Android Architect path 18 Object-oriented database architecture design

preface

SqliteopenHelper is often used in the project to implement the database add, delete, change and search, but it is very cumbersome to use, need to write a lot of long-winded code. So the design of object-oriented database framework is the way to solve the above problems.

OOP database design UML class diagram

Role:

• BaseDaoFactory: Used to create and initialize databases
• IBaseDao: add, delete, modify, and check methods interface
• BaseDao: an abstract template class that implements subclass UserDao.
• Beans: Use annotations to define related field names and types in a table, such as UserBean
• ConcreteDao: Create a table, specifying fields and their lengths, corresponding to fields in the UserBean (UserDao)
• Client: Calls a class, such as an Activity

2. Implementation of each role

BaseDaoFactory:

public class BaseDaoFactory {

    private static BaseDaoFactory instance = new BaseDaoFactory();

    private String sqliteDatabasePath;

    private SQLiteDatabase sqLiteDatabase;

    public BaseDaoFactory(a) {
        sqliteDatabasePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/teacher.db";
        openDatabase();
    }

    public static BaseDaoFactory getInstance(a) {
        return instance;
    }

    public synchronized <T extends BaseDao<M>, M> T getDataHelper(Class<T> clazz, Class<M> entityClass) {
        BaseDao baseDao = null;
        try {
            baseDao = clazz.newInstance();
            baseDao.init(entityClass, sqLiteDatabase);
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return (T) baseDao;
    }
    /** * If targetSdkVersion is greater than 22, request read/write permission for the storage */
    // Open the database operation
    private void openDatabase(a) {

        this.sqLiteDatabase = SQLiteDatabase.openOrCreateDatabase(sqliteDatabasePath, null); }}Copy the code

IBaseDao:

public interface IBaseDao<T>{
    / * * *@param entity
     * @return* /
    Long insert(T entity);

    /** * Update data *@param entity
     * @param where
     * @return* /
    int update(T entity,T where);

    /** * delete data *@param where
     * @return* /
    int delete(T where);

    List<T> query(T where);

    List<T> query(T where,String orderBy,Integer startIndex,Integer limit);
}
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BaseDao:

/** * Created by Xionghu on 2018/2/2. * Desc: Actually dealing with the bottom layer **@param <T>
 */

public abstract class BaseDao<T> implements IBaseDao<T> {

    /** * holds a reference to the database action class */
    private SQLiteDatabase database;

    /** ** ensure instantiation once */
    private boolean isInit = false;

    /** * holds the Java type * User */ corresponding to the operation data table
    private Class<T> entityClass;

    / * * * to maintain the name of the table with the member variable name * key mapping relations -- -- -- - > value -- -- -- -- > table name * Field * /
    private HashMap<String, Field> cacheMap;

    private String tableName;

    / * * *@param entity
     * @param sqLiteDatabase
     * @returnInstantiate once */
    protected synchronized boolean init(Class<T> entity, SQLiteDatabase sqLiteDatabase) {
        if(! isInit) { entityClass = entity; Log.d("sqlite", entityClass.getSimpleName());
            database = sqLiteDatabase;
            if (entity.getAnnotation(DbTable.class) == null) {
                tableName = entity.getClass().getSimpleName();
            } else {
                tableName = entity.getAnnotation(DbTable.class).value();
            }
            if(! database.isOpen()) {return false;
            }
            if(! TextUtils.isEmpty(createTable())) { database.execSQL(createTable()); } cacheMap =new HashMap<>();
            initCacheMap();
            isInit = true;
        }
        return isInit;
    }

    /** * Maintain the mapping */
    private void initCacheMap(a) {
        String sql = "select * from " + this.tableName + " limit 1 , 0 ";
        Cursor cursor = null;
        try {

            cursor = database.rawQuery(sql, null);
            /** * array of column names */
            String[] columnNames = cursor.getColumnNames();
            /** * get the Field array */
            Field[] colmunFields = entityClass.getFields();
            for (Field field : colmunFields) {
                field.setAccessible(true);
            }
            /** ** start to find the corresponding */
            for (String colmunName : columnNames) {
                /** ** field = User */
                Field colmunFiled = null;
                for (Field field : colmunFields) {
                    String fileName = null;
                    if(field.getAnnotation(DbFiled.class) ! =null) {
                        fileName = field.getAnnotation(DbFiled.class).value();
                    } else {
                        fileName = field.getName();
                    }
                    /** * if the table name is equal to the annotation name of the member variable */
                    if (colmunName.equals(fileName)) {
                        colmunFiled = field;
                        break; }}// Find the corresponding relationship
                if(colmunFiled ! =null) { cacheMap.put(colmunName, colmunFiled); }}}catch (Exception e) {
            e.printStackTrace();
        } finally{ cursor.close(); }}@Override
    public Long insert(T entity) {
        Map<String, String> map = getValues(entity);
        ContentValues values = getContentValues(map);
        Long result = database.insert(tableName, null, values);
        return result;
    }

    / * * *@param entity
     * @param where
     * @return* /
    @Override
    public int update(T entity, T where) {
        int result = -1;
        Map values = getValues(entity);

