Android 架构之数据库框架搭建
目录
- 1、先创建对应相关操作的注解
- 1.1 bTable 标识表
- 1.2 DbPrimaryKey 标识主键
- 1.3 DbFiled 标识成员属性
- 2、创建对应表操作类Dao层
- 2.1 建 待实现的基层 IBaseDao
- 2.2 建已实现的基层 BaseDao
- 2.3 建对应model 的Dao层
- 3、创建数据库工厂
- 4、创建对应model
- 5、最终使用
前言:
你还在苦恼的写SQL么?你还在为数据库升级而烦恼么?你还在因查询数据而写繁琐不可用的代码么? 在这,这些都将不复存在!在本篇中,将会让你一点一滴从无到有创建一个不再为数据库而烦恼的框架。
在开始之前我们先欣赏一下本章实现的最终效果 效果展示
如图所示:
- 对应的
model
,可直接成为表结构,不再写对应的Create table xxx
对应的SQL了 - 对应
model
的Dao层,里面封装了数据表的基本操作(增删改查) - 对应的增删改查操作,再也不用SQL了,全用对象处理
接下来开始实战了
1、先创建对应相关操作的注解
1.1 bTable 标识表
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) public @interface DbTable { //表名 String value(); }
1.2 DbPrimaryKey 标识主键
@Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) public @interface DbPrimaryKey { //表列名 String value(); //是否为自动增长 boolean isAuto() default false; }
1.3 DbFiled 标识成员属性
@Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) public @interface DbFiled { //表列名 String value(); /* 这里可以像主键一样,添加其他属性,比如是否唯一约束,是否非空等 甚至可以将主键的约束放在这里来,只是表明可以这样做,具体怎样扩展,完全可以按你们想法来 */ }
2、创建对应表操作类Dao层
2.1 建 待实现的基层 IBaseDao
public interface IBaseDao<T> { Long insert(T entity); int update(T entity, T where); /** * 删除数据 * * @param where * @return */ int delete(T where); /** * 查询数据 */ List<T> query(T where); List<T> query(T where, String groupBy, String orderBy, String having, Integer startIndex, Integer limit); }
代码分析:
这里创建了基类 IBaseDao ,拥有待实现的增删改查, T 代表对应的 数据表结构的 model
。
2.2 建已实现的基层 BaseDao
public class BaseDao<T> implements IBaseDao<T> { private static final String TAG = "hqk"; /** * 持有数据库操作类的引用 */ private SQLiteDatabase database; /** * 持有操作数据库表所对应的java类型 * User */ private Class<T> entityClass; /** * 保证实例化一次 */ private boolean isInit = false; private String tableName; // 检查表 private HashMap<String, Field> cacheMap; protected BaseDao() { } protected synchronized boolean init(Class<T> entity, SQLiteDatabase sqLiteDatabase) { if (!isInit) { //初始化完了 自动建表 entityClass = entity; database = sqLiteDatabase; if (entity.getAnnotation(DbTable.class) == null) { tableName = entity.getClass().getSimpleName(); } else { tableName = entity.getAnnotation(DbTable.class).value(); } if (!database.isOpen()) { return false; } String sql = createTable(); database.execSQL(sql); //建立好映射关系 initCacheMap(); isInit = true; } return true; } /** * 将真实表中的列名 + 成员变量进行 映射 * 缓存对应的 表 Model里的属性名以及对应表列名 */ private void initCacheMap() { cacheMap = new HashMap<>(); //这里没有必要查询 对应表中的任何数据,只想要对应表列名,所以 这 limit 0 String sql = "select * from " + tableName + " limit 0"; Cursor cursor = database.rawQuery(sql, null); String[] columnNames = cursor.getColumnNames(); Field[] columnFields = entityClass.getDeclaredFields(); //获取对应表中的列名数组,以及对应表Model里面的属性数组 for (String columnName : columnNames) { Field resultField = null; for (Field field : columnFields) { //拿到对应属性的注解值 String fieldAnnotationName = field.getAnnotation(DbFiled.class).value(); //如果对应的属性注解值与数据库表列名相同,则拿到对应属性值 if (columnName.equals(fieldAnnotationName)) { resultField = field; break; } } if (resultField != null) { cacheMap.put(columnName, resultField); } } } /** * 组装 创建表的SQL语句 * * @return */ private String createTable() { StringBuffer stringBuffer = new StringBuffer(); //开始组装 SQL语句 stringBuffer.append("create table if not exists "); stringBuffer.append(tableName + " ("); Field[] fields = entityClass.getDeclaredFields(); for (Field field : fields) { Class type = field.getType(); String primaryKey = null; try { primaryKey = field.getAnnotation(DbPrimaryKey.class).value(); } catch (Exception e) { } Log.i(TAG, "createTable primaryKey " + primaryKey); Log.i(TAG, "createTable type " + type); if (type == String.class) { if (null == primaryKey) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " TEXT,"); } else { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " TEXT PRIMARY KEY,"); } } else if (type == Double.class) { if (null == primaryKey) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " DOUBLE,"); } else { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " DOUBLE PRIMARY KEY,"); } } else if (type == Integer.class) { if (null == primaryKey) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " INTEGER,"); } else { boolean isAuto = field.getAnnotation(DbPrimaryKey.class).isAuto(); if (isAuto) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " INTEGER PRIMARY KEY AUTOINCREMENT,"); } else { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " INTEGER PRIMARY KEY,"); } } } else if (type == Long.class) { if (null == primaryKey) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " BIGINT,"); } else { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " BIGINT