@Use of data annotation (instead of get and set methods in entity classes)

Use @Data annotation And lombok, a farewell Java Attribute set and get Method

@Data The main function of annotations is to improve the simplicity of code , Using this annotation can save a lot of... In the code get()、 set()、 toString() Other methods ;

To use @Data Annotations should be introduced first lombok,lombok What is it? , It is a tool class library , Code can be simplified in the form of simple annotations , Improve development efficiency .

stay maven Add dependency to ：

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.4</version>
    <scope>provided</scope>
</dependency>

Add plug-ins to the compiler
Here we use IDEA For example , stay setting Of plugin Search inside lombok plugin, Installing a plug-in .（ This plug-in must be installed , Otherwise it doesn't work ）

Use
Add... Directly to the corresponding entity class @Data Annotations can be ;

Like a simple one Person class , In a conventional way ：

public class Person {
    
    private String name;
    private String address;
    private Integer age;
    private String hobbit;
    private String phone;

    public Person() {
    
    }

    public Person(String name, String address, Integer age, String hobbit, String phone) {
    
        this.name = name;
        this.address = address;
        this.age = age;
        this.hobbit = hobbit;
        this.phone = phone;
    }

    public String getName() {
    
        return name;
    }

    public void setName(String name) {
    
        this.name = name;
    }

    public String getAddress() {
    
        return address;
    }

    public void setAddress(String address) {
    
        this.address = address;
    }

    public Integer getAge() {
    
        return age;
    }

    public void setAge(Integer age) {
    
        this.age = age;
    }

    public String getHobbit() {
    
        return hobbit;
    }

    public void setHobbit(String hobbit) {
    
        this.hobbit = hobbit;
    }

    public String getPhone() {
    
        return phone;
    }

    public void setPhone(String phone) {
    
        this.phone = phone;
    }

    @Override
    public String toString() {
    
        return "Person{" +
                "name='" + name + '\'' +
                ", address='" + address + '\'' +
                ", age=" + age +
                ", hobbit='" + hobbit + '\'' +
                ", phone='" + phone + '\'' +
                '}';
    }
}

use @Data Writing ：

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person {
    
    private String name;
    private String address;
    private Integer age;
    private String hobbit;
    private String phone;
}

Automatic generation of related methods ：

A few common notes ：
@Data ： Note on class , Provide a class of get、set、equals、hashCode、canEqual、toString Method
@AllArgsConstructor ： Note on class , Provide the full parameter construction of the class
@NoArgsConstructor ： Note on class , Provides a parameterless construction of a class
@Setter ： Note on properties , Provide set Method
@Getter ： Note on properties , Provide get Method
@EqualsAndHashCode ： Note on class , Provide the corresponding equals and hashCode Method
@Log4j/@Slf4j ： Note on class , Provide the corresponding Logger object , A variable called log

principle
Lombok In essence, it is a realization “JSR 269 API” The program . In the use of javac In the process of , The specific process of its effect is as follows ：

javac Analyze the source code , An abstract syntax tree is generated （AST）
During the operation, the call is implemented “JSR 269 API” Of Lombok Program
here Lombok Just for the first step AST To deal with , find @Data The syntax tree corresponding to the class where the annotation is located （AST）, Then modify the syntax tree （AST）, increase getter and setter The corresponding tree node of the method definition
javac Use the modified abstract syntax tree （AST） Generate bytecode file , That is to class Add new nodes （ Code block ）

Advantages and disadvantages
advantage ：

It can generate constructors automatically in the form of annotations 、getter/setter、equals、hashcode、toString Other methods , Improve the development efficiency
Make the code simple , Don't pay too much attention to the corresponding methods
When the property is modified , It also simplifies the maintenance of the getter/setter Such method

shortcoming ：

Overload of multiple parameter constructors is not supported
Although the manual creation is omitted getter/setter The trouble with the method , But it greatly reduces the readability and integrity of the source code , Reduce the comfort of reading source code
image lombok This plug-in , It's not just plug-ins anymore , It is compiled by the compiler through the operation AST（ Abstract syntax tree ） Change bytecode generation , In disguise, it is changing java grammar , It changes the way you write source code , It is not like spring Dependency injection is also a runtime feature , It's a compile time feature . If a project has many such plug-ins , It will greatly reduce the comfort of reading source code .

lombok It just saves some trouble of manually generating code , But these getter/setter And so on , use IDE Shortcut keys can also be easily generated . Besides, , Sometimes by giving getter/setter Add a little bit of business code （ But this is not usually recommended ）, It can greatly simplify the code of some business scenarios .

Use or not , How to choose between , Naturally, it depends on the needs of the project , Flexible use of .