Java Lombok：省略@AllArgsConstructor 中的一个字段？

Question

If I specify @AllArgsConstructor using Lombok , it will generate a constructor for setting all the declared (not final, not static) fields. Is it possible to omit some field and this leave generated constructor for all other fields?

Answer 1

No that is not possible. There is a feature request to create a @SomeArgsConstructor where you can specify a list of involved fields.

Full disclosure: I am one of the core Project Lombok developers.

Answer 2

Alternatively, you could use @RequiredArgsConstructor . This adds a constructor for all fields that are either @NonNull or final .

See the documentation

Answer 3

在某些情况下，解决它的一个好方法是使用@Builder

Answer 4

Just in case it helps, initialized final fields are excluded.

@AllArgsConstructor
class SomeClass {
    final String s;
    final int i;
    final List<String> list = new ArrayList<>(); // excluded in constructor
}

var x = new SomeClass("hello", 1);

It makes sense especially for collections, or other mutable classes.

This solution can be used together with the other solution here , about using @RequiredArgsConstructor :

@RequiredArgsConstructor
class SomeClass2 {
    final String s;
    int i; // excluded because it's not final
    final List<String> list = new ArrayList<>(); // excluded because it's initialized
}

var x = new SomeClass2("hello");

Answer 5

You can initialise those particular fields with some default values or null and then create the constructor omitting those fields. But remember, now you can't pass the omitted fields in the constructor anymore.

@AllArgsConstructor
Public class MyClass{
        @JsonProperty
        String omitThisField = null;
        @JsonProperty
        String reqField1;
        @JsonProperty 
        String reqField2;
}

MyClass myClass = new MyClass("req field1", "req field2");

But this won't work now:

//MyClass myClass = new MyClass("omitted field", "req field1", "req field2");

Answer 6

This can be done using two annotations from lombok @RequiredArgsConstructor and @NonNull .

Please find the example as follows

package com.ss.model;

import lombok.*;

@Getter
@Setter
@RequiredArgsConstructor
@ToString
public class Employee {

    private int id;
    @NonNull
    private String firstName;
    @NonNull
    private String lastName;
    @NonNull
    private int age;
    @NonNull
    private String address;
}

And then you can create a constructor as below

Employee employee = new Employee("FirstName", "LastName", 27, "Address");