PRIMARY KEY,"); } } else if (type == byte[].class) { if (null == primaryKey) { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " BLOB,"); } else { stringBuffer.append(field.getAnnotation(DbFiled.class).value() + " BLOB PRIMARY KEY,"); } } else { /* 不支持的类型 */ continue; } } //循环完成后,最后一项会有 逗号 ,如果最后一个是逗号,则删除最后一个字符 if (stringBuffer.charAt(stringBuffer.length() - 1) == ',') { stringBuffer.deleteCharAt(stringBuffer.length() - 1); } //SQL 语句 收尾 stringBuffer.append(")"); Log.i(TAG, "createTable: " + stringBuffer.toString()); return stringBuffer.toString(); } @Override public Long insert(T entity) { Map<String, String> map = getValues(entity); ContentValues contentValues = getContentValues(map); return database.insert(tableName, null, contentValues); } /** * 获取对应 model 属性以及对应的注解值(表列名值) * * @param entity 对应 表结构的model * @return 返回 key= 列名,value=属性的值 map集合 */ private Map<String, String> getValues(T entity) { HashMap<String, String> map = new HashMap<>(); //获取对应缓存 model 里面的属性键 Iterator<Field> fieldIterator = cacheMap.values().iterator(); while (fieldIterator.hasNext()) { Field field = fieldIterator.next(); field.setAccessible(true); try { Object object = field.get(entity); if (object == null) { continue; } String value = object.toString(); String key = field.getAnnotation(DbFiled.class).value(); //遍历 取出对应 属性的值 以及对应的 注解值,并添加至Map里 if (!TextUtils.isEmpty(key) && !TextUtils.isEmpty(value)) { map.put(key, value); } } catch (IllegalAccessException e) { e.printStackTrace(); } } return map; } /** * 数据库数据结构的封装 * * @param map 带有 以表列名为键,的map * @return 数据库需要的封装格式 */ 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; } @Override public int update(T entity, T where) { Map values = getValues(entity); ContentValues contentValues = getContentValues(values); //条件 Map whereMap = getValues(where); Condition condition = new Condition(whereMap); return database.update(tableName, contentValues, condition.whereClause, condition.whereArgs); } class Condition { String whereClause; String[] whereArgs; public Condition(Map<String, String> whereClause) { boolean flag = false; if (true && flag) { } ArrayList list = new ArrayList(); StringBuilder stringBuilder = new StringBuilder(); // 这里之所以先添加 1=1 这个条件 是因为 // SQL where 后面需要给条件判断,而下面 while 循环 直接添加了 and // SQL 语句就变成了 where and 这显然不符合SQL语句 // 因此 加上 1=1 就变成了 where 1=1 and xx。起了一个呈上去下的作用 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) { stringBuilder.append(" and " + key + " =?"); list.add(value); } } this.whereClause = stringBuilder.toString(); this.whereArgs = (String[]) list.toArray(new String[list.size()]); } } @Override public int delete(T where) { Map map = getValues(where); Condition condition = new Condition(map); return database.delete(tableName, condition.whereClause, condition.whereArgs); } @Override public List<T> query(T where) { return query(where, null, null, null, null, null ); } //所有 条件 @Override public List<T> query(T where, String groupBy, String orderBy, String having,Integer startIndex, Integer limit) { String limitString=null; if(startIndex!=null&&limit!=null) { limitString=startIndex+" , "+limit; } Map map=getValues(where); Condition condition=new Condition(map); Cursor cursor= database.query(tableName, null, condition.whereClause, condition.whereArgs, groupBy, having, orderBy, limitString ); // 封装 --返回 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 { // cachmap ---对象中的成员变量 Filed annotion-- tb_name //cacheMap name ---Filed 1 // tb_name ---Filed 2 item=where.getClass().newInstance(); Iterator iterator=cacheMap.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry entry= (Map.Entry) iterator.next(); //tb_name /** * 得到列名 */ String colomunName= (String) entry.getKey(); // 通过列名查找到游标的索性 Integer colmunIndex= cursor.getColumnIndex(colomunName); // Filed //反射的成员 cursor Field field= (Field) entry.getValue(); Class type=field.getType(); if(colmunIndex!=-1) { // if (type == String.class) { 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==byte[].class) { field.set(item,cursor.getBlob(colmunIndex)); /* 不支持的类型 */ }else { continue; } } } list.add(item); } catch ( Exception e) { e.printStackTrace(); } } return list; } }
代码分析:
在这个BaseDao
里面,几乎分担了数据表大部分的脏活累活,根据model
结构自动生成对应SQL
并创建对应表,以及基础的增删改查操作。
2.3 建对应model 的Dao层
1.UserDao
