关于设计模式:设计模式建造者模式

建造者模式

• 定义：将一个简单对象的构建与它的示意拆散，使得同样的构建过程能够创立不同的示意
• 用户只需指定须要建造的类型就能够失去它们，建造过程及细节不须要晓得
• 类型：创立型

• 实用场景：

  • 如果一个对象有非常复杂的内部结构（很多属性）
  • 想把简单对象的创立和应用拆散

• 长处：

  • 封装性好，创立和应用拆散
  • 扩展性好、建造类之间独立、肯定水平上解耦

• 毛病：

  • 产生多余的Builder对象
  • 产品外部发生变化，建造者都要批改，老本较大

代码示例

版本一：

public class Course {    private String courseName;    private String coursePPT;    private String courseVideo;    private String courseArticle;//    question&Answer    private String courseQA;    public String getCourseName() {        return courseName;    }    public void setCourseName(String courseName) {        this.courseName = courseName;    }    public String getCoursePPT() {        return coursePPT;    }    public void setCoursePPT(String coursePPT) {        this.coursePPT = coursePPT;    }    public String getCourseVideo() {        return courseVideo;    }    public void setCourseVideo(String courseVideo) {        this.courseVideo = courseVideo;    }    public String getCourseArticle() {        return courseArticle;    }    public void setCourseArticle(String courseArticle) {        this.courseArticle = courseArticle;    }    public String getCourseQA() {        return courseQA;    }    public void setCourseQA(String courseQA) {        this.courseQA = courseQA;    }    @Override    public String toString() {        return "Course{" +                "courseName='" + courseName + '\'' +                ", coursePPT='" + coursePPT + '\'' +                ", courseVideo='" + courseVideo + '\'' +                ", courseArticle='" + courseArticle + '\'' +                ", courseQA='" + courseQA + '\'' +                '}';    }}

public abstract class CourseBuilder {    public abstract void buildCourseName(String courseName);    public abstract void buildCoursePPT(String coursePPT);    public abstract void buildCourseVideo(String courseVideo);    public abstract void buildCourseArticle(String courseArticle);    public abstract void buildCourseQA(String courseQA);    public abstract Course makeCourse();}

public class CourseActualBuilder extends CourseBuilder{    private Course course = new Course();    @Override    public void buildCourseName(String courseName) {        course.setCourseName(courseName);    }    @Override    public void buildCoursePPT(String coursePPT) {        course.setCoursePPT(coursePPT);    }    @Override    public void buildCourseVideo(String courseVideo) {        course.setCourseVideo(courseVideo);    }    @Override    public void buildCourseArticle(String courseArticle) {        course.setCourseArticle(courseArticle);    }    @Override    public void buildCourseQA(String courseQA) {        course.setCourseQA(courseQA);    }    @Override    public Course makeCourse() {        return course;    }}

public class Coach {    private CourseBuilder courseBuilder;    public void setCourseBuilder(CourseBuilder courseBuilder) {        this.courseBuilder = courseBuilder;    }    public Course makeCourse(String courseName,String coursePPT,                             String courseVideo,String courseArticle,                             String courseQA){        courseBuilder.buildCourseName(courseName);        courseBuilder.buildCoursePPT(coursePPT);        courseBuilder.buildCourseVideo(courseVideo);        courseBuilder.buildCourseArticle(courseArticle);        courseBuilder.buildCourseQA(courseQA);        return  courseBuilder.makeCourse();    }}

测试类：

public class Test {    public static void main(String[] args) {        CourseBuilder courseBuilder = new CourseActualBuilder();        Coach coach = new Coach();        coach.setCourseBuilder(courseBuilder);        Course course = coach.makeCourse("Java设计模式","Java设计模式PPT","Java设计模式视频",                "Java设计模式手记","Java设计模式问答");        System.out.println(course);    }}

版本二：

public class Course {    private String courseName;    private String coursePPT;    private String courseVideo;    private String courseArticle;//    question&Answer    private String courseQA;    public Course(CourseBuilder courseBuilder) {        this.courseName = courseBuilder.courseName;        this.coursePPT = courseBuilder.coursePPT;        this.courseVideo = courseBuilder.courseVideo;        this.courseArticle = courseBuilder.courseArticle;        this.courseQA = courseBuilder.courseQA;    }    @Override    public String toString() {        return "Course{" +                "courseName='" + courseName + '\'' +                ", coursePPT='" + coursePPT + '\'' +                ", courseVideo='" + courseVideo + '\'' +                ", courseArticle='" + courseArticle + '\'' +                ", courseQA='" + courseQA + '\'' +                '}';    }    public static class CourseBuilder {        private String courseName;        private String coursePPT;        private String courseVideo;        private String courseArticle;        //    question&Answer        private String courseQA;        public CourseBuilder buildCourseName(String courseName){            this.courseName = courseName;            return this;        }        public CourseBuilder buildCoursePPT(String coursePPT){            this.coursePPT = coursePPT;            return this;        }        public CourseBuilder buildCourseVideo(String courseVideo){            this.courseVideo = courseVideo;            return this;        }        public CourseBuilder buildCourseArticle(String courseArticle){            this.courseArticle = courseArticle;            return this;        }        public CourseBuilder buildCourseQA(String courseQA){            this.courseQA = courseQA;            return this;        }        public Course build(){            return new Course(this);        }    }}

测试类：

public class Test {    public static void main(String[] args) {        CourseBuilder courseBuilder = new CourseActualBuilder();        Coach coach = new Coach();        coach.setCourseBuilder(courseBuilder);        Course course = coach.makeCourse("Java设计模式","Java设计模式PPT","Java设计模式视频",                "Java设计模式手记","Java设计模式问答");        System.out.println(course);    }}

利用场景

JDK：

• StringBuilder（线程不平安）
• StringBuffer（线程平安）
• guava（CacheBuilder）
• Spring（BeanDefinitionBuilder）
• Mybatis（SqlSessionFactoryBuilder（XMLConfigBuilder））