public static void main(String[] args) throws Exception {
    ReplicationDriver driver = new ReplicationDriver();

    Properties props = new Properties();

    // We want this for failover on the slaves
    props.put("autoReconnect", "true");

    // We want to load balance between the slaves
    props.put("roundRobinLoadBalance", "true");

    props.put("user", "foo");
    props.put("password", "bar");

    //
    // Looks like a normal MySQL JDBC url, with a
    // comma-separated list of hosts, the first 
    // being the 'master', the rest being any number
    // of slaves that the driver will load balance against
    //

    Connection conn =
        driver.connect("jdbc:mysql://master,slave1,slave2,slave3/test",
            props);

    //
    // Perform read/write work on the master
    // by setting the read-only flag to "false"
    //

  //这个节点应该是通过spring的事务管理来设置，同时这个conn对象应该不是一个真正的connection，
	    //而是一个代理类，通过设置readonly，代理类会去使用不同的connection，
	    //那么问题是它该代理类使用的connection是哪里取的，抑或说难道它每次都会新开一个connection？，需要看源代码
	    
conn.setReadOnly(false);

    conn.setAutoCommit(false);
    conn.createStatement().executeUpdate("UPDATE some_table ....");
    conn.commit();

    //
    // Now, do a query from a slave, the driver automatically picks one
    // from the list
    //

    conn.setReadOnly(true);

    ResultSet rs = 
      conn.createStatement().executeQuery("SELECT a,b FROM alt_table");

     .......
  }

public ReplicationDriver() throws SQLException {
	}

	static {
		try {
			DriverManager.registerDriver(new NonRegisteringReplicationDriver());
		} catch (SQLException E) {
			throw new RuntimeException("Can't register driver!");
		}
	}

public Connection connect(String url, Properties info) throws SQLException {
		Properties parsedProps = parseURL(url, info);
		if (parsedProps == null) {
			return null;
		}
		Properties masterProps = (Properties) parsedProps.clone();
		Properties slavesProps = (Properties) parsedProps.clone();
		slavesProps.setProperty("com.mysql.jdbc.ReplicationConnection.isSlave",
				"true");
		
		String hostValues = parsedProps.getProperty("HOST");
		
		if (hostValues != null) {
			StringTokenizer st = new StringTokenizer(hostValues, ",");
			StringBuffer masterHost = new StringBuffer();
			StringBuffer slaveHosts = new StringBuffer();
			if (st.hasMoreTokens()) {
				String hostPortPair[] = parseHostPortPair(st.nextToken());
				if (hostPortPair[0] != null) {
					masterHost.append(hostPortPair[0]);
				}
				if (hostPortPair[1] != null) {
					masterHost.append(":");
					masterHost.append(hostPortPair[1]);
				}
			}
			boolean firstSlaveHost = true;
			do {
				if (!st.hasMoreTokens()) {
					break;
				}
				String hostPortPair[] = parseHostPortPair(st.nextToken());
				if (!firstSlaveHost) {
					slaveHosts.append(",");
				} else {
					firstSlaveHost = false;
				}
				if (hostPortPair[0] != null) {
					slaveHosts.append(hostPortPair[0]);
				}
				if (hostPortPair[1] != null) {
					slaveHosts.append(":");
					slaveHosts.append(hostPortPair[1]);
				}
			} while (true);
			if (slaveHosts.length() == 0) {
				throw SQLError
						.createSQLException(
								"Must specify at least one slave host to connect to for master/slave replication "
										+ "load-balancing functionality",
								"01S00");
			}
			masterProps.setProperty("HOST", masterHost.toString());
			slavesProps.setProperty("HOST", slaveHosts.toString());
		}
		return new ReplicationConnection(masterProps, slavesProps);
	}

public ReplicationConnection(Properties masterProperties,
			Properties slaveProperties) throws SQLException {
		Driver driver = new Driver();
		
		StringBuffer masterUrl = new StringBuffer("jdbc:mysql://");
		StringBuffer slaveUrl = new StringBuffer("jdbc:mysql://");
		String masterHost = masterProperties.getProperty("HOST");
		if (masterHost != null) {
			masterUrl.append(masterHost);
		}
		String slaveHost = slaveProperties.getProperty("HOST");
		if (slaveHost != null) {
			slaveUrl.append(slaveHost);
		}
		String masterDb = masterProperties.getProperty("DBNAME");
		masterUrl.append("/");
		if (masterDb != null) {
			masterUrl.append(masterDb);
		}
		String slaveDb = slaveProperties.getProperty("DBNAME");
		slaveUrl.append("/");
		if (slaveDb != null) {
			slaveUrl.append(slaveDb);
		}