public class UserDao<User> extends BaseDao<User> { @Override public Long insert(User entity) { return super.insert(entity); } @Override public List<User> query(User where) { return super.query(where); } @Override public int delete(User where) { return super.delete(where); } @Override public int update(User entity, User where) { return super.update(entity, where); } @Override public List<User> query(User where, String groupBy, String orderBy, String having, Integer startIndex, Integer limit) { return super.query(where, groupBy, orderBy, having, startIndex, limit); } }
2.PhotoDao
public class PhotoDao<Photo> extends BaseDao<Photo> { @Override public Long insert(Photo entity) { return super.insert(entity); } @Override public int update(Photo entity, Photo where) { return super.update(entity, where); } @Override public List<Photo> query(Photo where) { return super.query(where); } @Override public int delete(Photo where) { return super.delete(where); } }
代码分析:
虽然 BaseDao
已经完成了几乎所有的操作,但是一旦遇到多表查询的时候,光是一个BaseDao
远远不够。所以这里还是选择创建不同model
的Dao
层,并继承与BaseDao
。也就是说,有多少表,最好就创建对应多少个Dao层。
3、创建数据库工厂
public class BaseDaoFactory { private final String TAG = "hqk"; private SQLiteDatabase sqLiteDatabase; private String sqliteDatabasePath; private static BaseDaoFactory instance = new BaseDaoFactory(); //饿汉单例模式 public static BaseDaoFactory getInstance() { return instance; } public BaseDaoFactory() { //读者可随意更改路径以及对应数据库名,这里演示暂时放在根目录 sqliteDatabasePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/hqk.db"; sqLiteDatabase = SQLiteDatabase.openOrCreateDatabase(sqliteDatabasePath, null); Log.i(TAG, "sqliteDatabasePath : " + sqliteDatabasePath); Log.i(TAG, "sqLiteDatabase : " + sqLiteDatabase.getPath()); } /** * @param clazz * @param entityClass * @param <R> 我们在这可以把它看成某一个对象,它继承与 BaseDao<T> ,而里面的T 就是下面的那个空对象 * @param <T> 我们在这可以吧它看成某一个空对象 T * @return */ public synchronized <R extends BaseDao<T>, T> R createBaseDao(Class<R> clazz, Class<T> entityClass) { BaseDao baseDao = null; try { baseDao = clazz.newInstance(); baseDao.init(entityClass, sqLiteDatabase); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } return (R) baseDao; } }
代码分析:
这里也没啥好分析的,就一个数据库创建,以及对应model
的初始化。唯一值得注意的就是初始化的时候用了俩个泛型,具体什么意思,可按照代码注释理解。
4、创建对应model
1.User
@DbTable("tb_user") public class User { @DbPrimaryKey(value = "tb_id", isAuto = true) @DbFiled("tb_id") public Integer id; @DbFiled("tb_name") public String name;// @DbFiled("tb_age") public Integer age; public User(String name, Integer age) { this.name = name; this.age = age; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public User() { } }
2.Photo
@DbTable("tb_photo") public class Photo { @DbFiled("time") private String time; @DbFiled("id") private Long id; @DbFiled("path") private String path; public Photo( ) { } public Photo(String time, Long id, String path) { this.time = time; this.id = id; this.path = path; } public void setTime(String time) { this.time = time; } public void setId(Long id) { this.id = id; } public void setPath(String path) { this.path = path; } }
代码分析:
这俩类就是对应表结构model
类,用到了对应注解,相信通过注解能够清楚知道对应表结构是怎样的。
5、最终使用
ainActivity
public class MainActivity extends AppCompatActivity { UserDao<User> userDao; PhotoDao<Photo> photoDao; private ArrayList<User> listUser = new ArrayList<>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); requestPermission(this); } public void save(View view) { User user = new User("hqk", 18); long size = userDao.insert(user); Photo photo = new Photo("time", System.currentTimeMillis(), "path"); long photoSize = photoDao.insert(photo); Toast.makeText(this, "save line : " + size, Toast.LENGTH_LONG).show(); } public void update(View view) { User where = new User(); where.setAge(18); int size = userDao.update(new User("TOM", 99), where); Toast.makeText(this, "update Size : " + size, Toast.LENGTH_LONG).show(); } public void delete(View view) { User where = new User(); where.setAge(18); int size = userDao.delete(where); Toast.makeText(this, "delete Size : " + size, Toast.LENGTH_LONG).show(); } public void queryList(View view) { listUser.clear(); listUser.addAll(userDao.query(new User())); Toast.makeText(this, "查询条数为:" + listUser.size(), Toast.LENGTH_LONG).show(); } public void requestPermission( Activity activity) { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(activity, new String[]{ Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE }, 1); return; } createTable(); } private void createTable() { userDao = BaseDaoFactory.getInstance().createBaseDao(UserDao.class, User.class); photoDao = BaseDaoFactory.getInstance().createBaseDao(PhotoDao.class, Photo.class); } @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { super.onRequestPermissionsResult(requestCode, permissions, grantResults); createTable(); } }
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