前面说了OrmLite的基本使用，现在说下更规范的做法以及常用的一些功能。
1.DatabaseHelper
package com.example.ormlite.db;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import com.example.ormlite.bean.Article;
import com.example.ormlite.bean.User;
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;
/**
* 1.整个DatabaseHelper使用单例只对外公布一个对象，保证app中只存在一个SQLite Connection，参考文章：http://www.touchlab.co/2011/10/single-sqlite-connection/
* 2.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getDao(T t)进行获取
* getDao为一个泛型方法，会根据传入的Class对象进行创建Dao，并且用一个Map来保存对所有的Dao对象，只有第一次调用时才会去调用底层的getDao()。
* @author Administrator
*
*/
public class DatabaseHelperTwo extends OrmLiteSqliteOpenHelper{ private static final String TABLE_NAME="sqlite-test.db";
private static DatabaseHelperTwo instance; private Map<String,Dao> daos=new HashMap<String,Dao>();
public DatabaseHelperTwo(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();
}
} /**
* 单例获取该Helper
* @param context
* @return
*/
public static synchronized DatabaseHelperTwo getHelper(Context context){
context=context.getApplicationContext();
if(instance==null){
synchronized(DatabaseHelperTwo.class){
if(instance==null){
instance=new DatabaseHelperTwo(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;
}
}
}
2.编写Dao类
package com.example.ormlite.dao;
import java.sql.SQLException;
import com.example.ormlite.bean.User;
import com.example.ormlite.db.DatabaseHelperTwo;
import com.j256.ormlite.dao.Dao;
import android.content.Context; public class UserDaoTwo {
private Context context;
private Dao<User,Integer> userDaoImpl;
private DatabaseHelperTwo helper; @SuppressWarnings("unchecked")
public UserDaoTwo(Context context){
this.context=context;
try {
helper=DatabaseHelperTwo.getHelper(context);
userDaoImpl=helper.getDao(User.class);
} catch (SQLException e) {
e.printStackTrace();
}
} public void add(User user){
try {
userDaoImpl.create(user);
} catch (SQLException e) {
e.printStackTrace();
}
}
//......other operations
}
3.外键引用
package com.example.ormlite.bean;
import com.j256.ormlite.field.DatabaseField;
import com.j256.ormlite.table.DatabaseTable;
/**
* ORMLite外键引用
* 需求：两个表User,Article,其中Article中需要存储User的主键作为关联，在ORMLite中如何实现？
* 直接在Article中声明一个Int类型userId属性，当作普通属性处理搞定，也是可行的。但是并没有体现面向对象的思想。
* 可按如下实现：
* 1.不去定义一个int类型的userId,而是直接定义一个User成员变量，表示本Article属于该User。
* 2.在User user属性上添加：@DatabaseField(canBeNull=true,foreign=true,columnName="user_id")
* canBeNull--表示不能为null;foreign=true表示一个外键;columnName列名
* @author Administrator
*
*/
@DatabaseTable(tableName="tb_article")
public class Article {
@DatabaseField(generatedId=true)
private int id;
@DatabaseField(columnName="title")
private String title;
@DatabaseField(canBeNull=true,foreign=true,columnName="user_id")
private User user;
public Article() {
super();
// TODO Auto-generated constructor stub
}
public Article(String title, User user) {
super();
this.title = title;
this.user = user;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String toString() {
return "Article [id=" + id + ", title=" + title + ", user=" + user
+ "]";
}
}
接下来编写ArticleDao:
package com.example.ormlite.dao;
import java.sql.SQLException;
import java.util.List;
import android.content.Context;
import com.example.ormlite.bean.Article;
import com.example.ormlite.bean.User;
import com.example.ormlite.db.DatabaseHelperTwo;
import com.j256.ormlite.dao.Dao; public class ArticleDao {
private Dao<Article,Integer> articleDaoImpl;
private DatabaseHelperTwo helper; @SuppressWarnings("unchecked")
public ArticleDao(Context context){
helper=DatabaseHelperTwo.getHelper(context);
try {
articleDaoImpl=helper.getDao(Article.class);
} catch (SQLException e) {
e.printStackTrace();
}
} /**
* 添加
* @param article
*/
public void add(Article article){
try {
articleDaoImpl.create(article);
} catch (SQLException e) {
e.printStackTrace();
}
} /**
* 通过Id得到一个Article
* @param id
* @return
*/
@SuppressWarnings("unchecked")
public Article getArticleWithUser(int id){
Article article=null;
try {
article=articleDaoImpl.queryForId(id);
//如何做到只传一个Article的id,然后能够拿到Article对象，且内部的user属性直接赋值？
//方式1
helper.getDao(User.class).refresh(article.getUser());
//方式2
//在user属性的注解上：@DatabaseField(canBeNull = true, foreign = true, columnName = "user_id", foreignAutoRefresh = true)
//foreignAutoRefresh =true,当调用queryForId时，拿到Article对象则直接携带了user
} catch (SQLException e) {
e.printStackTrace();
}
return article;
} /**
* 通过Id得到一片文章
* @param id
