这几天花了点时间弄了个 db4o 连接池，比较简单，连接池原型是论坛上面的一篇文章。很简单，欢迎拍砖。
从 servlet 开始，在这里初始化连接池：
package
com;
import
java.io.File;
import
java.util.Enumeration;
import
javax.servlet.ServletConfig;
import
javax.servlet.ServletException;
import
javax.servlet.http.HttpServlet;
public
class
ConnectionPollServlet
extends
HttpServlet {
private
static
final
String XML_FILE_PROPERTY
=
"
xmlFile
"
;
/**
* servlet init
*/
public
void
init(ServletConfig servletConfig)
throws
ServletException{
super
.init(servletConfig);
String appDir
=
servletConfig.getServletContext().getRealPath(
"
/
"
);
Enumeration names
=
servletConfig.getInitParameterNames();
while
(names.hasMoreElements()){
String name
=
(String) names.nextElement();
String value
=
servletConfig.getInitParameter(name);
if
(name.equals(XML_FILE_PROPERTY)) {
File file
=
new
File(value);
if
(file.isAbsolute()) {
XMLReader.configure(value);
}
else
{
XMLReader.configure(appDir
+
File.separator
+
value);
}
}
}
}
/**
* servlet destroy
*/
public
void
destroy() {
super
.destroy();
ConnectionPoll.destroy();
}
}
然后是 XML 解析类：
package com;
import java.io.File;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class XMLReader {
/**
* parse XML file
* @param xmlFileName
*/
public static void configure(String xmlFileName) {
try {
File file = new File(xmlFileName);
SAXReader reader = new SAXReader();
Document doc = reader.read(file);
Element root = doc.getRootElement();
String fileName = file.getParent()+"\\"
+root.elementText("fileName");
String sport = root.elementText("port");
String sminConn = root.elementText("minConn");
String sidelTime = root.elementText("idelTime");
int port = Integer.parseInt(sport);
int minConn = Integer.parseInt(sminConn);
int idelTime = Integer.parseInt(sidelTime);
ConnectionPoll.init(fileName,port,minConn,idelTime);
} catch (DocumentException e) {
e.printStackTrace();
}
}
}
连接池类：
package com;
import java.util.concurrent.ConcurrentLinkedQueue;
import com.db4o.Db4o;
import com.db4o.ObjectContainer;
import com.db4o.ObjectServer;
public class ConnectionPoll {
private static int idelTime;
private static ConcurrentLinkedQueue<ObjectContainer> connectionQueue;
private ConnectionPoll(){
}
/**
* init pool
*/
protected static void init(String fileName,int port,int minConn,int it) {
idelTime=it;
ObjectServer objectServer = Db4o.openServer(fileName,port);
connectionQueue = new ConcurrentLinkedQueue<ObjectContainer>();
for (int i = 0; i<minConn; i++) {
connectionQueue.offer(objectServer.openClient());
}
}
/**
* get connection
* @return ObjectContainer
* @throws ConnectionTimeoutException
* @throws InterruptedException
*/
public static synchronized ObjectContainer getConnection() throws ConnectionTimeoutException{
long expiration = System.currentTimeMillis() + idelTime;
while (connectionQueue.isEmpty())
{
if (expiration < System.currentTimeMillis())
{
throw new ConnectionTimeoutException("connection timeout!");
}
}
ObjectContainer objectContainer = connectionQueue.poll();
return objectContainer;
}
/**
* release connection
* @return ObjectContainer
* @throws InterruptedException
*/
public static synchronized void releaseConnection(ObjectContainer objectContainer) {
connectionQueue.offer(objectContainer);
}
/**
* destroy connection
*
*/
protected static void destroy() {
while (connectionQueue.iterator().hasNext()){
ObjectContainer objectContainer = connectionQueue.poll();
objectContainer.close();
}
}
}
超时异常类：
package com;
public class ConnectionTimeoutException extends Exception{
public ConnectionTimeoutException()
{
}
public ConnectionTimeoutException(String s)
{
super(s);
}
}
XML 配置文件，从上到下依次是，数据库文件名、端口、初始连接数、等待时间：
<?xml version="1.0" encoding="utf-8"?>
<config>
<fileName>auto.yap</fileName>
<port>1010</port>
<minConn>10</minConn>
<idelTime>1000</idelTime>
</config>
web.xml 用于初始化的时候加载：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<servlet>
<servlet-name>ConnectionPoll</servlet-name>
<servlet-class>com.ConnectionPollServlet</servlet-class>
<init-param>
<param-name>xmlFile</param-name>
<param-value>WEB-INF/poolConfig.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
</web-app>
数据库文件和参数配置文件都放在 WEB-INF 文件夹下。这个连接池还未实现 maxConn（最大连接数）和对多数据库文件的支持以及日志等。
请注意！引用、转贴本文应注明原作者：Rosen Jiang 以及出处：http://www.blogjava.net/rosen