//从这里可以看出，笔者前文提出的猜想是正确的，每一个ReplicationDriver其实是两个Connection的代理，这两个
		//Connection才是真正访问DB的connection。		masterConnection = (com.mysql.jdbc.Connection) driver.connect(masterUrl
				.toString(), masterProperties);
		slavesConnection = (com.mysql.jdbc.Connection) driver.connect(slaveUrl
				.toString(), slaveProperties);
		currentConnection = masterConnection;
	}

public class EasyReplicationDriver extends EasyNonRegisteringReplicationDriver
		implements Driver {

	public EasyReplicationDriver() throws SQLException {
	}

	static {
		try {
			DriverManager.registerDriver(new EasyNonRegisteringReplicationDriver());
		} catch (SQLException E) {
			throw new RuntimeException("Can't register driver!");
		}
	}
}

/**
 * @author ahuaxuan(aaron zhang)
 * @since 2008-6-18
 * @version $Id$

 */

public class EasyNonRegisteringReplicationDriver extends NonRegisteringDriver {

	public EasyNonRegisteringReplicationDriver() throws SQLException {
	}

	public Connection connect(String url, Properties info) throws SQLException {
		Properties parsedProps = parseURL(url, info);
		if (parsedProps == null) {
			return null;
		}
		Properties masterProps = (Properties) parsedProps.clone();
		Properties slavesProps = (Properties) parsedProps.clone();
		slavesProps.setProperty("com.mysql.jdbc.ReplicationConnection.isSlave",
				"true");
		
		String hostValues = parsedProps.getProperty("HOST");
		
		if (hostValues != null) {
			StringTokenizer st = new StringTokenizer(hostValues, ",");
			StringBuffer masterHost = new StringBuffer();
			StringBuffer slaveHosts = new StringBuffer();
			if (st.hasMoreTokens()) {
				String hostPortPair[] = parseHostPortPair(st.nextToken());
				if (hostPortPair[0] != null) {
					masterHost.append(hostPortPair[0]);
				}
				if (hostPortPair[1] != null) {
					masterHost.append(":");
					masterHost.append(hostPortPair[1]);
				}
			}
			boolean firstSlaveHost = true;
			do {
				if (!st.hasMoreTokens()) {
					break;
				}
				String hostPortPair[] = parseHostPortPair(st.nextToken());
				if (!firstSlaveHost) {
					slaveHosts.append(",");
				} else {
					firstSlaveHost = false;
				}
				if (hostPortPair[0] != null) {
					slaveHosts.append(hostPortPair[0]);
				}
				if (hostPortPair[1] != null) {
					slaveHosts.append(":");
					slaveHosts.append(hostPortPair[1]);
				}
			} while (true);
			/*if (slaveHosts.length() == 0) {
				throw SQLError
						.createSQLException(
								"Must specify at least one slave host to connect to for master/slave replication "
										+ "load-balancing functionality",
								"01S00");
			}*/
			masterProps.setProperty("HOST", masterHost.toString());
			slavesProps.setProperty("HOST", slaveHosts.toString());
		}
		return new EasyReplicationConnection(masterProps, slavesProps);
	}

public EasyReplicationConnection(Properties masterProperties,
			Properties slaveProperties) throws SQLException {
		Driver driver = new Driver();
		
		StringBuffer masterUrl = new StringBuffer("jdbc:mysql://");
		StringBuffer slaveUrl = new StringBuffer("jdbc:mysql://");
		String masterHost = masterProperties.getProperty("HOST");
		if (masterHost != null) {
			masterUrl.append(masterHost);
		}
		String slaveHost = slaveProperties.getProperty("HOST");
		if (slaveHost != null) {
			slaveUrl.append(slaveHost);
		}
		String masterDb = masterProperties.getProperty("DBNAME");
		masterUrl.append("/");
		if (masterDb != null) {
			masterUrl.append(masterDb);
		}
		String slaveDb = slaveProperties.getProperty("DBNAME");
		slaveUrl.append("/");
		if (slaveDb != null) {
			slaveUrl.append(slaveDb);
		}
		
