greenDaoMaster的学习研究

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J***A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J***A项目保持在同一个文件夹下。

接着就可以运行刚才的J***A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;

}



}