设计模式解析与实战之原型模式

最新推荐文章于 2025-12-06 15:58:48 发布

原创最新推荐文章于 2025-12-06 15:58:48 发布 · 946 阅读

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#设计模式

本文解析了设计模式中的原型模式，介绍了其基本概念与实现方式，并通过具体示例对比了浅拷贝与深拷贝的区别。

买了大神关爱民与何红辉所著书籍《设计模式解析与实战》，观后有所感、有所悟。

所谓的原型模式我更喜欢叫它复制拷贝，调用简单，通过类实现Cloneable空接口（该接口是一个标识接口，表示该类可以拷贝，如果不实现该接口，将会抛出异常）调用clone方法拷贝。性能比new 更好，但是开发中需要注意clone方法不会执行类的构造方法。下面看一段代码实例：

public class User implements Cloneable{

    private String userName;

    private String password;

    private String icon;

    private ArrayList<Image> mImageList=new ArrayList<Image>();

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getIcon() {
        return icon;
    }

    public void setIcon(String icon) {
        this.icon = icon;
    }

    public ArrayList<Image> getmImageList() {
        return mImageList;
    }

    public void setmImageList(ArrayList<Image> mImageList) {
        this.mImageList = mImageList;
    }

    public void addImage(Image mImage){
        this.mImageList.add(mImage);
    }

    @Override
    protected User clone() throws CloneNotSupportedException {

        return (User) super.clone();
    }

    @Override
    public String toString() {
        return "User [userName=" + userName + ", password=" + password
                + ", icon=" + icon + ", mImageList=" + mImageList + "]";
    }

}

测试代码：



public class CloneTest {

    public static void main(String[] args) throws CloneNotSupportedException {
        User mUser=new User();
        mUser.setIcon("xxxxx/icon/xxx.jpg");
        mUser.setPassword("password123");
        mUser.setUserName("usernameadmin");

        Image mImage=new Image();
        mImage.setImageUrl("image123434.jpg");
        mImage.setName("imageName12334");
        mImage.setUploadTime("2015-09-20 12:13:14");
        mUser.addImage(mImage);

        System.out.println("原型拷贝前：-----"+mUser.toString()+"\n");


        User cloneUser=mUser.clone();
        System.out.println("原型拷贝前：-----"+mUser.toString());
        System.out.println("原型拷贝后：-----"+cloneUser.toString()+"\n");

        cloneUser.setPassword("123456");

        System.out.println("修改拷贝后原型：-----"+mUser.toString());
        System.out.println("修改拷贝后cloneUser：-----"+cloneUser.toString()+"\n");
    }
}

测试结果：

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
原型拷贝后：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

修改拷贝后原型：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
修改拷贝后cloneUser：-----User [userName=usernameadmin, password=123456, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

通过上述测试代码和结果，可以发现，调用clone方法拷贝了一份一模一样的对象，修改原型的值（simple:int）不会影响原型数据，即浅拷贝。再看一段代码测试结果：

        Image mImage2=new Image();
        mImage2.setImageUrl("image123434.jpg");
        mImage2.setName("imageName12334");
        mImage2.setUploadTime("2015-09-20 12:13:14");
        cloneUser.addImage(mImage2);

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
原型拷贝后：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

修改拷贝后原型：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg], Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
修改拷贝后cloneUser：-----User [userName=usernameadmin, password=123456, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg], Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

观察上面结果，发现修改mImageList后原型同时被修改了，造成这个问题的解决办法就需要用到深拷贝，即再拷贝对象时，对于引用字段也要采取拷贝形式，不只是单纯的引用的形式，clone方法修改如下：

@Override
    protected User clone() throws CloneNotSupportedException {
        User mCloneUser=(User) super.clone();
        mCloneUser.setmImageList((ArrayList<Image>) this.mImageList.clone());
        return mCloneUser;
    }


结果如下：

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

原型拷贝前：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
原型拷贝后：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

