通过BeanFactory实现创建对象

说明：

          其作用是减少层与层之间的依赖。

实现步骤：

        编写2个类（Student，Teacher）再编写beans.properties文件，接着编写BeanFactory类，最后编写测试类BeanTest，参考代码如下：

/**
 *beans.properties文件的内容(位于与src平级的config资源包下)
 */
Student=com.xxx.generic.demo.Student
Teacher=com.xxx.generic.demo.Teacher

/**
 *BeanFactory类的参考代码
 */
import java.io.InputStream;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class BeanFactory {
	private BeanFactory() {
	}

	private static Map<String, String> beans = new HashMap<>();
	static {
		InputStream is = BeanFactory.class.getClassLoader().getResourceAsStream("beans.properties");
		Properties prop = new Properties();
		try {
			prop.load(is);
			Enumeration<String> keys = (Enumeration<String>) prop.propertyNames();
			while (keys.hasMoreElements()) {
				String key = keys.nextElement();
				String value = prop.getProperty(key);
				beans.put(key, value);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (is != null) {
				try {
					is.close();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}
	}

	public static <T> T getBean(Class<T> clazz) {
		T t = null;
		String className = clazz.getSimpleName();
		Set<String> keys = beans.keySet();
		for (String key : keys) {
			if (key.equals(className)) {
				String value = beans.get(key);
				try {
					t = (T) Class.forName(value).newInstance();
				} catch (Exception e) {
					e.printStackTrace();
				}
				break;
			}
		}
		return t;
	}
}

/**
 *BeanTest类参考代码
 */
public class BeanTest {
	public static void main(String[] args) {
		Student s = BeanFactory.getBean(Student.class);
		System.out.println(s + ":我是" + s.getClass().getSimpleName() + "的一个对象。");
		Teacher t = BeanFactory.getBean(Teacher.class);
		System.out.println(t + ":我是" + t.getClass().getSimpleName() + "的一个对象。");
	}
}

运行结果如下：