The design ideas and technical principles of the MapperDao framework in the Java library (Analysis of the Design Ideas and Technical Principles of the MapperDao framework in Java Class Libraries)
The Mapperdao framework is an ORM (object relationship mapping) framework for the Java class library. It aims to simplify the development of the data access layer and provide a convenient and flexible way to mappore the object and database table.
Design ideas:
1. Object -oriented: Mapperdao framework operates data in an object -oriented manner, and mappore the Java object with the database table.Developers can use the relationship and mapping rules between the simple annotation and definition objects.
2. Database irrational: The framework provides an abstract layer that allows developers to interact with different types of database without modifying the code.By configured files, you can easily switch the database type, so that the application has better flexibility.
3. Simplify SQL query: Mapperdao framework provides a convenient way to perform CRUD operations. Developers only need to define simple interface methods without writing complex SQL statements.The framework will automatically generate SQL query statements according to the method of the method, simplifying the development work.
4. One -to -one and one -to -one relationship: The framework supports complex relationships such as one -to -one and one -to -one.Through annotations, the relationship between objects can be defined, and the framework will automatically handle the associated operations between objects.
Technical principle:
1. Reflex: The framework uses the reflex mechanism of Java to obtain the attributes and methods of the object, and mappides the object and the database table according to the mapping rules defined by the annotation.
2. SQL analysis: The framework will analyze the naming agreement of the interface method to generate the corresponding SQL query statement.For example, the verbs and nouns in the method name can automatically generate SQL operations such as query, inserting, updating, and deletion.
3. Affairs management: The framework provides transaction management functions to ensure the consistency of data.Developers can use annotations to define the scope of transactions, and the framework will automatically handle the submission and rollback of transactions.
The following is a simple Java code example, demonstrating how to use the MapperDao framework for the mapping of the object and the database table:
// Define the physical class
@Entity(table = "user_table")
class User {
@Id(autoGenerated = true)
int id;
String username;
String email;
}
// Definition interface
@Dao
interface UserDao {
@Select
User findById(int id);
@Insert
void insert(User user);
@Update
void update(User user);
@Delete
void delete(User user);
}
// Configuration file
mapperdao {
database = "mysql"
url = "jdbc:mysql://localhost:3306/mydb"
username = "root"
password = "password"
}
// Use the framework for operation
DaoFactory factory = DaoFactoryBuilder.build(Configuration.fromPropertiesFile("mapperdao.properties"));
UserDao userDao = factory.getDao(UserDao.class);
User user = new User();
user.setUsername("John");
user.setEmail("john@example.com");
userDao.insert(user);
User retrievedUser = userDao.findById(user.getId());
retrievedUser.setUsername("John Doe");
userDao.update(retrievedUser);
userDao.delete(retrievedUser);
The above examples demonstrate how to define the physical class and interfaces, and use the MapperDao framework to insert, query, update, and delete operations.The database information is set in the configuration file so that the frame is connected to the database.Finally, by calling the corresponding interface method, the durable operation of the data can be completed.
In summary, the Mapperdao framework is simplified by using objective design ideas and using reflection and other technical principles to simplify the development of the data access layer in the Java library, providing a convenient and flexible way to operate the object and the database table between the object and the database table.The mapping relationship.
