Java设计模式之构建者模式

矫情吗；* 2022-12-27 11:27 58阅读 0赞

## Java设计模式之构建者模式 ##

1.  定义  
    构建器模式：将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。
    
    有点抽象，太扯了。  
    就是为了方便创建复杂对象，构建对象有很多方式，为什么采用这种方式，方便。

*  通过构造函数创建对象
 *  通过创建空对象然后set属性
 *  自定义不同参数的构造函数
 *  lombok提供的注解@Builder链式调用

1.  场景  
    当一个类的构造函数参数个数超过4个，而且这些参数有些是可选的参数，考虑使用构造者模式。
2.  案例

/** * Car对象 * 通过lombok的@Builder方式创建 * * @author 20023262 * @date 2020/12/10 * @since 1.0 */
    @Setter
    @Getter
    @ToString
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class Car { 
        private Integer number;
        private String name;
        private String brand;
    }

/** * Person对象 * 通过不同参数自定义构造函数方式创建对象 * * @author 20023262 * @date 2020/12/10 * @since 1.0 */
    @Setter
    @Getter
    @ToString
    @NoArgsConstructor
    public class Person { 
        //必要参数
        private int id;
        private String name;
        //可选参数
        private int age;
        private String sex;
        private String phone;
        private String address;
        private String desc;
    
        /** * 各个参数构造函数 */
        public Person(int id, String name) { 
            this(id, name, 0);
        }
    
        public Person(int id, String name, int age) { 
            this(id, name, age, "");
        }
    
        public Person(int id, String name, int age, String sex) { 
            this(id, name, age, sex, "");
        }
    
        public Person(int id, String name, int age, String sex, String phone) { 
            this(id, name, age, sex, phone, "");
        }
    
        public Person(int id, String name, int age, String sex, String phone, String address) { 
            this(id, name, age, sex, phone, address, "");
        }
    
        public Person(int id, String name, int age, String sex, String phone, String address, String desc) { 
            this.id = id;
            this.name = name;
            this.age = age;
            this.sex = sex;
            this.phone = phone;
            this.address = address;
            this.desc = desc;
        }
    
    }

/** * 自定义构建者模式对象 * * @author 20023262 * @date 2020/12/10 * @since 1.0 */
    @Getter
    @Setter
    @ToString
    @NoArgsConstructor
    @AllArgsConstructor
    public class PersonOne { 
        //必要参数
        private int id;
        private String name;
        //可选参数
        private int age;
        private String sex;
        private String phone;
        private String address;
        private String desc;
    
        /** * 通过builder将值设置到PersonOne对象 */
        private PersonOne(Builder builder) { 
            this.id = builder.id;
            this.name = builder.name;
            this.age = builder.age;
            this.sex = builder.sex;
            this.phone = builder.phone;
            this.address = builder.address;
            this.desc = builder.desc;
        }
    
        public static class Builder { 
            //必要参数
            private final int id;
            private final String name;
            //可选参数
            private int age;
            private String sex;
            private String phone;
            private String address;
            private String desc;
    
            /** * 设置必须参数 */
            public Builder(int id, String name) { 
                this.id = id;
                this.name = name;
            }
    
            /** * 以下设置可选参数 */
            public Builder age(int val) { 
                this.age = val;
                return this;
            }
    
            public Builder sex(String val) { 
                this.sex = val;
                return this;
            }
    
            public Builder phone(String val) { 
                this.phone = val;
                return this;
            }
    
            public Builder address(String val) { 
                this.address = val;
                return this;
            }
    
            public Builder desc(String val) { 
                this.desc = val;
                return this;
            }
    
            /** * 通过builder方法创建PersonOne对象 */
            public PersonOne build() { 
                return new PersonOne(this);
            }
        }
    }

/** * 构建者模式 * * @author 20023262 * @date 2020/12/10 * @since 1.0 */
    public class BuilderTest { 
    
        /** * 方式一 * 通过lombok的Builder方式链式创建对象 */
        @Test
        public void builderCarTest() { 
            Car car = Car.builder().number(1001).name("帕梅拉").brand("Porsche").build();
        }
    
        /** * 构建对象 */
        @Test
        public void builderPersonTest() { 
    
            /** * 通过创建空对象，依次set属性 */
            Person person = new Person();
            person.setId(1);
            person.setName("王小二");
            person.setAge(18);
            person.setSex("男");
            person.setPhone("15765481256");
            person.setAddress("成都");
            person.setDesc("产品");
    
            /** * 通过构造函数 */
            Person person1 = new Person(3, "张三");
            Person person2 = new Person(3, "李四", 32);
            Person person3 = new Person(1, "赵柳", 21, "女", "123123", "sc", "ceshi");
    
            /** * 自定义Builder */
            PersonOne personOne = new PersonOne.Builder(1, "大疆").age(19).sex("nan").phone("123").address("bj").desc("air").build();
            System.out.println("自定义Builder创建PersonOne:"+personOne);
    
    
        }
    
    }