修改拷贝后原型：-----User [userName=usernameadmin, password=password123, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]
修改拷贝后cloneUser：-----User [userName=usernameadmin, password=123456, icon=xxxxx/icon/xxx.jpg, mImageList=[Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg], Image [uploadTime=2015-09-20 12:13:14, name=imageName12334, imageUrl=image123434.jpg]]]

在源码中该模式应用的范围也挺广的，Simple ArrayList:

public class ArrayList<E> extends AbstractList<E>
        implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
            .............此处略.............
   /**
     * Returns a shallow copy of this <tt>ArrayList</tt> instance.  (The
     * elements themselves are not copied.)
     *
     * @return a clone of this <tt>ArrayList</tt> instance
     */
    public Object clone() {
        try {
            @SuppressWarnings("unchecked")
                ArrayList<E> v = (ArrayList<E>) super.clone();
            v.elementData = Arrays.copyOf(elementData, size);
            v.modCount = 0;
            return v;
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError();
        }
    }
}

下面是一个简单的登录实战实例：

public class User {

    private String userName;
    private String password;

    /**登录成功后返回的信息*/
    private UserSession mUserSession=new UserSession();

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public UserSession getUserSession() {
        return mUserSession;
    }

    public void setUserSession(UserSession mUserSession) {
        this.mUserSession = mUserSession;
    }

    @Override
    protected User clone(){
        User cloneUser=null;
        try {
            cloneUser = (User) super.clone();
            cloneUser.setUserSession(this.mUserSession);
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return cloneUser;
    }
}

接口定义（别问我为什么要这么定义接口，想知道就去看高老师视频吧，我不会告诉你的）：

/**
 * 用户接口
 * @author LanYan
 *
 */
public interface OnAccountListener {

    /**
     * 登录结果回调接口
     */
    interface OnLoginCallback{

        /**
         * 登录成功
         * @param mUserSession
         */
        void onLoginSuccess(UserSession mUserSession);

        /**
         * 登录失败
         * @param e
         * @param code
         * @param message
         */
        void onLoginFail(Exception e,int code,String message);
    }

    /**
     * 登录接口
     */
    interface OnLoginListener{

        /**
         * 登录方法传入参数 用户名 和登录密码
         * @param userName
         * @param password
         * @param onLoginCallback
         */
        void onLogin(String userName,String password,OnLoginCallback onLoginCallback);
    }

    /**
     * http请求成功后如果需要数据同步，就调用此方法
     */
    interface OnSyncListener{

        /**
         * 同步方法
         * @param mUserSession
         */
        void sync(UserSession mUserSession);
    }

}

登录实现类：

import clonable.simple.OnAccountListener;

public class UserImpl implements OnAccountListener.OnLoginListener ,OnAccountListener.OnSyncListener{

    private static UserImpl instance;

    public static UserImpl getInstance() {

        if(instance==null){
            synchronized (UserImpl.class) {
                instance=new UserImpl();
            }
        }
        return instance;
    }

    @Override
    public void onLogin(String userName, String password,
            OnAccountListener.OnLoginCallback onLoginCallback) {
        ............此处略...............
    }

    @Override
    public void sync(UserSession mUserSession) {
        ............此处略...............
    }

}

下面是测试代码：


public class LoginTest{

    static User mCloneUser;

    public static void main(String[] args) {

        User mUser=new User();
        mUser.setUserName("admin");
        mUser.setPassword("123456");

        mCloneUser=mUser.clone();

        UserImpl.getInstance().onLogin(mCloneUser.getUserName(),mCloneUser.getPassword(),new OnLoginCallback() {

            @Override
            public void onLoginSuccess(UserSession mUserSession) {
                mCloneUser.setUserSession(mUserSession);
                UserImpl.getInstance().sync(mUserSession);
            }

            @Override
            public void onLoginFail(Exception e, int code, String message) {

            }
        });
    }

}