设计模式之工厂模式

/**
* 生产的接口 就相当于模子
*/
public interface Person {

public void talk();

public void cry();

}

/**
* 要生产的人
*/
public class BlackPerson implements Person {
@Override
public void talk() {
System.out.println("黑人说话");
}

@Override
public void cry() {
System.out.println("黑人哭");
}
}

/**
* 生产出来的人
*/
public class YellowPerson implements Person {
@Override
public void talk() {
System.out.println("黄种人说话");
}

@Override
public void cry() {
System.out.println("黄种人哭");
}
}

/**
* 生产工厂
*/
public class PersonFactory  {

private static Person person;
private static int rand;

//生产人类,根据实现类名单个生产
public  static Person createPerson(Class c){
try {
//用反射通过类名获得要生产的对象 本例中的:黑人和黄种人
person = (Person) Class.forName(c.getName()).newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return person;
}

//批量生产
public static Person createPerson(){
//获得这个接口有多少实现的实体类(产品)
List<Class> concreteHumanList =
ClassUtils.getAllClassByInterface(Person.class);
Random random = new Random();

if(concreteHumanList.size()!=0){
rand = random.nextInt(concreteHumanList.size());
}else{
return null;
}
person = createPerson(concreteHumanList.get(rand));
return person;
}
}

/**
* 查找接口所在的包下所有实现的类.
*/
public class ClassUtils {
//给一个接口，返回这个接口的所有实现类
public static List<Class> getAllClassByInterface(Class c){
List<Class> returnClassList = new ArrayList<Class>(); //返回结果
//如果不是一个接口，则不做处理
if(c.isInterface()){
//获得当前的包名
String packageName = c.getPackage().getName();
try {
//获得当前包下以及子包下的所有类
List<Class> allClass = getClasses(packageName);
//判断是否是同一个接口
for(int i=0;i<allClass.size();i++){
if(c.isAssignableFrom(allClass.get(i))){ //判断是不是一个接口
if(!c.equals(allClass.get(i))){ //本身不加进去
returnClassList.add(allClass.get(i));
}
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}
return returnClassList;
}
//从一个包中查找出所有的类，在jar包中不能查找
private static List<Class> getClasses(String packageName)
throws ClassNotFoundException, IOException {
ClassLoader classLoader = Thread.currentThread()
.getContextClassLoader();
String path = packageName.replace('.', '/');
Enumeration<URL> resources = classLoader.getResources(path);
List<File> dirs = new ArrayList<File>();
while (resources.hasMoreElements()) {
URL resource = resources.nextElement();
dirs.add(new File(resource.getFile()));
}
ArrayList<Class> classes = new ArrayList<Class>();
for (File directory : dirs) {
classes.addAll(findClasses(directory, packageName));
}
return classes;
}
private static List<Class> findClasses(File directory, String packageName)
throws ClassNotFoundException {
List<Class> classes = new ArrayList<Class>();
if (!directory.exists()) {
return classes;
}
File[] files = directory.listFiles();
for (File file : files) {
if (file.isDirectory()) {
assert !file.getName().contains(".");
classes.addAll(findClasses(file, packageName + "." +
file.getName()));
} else if (file.getName().endsWith(".class")) {
classes.add(Class.forName(packageName + '.' +
file.getName().substring(0, file.getName().length() - 6)));
}
}
return classes;
}
}