1??概述

定義 : 允許一個(gè)對(duì)象在其內(nèi)部狀態(tài)改變時(shí),改變它的行為;
類型 : 行為型;

2??使用場(chǎng)景

一個(gè)對(duì)象存在多個(gè)狀態(tài)(不同狀態(tài)下行為不同)且狀態(tài)可相互切換;

3??優(yōu)點(diǎn)

將不同的狀態(tài)隔離;
把各種狀態(tài)的轉(zhuǎn)換邏輯,分布到State的子類中,減少相互間的依賴;
增加新的狀態(tài)比較簡(jiǎn)單;

4??缺點(diǎn)

狀態(tài)多的業(yè)務(wù)場(chǎng)景導(dǎo)致類的數(shù)目增加,系統(tǒng)將會(huì)變得比較復(fù)雜;

5??狀態(tài)模式Coding

1 創(chuàng)建CourseVideoState抽象類

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 創(chuàng)建CourseVideoContext類

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

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

3 創(chuàng)建不同的狀態(tài)類

/**
 * 暫停狀態(tài)
 */
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("暫停播放課程視頻狀態(tài)");
    }

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

/**
 * 播放狀態(tài)
 */
public class PlayState extends CourseVideoState {

    @Override
    public void play() {
        System.out.println("正常播放課程視頻狀態(tài)");
    }

    @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);
    }
}

/**
 * 快進(jìn)狀態(tài)
 */
public class SpeedState extends CourseVideoState {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        System.out.println("快進(jìn)播放課程視頻狀態(tài)");
    }

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

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

/**
 * 停止?fàn)顟B(tài)
 */
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?fàn)顟B(tài)不能快進(jìn)!!");
    }

    @Override
    public void pause() {
        System.out.println("ERROR 停止?fàn)顟B(tài)不能暫停!!");
    }

    @Override
    public void stop() {
        System.out.println("停止播放課程視頻狀態(tài)");
    }
}

4 UML類圖

5 編寫(xiě)測(cè)試類

public class Test {
    public static void main(String[] args) {
        CourseVideoContext courseVideoContext = new CourseVideoContext();
        courseVideoContext.setCourseVideoState(new PlayState());
        System.out.println("當(dāng)前狀態(tài):"+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.pause();
        System.out.println("當(dāng)前狀態(tài):"+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.speed();
        System.out.println("當(dāng)前狀態(tài):"+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.stop();
        System.out.println("當(dāng)前狀態(tài):"+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.speed();
    }
}

6??狀態(tài)模式源碼解析

JSF : javax.faces.lifecycle execute()