* @return
*/
public Article getArticleById(int id){
Article article=null;
try {
article=articleDaoImpl.queryForId(id);
} catch (SQLException e) {
e.printStackTrace();
}
return article;
} public List<Article> getArticleListByUserId(int userId){
try {
return articleDaoImpl.queryBuilder().where().eq("user_id", userId).query();
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
}
测试：
package com.example.ormlite.test;
import java.util.List;
import android.test.AndroidTestCase;
import android.util.Log;
import com.example.ormlite.bean.Article;
import com.example.ormlite.bean.User;
import com.example.ormlite.dao.ArticleDao;
import com.example.ormlite.dao.UserDao;
import com.example.ormlite.dao.UserDaoTwo; public class OrmLiteDbTestTwo extends AndroidTestCase{
public void AddArticle(){
User u=new User();
u.setName("yq");
u.setDesc("developer");
new UserDao(getContext()).add(u); Article article=new Article();
article.setTitle("ORMLite的使用");
article.setUser(u);
new ArticleDao(getContext()).add(article);
} public void testGetArticleById(){
Article article = new ArticleDao(getContext()).getArticleById(1);
Log.i("OrmLiteDbTestTwo", article.getUser().toString() + " , " + article.getTitle());
} /**
* 通过id获取一个携带User的Article
*/
public void testGetArticleWithUser(){
Article article = new ArticleDao(getContext()).getArticleWithUser(1);
Log.i("OrmLiteDbTestTwo", article.getUser().toString() + " , " + article.getTitle());
} public void testSGetArticleListByUserId(){
List<Article> articles =new ArticleDao(getContext()).getArticleListByUserId(1);
Log.i("OrmLiteDbTestTwo", articles.toString());
}
}
4.关联一个集合
每个User关联一个或多个Article,如果在User中声明一个Collection<Article> articles,可否做到在查询User的时候一并能够获取到articles的值？
是可以的。在User中加属性：
@ForeignCollectionField
private Collection<Article> articles;
UserDao中加方法：
public User getUserById(int id){
try {
return userDaoImpl.queryForId(id);
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
测试中加方法：
public void testGetUserById(){
User user=new UserDaoTwo(getContext()).getUserById(2);
Log.i("OrmLiteDbTestTwo", user.getName());
if(user.getArticles()!=null){
for (Article article : user.getArticles()) {
Log.i("OrmLiteDbTestTwo", article.toString());
}
}
}
5.查询条件QueryBuilder的使用
（1）简单的where等于
articleDaoImpl.queryBuilder().where().eq("user_id", userId).query(); //返回Article的列表
（2）where and
QueryBuilder<Article, Integer> queryBuilder=articleDaoImpl.queryBuilder();
Where<Article, Integer> where=queryBuilder.where();
where.eq("user_id", 2);
where.and();
where.eq("name", "xxx"); //或者
articleDaoImpl.queryBuilder().where().eq("user_id", userId).and().eq("name", "xxx");
上述的两种方法都相当于：select * from tb_article where user_id = 2 and name = 'xxx' ;
（3）复杂查询
where.or(
where.and(
where.eq("user_id", 1),where.eq("name", "xxx")),
where.and(
where.eq("user_id", 2),where.eq("name", "yyy")));
select * from tb_article where ( user_id = 1 and name = 'xxx' ) or ( user_id = 2 and name = 'yyy' ) ;
再复杂的查询也可通过拼凑获得。
6.updateBuilder、deleteBuilder
使用queryBuilder是我们希望查询完后直接返回List<Bean>集合，对于update我们并不关注返回值，可以直接用articleDaoImpl.updateRaw(statement, arguments);传入sql和参数即可。也就没必要去用
articleDaoImpl.updateBuilder().updateColumnValue("name","zzz").where().eq("user_id", 1);这么痛苦了。
同理，deleteBuilder也建议直接瓶邪sql，当然很简单的除外。
7.事务
在Dao中直接写如下代码：
TransactionManager.callInTransaction(helper.getConnectionSource(),
new Callable<Void>() { @Override
public Void call() throws Exception { return null;
}
});
8.其他操作
1.当Bean继承BaseDaoEnable时，可以使用bean.create(bean); bean.update(bean)一类操作
例如：
package com.example.ormlite.bean;
import com.j256.ormlite.field.DatabaseField;
import com.j256.ormlite.misc.BaseDaoEnabled;
import com.j256.ormlite.table.DatabaseTable; @DatabaseTable(tableName = "tb_student")
public class Student extends BaseDaoEnabled<Student, Integer>
{
@DatabaseField(generatedId = true)
private int id; @DatabaseField
private String name; public Student(){
} 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;
}
}
Dao dao=DatabaseHelperTwo.getHelper(context).getDao(Student.class);
Student stu=new Student();
stu.setDao(dao);
stu.setName("qq");
stu.create();
前提是dao需要手动设置，如果dao为null会报错。
2.Join
Article与User做Join操作:
QueryBuilder<Article, Integer> articleBuilder = articleDaoImpl.queryBuilder();
QueryBuilder userBuilder = helper.getDao(User.class).queryBuilder();
articleBuilder.join(userBuilder);
其他具体的查看官方文档。
源码下载：http://pan.baidu.com/s/1ntMX99n 提取码：jri5