		//从这里可以看出，笔者前文提出的猜想是正确的，每一个ReplicationDriver其实是两个Connection的代理，这两个
		//Connection才是真正访问DB的connection。
		masterConnection = (com.mysql.jdbc.Connection) driver.connect(masterUrl
				.toString(), masterProperties);
		
		if (slaveUrl.toString().contains("///")) {
			if (logger.isDebugEnabled()) {
				logger.debug(" ----- the salveUrl contains the '///', " +
						"that means there is no slaver, make slavesConnection = masterConnection --");
			}
			slavesConnection = masterConnection;
		} else {
			slavesConnection = (com.mysql.jdbc.Connection) driver.connect(slaveUrl
					.toString(), slaveProperties);
		}

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@Service("userService")
public class UserServiceImpl extends BaseServiceSupport implements UserService {

	public void xxx() {

	}
}

<context:component-scan base-package="xxxxxxx"/>

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
		<property name="locations">
			<list>
				<value>classpath:jdbc.properties</value>
			</list>
		</property>
	</bean>	

@Service
public class ImageFileUpload implements Serializable {

    @Properties(name="pic.address" )
    private String picAddress;

    @Properties(name="pic.url" )
    private String picUrl;

    private String picServerUrl;
}

/**
 * @author ahuaxuan(aaron zhang)
 * @since 2008-4-7
 * @version $Id: Properties.java 261 2008-04-07 07:03:41Z aaron $
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME) 
public @interface Properties {

//	String bundle();
	
	String name();
}

/**
 * @author ahuaxuan(aaron zhang)
 * @since 2008-4-7
 * @version $Id: AnnotationBeanPostProcessor.java 260 2008-04-07 07:03:35Z aaron $
 */
public class AnnotationBeanPostProcessor extends PropertyPlaceholderConfigurer implements BeanPostProcessor, InitializingBean {

	private static transient Log logger = LogFactory.getLog(AnnotationBeanPostProcessor.class);
	
	private java.util.Properties pros;
	
	@SuppressWarnings("unchecked")
	private Class[] enableClassList = {String.class};
	
	@SuppressWarnings("unchecked")
	public void setEnableClassList(Class[] enableClassList) {
		this.enableClassList = enableClassList;
	}

	public Object postProcessAfterInitialization(Object bean, String beanName)
			throws BeansException {
		
		Field [] fields = bean.getClass().getDeclaredFields();
		
		for (Field field : fields) {
			if (logger.isDebugEnabled()) {
				StringBuilder sb = new StringBuilder();
				sb.append(" ========= ")
					.append(field.getType())
					.append(" ============ ")
					.append(field.getName())
					.append(" ============ ")
					.append(field.isAnnotationPresent(Properties.class));
				
				logger.debug(sb.toString());
			}
			
			if (field.isAnnotationPresent(Properties.class)) {
				if (filterType(field.getType().toString())) {
					Properties p = field.getAnnotation(Properties.class);
					try {
//						StringBuilder sb = new StringBuilder();
//						sb.append("set").append(StringUtils.upperCase(field.getName().substring(0, 1)))
//										.append(field.getName().substring(1, field.getName().length()));
//						
//						Method method = bean.getClass().getMethod(sb.toString(), String.class);
//						method.invoke(bean, pros.getProperty(p.name()));
本来我是通过set方法来把properties文件中的值注入到对应的属性上去的，后来downpour提供了更好的方案，就是下面这两行代码，虽然这样做破坏了private的功能，同时破坏了封装，但是确实节省了很多代码，建议大家在业务代码中不要这样做，如果做框架代码可以考虑一下。

						ReflectionUtils.makeAccessible(field);
						field.set(bean, pros.getProperty(p.name()));
					} catch (Exception e) {
						logger.error(" --- ", e);
					} 
				}
			}
		}
		
		
		return bean;
	}
	
	@SuppressWarnings("unchecked")
	private boolean filterType(String type) {
		
		if (type != null) {
			for (Class c : enableClassList) {
				if (c.toString().equals(type)) {
					return true;
				}
			}
			
			return false;
		} else {
			return true;
		}
	}

	public Object postProcessBeforeInitialization(Object bean, String beanName)
			throws BeansException {
		return bean;
	}

	public void afterPropertiesSet() throws Exception {
		pros = mergeProperties();
	}
}

