When interacting with a database in Java, there are several reasons for designing entity classes:
1.: 对象关系映射（ORM）Entity classes provide a way to map tables in the database to Java objects. In this way, developers can operate the database in an object-oriented manner without writing a large number of SQL statements. ORM框架(such as Hibernate, MyBatis, etc.) can automatically map entity classes to database tables, simplifying the code.
2. Data encapsulation: Entity classes encapsulate fields in database tables as properties of Java objects, and provide getter and setter methods to access and modify these properties.
3. Business logic implementation: Entity classes can contain business logic methods related to database tables to perform certain operations in Java applications. This separates business logic from data access code, making the code clearer and maintainable.
4. Type safety: Using entity classes ensures that type errors are detected at compile time. If you concatenate strings directly in SQL statements, runtime errors may occur.
5. Code reuse: If there are multiple places that need to interact with the same database table, you can create an entity class and reuse it where needed.
Designing entity classes can make Java's interaction with the database simpler, more intuitive, and type-safe, while improving the readability, maintainability, and reusability of the code.
ORM framework
The ORM framework is a development framework used to establish mapping relationships between entity classes and database tables. Its full name is Object Relation Mapping, which is object relational mapping.
Through the ORM framework, Java objects and database tables can be mapped, allowing developers to indirectly operate database tables by operating entity classes without writing direct SQL statements.
ORM frameworks can provide many features, such as:
Database connection management: The ORM framework can provide a connection pool to manage and reuse database connections to improve performance and availability.
Table mapping: The ORM framework can map Java entity classes to database tables, automatically generate and maintain table structures, and reduce the workload of manually writing SQL statements.
Add, delete, modify, and query data: The ORM framework can provide a simple and easy-to-use API so that developers can add, delete, modify, and query data in an object-oriented manner.
Data type conversion: The ORM framework can automatically handle type conversion between Java objects and database table fields to ensure the correctness and consistency of data.
Transaction management: The ORM framework can provide transaction management functions to ensure data consistency and integrity.
Common ORM frameworks include: Hibernate, MyBatis, iBatis, Spring Data JPA, etc. They all provide rich functions and flexible configurations to meet different development needs.