java设计模式精讲 Debug 方式+内存分析 第4章 简单工厂模式

4-1 简单工厂讲解

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4-2 简单工厂coding

有一个视频的基类（是一个抽象类）

public abstract class Video {
    public abstract void product();
}

有两个类继承它，并对里面的方法进行实现：

public class JavaVideo extends Video {
    @Override
    public void product() {
        System.out.println("录制Java课程视频");
    }
}

public class Python extends Video {
    @Override
    public void product() {
        System.out.println("录制Python的课程视频");
    }
}

现在，我们有一个简单工厂类：

public class VideoFactory {
    public Video getVideo(String type) {
        if ("java".equalsIgnoreCase(type)) {
            return new JavaVideo();
        } else if ("python".equalsIgnoreCase(type)) {
            return new Python();
        }
        return null;
    }
}

测试代码如下：

public class Test {
    public static void main(String[]args){
        VideoFactory videoFactory = new VideoFactory();
        Video video = videoFactory.getVideo("java");
        if (video == null) {
            return;
        }
        video.product();
    }
}

执行结果：

录制Java课程视频

这个就是现在的类图：

具体的产生类的方法都在工厂类里面，这个就是简单工厂模式;

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但是，如果我们还要录制一个FE的前端课程，那么，我们就要对工厂类里面的方法进行扩展，那么这个并不符合开闭原则：

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现在，我们来用反射来演进一下：

public class VideoFactory {
    public Video getVideo(Class clazz) {
        Video video = null;
        try {
            video = (Video) Class.forName(clazz.getName()).newInstance();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return video;
    }
}

测试如下：

public class Test {
    public static void main(String[]args){
        VideoFactory videoFactory = new VideoFactory();
        Video video = videoFactory.getVideo(JavaVideo.class);
        if (video == null) {
            return;
        }
        video.product();
    }
}

这里从一定原则上讲是符合开闭原则的：
如果我们要new什么类，那我们就只需要传入这个类的类型就可以了，而这个工厂是需要变化的;

4-3 简单工厂JDK源码解析

现在，我们来看一下，在JDK源码里面使用简单工厂的类：

• Calendar
  

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• DriverManager里面的getConnection()方法：
  

以下是之后要查看源码需要导入的依赖：

<dependencies>
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-servlet-api</artifactId>
            <version>7.0.64</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-oxm</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>


        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.7.3</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>${org.mybatis.spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>${org.mybatis.version}</version>
        </dependency>

        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.6.11</version>
        </dependency>

        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.12</version>
        </dependency>

        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>1.4</version>
            <!--<scope>runtime</scope>-->
        </dependency>


        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.2</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.1.2</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>20.0</version>
        </dependency>


        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.5</version>
        </dependency>


        <dependency>
            <groupId>commons-collections</groupId>
            <artifactId>commons-collections</artifactId>
            <version>3.2.1</version>
        </dependency>


        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <!--<scope>test</scope>-->
        </dependency>

        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
            <version>2.3</version>
        </dependency>


        <!-- id加密解密 -->
        <dependency>
            <groupId>org.hashids</groupId>
            <artifactId>hashids</artifactId>
            <version>1.0.1</version>
        </dependency>


        <!-- ftpclient -->
        <dependency>
            <groupId>commons-net</groupId>
            <artifactId>commons-net</artifactId>
            <version>3.1</version>
        </dependency>

        <!-- file upload -->

        <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.2.2</version>
        </dependency>

        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.0.1</version>
        </dependency>




        <!-- mybatis pager -->

        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>4.1.0</version>
        </dependency>

        <dependency>
            <groupId>com.github.miemiedev</groupId>
            <artifactId>mybatis-paginator</artifactId>
            <version>1.2.17</version>
        </dependency>

        <dependency>
            <groupId>com.github.jsqlparser</groupId>
            <artifactId>jsqlparser</artifactId>
            <version>0.9.4</version>
        </dependency>


        <!-- alipay -->
        <dependency>
            <groupId>commons-codec</groupId>
            <artifactId>commons-codec</artifactId>
            <version>1.10</version>
        </dependency>
        <dependency>
            <groupId>commons-configuration</groupId>
            <artifactId>commons-configuration</artifactId>
            <version>1.10</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.1</version>
        </dependency>
        <dependency>
            <groupId>com.google.zxing</groupId>
            <artifactId>core</artifactId>
            <version>2.1</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.3.1</version>
        </dependency>
        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-core</artifactId>
            <version>1.3</version>
        </dependency>

        <!-- 二期新增的 -->

        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.6.0</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.18</version>
        </dependency>

        <!-- spring session 单点登录 -->
        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>
            <version>1.2.0.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson</artifactId>
            <version>2.9.0</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-avro</artifactId>
            <version>2.9.0</version>
        </dependency>
    </dependencies>

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LoggerFactory这个类里面的getLogger方法：