Android之greenDao,一个orm的使用

 

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

 greenDaoMaster的学习研究
分类： 心得笔记 2013-07-20 16:59 603人阅读 评论(11) 收藏 举报
greenDao
最近一直在研究一个第三方的开源框架，greenDaoMaster是一个移动开发的ORM框架，由于网上一直查不到使用资料，所以自己摸索总结下用法。
首先需要新建一个JAVA项目用来自动生成文件。需要导入greendao-generator-1.3.0.jar和freemarker.jar到项目中
示例代码如下：
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/* 
 * Copyright (C) 2011 Markus Junginger, greenrobot (http://greenrobot.de) 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License. 
 */  
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);  
    }  
  
}  
来分析这段代码：
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Schema schema = new Schema(3, "de.greenrobot.daoexample");  

Schema对象接受2个参数，第一个参数是DB的版本号，通过更新版本号来更新数据库。第二个参数是自动生成代码的包路径。包路径系统自动生成
在来看这段代码
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Entity note = schema.addEntity("Note");  
        note.addIdProperty();  
        note.addStringProperty("text").notNull();  
        note.addStringProperty("comment");  
        note.addDateProperty("date");  

Entity表示一个实体可以对应成数据库中的表
系统自动会以传入的参数作为表的名字，这里表名就是NOTE
当然也可以自己设置表的名字，像这样：
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order.setTableName("ORDERS");  

接下来是一些字段参数设置。
如果想ID自动增长可以像这样：
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order.addIdProperty().autoincrement();  

再来看这一段：
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new DaoGenerator().generateAll(schema, "../DaoExample/src-gen");  

第一个参数是Schema对象，第二个参数是希望自动生成的代码对应的项目路径。
试了下src-gen这个文件夹必须手动创建,这里路径如果错了会抛出异常。
好了先别慌运行这段程序。新建一个Android项目名字是DaoExample，和刚才的JAVA项目保持在同一个文件夹下。
接着就可以运行刚才的JAVA程序，会看到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
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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 D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\NoteDao.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\Note.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\CustomerDao.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\Customer.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\OrderDao.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\Order.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\DaoMaster.java  
Written D:\android workspace\Open Source\greenDAO-master\DaoExample\src-gen\de\greenrobot\daoexample\DaoSession.java  
Processed 3 entities in 7743ms  

可以看到DaoMaster中封装了SQLiteDatabase和SQLiteOpenHelper
来看看如何使用GreenDao实现CRUD
如下代码实现插入一个Note对象：
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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);  
代码变得如此简单。
官方推荐将取得DaoMaster对象的方法放到Application层这样避免多次创建生成Session对象。
感觉这个框架和Web的Hibernate有异曲同工之妙。
这里列出自己实际开发中的代码方便记忆：
首先是在Application层实现得到DaoMaster和DaoSession的方法：
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public class BaseApplication extends Application {  
      
    private static BaseApplication mInstance;  
    private static DaoMaster daoMaster;  
    private static DaoSession daoSession;  
      
    @Override  
    public void onCreate() {  
        super.onCreate();  
        if(mInstance == null)  
            mInstance = this;  
    }  
      
    /** 
     * 取得DaoMaster 
     *  
     * @param context 
     * @return 
     */  
    public static DaoMaster getDaoMaster(Context context) {  
        if (daoMaster == null) {  
            OpenHelper helper = new DaoMaster.DevOpenHelper(context,Constants.DB_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;  
    }  
}  

然后写一个Db工具类：
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public class DbService {  
      
    private static final String TAG = DbService.class.getSimpleName();  
    private static DbService instance;  
    private static Context appContext;  
    private DaoSession mDaoSession;  
    private NoteDao noteDao;  
      
      
    private DbService() {  
    }  
  
    public static DbService getInstance(Context context) {  
        if (instance == null) {  
            instance = new DbService();  
            if (appContext == null){  
                appContext = context.getApplicationContext();  
            }  
            instance.mDaoSession = BaseApplication.getDaoSession(context);  
            instance.noteDao = instance.mDaoSession.getNoteDao();  
        }  
        return instance;  
    }  
      
      
    public Note loadNote(long id) {  
        return noteDao.load(id);  
    }  
      
    public List<Note> loadAllNote(){  
        return noteDao.loadAll();  
    }  
      
    /** 
     * query list with where clause 
     * ex: begin_date_time >= ? AND end_date_time <= ? 
     * @param where where clause, include 'where' word 
     * @param params query parameters 
     * @return 
     */  
      
    public List<Note> queryNote(String where, String... params){  
        return noteDao.queryRaw(where, params);  
    }  
      
      
    /** 
     * insert or update note 
     * @param note 
     * @return insert or update note id 
     */  
    public long saveNote(Note note){  
        return noteDao.insertOrReplace(note);  
    }  
      
      
    /** 
     * insert or update noteList use transaction 
     * @param list 
     */  
    public void saveNoteLists(final List<Note> list){  
            if(list == null || list.isEmpty()){  
                 return;  
            }  
            noteDao.getSession().runInTx(new Runnable() {  
            @Override  
            public void run() {  
                for(int i=0; i<list.size(); i++){  
                    Note note = list.get(i);  
                    noteDao.insertOrReplace(note);  
                }  
            }  
        });  
          
    }  
      
    /** 
     * delete all note 
     */  
    public void deleteAllNote(){  
        noteDao.deleteAll();  
    }  
      
    /** 
     * delete note by id 
     * @param id 
     */  
    public void deleteNote(long id){  
        noteDao.deleteByKey(id);  
        Log.i(TAG, "delete");  
    }  
      
    public void deleteNote(Note note){  
        noteDao.delete(note);  
    }  
      
}  

DB常量：
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public class Constants {  
    public static final String DB_NAME = "note_db";  
}  

Note实体类：
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// THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT. Enable "keep" sections if you want to edit.   
/** 
 * Entity mapped to table note. 
 */  
public class Note {  
  
    private Long id;  
    /** Not-null value. */  
    private String title;  
    /** Not-null value. */  
    private String content;  
    private java.util.Date createDate;  
  
    public Note() {  
    }  
  
    public Note(Long id) {  
        this.id = id;  
    }  
  
    public Note(Long id, String title, String content, java.util.Date createDate) {  
        this.id = id;  
        this.title = title;  
        this.content = content;  
        this.createDate = createDate;  
    }  
  
    public Long getId() {  
        return id;  
    }  
  
    public void setId(Long id) {  
        this.id = id;  
    }  
  
    /** Not-null value. */  
    public String getTitle() {  
        return title;  
    }  
  
    /** Not-null value; ensure this value is available before it is saved to the database. */  
    public void setTitle(String title) {  
        this.title = title;  
    }  
  
    /** Not-null value. */  
    public String getContent() {  
        return content;  
    }  
  
    /** Not-null value; ensure this value is available before it is saved to the database. */  
    public void setContent(String content) {  
        this.content = content;  
    }  
  
    public java.util.Date getCreateDate() {  
        return createDate;  
    }  
  
    public void setCreateDate(java.util.Date createDate) {  
        this.createDate = createDate;  
    }  
  
}