Type of model - state model (XI)

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

1. Definitions

It allows an object to change its internal state, to alter its behavior

2. Applicable scene

A plurality of state objects exist (different behavior under different conditions), and the state can be converted to each other
for example: electricity supplier order status torsion

3. The class diagram and role

The Context : It is the object containing the state, it can handle some of the requests, which will eventually produce a response state associated with.

State : state of the interface, which defines the behavior of each state of the collection, these actions will be in use in Context.

ConcreteState : specific state, to achieve specific state-related class actions.

4. The relevant design patterns

Flyweight state mode and
state mode and can be used in combination Flyweight

Example 5. Mode

Background: The player state of the video switch

(1) Video Status abstract class

/**
 * Create by lastwhisper on 2019/2/11
 */
public abstract class CourseVideoState {
    protected CourseVideoContext courseVideoContext;

    public void setCourseVideoContext(CourseVideoContext courseVideoContext) {
        this.courseVideoContext = courseVideoContext;
    }

    public abstract void play();

    public abstract void speed();

    public abstract void pause();

    public abstract void stop();
}

(2) Video context

/**
 * Create by lastwhisper on 2019/2/11
 */
public class CourseVideoContext {
    private CourseVideoState courseVideoState;
    public final static PlayState PLAY_STATE = new PlayState();
    public final static StopState STOP_STATE = new StopState();
    public final static PauseState PAUSE_STATE = new PauseState();
    public final static SpeedState SPEED_STATE = new SpeedState();

    public CourseVideoState getCourseVideoState() {
        return courseVideoState;
    }

    public void setCourseVideoState(CourseVideoState courseVideoState) {
        this.courseVideoState = courseVideoState;
        this.courseVideoState.setCourseVideoContext(this);
    }

    public void play() {
        this.courseVideoState.play();
    }

    public void speed() {
        this.courseVideoState.speed();
    }

    public void pause() {
        this.courseVideoState.pause();
    }

    public void stop() {
        this.courseVideoState.stop();
    }
}

(3) the state of various specific class of video

PlayState normal course video playback state

/**
 * Create by lastwhisper on 2019/2/11
 */
public class PlayState extends CourseVideoState {

    @Override
    public void play() {
        System.out.println("正常播放课程视频状态");
    }

    @Override
    public void speed() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.SPEED_STATE);
    }

    @Override
    public void pause() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PAUSE_STATE);
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

SpeedState fast-forward the video state curriculum

/**
 * Create by lastwhisper on 2019/2/11
 */
public class SpeedState extends CourseVideoState  {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        System.out.println("快进播放课程视频状态");
    }

    @Override
    public void pause() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PAUSE_STATE);
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

PauseState pause video playback state curriculum

/**
 * Create by lastwhisper on 2019/2/11
 */
public class PauseState extends CourseVideoState  {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.SPEED_STATE);
    }

    @Override
    public void pause() {
        System.out.println("暂停播放课程视频状态");
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

StopState stop playing video course status

/**
 * Create by lastwhisper on 2019/2/11
 */
public class StopState extends CourseVideoState  {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        System.out.println("ERROR 停止状态不能快进！！");
    }

    @Override
    public void pause() {
        System.out.println("ERROR 停止状态不能暂停！！");
    }

    @Override
    public void stop() {
        System.out.println("停止播放课程视频状态");
    }
}

(4) test

/**
 * Create by lastwhisper on 2019/2/11
 */
public class Test {
    public static void main(String[] args){
        CourseVideoContext courseVideoContext = new CourseVideoContext();
        courseVideoContext.setCourseVideoState(new PlayState());
        System.out.println("当前状态"+ courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.pause();
        System.out.println("当前状态"+ courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.speed();
        System.out.println("当前状态"+ courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.stop();
        System.out.println("当前状态"+ courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.speed();
    }
}

Test Results:

(5) FIG class

6. pros and cons

advantage:

• The different states isolation
• Converting various logic states, the subclass distribution of the State, the reduction of mutual dependence
• Very simple to add new state

Disadvantages:

• Multi-state business scenario leads to an increase the number of classes, the system becomes complicated

7. Extended -JDK1.7 source mode and a frame in a state

javax.faces.lifecycle.Lifecycle、javax.faces.webapp.FacesServlet