Android开源:数据库ORM框架GreenDao学习心得及使用总结

    xiaoxiao2025-02-05  9

     最近在对开发项目的性能进行优化。由于项目里涉及了大量的缓存处理和数据库运用,需要对数据库进行频繁的读写、查询等操作。因此首先想到了对整个项目的数据库框架进行优化。

       原先使用android本身内置的sqllite,也就是用的最基本的SQLiteOpenHelper方法,这种方法对自己来说比较方便易懂。但是在使用过程中感觉很繁琐,从建表到对表的增删改查等操作,如果表对象的属性很多,就需要使用大量的代码来执行建表、插入等。在代码执行中还需要对数据库和游标的进行及时关闭(开启使用,用完关闭),而且还需要部分sql语言,这在开发中产生bug进行调试时尤其不方便。

         目前android经常用的orm框架主要有greenDAO、OrmLite、AndrORM。 综合了网上的各种评价,greenDAO的运行效率最高,内存消耗最少,性能最佳。因此决定采用greenDAO框架,对项目的orm框架进行改进。

    greenDAO与ORMLite性能对比

    经过两天的修改,终于将项目里的数据库相关的都优化完了。在这过程中,发现greenDAO的性能确实不错,而且使用相当方便,不再需要涉及到任何的sql语言,可以直接通过对象类进行建表、增删改查等,尤其是api接口又方便易懂。在摸索学习中发现国内相关学习资料实在实在是太少,遂决定在此记录下自己对使用这个orm框架的一些心得和方法总结。

    一、greenDAO相关

    1.greenDAO官网:http://greendao-orm.com/

    2.项目下载地址:https://github.com/greenrobot/greenDAO(或者官网)

    greenDAO是一个可以帮助Android开发者快速将Java对象映射到SQLite数据库的表单中的ORM解决方案,通过使用一个简单的面向对象API,开发者可以对Java对象进行存储、更新、删除和查询。

    greenDAO的主要设计目标:

       *最大性能(最快的Android ORM)

       *易于使用API

       *高度优化

       *最小内存消耗

    二、使用步骤

    官方Demo里共有六个工程目录,分别为:

    (1).DaoCore:库目录,即jar文件greendao-1.3.0-beta-1.jar的代码;

    (2).DaoExample:android范例工程;

    (3).DaoExampleGenerator:DaoExample工程的DAO类构造器,java工程;

    (4).DaoGenerator:DAO类构造器,java工程;

    (5).DaoTest、PerformanceTestOrmLite:其他测试相关的工程

    (一)DAO类构造

    首先需要新建一个java工程来生成DAO类文件,该工程需要导入greendao-generator.jar和freemarker.jar文件到项目中。

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 package  de.greenrobot.daogenerator.gentest; import  de.greenrobot.daogenerator.DaoGenerator; import  de.greenrobot.daogenerator.Entity; import  de.greenrobot.daogenerator.Property; import  de.greenrobot.daogenerator.Schema; import  de.greenrobot.daogenerator.ToMany; /**   * Generates entities and DAOs for the example project DaoExample.   *   * Run it as a Java application (not Android).   *   * @author Markus   */ public  class  ExampleDaoGenerator {                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          public  static  void  main(String[] args)  throws  Exception      {          Schema schema =  new  Schema( 3 ,  "de.greenrobot.daoexample" );                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  addNote(schema);          addCustomerOrder(schema);                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  new  DaoGenerator().generateAll(schema,  "../DaoExample/src-gen" );      }                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          private  static  void  addNote(Schema schema)      {          Entity note = schema.addEntity( "Note" );          note.addIdProperty();          note.addStringProperty( "text" ).notNull();          note.addStringProperty( "comment" );          note.addDateProperty( "date" );      }                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          private  static  void  addCustomerOrder(Schema schema)      {          Entity customer = schema.addEntity( "Customer" );          customer.addIdProperty();          customer.addStringProperty( "name" ).notNull();                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  Entity order = schema.addEntity( "Order" );          order.setTableName( "ORDERS" );  // "ORDER" is a reserved keyword          order.addIdProperty();          Property orderDate = order.addDateProperty( "date" ).getProperty();          Property customerId = order.addLongProperty( "customerId" ).notNull().getProperty();          order.addToOne(customer, customerId);                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  ToMany customerToOrders = customer.addToMany(order, customerId);          customerToOrders.setName( "orders" );          customerToOrders.orderAsc(orderDate);      }                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     }

