ResourceBundle类的作用就是读取资源属性文件（properties），然后根据.properties文件的名称信息（本地化信息），匹配当前系统的国别语言信息（也可以程序指定），然后获取相应的properties文件的内容。
properties

1.ResourceBundle的常用方法：

1.1根据资源文件path加载资源

String sourcePath = "XXXXX.properties"
ResourceBundle resourceBundle = ResourceBundle.getBundle(sourcePath);

1.2获取资源文件中所有的key

Enumeration<String> keys = resourceBundle.getKeys();

1.3根据key读取对应的value值

String value = resourceBundle.getString(key);

使用场景
ResourceBundle已经给我们提供了通过key获取value的方法，相对来说比较方便。如果我们需要获取配置文件中的用户名，则如下代码就可以实现。

String userName= resourceBundle.getString("userName");

但是假设配置属性很多时，我们就需要重复写很多这样的荣誉代码，有没有适合Java编程思想里面的好的方式，将这些属性映射到java对象中，然后我们自己从java对象中获取嗯？
这里我们可以通过反射的手段将properties的属性值的key和java对象的属性字段进行匹配，如果配置文件的key值等于对象的属性字段，则将key对应的value映射到java对象的字段的属性上。

2.代码实现

2.1代码结构如下

2.2database.properties

##驱动名称：不推荐com.mysql.jdbc.Driver，而是推荐使用com.mysql.cj.jdbc.Driver
driverName = com.mysql.cj.jdbc.Driver
##数据库连接地址
url = jdbc:mysql://127.0.0.1:3306/testdb
userName = root
passWord = root

##连接池名字
poolName = Hutao Connection Pool

##空闲池，最小连接数
minConnections = 1

##空闲池，最大连接数
maxConnections = 10

##初始化连接数
initConnections = 5

##重复获得连接的频率 一秒
connTimeOut = 1000

##最大允许的连接数，和数据库对应
maxActiveConnections = 100

##连接超时时间，默认20分钟 1000 * 60 * 20
connectionTimeOut = 1200000

2.2DbProperties对象

该对象的所有属性名称和配置文件中的key保持一致

public class DbProperties {

	
	private String driverName;

	private String url;

	private String userName;

	private String passWord;

	private String poolName;

	
	private int minConnections;

	
	private int maxConnections;

	
	private int initConnections;

	
	private long connTimeOut;

	
	private int maxActiveConnections;

	
	private long connectionTimeOut;

	public String getDriverName() {
		return driverName;
	}

	public void setDriverName(String driverName) {
		this.driverName = driverName;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public String getPassWord() {
		return passWord;
	}

	public void setPassWord(String passWord) {
		this.passWord = passWord;
	}

	public String getPoolName() {
		return poolName;
	}

	public void setPoolName(String poolName) {
		this.poolName = poolName;
	}

	public int getMinConnections() {
		return minConnections;
	}

	public void setMinConnections(int minConnections) {
		this.minConnections = minConnections;
	}

	public int getMaxConnections() {
		return maxConnections;
	}

	public void setMaxConnections(int maxConnections) {
		this.maxConnections = maxConnections;
	}

	public int getInitConnections() {
		return initConnections;
	}

	public void setInitConnections(int initConnections) {
		this.initConnections = initConnections;
	}

	public long getConnTimeOut() {
		return connTimeOut;
	}

	public void setConnTimeOut(long connTimeOut) {
		this.connTimeOut = connTimeOut;
	}

	public int getMaxActiveConnections() {
		return maxActiveConnections;
	}

	public void setMaxActiveConnections(int maxActiveConnections) {
		this.maxActiveConnections = maxActiveConnections;
	}

	public long getConnectionTimeOut() {
		return connectionTimeOut;
	}

	public void setConnectionTimeOut(long connectionTimeOut) {
		this.connectionTimeOut = connectionTimeOut;
	}

	@Override
	public String toString() {
		return "DbProperties [driverName=" + driverName + ", url=" + url + ", userName=" + userName + ", passWord="
				+ passWord + ", poolName=" + poolName + ", minConnections=" + minConnections + ", maxConnections="
				+ maxConnections + ", initConnections=" + initConnections + ", connTimeOut=" + connTimeOut
				+ ", maxActiveConnections=" + maxActiveConnections + ", connectionTimeOut=" + connectionTimeOut + "]";
	}
}

public class DbPoolManager {
	
	private static String sourcePath = "com/hutao/resources/database";
	
	
	private static DbProperties properties = null;
	
	
	static {
		try {
			if(properties == null) {
				synchronized(DbPoolManager.class) {
					if(properties == null) {
						properites2Object();
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}
	
	
	private static void properites2Object() throws NoSuchFieldException, IllegalAccessException {
		properties = new DbProperties();
		ResourceBundle resourceBundle = ResourceBundle.getBundle(sourcePath);
		//获取资源文件中所有的key
		Enumeration<String> keys = resourceBundle.getKeys();
		while (keys.hasMoreElements()) {
			String key = (String) keys.nextElement();
			//反射获取类中的属性字段
			Field field= DbProperties.class.getDeclaredField(key);
			//属性字段的类型
			Type genericType = field.getGenericType();
			//属性设置可访问
			field.setAccessible(true);
			//根据key读取对应的value值
			String value = resourceBundle.getString(key);
			if("int".equals(genericType.getTypeName())) {
				//反射给属性赋值
				field.set(properties, Integer.parseInt(value));
			}else if("long".equals(genericType.getTypeName())) {
				field.set(properties, Long.parseLong(value));
			}else if("java.lang.String".equals(genericType.getTypeName())) {
				field.set(properties,value);
			}
		}
	}
}

演示效果