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：

/** 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 keywordorder.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：

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

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：

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：

  order.addIdProperty().autoincrement();

再来看这一段：

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

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：

   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：

public class BaseApplication extends Application {private static BaseApplication mInstance;private static DaoMaster daoMaster;private static DaoSession daoSession;@Overridepublic 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：

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() {@Overridepublic 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：

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

Note实体类：

// 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;}}