        /** * conditional object conversion map */
        Map whereClause = getValues(where);
        Condition condition = new Condition(whereClause);
        ContentValues contentValues = getContentValues(values);
        result = database.update(tableName, contentValues, condition.getWhereClause(), condition.getWhereArgs());

        return result;
    }

    @Override
    public int delete(T where) {
        Map map = getValues(where);
        Condition condition = new Condition(map);

        /** * id=1 new String[]{ String.value(1)} */
        int result = database.delete(tableName, condition.getWhereClause(), condition.getWhereArgs());
        return result;
    }

    // Query all data
    @Override
    public List<T> query(T where) {
        return query(where, null.null.null);
    }

    @Override
    public List<T> query(T where, String orderBy, Integer startIndex, Integer limit) {
        Map map = getValues(where);
        String limitString = null;
        if(startIndex ! =null&& limit ! =null) {
            limitString = startIndex + "," + limit;
        }
        Condition condition = new Condition(map);
        Cursor cursor = database.query(tableName, null, condition.getWhereClause(), condition.getWhereArgs(),
                null.null, orderBy, limitString);
        List<T> result = getResult(cursor, where);
        cursor.close();
        return result;
    }


    private List<T> getResult(Cursor cursor, T where) {
        ArrayList list = new ArrayList();
        Object item;
        while (cursor.moveToNext()) {
            try {
                item = where.getClass().newInstance();
                /** * column name * Member variable name Filed */
                Iterator iterator = cacheMap.entrySet().iterator();
                while (iterator.hasNext()) {
                    Map.Entry entry = (Map.Entry) iterator.next();
                    /** * get the column name */
                    String colomunName = (String) entry.getKey();
                    /** * then get the column name in the cursor position */
                    Integer colmunIndex = cursor.getColumnIndex(colomunName);

                    Field field = (Field) entry.getValue();
                    Class type = field.getType();
                    if(colmunIndex ! = -1) {
                        if (type == String.class) {
                            // Reflection mode assignment
                            field.set(item, cursor.getString(colmunIndex));
                        } else if (type == Double.class) {
                            field.set(item, cursor.getDouble(colmunIndex));
                        } else if (type == Integer.class) {
                            field.set(item, cursor.getInt(colmunIndex));
                        } else if (type == Long.class) {
                            field.set(item, cursor.getLong(colmunIndex));
                        } else if (type == Float.class) {
                            field.set(item, cursor.getFloat(colmunIndex));
                        } else if (type == byte[].class) {
                            field.set(item, cursor.getBlob(colmunIndex));
                        } else {
                            continue;
                        }

                    }


                }
                list.add(item);
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch(IllegalAccessException e) { e.printStackTrace(); }}return list;
    }

    /** * convert to ContentValues **@param map
     * @return* /
    private ContentValues getContentValues(Map<String, String> map) {
        ContentValues contentValues = new ContentValues();
        Set keys = map.keySet();
        Iterator<String> iterator = keys.iterator();
        while (iterator.hasNext()) {
            String key = iterator.next();
            String value = map.get(key);
            if(value ! =null) { contentValues.put(key, value); }}return contentValues;
    }


    private Map<String, String> getValues(T entity) {
        HashMap<String, String> result = new HashMap<>();
        Iterator<Field> fieldsIterator = cacheMap.values().iterator();
        /** * loop over the map's Field */
        while (fieldsIterator.hasNext()) {
            Field columnToField = fieldsIterator.next();
            String cacheKey = null;
            String cacheValue = null;
            if(columnToField.getAnnotation(DbFiled.class) ! =null) {
                cacheKey = columnToField.getAnnotation(DbFiled.class).value();
            } else {
                cacheKey = columnToField.getName();
            }
            try {
                if (null == columnToField.get(entity)) {
                    continue;
                }
                cacheValue = columnToField.get(entity).toString();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            result.put(cacheKey, cacheValue);
        }
        return result;
    }


    /** * create table **@return* /
    protected abstract String createTable(a);

    /** * encapsulates the change statement */
    class Condition {


        /** * name=? && password = ? * /
        private String whereClause;

        private String[] whereArgs;


        public Condition(Map<String, String> whereClause) {
            ArrayList list = new ArrayList();
            StringBuilder stringBuilder = new StringBuilder();

            stringBuilder.append(" 1=1 ");

            Set keys = whereClause.keySet();
            Iterator iterator = keys.iterator();
            while (iterator.hasNext()) {
                String key = (String) iterator.next();
                String value = whereClause.get(key);

                if(value ! =null) {
                    * 1=1 and name =? and password = ? * /
                    stringBuilder.append(" and " + key + "=?"); list.add(value); }}this.whereClause = stringBuilder.toString();
            this.whereArgs = (String[]) list.toArray(new String[list.size()]);
        }

        public String getWhereClause(a) {
            return whereClause;
        }

        public void setWhereClause(String whereClause) {
            this.whereClause = whereClause;
        }

        public String[] getWhereArgs() {
            return whereArgs;
        }

        public void setWhereArgs(String[] whereArgs) {
            this.whereArgs = whereArgs; }}}Copy the code

