How to use the ORMLITE CORE framework to implement the data persistence function
How to use the ORMLITE CORE framework to implement data persistence function
ORMLITE CORE is a lightweight, flexible scalability Java object relationship mapping (ORM) framework.It aims to simplify the development of the data durable layer so that developers can more conveniently operate the database in Java applications.
This article will introduce how to use the ORMLITE CORE framework to implement the durable function of data.The following is the step of implementation:
Step 1: Import the ORMLITE core library
First, we need to add the dependencies of the ORMLite Core library to the project.You can add the following dependencies to the project's construction file through Maven or Gradle:
compile 'com.j256.ormlite:ormlite-core:5.6'
Step 2: Define the physical class
When using ORMLITE CORE, we need to define the physical class corresponding to the database table.Each entity class will be mapped to a database table, and the attributes of each class will be mapped to the column of the table.
@DatabaseTable(tableName = "users")
public class User {
@DatabaseField(id = true)
private int id;
@DatabaseField
private String name;
@DatabaseField
private int age;
// getters and setters
}
In the above example, we define a database table called "Users" and add three properties: ID, name, and Age.
Step 3: Create a database management class
Next, we need to create a database management class and initialize the ORMLITE framework.
public class DatabaseManager {
private static final String DATABASE_NAME = "mydatabase.db";
private static final int DATABASE_VERSION = 1;
private static DatabaseManager instance;
private DatabaseHelper databaseHelper;
private DatabaseManager(Context context) {
databaseHelper = new DatabaseHelper(context);
}
public static synchronized DatabaseManager getInstance(Context context) {
if (instance == null) {
instance = new DatabaseManager(context);
}
return instance;
}
public DatabaseHelper getDatabaseHelper() {
return databaseHelper;
}
}
In the above code, we use a singles mode to create a database management class and provide an instance acquisition method.
Step 4: Create a database help class
Next, we need to create a database help class to inherit the `OresqliteOpenhelper` class provided by Oremlite, and implement the abstract method in it.
public class DatabaseHelper extends OrmLiteSqliteOpenHelper {
private static final String DATABASE_NAME = "mydatabase.db";
private static final int DATABASE_VERSION = 1;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase database, ConnectionSource connectionSource) {
try {
TableUtils.createTable(connectionSource, User.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);
onCreate(database, connectionSource);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Here, we create database tables by rewriting the `OnCreate` method, and update the database by rewriting the` Onupgrade` method.
Step 5: Use the database
Now, we have set up the ORMLITE CORE framework and can start using the database.
// Get the database management example
DatabaseManager databaseManager = DatabaseManager.getInstance(context);
// Get the database access class
DatabaseHelper databaseHelper = databaseManager.getDatabaseHelper();
// Create User object
User user = new User();
user.setId(1);
user.setname ("Xiaoming");
user.setAge(18);
// Insert a data to the database
try {
Dao<User, Integer> userDao = databaseHelper.getDao(User.class);
userDao.create(user);
} catch (SQLException e) {
e.printStackTrace();
}
// Query database data
List<User> userList = null;
try {
Dao<User, Integer> userDao = databaseHelper.getDao(User.class);
userList = userDao.queryForAll();
} catch (SQLException e) {
e.printStackTrace();
}
// Update database data
if (userList != null && !userList.isEmpty()) {
User firstUser = userList.get(0);
firstuser.setName ("Little Red");
try {
Dao<User, Integer> userDao = databaseHelper.getDao(User.class);
userDao.update(firstUser);
} catch (SQLException e) {
e.printStackTrace();
}
}
In the above code, we first obtained the database management instance and obtained the database access class through it.Then, we created a User object and inserted it into the database using a database access class.Next, we check all the data in the database and update the name field of the first data.
In summary, it is very simple to use the ORMLITE CORE framework to implement the data persistence function.By defining physical classes, creating database management and helping classes, and using database to access the class to operate databases, we can easily perform data persistent operations in Java applications.
