Behavioral patterns - Chain of Responsibility pattern (IX)

The project source address: https: //github.com/ggb2312/JavaNotes/tree/master/design-pattern (design patterns relevant code and notes)

1. Definitions

Receiving a request to create a chain of this request object

2. Applicable scene

• One or more cooperative processing among the processing requires a plurality of object requests

Application examples: struts interceptors, servlet filter, Dubbo the Filter, Mybatis in the Plugin

3. relevant design patterns

Chain of Responsibility pattern and status mode

• Who the Chain of Responsibility pattern of each object does not specify a process object is a set order, and the responsibility of the chain element by the client, until it is processed to a chain of responsibility, or the end of the entire chain of responsibility.
• State model is to make each object knows who the next target processing yes.

Example 4. Mode

Background : Mu lesson course line network at the time of release, to go through the approval of a two people, a man Notes check, another person is to check the video, we will encounter this situation in which oa system, a approval grade level. This is a chain.

(1) Course category

public class Course {
    private String name;
    private String article;
    private String video;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getArticle() {
        return article;
    }

    public void setArticle(String article) {
        this.article = article;
    }

    public String getVideo() {
        return video;
    }

    public void setVideo(String video) {
        this.video = video;
    }

    @Override
    public String toString() {
        return "Course{" +
                "name='" + name + '\'' +
                ", article='" + article + '\'' +
                ", video='" + video + '\'' +
                '}';
    }
}

(2) approval by the abstract class

/**
 * 批准者
 */
public abstract class Approver {
    /** 责任链的核心就是在类里面包含了一个自己同样类型的一个对象 */
    protected Approver approver;

    public void setNextApprover(Approver approver) {
        this.approver = approver;
    }

    public abstract void deploy(Course course) ;
}

(3) Notes approver

public class ArticleApprover extends Approver{

    @Override
    public void deploy(Course course) {
        if (StringUtils.isNoneEmpty(course.getArticle())) {
            System.out.println(course.getName() + "含有手记，批准");
            if (approver != null) {
                approver.deploy(course);
            }
        } else {
            System.out.println(course.getName() + "不含有手记，不批准，流程结束");
            return;
        }
    }
}

Approver (4) Video

public class VideoApprover extends Approver {
    @Override
    public void deploy(Course course) {
        if (StringUtils.isNoneEmpty(course.getVideo())) {
            System.out.println(course.getName() + "含有视频，批准");
            if (approver != null) {
                approver.deploy(course);
            }
        } else {
            System.out.println(course.getName() + "不含有视频，不批准，流程结束");
            return;
        }
    }
}

(5) Testing

public class Test {
    public static void main(String[] args) {
        Approver articleApprover = new ArticleApprover();
        Approver videoApprover = new VideoApprover();

        Course course = new Course();
        course.setName("Java设计模式精讲");
        course.setArticle("Java设计模式精讲的手记");
        course.setVideo("Java设计模式精讲的视频");
        /** 先通过手记的审核才交给视频的审核，视频的审核过了才能进行发布上线 */
        articleApprover.setNextApprover(videoApprover);
        articleApprover.deploy(course); 
    }
}

Test Results:

The advantages and disadvantages

advantage:

• The sender and receiver request (processing request) Decoupling
• The chain of responsibility can be dynamically combined

Disadvantages:

• Chain of responsibility is too long or the processing time is too long, affecting performance
• The chain of responsibility there may be excessive

6. -JDK1.7 source and extended chain of responsibility pattern frame

javax.servlet.Filter的doFilter、FilterChain

SpringSecurity