    在main方法中,

    1 Schema schema =  new  Schema( 3 ,  "de.greenrobot.daoexample" );

    该方法第一个参数用来更新数据库版本号,第二个参数为要生成的DAO类所在包路径。

    然后进行建表和设置要生成DAO文件的目标工程的项目路径。

    1 2 3 addNote(schema); addCustomerOrder(schema); new  DaoGenerator().generateAll(schema,  "../DaoExample/src-gen" );

    其中src-gen这个目录名需要在运行前手动创建,否则会报错。

    如果运行后出现以下错误,则导入DaoGenerator项目的dao.ftl文件即可(或者直接使用DaoGenerator来生成DAO文件)。

    1 2 3 4 5 Exception in thread  "main"  java.io.FileNotFoundException: Template  "dao.ftl"  not found.      at freemarker.template.Configuration.getTemplate(Configuration.java: 742 )      at freemarker.template.Configuration.getTemplate(Configuration.java: 665 )      at de.greenrobot.daogenerator.DaoGenerator.<init>(DaoGenerator.java: 68 )      at de.greenrobot.daogenerator.gentest.ExampleDaoGenerator.main(ExampleDaoGenerator.java: 41 )

    运行后出现以下的提示说明DAO文件自动生成成功了,刷新一下DaoExample项目即可看到。

    1 2 3 4 5 6 7 8 9 10 11 12 13 greenDAO Generator Copyright  2011 - 2013  Markus Junginger, greenrobot.de. Licensed under GPL V3. This program comes with ABSOLUTELY NO WARRANTY Processing schema version  3 ... Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\NoteDao.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\Note.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\CustomerDao.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\Customer.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\OrderDao.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\Order.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\DaoMaster.java Written F:\Android_Ex\work_10\DaoExample\src-gen\de\greenrobot\daoexample\DaoSession.java Processed  3  entities in 204ms

    运行后可以看到,DaoExample项目src-gen下面自动生成了8个文件,3个实体对象,3个dao,1个DaoMaster,1个DaoSession.

    (二)创建表

    1.创建一个实体类

    1 Entity note = schema.addEntity( "Note" );

    默认表名就是类名,也可以自定义表名

    1 dao.setTableName( "NoteList" );

    greenDAO会自动根据实体类属性创建表字段,并赋予默认值。例如在数据库方面的表名和列名都来源于实体类名和属性名。默认的数据库名称是大写使用下划线分隔单词,而不是在Java中使用的驼峰式大小写风格。例如,一个名为“CREATIONDATE”属性将成为一个数据库列“CREATION_DATE”。

    设置一个自增长ID列为主键:

    1 dao.addIdProperty().primaryKey().autoincrement();

    设置其他各种类型的属性:

    1 2 3 dao.addIntProperty( "cityId" ); dao.addStringProperty( "infoType" ).notNull(); //非null字段 dao.addDoubleProperty( "Id" );

    在生成的实体类中,int类型为自动转为long类型。

    如果在编译过程中出现以下错误,那么有可能是主键的类型错误所致:

    1 java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

          在使用greenDAO时,一个实体类只能对应一个表,目前没法做到一个表对应多个实体类,或者多个表共用一种对象类型。后续的升级也不会针对这一点进行扩展。

    (二)表的增删改查

         增删改查相当方便,完全的面向对象,不需要涉及到任何的sql语言。

    1.查询

    范例1:查询某个表是否包含某个id:

    1 2 3 4 5 6 7 public  boolean  isSaved( int  ID) {      QueryBuilder<SaveList> qb = saveListDao.queryBuilder();      qb.where(Properties.Id.eq(ID));      qb.buildCount().count();      return  qb.buildCount().count() >  0  ?  true  :  false ; }

    范例2:获取整个表的数据集合,一句代码就搞定!

