This is the 17th day of my participation in the August Text Challenge.More challenges in August
define
Some information about a class is hidden inside the class, not allowed to be accessed directly by external members, and if necessary, exposed. For private class members, for example, get/set is considered
disadvantages
There would be a lot of boilerplate code, and the class would be very redundant. The good news is that ides provide one-click generation
advantages
For some private members, you can choose whether to expose them or not. At the same time, you can also process the output data and verify the input data in this step
Lombok plug-in
Due to conventional wisdom in Java development, when we write entity classes, we define attributes as private and then provide the full set of GET /set. Of course, you can take advantage of lombok’s @data annotation to get rid of this hassle
advantages
Using annotations can simplify a lot of Java boilerplate code
disadvantages
Forcing project participants to use all of them is the problem with strong coupling
If it is a new project, it is suggested that the team use this when planning. It is a real fragrance
Commonly used annotations
@data, NoArgsConstructor, @toString
@Data
Provide standard get/set methods for all attributes
@NoArgsConstructor
Provides a no-parameter constructor
@ToString
Override toString() in class to output jSON-like, easy-to-read data
@AllArgsConstructor
A constructor that provides full arguments, the order of which depends on the order in which the attributes are defined
This is not recommended if the class changes frequently, as it may affect other code that uses older full-parameter constructors
@EqualsAndHashCode
Rewrite equals(), hashCode()
Just a few of the most commonly used items in the project are listed here on Lombok’s website
The principle of
Lombok uses apis provided by Java’s plug-in annotation processor to read, modify, and add arbitrary elements to the abstract syntax tree. If the syntax tree is modified because of these annotations, the compiler reanalyzes the syntax and syntax until all of the plug-in annotations have not modified the syntax tree.
So, if we need to use Lombok, we also need to configure our IDE so that it can be associated with the corresponding methods provided by annotations as we code
scope
Third party: can also be called consumer of library class, consumer of service
We are generally developers of library classes and service providers
public
Global scope: a variable or method is declared to support global calls
default
When we need to develop a slightly more complex library class, we usually put all the related files in a package directory for other components to call each other, but we don’t want to expose them to third parties
Public is the default scope for non-scoped methods and variables declared in interfaces
protected
Properties and methods in a parent class need to be available to subclasses of different packages without being exposed to arbitrary access
private
Private, available to you only
For example, if we want to implement a simple singleton pattern, we need to declare the constructor private, so that someone else does not inadvertently initialize a new instance that overwrites our carefully written instance
The benefits of controlling scope
One purpose of strictly limiting the scope of services and preventing services that are used internally from being used by third parties is that we need to have the right to iterate and upgrade the internal services, which are then assembled and packaged to become higher level services for external invocation. For services provided externally, it is strictly required that method names, outgoing parameters and incoming parameters cannot be changed (to avoid any impact on third-party callers).
If it is necessary to optimize and rewrite the methods serving third parties due to the defects of library class design, it is recommended to use the annotation @deprecated to indicate method/class expiration provided by Java on the relevant methods first, to provide several versions of buffer time for third parties, and then remove it