Android ORM - OrmLite

AndroidRefine 2016-11

系列博文
Android ORM - GreenDAO
Android ORM - OrmLite

先普及一下数据库的关联关系，可以直接参看博文数据库设计(一对一、一对多、多对多）

OrmLite是什么

相信大家在android开发过程中大多数项目都需要使用android的数据库sqllite，但是每次直接利用android提供的api来增删改查数据表有点繁琐，做javaweb的都知道有一款数据库框架叫Hibernate ，android端同样有类似这样的框架OrmLite,

Demo

这里通过一个简单的栗子直观感受一下ORM框架数据持久化提供的便利

配置文件

看一下gradle配置文件

gradle.build

//ORMLite
compile group: 'com.j256.ormlite', name: 'ormlite-android', version: '5.0'
compile 'com.j256.ormlite:ormlite-core:5.0'

获取ORMLite的maven地址可供参考

源码文件

首先是POJO类

LiteInfo.java

package okhttp.mutex.com.orm_demo.ormlite;
import com.j256.ormlite.field.DatabaseField;
import com.j256.ormlite.table.DatabaseTable;
@DatabaseTable(tableName = "lite_info")
public class LiteInfo {
    @DatabaseField(id = true)
    private long id;
    @DatabaseField
    private String name;
    @DatabaseField
    private int age;
    public LiteInfo() {
    }
    public LiteInfo(long id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String namel) {
        this.name = namel;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "LiteInfo{" +
                "id=" + id +
                ", namel='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

简要介绍一下上面的注解

• @DatabaseTable：表示定义了一个数据表，如果不指定名字，在Android中会以类名作为表名，如packageInfo就是SQLite数据库中的表名，我们也可以指定表名，@DatabaseTable(tableName = "tb_package") 。
• @DatabaseField：表示定义了数据中的一个字段，id表示数据中的一个主键，如果指定为generatedId，表示自动增长id，我们不需要给它赋值。其他字段，可以使用columnName来指定字段名，canBeNull表示是否为空，这些赋值可以按照以下来指定
  -（id = true, canBeNull = false）

然后定义OrmLiteHelper继承自OrmLiteSqliteOpenHelper

OrmLiteHelper.java

package okhttp.mutex.com.orm_demo.ormlite;
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 java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
public class OrmLiteHelper extends OrmLiteSqliteOpenHelper {
    private static final String TAB_NAME = "orm_lite_table_name";
    private static OrmLiteHelper sORMLITEHELPER;
    private Map<String, Dao> mDaoMap = new HashMap<>();
    private OrmLiteHelper(Context context) {
        super(context, TAB_NAME, null, 1);
    }
    public static void createInstance(Context context) {
        if (sORMLITEHELPER == null) {
            synchronized (OrmLiteHelper.class) {
                if (sORMLITEHELPER == null) {
                    sORMLITEHELPER = new OrmLiteHelper(context);
                }
            }
        }
    }
    public static OrmLiteHelper getInstance() {
        return sORMLITEHELPER;
    }
    public Dao getLiteDao(Class clazz) throws SQLException {
        Dao dao = null;
        String className = clazz.getSimpleName();
        synchronized (this) {
            if (mDaoMap.containsKey(className)) {
                dao = mDaoMap.get(className);
            }
            if (dao == null) {
                dao = super.getDao(clazz);
                mDaoMap.put(className, dao);
            }
        }
        return dao;
    }
    @Override
    public void close() {
        for (String key : mDaoMap.keySet()) {
            Dao dao = mDaoMap.get(key);
            dao = null;
        }
        super.close();
    }
    @Override
    public void onCreate(SQLiteDatabase database, ConnectionSource connectionSource) {
        try {
            TableUtils.createTable(connectionSource, LiteInfo.class);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void onUpgrade(SQLiteDatabase database, ConnectionSource connectionSource, int oldVersion, int newVersion) {
        try {
            TableUtils.dropTable(connectionSource, LiteInfo.class, true);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        onCreate(database, connectionSource);
    }
}

接着定义DAO类LiteInfoDao

LiteInfoDao.java

package okhttp.mutex.com.orm_demo.ormlite;
import com.j256.ormlite.dao.Dao;
import com.j256.ormlite.stmt.PreparedQuery;
import java.sql.SQLException;
import java.util.List;
public class LiteInfoDao {
    private Dao<LiteInfo, Long> mLiteDao;
    public LiteInfoDao() {
        OrmLiteHelper helper = OrmLiteHelper.getInstance();
        try {
            mLiteDao = helper.getLiteDao(LiteInfo.class);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    /**
     * 插入一条数据
     *
     * @param info
     */
    public void addInfo(LiteInfo info) {
        if (mLiteDao == null)
            return;
        try {
            mLiteDao.createIfNotExists(info);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    public LiteInfo queryInfo(long id) {
        try {
            return mLiteDao.queryForId(id);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    public List<LiteInfo> query() {
        try {
            return mLiteDao.queryForAll();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
}

最后测试一下上面是否工作正常

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private LiteInfoDao mOrmDao;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mOrmDao = new LiteInfoDao();
        initOrmInfo();
        queryOrmOri();
        queryOrmOri(1);
    }
    private void queryOrmOri() {
        List<LiteInfo> list = mOrmDao.query();
        for (LiteInfo info : list) {
            Log.i("mutex", info.toString());
        }
    }
    private void queryOrmOri(long id) {
        LiteInfo info = mOrmDao.queryInfo(id);
        Log.w("mutex", info.toString());
    }
    private void initOrmInfo() {
        for (int i = 0; i < 10; i++) {
            LiteInfo info = new LiteInfo(i, "name" + i, i + 20);
            mOrmDao.addInfo(info);
        }
    }
}

验证结果

参考文章：
GreenDAO Website Github
OrmLite Website Github