[design pattern] Builder Pattern

유형: 생성자 패턴

복잡한 객체의 구성 요소들을 조합해 생성하는 패턴으로, 그 생성과 조합에 대한 책임을 객체가 직접 지지않고 Builder에게 위임한다.

 

필요한 구성 요소의 조합에 따라 각각의 생성자가 필요

public class Person {
    private String firstName;
    private String middleName;
    private String lastName;
    private Integer age;
    private String mothersName;
    private Double height;
    private Double weight;
    
    public Person(String firstName, String middleName, String lastName, int age, double height, double weight) {
        this.firstName = firstName;
        this.middleName = middleName;
       	this.lastName = lastName;
       	this.age = age;
       	this.height = height;
       	this.weight = weight;
    }
    
    public Person(String firstName, String middleName, String lastName, int age) {
        this.firstName = firstName;
        this.middleName = middleName;
       	this.lastName = lastName;
       	this.age = age;
    }
    
    public Person(String firstName, String middleName, String lastName) {
        this.firstName = firstName;
        this.middleName = middleName;
       	this.lastName = lastName;
    }
    
    public Person(String firstName, String lastName) {
        this.firstName = firstName;
       	this.lastName = lastName;
    }
    /* getters */
}

 

Person 객체의 생성을 Builder에게 위임한다.

public class Person {
    private String firstName;
    private String middleName;
    private String lastName;
    private Integer age;
    private String mothersName;
    private Double height;
    private Double weight;
    
    public Person(String firstName, String middleName, String lastName, int age, double height, double weight) {
        this.firstName = firstName;
        this.middleName = middleName;
       	this.lastName = lastName;
       	this.age = age;
       	this.height = height;
       	this.weight = weight;
    }

    public static class Builder {
        private String firstName;
        private String middleName;
        private String lastName;
        private Integer age;
        private Double height;
        private Double weight;
        
        public Builder(){}
        
        public Builder setFirstName(String firstName) {
            this.firstName = firstName;
            return this;
        }

        public Builder setMiddleName(String middleName) {
            this.middleName = middleName;
            return this;
        }

        public Builder setLastName(String lastName) {
            this.lastName = lastName;
            return this;
        }
        
        public Builder setAge(Integer age) {
            this.age = age;
            return this;
        }
        
        public Builder setHeight(Double height) {
            this.height = height;
            return this;
        }
        
        public Builder setWeight(Double weight) {
            this.weight = weight;
            return this;
        }
        
        public Person build() {
            return new Person(firstName, middleName, lastName, age, height, weight);
        }
    }
}

 

필요한 구성 요소를 조합하여 객체를 생성한다.

Person person = new Person.Builder()
                    .setAge(30)
                    .setFirstName("Michael")
                    .setLastName("Jordan")
                    .setHeight(198)
                    .build();