    1 2 3 4 public  List<PhotoGalleryDB> getPhotoGallery() {      return  photoGalleryDao.loadAll(); // 获取图片相册 }

    范例3:通过一个字段值查找对应的另一个字段值(为简便直接使用下面方法,也许有更简单的方法,尚未尝试)

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 /** 通过图片id查找其目录id */ public  int  getTypeId( int  picId) {      QueryBuilder<PhotoGalleryDB> qb = photoGalleryDao.queryBuilder();      qb.where(Properties.Id.eq(picId));      if  (qb.list().size() >  0 )      {          return  qb.list().get( 0 ).getTypeId();      }      else      {          return  - 1 ;      } }

    范例4:查找所有第一姓名是“Joe”并且以lastname排序。

    1 2 3 4 List joes = userDao.queryBuilder() .where(Properties.FirstName.eq( "Joe" )) .orderAsc(Properties.LastName) .list();

    范例5:多重条件查询

    (1)获取id为cityId并且infotype为HBContant.CITYINFO_SL的数据集合:

    1 2 3 4 5 6 7 public  List<CityInfoDB> getSupportingList( int  cityId) {      QueryBuilder<CityInfoDB> qb = cityInfoDao.queryBuilder();      qb.where(qb.and(Properties.CityId.eq(cityId),Properties.InfoType.eq(HBContant.CITYINFO_SL)));      qb.orderAsc(Properties.Id); // 排序依据      return  qb.list(); }

    (2)获取firstname为“Joe”并且出生于1970年10月以后的所有user集合:

    1 2 3 4 5 QueryBuilder qb = userDao.queryBuilder(); qb.where(Properties.FirstName.eq( "Joe" ), qb.or(Properties.YearOfBirth.gt( 1970 ), qb.and(Properties.YearOfBirth.eq( 1970 ), Properties.MonthOfBirth.ge( 10 )))); List youngJoes = qb.list();

    范例6:获取某列对象

    1 picJsonDao.loadByRowId(picId);

    2.增添/插入、修改

    插入数据更加简单,也是只要一句代码便能搞定!

    1 2 3 4 public  void  addToPhotoTable(Photo p) {      photoDao.insert(p); }

    插入时需要new一个新的对象,范例如下:

    1 2 3 4 5 6 7 DevOpenHelper helper =  new  DaoMaster.DevOpenHelper( this ,  "notes-db" ,  null );   db = helper.getWritableDatabase();   daoMaster =  new  DaoMaster(db);   daoSession = daoMaster.newSession();   noteDao = daoSession.getNoteDao();   Note note =  new  Note( null , noteText, comment,  new  Date());   noteDao.insert(note);

    修改更新:

    1 2 photoDao.insertOrReplace(photo); photoDao.insertInTx(photo);

    3.删除:

    (1)清空表格数据

    1 2 3 4 5 /** 清空相册图片列表的数据 */ public  void  clearPhoto() {      photoDao.deleteAll(); }

    (2)删除某个对象

    1 2 3 4 5 6 public  void  deleteCityInfo( int  cityId) {      QueryBuilder<DBCityInfo> qb = cityInfoDao.queryBuilder();      DeleteQuery<DBCityInfo> bd = qb.where(Properties.CityId.eq(cityId)).buildDelete();      bd.executeDeleteWithoutDetachingEntities(); }

    参考:https://github.com/greenrobot/greenDAO/issues/34

    由上可见,使用greenDAO进行数据库的增删改查时及其方便,而且性能极佳。

    (三)常用方法笔记

    1.在Application实现得到DaoMaster和DaoSession的方法:

