Android上ORMLite的配置和简单使用

ORMLite和GreenDao是Android上最流行的ORM(对象关系映射)框架

现在来简单梳理下ORMLite在Android上的简单使用

1.在官网下载jar包,将这两个jar包放在libs目录下,然后同步工程(也就是将这两个jar包添加进library)



2.创建一个java类(User.java),这个类映射到数据库当中的一张表

@DatabaseTable(tableName = "user")
public class User {

public User() {
}

public User(int id, String name, String age, String address) {
this.id = id;
this.name = name;
this.age = age;
this.address = address;
}

@DatabaseField(id = true)
private int id;

@DatabaseField(columnName = "name")
private String name;

@DatabaseField(columnName = "age")
private String age;

@DatabaseField(columnName = "address")
private String address;

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 getAge() {
return age;
}

public void setAge(String age) {
this.age = age;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}
}

@DatabaseTable(tableName = “user”) : 代表此类对应于数据库当中的名为user的表

@DatabaseField() : 代表此字段是数据库当中的一个列名

例如:

@DatabaseField(id = true)

private int id; 代表id是此表的主键

@DatabaseField(columnName = “name”)

private String name; 代表name对应于user表中的name字段

更多@DatabaseField()括号中的注解请参考 :　ORMLite注解小计

3.新建一个继承自OrmLiteSqliteOpenHelper的类DatabaseHelper,主要用于创建、更新数据库，也可以用来获取数据库操作对象dao

public class DatabaseHelper extends OrmLiteSqliteOpenHelper {
private static final String DB_NAME = "ormtest.db";
private static final int DB_VERSION = 1;

private Dao<User, Integer> userDao;

private DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}

private static volatile DatabaseHelper mInstance;

/**
* 单例模式,获取DatabaseHelper的唯一实例
*
* @param context
* @return
*/
public static DatabaseHelper getInstance(Context context) {
if (mInstance == null) {
synchronized (DatabaseHelper.class) {
if (mInstance == null) {
mInstance = new DatabaseHelper(context);
}
}
}

return mInstance;
}

/**
* 如果还没有这个数据库的时候就会创建数据库,同时创建表格
*
* @param sqLiteDatabase
* @param connectionSource
*/
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase, ConnectionSource connectionSource) {

try {
//创建表
TableUtils.createTable(connectionSource, User.class);

} catch (SQLException e) {
e.printStackTrace();
}
}

/**
* 升级数据库
*
* @param sqLiteDatabase
* @param connectionSource
* @param i
* @param i1
*/
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, ConnectionSource connectionSource, int i, int i1) {
try {
TableUtils.dropTable(connectionSource, User.class, true);
onCreate(sqLiteDatabase, connectionSource);
} catch (SQLException e) {
e.printStackTrace();
}
}

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

4.从DatabaseHelper获取dao对象,用来操作数据库(增删改查)

DatabaseHelper helper = DatabaseHelper.getInstance(this);
try {
Dao<User, Integer> dao = helper.getDao(User.class);
dao.delete(new User());//删除数据

} catch (SQLException e) {
e.printStackTrace();
}

上面只罗列了删除(delete),还有增(create)、改（update）、查（query）的方法

（建议）自己封装一个dao，比如我这里自己封装了一个UserDao,里面包含了数据的增删改查的方法

public class UserDao {
private DatabaseHelper mHelper;
private Dao<User, Integer> mDao;

private static volatile UserDao mUserDao;

private UserDao(Context context) {
if (mDao == null) {
if (mHelper == null) {
mHelper = DatabaseHelper.getInstance(context);
}

try {
mDao = mHelper.getDao(User.class);
} catch (SQLException e) {
e.printStackTrace();
}
}
}

publ
bc5d
ic static UserDao getInstance(Context context) {
if (mUserDao == null) {
synchronized (UserDao.class) {
if (mUserDao == null) {
mUserDao = new UserDao(context);
}
}
}

return mUserDao;
}

/**
* Create a new row in the database from an object
* 创建一条新的记录到数据库中
*
* @param user
* @return 是否插入成功
*/
public boolean insert(User user) {
boolean flag = false;
try {
//插入或者更新的行数,单条插入成功就是1
int i = mDao.create(user);
flag = i == 1 ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}

return flag;
}

/**
* 批量插入数据
*
* @param user
* @return 是否插入成功
*/
public boolean insertAll(List<User> user) {
boolean flag = false;
try {
//插入或者更新的行数,单条插入成功就是1
int i = mDao.create(user);
flag = i == 1 ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}

return flag;
}

/**
* 删除一条数据
*
* @param user
* @return
*/
public boolean delete(User user) {
boolean flag = false;
try {
int rowCount = mDao.delete(user);
flag = rowCount == 1 ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}

/**
* 批量删除
*
* @param users
* @return
*/
public boolean deleteAll(List<User> users) {
boolean flag = false;
try {
int rowCount = mDao.delete(users);
flag = rowCount == 1 ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}

/**
* 更新数据
*
* @param user
* @return
*/
public boolean update(User user) {
boolean flag = false;
try {
int rowCount = mDao.update(user);
flag = rowCount == 1 ? true : false;
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}

/**
* 批量更新
*
* @param users
* @return
*/
public boolean updateAll(List<User> users) {
boolean flag = true;
try {
for (User user : users) {
int rowCount = mDao.update(user);
boolean b = rowCount == 1 ? true : false;
if (!b) {
flag = false;
}
}
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}

/**
* 使用QueryBuilder查询
*/
public List<User> query() {
QueryBuilder<User, Integer> builder = mDao.queryBuilder();
Where<User, Integer> where = builder.where();
try {
//相当于:select * from user where name = '张三' and age > 20
where.and(where.eq("name", "张三"), where.ge("age", 20));

//下面这条语句相当于:select * from user where (name = '张三' and age > 20 ) or address = '陕西'
where.and(where.eq("name", "张三"), where.ge("age", 20)).or().eq("address", "陕西");

List<User> users = where.query();
return users;
} catch (SQLException e) {
e.printStackTrace();
}

return null;
}

}

基本的使用就介绍到此,如果希望更加深入的了解,建议移步 官网