构造器模式

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。
遇到多个构造器参数时要考虑用构建器。
                     ———— 自Effective Java书中第二条

JDK中的使用

• java.lang.StringBuilder#append(boolean)
• java.nio.ByteBuffer#put(byte)

代码实现

使用Lombok中的@Builder可以快速实现构造器

@Data
public class StudentVo implements Serializable {
    private String no;
    private String name;
    private String sex;
    private Integer age;

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

    public static class StudentBuilder {
        private String no;
        private String name;
        private String sex;
        private Integer age;

        public StudentBuilder no(String no) {
            this.no = no;
            return this;
        }

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

        public StudentBuilder sex(String sex) {
            this.sex = sex;
            return this;
        }

        public StudentBuilder age(Integer age) {
            this.age = age;
            return this;
        }

        public StudentVo build() {
            StudentVo studentVo = new StudentVo();
            studentVo.setName(this.name);
            studentVo.setSex(this.sex);
            studentVo.setAge(this.age);
            studentVo.setNo(this.no);

            return studentVo;
        }
    }
}

单元测试

class StudentVoSpec extends Specification {
    def build() {
        when:
        def student = StudentVo.builder()
            .name("Jack")
            .build()
        then:
        student != null
        student.name == "Jack"
        student.sex == null
        student.age == null
        student.no == null

        when:
        student = StudentVo.builder()
            .name("zhangsan")
            .age(10)
            .sex("male")
            .build()
        then:
        student != null
        student.name == "zhangsan"
        student.age == 10
        student.sex == "male"
        student.no == null
    }
}