {
            cursor.moveToFirst();
        }

        return cursor.getBlob(0);
    }

}