轻量级数据库，不用写 SQL ，仅仅通过注解就能完成对数据库的操作

package com.devyk.ykdblib.db.imp; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.text.TextUtils; import android.util.Log; import com.devyk.ykdblib.annotation.YKField; import com.devyk.ykdblib.annotation.YKTable; import com.devyk.ykdblib.db.Condition; import com.devyk.ykdblib.db.IBaseDao; import java.lang.reflect.Field; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set; /** * <pre> * author : devyk on 2019-07-31 17:17 * blog : https://juejin.im/user/578259398ac2470061f3a3fb/posts * github : https://github.com/yangkun19921001 * mailbox : [email protected] * desc : This is BaseDaoImp * </pre> */ public class BaseDaoImp<T> implements IBaseDao<T> { private String TAG = getClass().getSimpleName(); /** * 持有数据库的引用 */ private SQLiteDatabase mSQLiteDatabase; /** * 表名 */ private String mTableName; /** * 持有操作数据库所对应的 java 类型 */ private Class<T> mEntityClass; /** * 标记：用来表示是否已经初始化操作 */ private boolean isInit = false; /** * 定义一个缓存空间 （key:字段名 value: 成员变量） */ private HashMap<String, Field> mCacheMap; /** * 初始化 * * @param sqLiteDatabase * @param entityClass */ public void init(SQLiteDatabase sqLiteDatabase, Class<T> entityClass) { this.mSQLiteDatabase = sqLiteDatabase; this.mEntityClass = entityClass; if (!isInit) { //自动建表，取得表名 if (entityClass != null && (entityClass.getAnnotation(YKTable.class) == null)) { //通过反射得到类名 this.mTableName = entityClass.getSimpleName(); } else { if (TextUtils.isEmpty(entityClass.getAnnotation(YKTable.class).value())) { //如果有注解但是注解为空的话，就取当前 类名 this.mTableName = entityClass.getSimpleName(); } else { //取得注解上面的表名 this.mTableName = entityClass.getAnnotation(YKTable.class).value(); } } //执行创建表的操作， 使用 getCreateTabeSql () 生成 sql 语句 String autoCreateTabSql = getCreateTableSql(); Log.i(TAG, "tagSQL-->" + autoCreateTabSql); //执行创建表的 SQL this.mSQLiteDatabase.execSQL(autoCreateTabSql); mCacheMap = new HashMap<>(); initCacheMap(); isInit = true; } } private void initCacheMap() { //取得所有字段名称 String sql = "select * from " + mTableName + " limit 1, 0";//创建一个空间 sql Cursor cursor = mSQLiteDatabase.rawQuery(sql, null); String[] columnNames = cursor.getColumnNames(); //2. 取得所有的成员变量 Field[] declaredFields = mEntityClass.getDeclaredFields(); //字段 跟 成员变量 for (String columnName : columnNames) { Field columnField = null; for (Field field : declaredFields) { //访问权限打开 field.setAccessible(true); String fileName = ""; //对象中成员变量名字 if (field.getAnnotation(YKField.class) != null) { fileName = field.getAnnotation(YKField.class).value(); } else { fileName = field.getName(); } if (columnName.equals(fileName)) {//匹配 columnField = field; break; } } if (columnField != null) { mCacheMap.put(columnName, columnField); } } } /** * 需要被执行创建表的 sql * * @return */ private String getCreateTableSql() { StringBuffer sb = new StringBuffer(); sb.append("create table if not exists ").append(mTableName + "("); //反射得到所有的成员变量 Field[] declaredFields = mEntityClass.getDeclaredFields(); for (Field declaredField : declaredFields) { //首先拿到成员的属性 Class<?> type = declaredField.getType(); //通过注解获取 if (declaredField.getAnnotation(YKField.class) != null) { //通过注解获取 if (type == String.class) { sb.append(declaredField.getAnnotation(YKField.class).value() + " TEXT,"); } else if (type == Integer.class) { sb.append(declaredField.getAnnotation(YKField.class).value() + " INTEGER,"); } else if (type == Long.class) { sb.append(declaredField.getAnnotation(YKField.class).value() + " BIGINT,"); } else if (type == Double.class) { sb.append(declaredField.getAnnotation(YKField.class).value() + " DOUBLE,"); } else if (type == byte[].class) { sb.append(declaredField.getAnnotation(YKField.class).value() + " BLOB,"); } else { //不支持的类型 continue; } } else { //通过反射获取 if (type == String.class) { sb.append(declaredField.getName() + " TEXT,"); } else if (type == Integer.class) { sb.append(declaredField.getName() + " INTEGER,"); } else if (type == Long.class) { sb.append(declaredField.getName() + " BIGINT,"); } else if (type == Double.class) { sb.append(declaredField.getName() + " DOUBLE,"); } else if (type == byte[].class) { sb.append(declaredField.getName() + " BLOB,"); } else { //不支持的类型 continue; } } } //删除最后一位 if (sb.charAt(sb.length() - 1) == ',') { sb.deleteCharAt(sb.length() - 1); } sb.append(")"); return sb.toString(); } /** * 插入数据 * @param entity * @return */ @Override public long insert(T entity) { //1. 准备好 ContentValues 中需要的数据 Map<String, String> map = getValues(entity); if (map == null || map.size() == 0) return 0; //2. 把数据转移到 ContentValues 中 ContentValues values = getContentValues(map); //将数据插入表中 return mSQLiteDatabase.insert(mTableName, null, values); } /** * @param map 成员变量的名字，成员变量的值 * @return */ private ContentValues getContentValues(Map<String, String> map) { ContentValues contentValues = new ContentValues(); Set<String> keys = map.keySet(); Iterator<String> iterator = keys.iterator(); while (iterator.hasNext()) { String key = iterator.next(); String values = map.get(key); if (values != null) { contentValues.put(key, values); } } return contentValues; } /** * key(字段) - values(成员变量) ---》getValues 后 ---》key (成员变量的名字) ---values 成员变量的值 id 1，name alan , password 123 * * @param entity * @return */ private Map<String, String> getValues(T entity) { HashMap<String, String> map = new HashMap<>(); //返回所有的成员变量 Iterator<Field> iterator = mCacheMap.values