<bean id="propertyConfigurer"
		class="xx.service.AnnotationBeanPostProcessor">
		<property name="locations">
			<list>
				<value>classpath:jdbc.properties</value>
			</list>
		</property>
	</bean>

@Component
public class Config implements Serializable{

	/**  */
	private static final long serialVersionUID = 8737228049639915113L;

	@Properties(name = " online.pay.accounts")
	private String accounts;
	
	@Properties(name = " online.pay.user")
	private String user;
	
	@Properties(name = " online.pay.password")
	private String password;
	
	@Properties(name = " online.transurl")
	private String transUrl;
	
	@Properties(name = " online.refundurl")
	private String refundUrl;
	
	@Properties(name = " online.query")
	private String queryUrl;

	```setter and getter method
}

@Service(“userService”)
public class UserServiceImpl implements UserService {
	@autowired
	private Config config;

	public void setConfig(Config config) {
		This.config = config;
	}
}

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/**
   * <p>Attempts to establish a connection with the data source that
   * this <code>DataSource</code> object represents.
   *
   * @return  a connection to the data source
   * @exception SQLException if a database access error occurs
   */
  Connection getConnection() throws SQLException;
      
  /**
   * <p>Attempts to establish a connection with the data source that
   * this <code>DataSource</code> object represents.
   *
   * @param username the database user on whose behalf the connection is 
   *  being made
   * @param password the user's password
   * @return  a connection to the data source
   * @exception SQLException if a database access error occurs
   * @since 1.4
   */
  Connection getConnection(String username, String password) 
    throws SQLException;

/**
 * @author ahuaxuan(aaron zhang)
 * @since 2008-2-25
 * @version $Id$
 */
public class MonitorDataSource implements DataSource {
	public DataSource realDataSource;

	public void setRealDataSource(DataSource realDataSource) {
		this.realDataSource = realDataSource;
	}

	public DataSource getRealDataSource() {
		return realDataSource;
	}
	public Connection getConnection() throws SQLException {
//表示由jamon来代理realDataSource返回的Connection
		return MonProxyFactory.monitor(realDataSource.getConnection());
	}

	public Connection getConnection(String username, String password)
			throws SQLException {
//表示由jamon来代理realDataSource返回的Connection

		return MonProxyFactory.monitor(realDataSource.getConnection(username,
				password));
	}
}

<bean id="writeMonitorDataSource" class="org.ahuaxuan.MonitorDataSource" destroy-method="close">
		<property name="realDataSource" ref="writeDataSource"/>
	</bean>

<bean id="writeDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
		<property name="driverClassName">
			<value>${jdbc.driverClassName}</value>
		</property>
		<property name="url">
			<value>${jdbc.url}</value>
		</property>
		<property name="username">
			<value>${jdbc.username}</value>
		</property>
		<property name="password">
			<value>${jdbc.password}</value>
		</property>
        <property name="maxActive">
            <value>${jdbc.maxActive}</value>
        </property>
        <property name="maxIdle">
        	<value>${jdbc.maxIdle}</value>
        </property>
        <property name="maxWait">
        	<value>${jdbc.maxWait}</value>
        </property>
</bean>

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public double caculateVectorSpace(Map<String, Integer> articleVectorMap, Map<String, Integer> classVectorMap) {
		if (articleVectorMap == null || classVectorMap == null) {
			if (logger.isDebugEnabled()) {
				logger.debug("itemVectorMap or classVectorMap is null");
			}
			
			return 20;
		}
		
		int dotItem = 0;
		double denominatorOne = 0;
		double denominatorTwo = 0;
		
		
		for (Entry<String, Integer> entry : articleVectorMap.entrySet()) {
			String word = entry.getKey();
			double categoryWordFreq = 0;
			double articleWordFreq = 0;
			
			if (classVectorMap.containsKey(word)) {
				categoryWordFreq = classVectorMap.get(word).intValue() / classVectorMap.size();
