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<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：

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;
    }

}