[Android第三方类库]greenDAO入门文章

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 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：

 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;

     @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：

 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 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 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 list){
             if(list == null || list.isEmpty()){
                  return;
             }
             noteDao.getSession().runInTx(new Runnable() {
             @Override
             public void run() {
                 for(int i=0; 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;
     }

 }

官方文档：http://greendao-orm.com/documentation/how-to-get-started/

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