				articleWordFreq = entry.getValue().intValue() / articleVectorMap.size();
			}
			
			dotItem += categoryWordFreq * articleWordFreq;
			denominatorOne += categoryWordFreq * categoryWordFreq;
			denominatorTwo += articleWordFreq * articleWordFreq;
		}
		
		double denominator = Math.sqrt(denominatorOne) * Math.sqrt(denominatorTwo);
		
		double ratio =  dotItem / denominator;
		
		return Math.acos(ratio);
	}

protected Map<String, List<MatchCondition>> analyse(Map<String, Map<String, Integer>> articleVectorMap, Map<String, Map<String, Integer>> categoryVectorMap) {
		
		Map<String, List<MatchCondition>> result = new HashMap<String, List<MatchCondition>>();
		
		for (Entry<String, Map<String, Integer>> categoryEntry : categoryVectorMap.entrySet()) {
			
			for (Entry<String, Map<String, Integer>> itemEntry : articleVectorMap.entrySet()) {
				double acos = caculateVector(itemEntry.getValue(), filterVectorMap(categoryEntry.getValue()));
				if (acos < vectorGene) {
					if (result.get(itemEntry.getKey()) != null) {
						List<MatchCondition> list = result.get(itemEntry.getKey());
						
						if (list.size() < kNum) {
							list.add(new MatchCondition(itemEntry.getKey(), categoryEntry.getKey(), acos));
						} else {
							if (list.size() == kNum) {
								Collections.sort(list, new MatchConditionComparator());
							}
							
							int n = 0;
							for (MatchCondition condition : list) {
								if (acos < condition.getAcos()) {
									list.set(n, new MatchCondition(itemEntry.getKey(), categoryEntry.getKey(), acos));
								}
								n++;
							}
						}
					} else {
						List<MatchCondition> list = new LinkedList<MatchCondition>();
						list.add(new MatchCondition(itemEntry.getKey(), categoryEntry.getKey(), acos));
						result.put(itemEntry.getKey(), list);
					}
					
				}
			}
			
		}
		
		return result;
	}

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protected Map<String, Map<String, Integer>> getClassVector(List<Category> categoryList) throws Exception {
		
		if (categoryList == null || categoryList.size() == 0) {
			if (logger.isDebugEnabled()) {
				logger.debug("The list of new categoryList which should be classified is null or size = 0");
			}
			return Collections.emptyMap();
		}
		
		Map<String, Map<String, Integer>> categoryMap = new HashMap<String, Map<String, Integer>>();
		
		Directory ramDir = new RAMDirectory();
		IndexWriter writer = new IndexWriter(ramDir, new PaodingAnalyzer(), true);
		
		for (Category cRc : categoryList) {
			for (Article item : cRc.getArticleList()) {
				
				Document doc = new Document();
				doc.add(new Field("description", item.getContent(), Field.Store.NO,
						Field.Index.TOKENIZED, TermVector.YES));
				doc.add(new Field("category", cRc.getId().toString(), Field.Store.YES, Field.Index.NO));
				writer.addDocument(doc);
			}
		}
		
		if (logger.isDebugEnabled()) {
			logger.debug("Generate the index in the memory, the size of categoryList list is " + categoryList.size());
		}
		
		writer.close();
		
		buildContentVectors(ramDir, categoryMap, "category", "description");
		return categoryMap;
		
	}

protected Map<String, Map<String, Integer>> getArticleVector(List<Article> articleList) throws Exception {
		if (articleList == null || articleList.size() == 0) {
			if (logger.isDebugEnabled()) {
				logger.debug("The list of articles which should be classified is null or size = 0");
			}
		}
		
		Map<String, Map<String, Integer>> articleMap = new HashMap<String, Map<String, Integer>>();
		
		Directory articleRamDir = new RAMDirectory();
//		IndexWriter writer = new IndexWriter(articleRamDir, new ChineseAnalyzer(), true);
		IndexWriter writer = new IndexWriter(articleRamDir, new PaodingAnalyzer(), true);
		
		for (Article article : articleList) {
			Document doc = new Document();
			doc.add(new Field("articleId", article.getId(),
					Field.Store.YES, Field.Index.NO));
			doc.add(new Field("description", article.getContent(), Field.Store.NO, Field.Index.TOKENIZED, TermVector.YES));
			writer.addDocument(doc);
		}
		
		writer.flush();
		writer.close();
		
		buildContentVectors(articleRamDir, articleMap, "articleId", "description"