Bean:

@DbTable("tb_user")
public class User {

    /** * public Integer userId; * The data is saved in the field named userId * note: *@DbFiled("teacher_id") * public Integer userId; Teacher_id = teacher_id = teacher_id = teacher_id = teacher_id = teacher_id
    public Integer userId;

    @DbFiled("name")
    public String name;
    @DbFiled("password")
    public String password;

    public User(Integer userId, String name, String password) {
        this.userId = userId;
        this.name = name;
        this.password = password;
    }

    public User(a) {}public Integer getUserId(a) {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getName(a) {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword(a) {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString(a) {
        return "User{" +
                "userId=" + userId +
                ", name='" + name + ' '' + ", password='" + password + ''' + '}'; }}Copy the code

@Target(ElementType.FIELD) // Constants for fields and enumerations
@Retention(RetentionPolicy.RUNTIME) // Annotations exist in the class bytecode file and can be retrieved at runtime
public @interface DbFiled {
    String value(a);
}
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@Target(ElementType.TYPE) // applies to interfaces, class enumerations, annotations
@Retention(RetentionPolicy.RUNTIME) // Annotations exist in the class bytecode file and can be retrieved at runtime
public @interface DbTable {
    String value(a);
}
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ConcreteDao:

public class UserDao extends BaseDao {

    @Override
    protected String createTable(a) {
        return "create table if not exists tb_user(userId int,name varchar(20),password varchar(20))"; }}Copy the code

public class FileDao extends BaseDao {
    @Override
    protected String createTable(a) {
        return "create table if not exists tb_file(time varchar(20),path varchar(20),description varchar(20))"; }}Copy the code

Client:

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "Main";
    IBaseDao<User> baseDao;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); baseDao = BaseDaoFactory.getInstance().getDataHelper(UserDao.class, User.class); }}Copy the code

3. Add, delete, change, check and test

Step1: add

    public void save(View view) {

        for (int i = 0; i < 20; i++) {
            User user = new User(i, "teacher"."123456");
            baseDao.insert(user);
        }

/** * Writes file data */
// BaseDao
      
        fileBeanBaseDao = BaseDaoFactory.getInstance().getDataHelper(FileDao.class, FileBean.class);
      
// fileBeanBaseDao.insert(new FileBean("2019-12-13", Environment.getExternalStorageDirectory() + "/kpioneer", "asdfg"));

    }
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Execute queryAll to print the data

02-06 17:51:06.151 4858-4858/com.haocai.haocaisqlite I/Main: Found20The data02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=0, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=1, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=2, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=3, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=4, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=5, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=6, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=7, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=8, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=9, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=10, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=11, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=12, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=13, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=14, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=15, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=16, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=17, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=18, name='teacher', password='123456'}
02-06 17:51:06.152 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=19, name='teacher', password='123456'}
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Step2: change

    public void update(View view) {
        for (int i = 10; i < 20; i++) {
            User where = new User();
            where.setUserId(i);
            User user = new User(i, "kpioneer"."8888");

            Name = teacherbaseDao.update(user, where); }}Copy the code

Execute queryAll to print the data

02-06 17:54:18.650 4858-4858/com.haocai.haocaisqlite I/Main: Found20The data02-06 17:54:18.650 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=0, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=1, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=2, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=3, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=4, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=5, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=6, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=7, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=8, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=9, name='teacher', password='123456'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=10, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=11, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=12, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=13, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=14, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=15, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=16, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=17, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=18, name='kpioneer', password='8888'}
02-06 17:54:18.651 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=19, name='kpioneer', password='8888'}
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Step3: check

    public void query(View view) {
        User where = new User();
        where.setName("teacher");
        List<User> list = baseDao.query(where);

        Log.i(TAG, "Found" + list.size() + "Piece of data");
        for (User user : list) {
            Log.i(TAG, user.toString());
        }

        System.out.println("-------- Query some data -------");
        User where2 = new User();
        where2.setName("teacher");
        where2.setUserId(5);
        List<User> list2 = baseDao.query(where2);
        Log.i(TAG, "Found" + list2.size() + "Piece of data");
    }
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Print data

02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: Found10The data02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=0, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=1, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=2, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=3, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=4, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=5, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=6, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=7, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=8, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=9, name='teacher', password='123456'}
02-06 17:58:49.530 4858-4858/ com. Haocai. Haocaisqlite I/System. Out: -- -- -- -- -- -- -- -- a query for a data -- -- -- -- -- -- --02-06 17:58:49.533 4858-4858/com.haocai.haocaisqlite I/Main: Found1The dataCopy the code

Step4: delete

    public void delete(View view) {
        User user = new User();
        user.setName("teacher");
        baseDao.delete(user);
    }
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Execute queryAll to print the data

02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: Found10The data02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=10, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=11, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=12, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=13, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=14, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=15, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=16, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=17, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=18, name='kpioneer', password='8888'}
02-06 18:00:29.196 4858-4858/com.haocai.haocaisqlite I/Main: User{userId=19, name='kpioneer', password='8888'}
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At this point, the object-oriented database architecture design is complete.