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 private  static  DaoMaster daoMaster; private  static  DaoSession daoSession; /**   * 取得DaoMaster   *   * @param context   * @return   */ public  static  DaoMaster getDaoMaster(Context context) {      if  (daoMaster ==  null )      {          OpenHelper helper =  new  DaoMaster.DevOpenHelper(context, HBContant.DATABASE_NAME,  null );          daoMaster =  new  DaoMaster(helper.getWritableDatabase());      }      return  daoMaster; } /**   * 取得DaoSession   *   * @param context   * @return   */ public  static  DaoSession getDaoSession(Context context) {      if  (daoSession ==  null )      {          if  (daoMaster ==  null )          {              daoMaster = getDaoMaster(context);          }          daoSession = daoMaster.newSession();      }      return  daoSession; }

    2.增删改查工具类:

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 public  class  DBHelper {      private  static  Context mContext;      private  static  DBHelper instance;                                                                                                                                                                                                                                                                                                                                          private  CityInfoDBDao cityInfoDao;                                                                                                                                                                                                                                                                                                                                          private  DBHelper()      {      }                                                                                                                                                                                                                                                                                                                                          public  static  DBHelper getInstance(Context context)      {          if  (instance ==  null )          {              instance =  new  DBHelper();              if  (mContext ==  null )              {                  mContext = context;              }                                                                                                                                                                                                                                                                                                                                                          // 数据库对象              DaoSession daoSession = HBApplication.getDaoSession(mContext);              instance.cityInfoDao = daoSession.getCityInfoDBDao();          }          return  instance;      }                                                                                                                                                                                                                                                                                                                                          /** 添加数据 */      public  void  addToCityInfoTable(CityInfo item)      {          cityInfoDao.insert(item);      }                                                                                                                                                                                                                                                                                                                                          /** 查询 */      public  List<EstateLoveListJson> getCityInfoList()      {          QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();          return  qb.list();      }                                                                                                                                                                                                                                                                                                                                          /** 查询 */      public  List<CityInfo> getCityInfo()      {          return  cityInfoDao.loadAll(); // 查找图片相册      }                                                                                                                                                                                                                                                                                                                                          /** 查询 */      public  boolean  isSaved( int  Id)      {          QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();          qb.where(Properties.Id.eq(Id));          qb.buildCount().count();          return  qb.buildCount().count() >  0  ?  true  :  false ; // 查找收藏表      }                                                                                                                                                                                                                                                                                                                                          /** 删除 */      public  void  deleteCityInfoList( int  Id)      {          QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();          DeleteQuery<CityInfo> bd = qb.where(Properties.Id.eq(Id)).buildDelete();          bd.executeDeleteWithoutDetachingEntities();      }                                                                                                                                                                                                                                                                                                                                          /** 删除 */      public  void  clearCityInfo()      {          cityInfoDao.deleteAll();      }                                                                                                                                                                                                                                                                                                                                          /** 通过城市id查找其类型id */      public  int  getTypeId( int  cityId)      {          QueryBuilder<CityInfo> qb = cityInfoDao.queryBuilder();          qb.where(Properties.Id.eq(cityId));          if  (qb.list().size() >  0 )          {              return  qb.list().get( 0 ).getTypeId();          }          else          {              return  0 ;          }      }                                                                                                                                                                                                                                                                                                                                          /** 多重查询 */      public  List<CityInfo> getIphRegionList( int  cityId)      {          QueryBuilder<CityInfoDB> qb = cityInfoDao.queryBuilder();          qb.where(qb.and(Properties.CityId.eq(cityId), Properties.InfoType.eq(HBContant.CITYINFO_IR)));          qb.orderAsc(Properties.Id); // 排序依据          return  qb.list();      } }

    另外,还有多表关联、惰性加载等功能,待后续研究。

    参考资料:

    1.https://github.com/greenrobot/greenDAO

    2.http://greendao-orm.com/documentation/how-to-get-started/

    3.http://blog.csdn.net/krislight/article/details/9391455

    4.http://blog.loadlimits.info/2013/01/androidのorm、greendaoを使ってみた/

    5.http://leebart.tumblr.com/post/58408230144/how-to-daogenerator

    6.http://www.androidanalyse.com/greendao-an-android-orm-for-sqlite/

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