BoneCP源码——从Manual configuration说起

BoneCP官网上有其配置的使用文档，看最基本的Manual configuration：

 

	Class.forName("org.hsqldb.jdbcDriver"); 	// load the DB driver
 	BoneCPConfig config = new BoneCPConfig();	// create a new configuration object
 	config.setJdbcUrl("jdbc:hsqldb:mem:test");	// set the JDBC url
	config.setUsername("sa");			// set the username
	config.setPassword("");				// set the password
	
	config.setXXXX(...);				// (other config options here)
	
	BoneCP connectionPool = new BoneCP(config); 	// setup the connection pool
	
	Connection connection;
	connection = connectionPool.getConnection(); 	// fetch a connection
	
	...  do something with the connection here ...
	
	connection.close();				// close the connection
	connectionPool.shutdown();			// close the connection pool

 其使用步骤为先加载数据库驱动，然后声明一个配置文件描述类BoneCPConfig，再根据该类实例化一个连接池实例BoneCP，根据该实例的getConnection()方法可得到一个数据库连接对象Connection，可进行数据库操作，最后关闭Connection对象和连接池。

 BoneCPConfig为配置文件类(Configuration class)，它在com.jolbox.bonecp包下：

package com.jolbox.bonecp;
/**
 * Configuration class.
 *
 * @author wallacew
 */
public class BoneCPConfig implements BoneCPConfigMBean, Cloneable, Serializable {
      ......
}

 BoneCPConfigMBean为配置接口，MBean interface for config。

 

BoneCP有四个构造函数：

	/**
	 * Default constructor. Attempts to fill settings in this order:
	 * 1. bonecp-default-config.xml file, usually found in the pool jar
	 * 2. bonecp-config.xml file, usually found in your application's classpath
	 * 3. Other hardcoded defaults in BoneCPConfig class.
	 */
	public BoneCPConfig(){
		// try to load the default config file, if available from somewhere in the classpath
		loadProperties("bonecp-default-config.xml");
		// try to override with app specific config, if available
		loadProperties("bonecp-config.xml");
	}
	/** Creates a new config using the given properties.
	 * @param props properties to set.
	 * @throws Exception on error
	 */
	public BoneCPConfig(Properties props) throws Exception {
		this();
		this.setProperties(checkNotNull(props));
	}
	/** Initialize the configuration by loading bonecp-config.xml containing the settings. 
	 * @param sectionName section to load
	 * @throws Exception on parse errors
	 */
	public BoneCPConfig(String sectionName) throws Exception{
		this(BoneCPConfig.class.getResourceAsStream("/bonecp-config.xml"), checkNotNull(sectionName));
	}

	/** Initialise the configuration by loading an XML file containing the settings. 
	 * @param xmlConfigFile file to load
	 * @param sectionName section to load
	 * @throws Exception 
	 */
	public BoneCPConfig(InputStream xmlConfigFile, String sectionName) throws Exception{
		this();
		setXMLProperties(xmlConfigFile, checkNotNull(sectionName));
	}

 上面构造函数提供了基于XML文件和Properties两种配置方式，默认构造函数去加载根目录下的默认配置文件bonecp-default-config.xml，该配置文件随着jar包一起发布，在根目录下：

	/**
	 * Loads the given properties file using the classloader.
	 * @param filename Config filename to load
	 * 
	 */
	protected void loadProperties(String filename) {
		ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
		if (classLoader != null){
			URL url = classLoader.getResource(filename);
			if (url != null){
				try {
					this.setXMLProperties(url.openStream(), null);
				} catch (Exception e) {
					// do nothing
				} 
			}
		}
	}

 对于以XML文件为参数的构造函数，先调用javax.xml包下的类对XML文件解析，然后再把XML文件转换成Properties形式去实例化（调用setProperties(Properties props)方法）：

/**
	 * @param xmlConfigFile
	 * @param sectionName
	 * @throws Exception
	 */
	private void setXMLProperties(InputStream xmlConfigFile, String sectionName)
			throws Exception {
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		DocumentBuilder db;
		// ugly XML parsing, but this is built-in the JDK.
		try {
			db = dbf.newDocumentBuilder();
			Document doc = db.parse(xmlConfigFile);
			doc.getDocumentElement().normalize();

			// get the default settings
			Properties settings = parseXML(doc, null);
			if (sectionName != null){
				// override with custom settings
				settings.putAll(parseXML(doc, sectionName));
			}
			// set the properties
			setProperties(settings);

		} catch (Exception e) {
			throw e;
		} finally {
			if (xmlConfigFile != null){ // safety
				xmlConfigFile.close();
			}
		}
	}

 对于setProperties(Properties props)方法是把配置文件读取并设置到字段的实现，先用Java返射机会，读出BoneCPConfig类中所有设置属性的方法，以is开头或set开头的方法：

	for (Method method: BoneCPConfig.class.getDeclaredMethods()){
			String tmp = null;
			if (method.getName().startsWith("is")){
				tmp = lowerFirst(method.getName().substring(2));
			} else if (method.getName().startsWith("set")){
				tmp = lowerFirst(method.getName().substring(3));
			} else {
				continue;
			}
                        ......
         }

 然后再根据方法的参数个数和参数类型进行赋值， BoneCPConfig将属性字段类型限制为4种类型：int、long、String、boolean：

if (method.getParameterTypes().length == 1 && method.getParameterTypes()[0].equals(int.class)){
				String val = props.getProperty(tmp);
				if (val == null){
					val = props.getProperty("bonecp."+tmp); // hibernate provider style
				}
				if (val != null) {
					try{
						method.invoke(this, Integer.parseInt(val));
					} catch (NumberFormatException e){
						// do nothing, use the default value
					}
				}
			} else if (method.getParameterTypes().length == 1 && method.getParameterTypes()[0].equals(long.class)){
				String val = props.getProperty(tmp);
				if (val == null){
					val = props.getProperty("bonecp."+tmp); // hibernate provider style
				}
				if (val != null) {
					try{
						method.invoke(this, Long.parseLong(val));
					} catch (NumberFormatException e){
						// do nothing, use the default value
					}
				}
			} else if (method.getParameterTypes().length == 1 && method.getParameterTypes()[0].equals(String.class)){
				String val = props.getProperty(tmp);
				if (val == null){
					val = props.getProperty("bonecp."+tmp); // hibernate provider style
				}
				if (val != null) {
					method.invoke(this, val);
				}
			} if (method.getParameterTypes().length == 1 && method.getParameterTypes()[0].equals(boolean.class)){
				String val = props.getProperty(tmp);
				if (val == null){
					val = props.getProperty("bonecp."+tmp); // hibernate provider style
				}
				if (val != null) {
					method.invoke(this, Boolean.parseBoolean(val));
				}
			}

个人认为这段代码写得不够优雅，至少相同部分可以提取出来，从设计的角度说这里也最好采用工厂方式便于多种实现。