java設計模式精講 Debug 方式+記憶體分析 第4章 簡單工廠模式
阿新 • • 發佈：2018-11-21
簡單工廠模式
4-1 簡單工廠講解
4-2 簡單工廠coding
有一個視訊的基類（是一個抽象類）
public abstract class Video {
public abstract void product();
}
有兩個類繼承它，並對裡面的方法進行實現：
public class JavaVideo extends Video {
@Override public class Python extends Video {
@Override
public void product() {
System.out.println("錄製Python的課程視訊");
}
}
現在，我們有一個簡單工廠類：
public class VideoFactory {
public Video getVideo(String type) { 測試程式碼如下：
public class Test {
public static void main(String[]args){
VideoFactory videoFactory = 執行結果：
錄製Java課程視訊
這個就是現在的類圖：
具體的產生類的方法都在工廠類裡面，這個就是簡單工廠模式;
但是，如果我們還要錄製一個FE的前端課程，那麼，我們就要對工廠類裡面的方法進行擴充套件，那麼這個並不符合開閉原則：
現在，我們來用反射來演進一下：
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;
}
}
測試如下：
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();
}
}
這裡從一定原則上講是符合開閉原則的：
如果我們要new什麼類，那我們就只需要傳入這個類的型別就可以了，而這個工廠是需要變化的;
4-3 簡單工廠JDK原始碼解析
現在，我們來看一下，在JDK原始碼裡面使用簡單工廠的類：
- Calendar
- DriverManager裡面的getConnection()方法：
以下是之後要檢視原始碼需要匯入的依賴：
<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