接下来创建Java产品族，Java视频JavaVideo类的代码如下。
public class JavaVideo implements IVideo {
public void record() {
System.out.println(“录制Java视频”);
}
}
扩展产品等级Java课堂笔记JavaNote类。
public class JavaNote implements INote {
public void edit() {
System.out.println(“编写Java笔记”);
}
}
创建Java产品族的具体工厂JavaCourseFactory。
public class JavaCourseFactory extends CourseFactory {
public INote createNote() {
super.init();
return new JavaNote();
}
public IVideo createVideo() {
super.init();
return new JavaVideo();
}
}
随后创建Python产品族，Python视频PythonVideo类的代码如下。
public class PythonVideo implements IVideo {
public void record() {
System.out.println(“录制Python视频”);
}
}
扩展产品等级Python课堂笔记PythonNote类。
public class PythonNote implements INote {
public void edit() {
System.out.println(“编写Python笔记”);
}
}
创建Python产品族的具体工厂PythonCourseFactory。
public class PythonCourseFactory implements CourseFactory {
public INote createNote() {
return new PythonNote();
}
public IVideo createVideo() {
return new PythonVideo();
}
}
最后来看客户端调用代码。
public static void main(String[] args) {
JavaCourseFactory factory = new JavaCourseFactory();
factory.createNote().edit();
factory.createVideo().record();
}
上面代码完整地描述了Java课程和Python课程两个产品族，也描述了视频和笔记两个产品等级。抽象工厂非常完美、清晰地描述了这样一层复杂的关系。但是，不知道大家有没有发现，如果再继续扩展 《一线大厂Java面试题解析+后端开发学习笔记+最新架构讲解视频+实战项目源码讲义》无偿开源 威信搜索公众号【编程进阶路】 产品等级，将源码Source也加入课程中，则代码从抽象工厂到具体工厂要全部调整，这显然不符合开闭原则。
[](()4 使用抽象工厂模式重构数据库连接池
还是演示课堂开始的JDBC操作案例，我们每次操作都需要重新创建数据库连接。其实每次创建都非常耗费性能，消耗业务调用时间。我们使用抽象工厂模式，将数据库连接预先创建好，放到容器中缓存着，当业务调用时就只需现取现用。我们来看代码。
Pool抽象类的代码如下。
public abstract class Pool {
public String propertiesName = “connection-INF.properties”;
private static Pool instance = null; //定义唯一实例
protected int maxConnect = 100; //最大连接数
protected int normalConnect = 10; //保持连接数
protected String driverName = null; //驱动字符串
protected Driver driver = null; //驱动变量
protected Pool() {
try
{
init();
loadDrivers(driverName);
}catch(Exception e)
{
e.printStackTrace();
}
}
private void init() throws IOException {
InputStream is = Pool.class.getResourceAsStream(propertiesName);
Properties p = new Properties();
p.load(is);
this.driverName = p.getProperty(“driverName”);
this.maxConnect = Integer.parseInt(p.getProperty(“maxConnect”));
this.normalConnect = Integer.parseInt(p.getProperty(“normalConnect”));
}
protected void loadDrivers(String dri) {
String driverClassName = dri;
try {
driver = (Driver) Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
System.out.println(“成功注册JDBC驱动程序” + driverClassName);
} catch (Exception e) {
System.out.println(“无法注册JDBC驱动程序:” + driverClassName + “,错误:” + e);
}
}
public abstract void createPool();
public static synchronized Pool getInstance() throws IOException,
InstantiationException, IllegalAccessException,
ClassNotFoundException {
if (instance == null) {
instance = (Pool) Class.forName(“org.e_book.sqlhelp.Pool”).newInstance();
}
return instance;
}
public abstract Connection getConnection();
public abstract Connection getConnection(long time);
public abstract void freeConnection(Connection con);
public abstract int getnum();
public abstract int getnumActive();
protected synchronized void release() {
//撤销驱动
try {
DriverManager.deregisterDriver(driver);
System.out.println("撤销JDBC驱动程序 " + driver.getClass().getName());
} catch (SQLException e) {
System.out
.println(“无法撤销JDBC驱动程序的注册:” + driver.getClass().getName());
}
}
}
DBConnectionPool数据库连接池的代码如下。
public final class DBConnectionPool extends Pool {
private int checkedOut; //正在使用的连接数
private Vector freeConnections = new Vector();
//存放产生的连接对象容器
private String passWord = null; //密码
private String url = null; //连接字符串
private String userName = null; //用户名
private static int num = 0; //空闲连接数
private static int numActive = 0; //当前可用的连接数
private static DBConnectionPool pool = null; //连接池实例变量
public static synchronized DBConnectionPool getInstance()
{
if(pool == null)
{
pool = new DBConnectionPool();
}
return pool;
}
private DBConnectionPool() {
try
{
init();
for (int i = 0; i < normalConnect; i++) { //初始normalConn个连接
Connection c = newConnection();
if (c != null) {
freeConnections.addElement©; //往容器中添加一个连接对象
num++; //记录总连接数
}
}
}catch(Exception e)
{
e.printStackTrace();
}
}
private void init() throws IOException
{
InputStream is = DBConnectionPool.class.getResourceAsStream(propertiesName);
Properties p = new Properties();
p.load(is);
this.userName = p.getProperty(“userName”);
this.passWord = p.getProperty(“passWord”);
this.driverName = p.getProperty(“driverName”);
this.url = p.getProperty(“url”);
this.driverName = p.getProperty(“driverName”);
this.maxConnect = Integer.parseInt(p.getProperty(“maxConnect”));
this.normalConnect = Integer.parseInt(p.getProperty(“normalConnect”));
}
public synchronized void freeConnection(Connection con) {
freeConnections.addElement(con);
num++;
checkedOut–;
numActive–;
notifyAll(); //解锁
}
private Connection newConnection() {
Connection con = null;
try {
if (userName == null) { //用户、密码都为空
con = DriverManager.getConnection(url);
} else {
con = DriverManager.getConnection(url, userName, passWord);
}
System.out.println(“连接池创建一个新的连接”);
} catch (SQLException e) {
System.out.println(“无法创建这个URL的连接” + url);
return null;
}
return con;
}
public int getnum() {
return num;
}
public int getnumActive() {
return numActive;
}
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) { //还有空闲的连接
num–;
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
System.out.println(“从连接池删除一个无效连接”);
con = getConnection();
}
} catch (SQLException e) {
System.out.println(“从连接池删除一个无效连接”);
con = getConnection();
