Java设计模式之建造者模式

        建造者模式属于创建型模式中的一种，我个人的理解是建造者模式是为了让开发者写出更优雅的代码。一般来说，创建一个对象，我们都是通过new关键字来创建，但是对应一些属性特别多的类，而且属性的类型又是很多都是相近的这种，我们在通过构造函数new对象的时候，很容易出现对象值赋值错误的问题。另外通过new对象，也不是很优雅，所以我们就不太希望别人通过new来创建对象。这种情况我们就可以使用建造者模式来处理，既能避免赋值错误，也能写出看起来很优雅的代码。如何实现呢？直接看源码

package com.study.rabbitmq.designPattern.Builder;

import java.util.Arrays;
import java.util.List;

/**
 * @Author alen
 * @DATE 2022/7/5 22:23
 * 建造者模式案例
 */
public class User {

    String name;

    int age;

    String mobile;

    String address;

    String nickName;

    String level;

    String headImage;

    int height;

    String lastLoginTime;

    List<String> goodsList;

    private User(String name, int age, String mobile, String address, String nickName, String level, String headImage, int height, String lastLoginTime, List<String> goodsList) {
        this.name = name;
        this.age = age;
        this.mobile = mobile;
        this.address = address;
        this.nickName = nickName;
        this.level = level;
        this.headImage = headImage;
        this.height = height;
        this.lastLoginTime = lastLoginTime;
        this.goodsList = goodsList;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", mobile='" + mobile + '\'' +
                ", address='" + address + '\'' +
                ", nickName='" + nickName + '\'' +
                ", level='" + level + '\'' +
                ", headImage='" + headImage + '\'' +
                ", height=" + height +
                ", lastLoginTime='" + lastLoginTime + '\'' +
                ", goodsList=" + goodsList +
                '}';
    }

    public static UserBuilder builder() {
        return new UserBuilder();
    }

    //创建一个内部类
    public static class UserBuilder {
        private String name;

        private int age;

        private String mobile;

        private String address;

        private String nickName;

        private String level;

        private String headImage;

        private int height;

        private String lastLoginTime;

        private List<String> goodsList;


        public UserBuilder name(String name) {
            this.name = name;
            return this;
        }

        public UserBuilder age(int age) {
            this.age = age;
            return this;
        }

        public UserBuilder mobile(String mobile) {
            this.mobile = mobile;
            return this;
        }

        public UserBuilder address(String address) {
            this.address = address;
            return this;
        }

        public UserBuilder nickName(String nickName) {
            this.nickName = nickName;
            return this;
        }

        public UserBuilder level(String level) {
            this.level = level;
            return this;
        }

        public UserBuilder headImage(String headImage) {
            this.headImage = headImage;
            return this;
        }

        public UserBuilder height(int height) {
            this.height = height;
            return this;
        }

        public UserBuilder lastLoginTime(String lastLoginTime) {
            this.lastLoginTime = lastLoginTime;
            return this;
        }

        public UserBuilder goodsList(String... goodsList) {
            this.goodsList = Arrays.asList(goodsList);
            return this;
        }

        public User build() {
            return new User(name, age, mobile, address, nickName, level, headImage, height, lastLoginTime, goodsList);
        }
    }

}

处理思路是在目标类中创建一个静态内部类，内部类中属性和目标类一样，并在内部类中提供一个方法builder()，内部类中提供属性赋值的方法，并在内部类中提供提一个build()方法对外响应目标类的对象。由于我们将构造函数私有化了，外部不能使用new来创建对象而使用build()来创建对象了，测试代码如下

package com.study.rabbitmq.designPattern;

import com.study.rabbitmq.designPattern.Builder.User;

/**
 * @Author alen
 * @DATE 2022/7/5 21:38
 */
public class Main {

    public static void main(String[] args) {
        User user = User.builder()
                .name("张三")
                .age(25)
                .mobile("15988886666")
                .address("上海市浦东新区")
                .nickName("老张")
                .level("A类")
                .headImage("https://www.baidu.com")
                .height(175)
                .lastLoginTime("2022-07-05 22:45:02")
                .goodsList("Iphone 13", "IMac", "IPod").build();
        System.out.println(user);
    }
}

使用建造者模式创建对象的过程中，我们就不大可能会出现赋值错误的问题了，创建对象也更加的优雅美观。建造者模式的学习分享就到这。。。