Android 數據庫框架OrmLite的使用（二）

前面說了OrmLite的基本使用，現在說下更規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.整個DatabaseHelper使用單例只對外公布一個對象，保證app中只存在一個SQLite Connection，參考文章：http://www.touchlab.co/2011/10/single-sqlite-connection/
 * 2.對每個Bean創建一個XXXDao來處理當前Bean的數據庫操作，當然真正去和數據庫打交道的對象，通過getDao(T t)進行獲取
 *      getDao為一個泛型方法，會根據傳入的Class對象進行創建Dao，並且用一個Map來保存對所有的Dao對象，只有第一次調用時才會去調用底層的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();
        }
    }
    
    /**
     * 單例獲取該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;
    }
    
    /**
     * 釋放資源
     */
    @Override
    public void close() {
        super.close();
        for (String key : daos.keySet()) {
            Dao dao=daos.get(key);
            dao=null;
        }
    }
}

2.編寫Dao類

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.外鍵引用

package com.example.ormlite.bean;
import com.j256.ormlite.field.DatabaseField;
import com.j256.ormlite.table.DatabaseTable;
/**
 * ORMLite外鍵引用
 * 需求：兩個表User,Article,其中Article中需要存儲User的主鍵作為關聯，在ORMLite中如何實現？
 * 直接在Article中聲明一個Int類型userId屬性，當作普通屬性處理搞定，也是可行的。但是並沒有體現面向對象的思想。
 * 可按如下實現：
 * 1.不去定義一個int類型的userId,而是直接定義一個User成員變量，表示本Article屬於該User。
 * 2.在User user屬性上添加：@DatabaseField(canBeNull=true,foreign=true,columnName="user_id")
 *      canBeNull--表示不能為null;foreign=true表示一個外鍵;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
                + "]";
    }
}

接下來編寫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();
        }
    }
    
    /**
     * 通過Id得到一個Article
     * @param id
     * @return
     */
    @SuppressWarnings("unchecked")
    public Article getArticleWithUser(int id){
        Article article=null;
        try {
            article=articleDaoImpl.queryForId(id);
            //如何做到只傳一個Article的id,然后能夠拿到Article對象，且內部的user屬性直接賦值？
            //方式1
            helper.getDao(User.class).refresh(article.getUser());
            //方式2
            //在user屬性的注解上：@DatabaseField(canBeNull = true, foreign = true, columnName = "user_id", foreignAutoRefresh = true)
            //foreignAutoRefresh =true,當調用queryForId時，拿到Article對象則直接攜帶了user
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return article;
    }
    
    /**
     * 通過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;
    }
}

測試：

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());
    }
    
    /**
     * 通過id獲取一個攜帶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.關聯一個集合

每個User關聯一個或多個Article,如果在User中聲明一個Collection<Article> articles,可否做到在查詢User的時候一並能夠獲取到articles的值？

是可以的。在User中加屬性：

@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;
    }

測試中加方法：

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.查詢條件QueryBuilder的使用

（1）簡單的where等於

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");

上述的兩種方法都相當於：select * from tb_article where user_id = 2 and name = 'xxx' ; 

（3）復雜查詢

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' )  ;

再復雜的查詢也可通過拼湊獲得。

6.updateBuilder、deleteBuilder

使用queryBuilder是我們希望查詢完后直接返回List<Bean>集合，對於update我們並不關注返回值，可以直接用articleDaoImpl.updateRaw(statement, arguments);傳入sql和參數即可。也就沒必要去用

articleDaoImpl.updateBuilder().updateColumnValue("name","zzz").where().eq("user_id", 1);這么痛苦了。

同理，deleteBuilder也建議直接瓶邪sql，當然很簡單的除外。

7.事務

在Dao中直接寫如下代碼：

TransactionManager.callInTransaction(helper.getConnectionSource(),
                    new Callable<Void>() {

                        @Override
                        public Void call() throws Exception {

                            return null;
                        }
                    });

8.其他操作

1.當Bean繼承BaseDaoEnable時，可以使用bean.create(bean); bean.update(bean)一類操作

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需要手動設置，如果dao為null會報錯。

2.Join

Article與User做Join操作:

QueryBuilder<Article, Integer> articleBuilder = articleDaoImpl.queryBuilder();  
            QueryBuilder userBuilder = helper.getDao(User.class).queryBuilder();  
            articleBuilder.join(userBuilder); 

其他具體的查看官方文檔。

源碼下載：http://pan.baidu.com/s/1ntMX99n 提取碼：jri5