ORMLITE JDBC framework core technical principles and applications

ORMLITE (Object Relational Mapping Lite) is a lightweight Java framework based on JDBC, which is used to simplify the development process of database operation and object relationship mapping.This article will introduce the core technical principles of the ORMLITE JDBC framework and its use in practical applications. 1. The core technical principle of Oremlite 1. Object relationship mapping (ORM) ORM is a technology that establishes a mapping relationship between the surface structure in the relational database and the Java object, so that developers can operate the database by operating the Java object without writing the traditional SQL statement.The ORMLITE framework maps the Java object and the field of the database table by annotating, naming rules and configuration files to realize the mutual conversion between the object and the database. 2. Data access object (DAO) The ORMLITE framework provides DAO classes to encapsulate common operations on databases, such as inserting, updating, deleting and querying.Developers only need to create a DAO object, and then call its method to perform the corresponding database operation.The DAO class provides methods such as Create, Update, Delete. They correspond to the addition, deletion, and modification of the database. They also provide methods such as QueryForall, QueryBuilder to query data that meets the specified conditions. 3. Database connection management The ORMLITE framework is connected to the database through JDBC.Developers need to provide database connection information, such as database URL, user name and password, and then use the database connection management class provided by ORMLITE for database connection and closing operations.When connecting the database, ORMLITE also supports the connection pool technology. The connection pool can provide reuse of connection to improve the database access efficiency. 2. ORMLITE's use in actual applications 1. Create a physical class First of all, the Java entity class corresponding to the database table structure needs to be created. This class needs to use the annotation provided by ORMLITE to identify the mapping relationship between the attributes and the database field.As follows: @DatabaseTable(tableName = "users") public class User { @DatabaseField(generatedId = true) private int id; @DatabaseField(canBeNull = false) private String name; @DatabaseField private int age; // Getters and setters } 2. Create a database connection Use the `ConnectionSource` object provided by ORMLITE to manage the connection of the database.The following code shows how to create a H2 database connection: String databaseUrl = "jdbc:h2:mem:db"; String username = "root"; String password = "password"; DataSource dataSource = new JdbcConnectionPool(databaseUrl, username, password); ConnectionSource connectionSource = new JdbcConnectionSource(dataSource); 3. Create DAO object Create DAO objects through the ConnectionSource object, and then use the DAO object to add, delete and modify the operation to add and delete. Dao<User, Integer> userDao = DaoManager.createDao(connectionSource, User.class); 4. Database operation Use the DAO object to operate the database table, such as inserting new records, updating records, deleting records or query data. // Insert a new record User user = new User(); user.setName("John"); user.setAge(25); userDao.create(user); // Query all records List<User> users = userDao.queryForAll(); for (User user : users) { System.out.println(user.getName() + " - " + user.getAge()); } // Inquiry records according to the condition QueryBuilder<User, Integer> queryBuilder = userDao.queryBuilder(); queryBuilder.where().eq("name", "John"); List<User> johns = queryBuilder.query(); 5. Close the database connection Finally, you need to manually close the database connection. connectionSource.close(); Summarize: The ORMLITE JDBC framework provides a simple and efficient way to operate the database and the objective mapping.By learning the core technical principles and practical applications of Oremlite, developers can improve development efficiency, simplify code writing, and focus more on the realization of business logic.