The "Hibernate" noun explanation for beginners of Java-ee

What is Hibernate? Explanation from different angles:

1, it is the middleware that connects Java application and relational database.

2. It encapsulates the JDBC API and is responsible for the persistence of Java objects.

3, in the Layered software architecture, it is located in the persistence layer, encapsulating all data access details, so that the business Luo grass-roots can focus on the implementation of business logic.

4, it is an ORM (object-relation Mapping Object-relational mapping) tool, can establish the object-oriented domain model and relational model mapping.

Application Tiering Architecture:

1, Presentation layer: To provide interface with the user interaction.

2, Business logic layer: to achieve a variety of business logic.

3, Data layer: Responsible for storage and management of the application of the persistence of business.

Software layering contains two meanings:

One is the physical layering, where each layer runs on a separate machine, which means creating a distributed software system;

One is the logical layering, which refers to the completion of specific functions within a single software module.

Software tiering must conform to the following characteristics:

1. Each layer is composed of a set of related classes or components to accomplish specific functions together.

2. There is a top-down dependency between layers and layers, where the upper component accesses the API of the underlying component, while the underlying component should not rely on the upper component.

3, each layer to the upper level of public API, but the specific implementation details of external transparency.

Benefits of software tiering:

The appropriate tiering will improve the following performance for the software.

1. Scalability: Refers to whether the application supports more users. For example, a database connection.

2, maintainability: When the demand changes, just modify a part of the software, will not affect the other parts of the code.

3. Scalability: The ease with which new features can be added to existing systems.

4, reusability: The program code is not redundant, the same program can meet a variety of needs.

5, Manageability: Management system of the degree of ease.

Disadvantages:

1, more layers of software design personnel requirements higher.

2, the more layered debugging more difficult.

Tables ensure uniqueness of each record through the main building, and the table's primary key should not have any business implications, because any column with business implications has the potential to change. One of the most important theories of relational database learning is not to give keywords any business meaning.

In the domain model, there are four relationships between classes.

1, Association: The application of the relationship between classes.

If Class A is associated with Class B, then the referenced class B is defined as the property of Class A. Associations can also be divided into individual associations and bidirectional associations.

2. Dependencies: Access relationships between classes.

If Class A accesses the properties or methods of Class B, or class A is responsible for instantiating Class B, you can say Class A relies on Class B.

3, aggregation: the relationship between the whole and part.

4, inheritance.