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：
[java] view plaincopy
/*
 * 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：
[java] view plaincopy
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
[java] view plaincopy
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：
[java] view plaincopy
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：
[java] view plaincopy
order.addIdProperty().autoincrement();  

再来看这一段：
[java] view plaincopy
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
[java] view plaincopy
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：
[java] view plaincopy
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：
[java] view plaincopy
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：
[java] view plaincopy
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：
[java] view plaincopy
public class Constants {
    public static final String DB_NAME = "note_db";
}  

Note实体类：
[java] view plaincopy
// 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;
    }  

}