android Sqlite数据库对象模型ORMLite框架学习

在Android项目中或多或少的都会使用数据库，为了提高我们的开发效率，当然少不了数据库ORM框架了，尤其是某些数据库操作特别频繁的app。
下面开始介绍ORMLite的入门用法~

1、下载 ORMLite Jar
首先去 ORMLite官网下载jar包，对于Android为：ormlite-android-4.48.jar 和 ormlite-core-4.48.jar ；

2、配置Bean类
有了jar,我们直接新建一个项目为：zhy_ormlite，然后把jar拷贝到libs下。
然后新建一个包：com.zhy.zhy_ormlite.bean专门用于存放项目中的Bean，首先新建一个User.java

package com.zhy.zhy_ormlite.bean;

import com.j256.ormlite.field.DatabaseField;
import com.j256.ormlite.table.DatabaseTable;

@DatabaseTable(tableName = "tb_user")
public class User
{
	@DatabaseField(generatedId = true)
	private int id;
	@DatabaseField(columnName = "name")
	private String name;
	@DatabaseField(columnName = "desc")
	private String desc;

	public User()
	{
	}

	public User(String name, String desc)
	{
		this.name = name;
		this.desc = desc;
	}

	public int getId()
	{
		return id;
	}

	public void setId(int id)
	{
		this.id = id;
	}

	public String getName()
	{
		return name;
	}

	public void setName(String name)
	{
		this.name = name;
	}

	public String getDesc()
	{
		return desc;
	}

	public void setDesc(String desc)
	{
		this.desc = desc;
	}

}

首先在User类上添加@DatabaseTable(tableName = "tb_user")，标明这是数据库中的一张表，标明为tb_user
然后分别在属性上添加@DatabaseField(columnName = "name") ，columnName的值为该字段在数据中的列名
@DatabaseField(generatedId = true) ，generatedId 表示id为主键且自动生成

3、编写DAO类

原生的数据库操作，需要继承SQLiteOpenHelper，这里我们需要继承OrmLiteSqliteOpenHelper，看代码：

package com.zhy.zhy_ormlite.db;

import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;

import com.j256.ormlite.android.apptools.OrmLiteSqliteOpenHelper;
import com.j256.ormlite.dao.Dao;
import com.j256.ormlite.support.ConnectionSource;
import com.j256.ormlite.table.TableUtils;
import com.zhy.zhy_ormlite.bean.Article;
import com.zhy.zhy_ormlite.bean.Student;
import com.zhy.zhy_ormlite.bean.User;

public  class DatabaseHelper extends OrmLiteSqliteOpenHelper
{
	private static final String TABLE_NAME = "sqlite-test.db";

	private Map<String, Dao> daos = new HashMap<String, Dao>();

	private DatabaseHelper(Context context)
	{
		super(context, TABLE_NAME, null, 4);
	}

	@Override
	public void onCreate(SQLiteDatabase database,
			ConnectionSource connectionSource)
	{
		try
		{
			TableUtils.createTable(connectionSource, User.class);
			TableUtils.createTable(connectionSource, Article.class);
			TableUtils.createTable(connectionSource, Student.class);
		} catch (SQLException e)
		{
			e.printStackTrace();
		}
	}

	@Override
	public void onUpgrade(SQLiteDatabase database,
			ConnectionSource connectionSource, int oldVersion, int newVersion)
	{
		try
		{
			TableUtils.dropTable(connectionSource, User.class, true);
			TableUtils.dropTable(connectionSource, Article.class, true);
			TableUtils.dropTable(connectionSource, Student.class, true);
			onCreate(database, connectionSource);
		} catch (SQLException e)
		{
			e.printStackTrace();
		}
	}

	private static DatabaseHelper instance;

	/**
	 * 单例获取该Helper
	 * 
	 * @param context
	 * @return
	 */
	public static synchronized DatabaseHelper getHelper(Context context)
	{
		context = context.getApplicationContext();
		if (instance == null)
		{
			synchronized (DatabaseHelper.class)
			{
				if (instance == null)
					instance = new DatabaseHelper(context);
			}
		}

		return instance;
	}

	public synchronized Dao getDao(Class clazz) throws SQLException
	{
		Dao dao = null;
		String className = clazz.getSimpleName();

		if (daos.containsKey(className))
		{
			dao = daos.get(className);
		}
		if (dao == null)
		{
			dao = super.getDao(clazz);
			daos.put(className, dao);
		}
		return dao;
	}

	/**
	 * 释放资源
	 */
	@Override
	public void close()
	{
		super.close();

		for (String key : daos.keySet())
		{
			Dao dao = daos.get(key);
			dao = null;
		}
	}

}

1、整个DatabaseHelper使用单例只对外公布出一个对象，保证app中只存在一个SQLite Connection
2、我们对每个Bean创建一个XXXDao来处理当前Bean的数据库操作，当然真正去和数据库打交道的对象，通过上面代码中的getDao（T t）进行获取
getDao为一个泛型方法，会根据传入Class对象进行创建Dao，并且使用一个Map来保持所有的Dao对象，只有第一次调用时才会去调用底层的getDao()。

4、Bean的Dao

package com.zhy.zhy_ormlite.db;

import java.sql.SQLException;

import android.content.Context;

import com.j256.ormlite.dao.Dao;
import com.zhy.zhy_ormlite.bean.User;

public class UserDao
{
	private Context context;
	private Dao<User, Integer> userDaoOpe;
	private DatabaseHelper helper;

	public UserDao(Context context)
	{
		this.context = context;
		try
		{
			helper = DatabaseHelper.getHelper(context);
			userDaoOpe = helper.getDao(User.class);
		} catch (SQLException e)
		{
			e.printStackTrace();
		}
	}

	/**
	 * 增加一个用户
	 * @param user
	 */
	public void add(User user)
	{
		try
		{
			userDaoOpe.create(user);
		} catch (SQLException e)
		{
			e.printStackTrace();
		}

	}//...other operations


}

5.事务操作

//事务操作
		TransactionManager.callInTransaction(helper.getConnectionSource(),
				new Callable<Void>()
				{

					@Override
					public Void call() throws Exception
					{
						return null;
					}
				});

ORMLite下载地址：http://ormlite.com/releases/


转自：http://blog.csdn.net/lmj623565791/article/details/39122981