工廠方法模式的定義

定義一個(gè)用于創(chuàng)建對(duì)象的接口，讓子類決定實(shí)例化哪一個(gè)類踏揣。Factory Method使一個(gè)類的實(shí)例化延遲到子類输硝。

工廠方法模式的本質(zhì)

延遲到子類來(lái)選擇實(shí)現(xiàn)柬采。

工廠方法模式的優(yōu)缺點(diǎn)

優(yōu)點(diǎn): 更容易擴(kuò)展對(duì)象的新版本细移。
缺點(diǎn): 具體的產(chǎn)品對(duì)象和工廠方法是耦合的。

示例1

public interface ExportFileApi {
    boolean export(String data);
}

public class ExportTxt implements ExportFileApi {
    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到txt文件");
        return true;
    }
}

public class ExportDB implements ExportFileApi {
    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到數(shù)據(jù)庫(kù)");
        return true;
    }
}

public abstract class ExportOperate {

    public boolean export(String data) {
        ExportFileApi api = factoryMethod();
        return api.export(data);
    }

    /**
     * 鉤子方法熊锭，由子類去選擇創(chuàng)建具體的類
     * @return
     */
    protected abstract ExportFileApi factoryMethod();
}

public class ExportOperateTxt extends ExportOperate {

    @Override
    protected ExportFileApi factoryMethod() {
        return new ExportTxt();
    }
}

public class ExportOperateDB extends ExportOperate {

    @Override
    protected ExportFileApi factoryMethod() {
        return new ExportDB();
    }
}

public class TestClient {
    public static void main(String[] args) {
        ExportOperate operate = new ExportOperateDB();
        operate.export("aaaa");
    }
}

去擴(kuò)展一個(gè)導(dǎo)出xml弧轧。

public class ExportXml implements ExportFileApi {

    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到xml");
        return true;
    }
}

public class ExportOperateXml extends ExportOperate {
    @Override
    protected ExportFileApi factoryMethod() {
        return new ExportXml();
    }
}

public class TestClient {
    public static void main(String[] args) {
        ExportOperate operate = new ExportOperateXml();
        operate.export("aaaa");
    }
}

示例2 參數(shù)化

public interface ExportFileApi {
    boolean export(String data);
}

public class ExportTxt implements ExportFileApi {
    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到txt文件");
        return true;
    }
}

public class ExportDB implements ExportFileApi {
    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到數(shù)據(jù)庫(kù)");
        return true;
    }
}

public class ExportXml implements ExportFileApi {

    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到xml");
        return true;
    }
}

public class ExportOperate {

    public boolean export(int type,String data) {
        ExportFileApi api = factoryMethod(type);
        return api.export(data);
    }

    protected ExportFileApi factoryMethod(int type) {
        ExportFileApi api = null;
        if (1 == type) {
            api = new ExportTxt();
        } else if (2 == type){
            api = new ExportDB();
        } else if (3 == type) {
            api = new ExportXml();
        }
        return api;
    }

}

public class TestClient {
    public static void main(String[] args) {
        ExportOperate op = new ExportOperate();
        op.export(2, "aaa");
    }
}

擴(kuò)展導(dǎo)出到MySQL

public class ExportDBMySQL implements ExportFileApi {
    @Override
    public boolean export(String data) {
        System.out.println("導(dǎo)出數(shù)據(jù)："+data+"到數(shù)據(jù)庫(kù)MySQL");
        return true;
    }
}

public class ExportOperate2 extends ExportOperate {

    @Override
    protected ExportFileApi factoryMethod(int type) {
        if (2 == type) {
            return new ExportDBMySQL();
        } else {
            return super.factoryMethod(type);
        }
    }
}

public class TestClient {
    public static void main(String[] args) {
        ExportOperate op = new ExportOperate2();
        op.export(2, "aaa");
    }
}