Why this filter's code is not working right?

Question

Hey, I have written a filter to record every request and write to a xml file. Everything works fine but the the code in filter's destroy is called twice. Don't know why? Is that there something wrong with my file writing code?? here is the code
Filter Code:
package xx;
import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.FilterChain;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import UserInfo;
public class RequestInspector implements Filter {
protected RequestRecorder recorder = null;
protected static String ipAddress;
protected static int hrId = -1;
public void init(FilterConfig config) {
String fileLoc = config.getInitParameter("FileLocation");
String fileName = config.getInitParameter("FileName");
ipAddress = config.getInitParameter("IPAddress");
try {
hrId = Integer.parseInt(config.getInitParameter("HRID"));
} catch (NumberFormatException nfe) {
} catch (NullPointerException npe) {
if (fileLoc != null && fileName != null && ipAddress != null && hrId != -1) {
recorder = RequestRecorder.getInstance(fileLoc, fileName);
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest)request;
HttpSession session = httpRequest.getSession(false);
UserInfo info = ((session==null) ? null : (UserInfo)session.getAttribute("USER_INFO"));
if ( request.getRemoteAddr().equals(ipAddress) && info != null && info.getHrId() == hrId && recorder != null) {
recorder.record(httpRequest);
} // if...
chain.doFilter(request, response);
public void destroy() {
if (recorder != null) {
recorder.stop();
RequestRecorder Code
package ids.util;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Vector;
import java.util.Hashtable;
import javax.servlet.http.HttpServletRequest;
public class RequestRecorder {
private static final Hashtable holder = new Hashtable(2);
private FileWriter writer = null;
private int counter = 0;
private RequestRecorder(String fileLocation, String fileName)
throws IOException {
writer = new FileWriter(new File(fileLocation, fileName));
initializeFile();
public static RequestRecorder getInstance(String fileLocation, String fileName) {
RequestRecorder recorder = null;
try {
String path = new File(fileLocation, fileName).getAbsolutePath();
recorder = (RequestRecorder) holder.get(path);
if (recorder == null) {
recorder = new RequestRecorder(fileLocation, fileName);
holder.put(path, recorder);
} catch (IOException ioe) {
return recorder;
public synchronized void record(HttpServletRequest request) throws IOException {
if (writer == null) {
return;
writer.write("\n\t\t<request path=\"" + request.getRequestURI() +"\" label=\"request" + (++counter) +"\">");
Enumeration params = request.getParameterNames();
while (params.hasMoreElements()) {
String param = (String)params.nextElement();
String[] paramValues = request.getParameterValues(param);
if (paramValues != null) {
for (int i=0; i<paramValues.length; i++) {
writer.write("\n\t\t\t<param>");
writer.write("\n\t\t\t\t<paramName>");
writer.write(param);
writer.write("</paramName>");
writer.write("\n\t\t\t\t<paramValue>");
writer.write(paramValues);
writer.write("</paramValue>");
writer.write("\n\t\t\t</param>");
} //for...
} //if...
} //while...
writer.write("\n\t\t\t<validate>");
writer.write("\n\t\t\t\t<byteLength min=\"20\" label=\"validation" + counter+"\"/>");
writer.write("\n\t\t\t</validate>");
writer.write("\n\t\t</request>");
writer.flush();
public void stop() {
if (writer != null) {
try {
finalizeFile();
writer.close();
writer = null;
} catch (IOException ioe) {
ioe.printStackTrace();
private synchronized void initializeFile() throws IOException {
writer.write("<?xml version=\"1.0\" standalone=\"no\"?>");
writer.write("\n<!DOCTYPE suite SYSTEM \"../conf/suite.dtd\">");
writer.write("\n<suite defaultHost=\"tiserver.com\" defaultPort=\"8899\" label=\"test\">");
writer.flush();
private synchronized void finalizeFile() throws IOException {
writer.write("\n\t</session>");
writer.write("\n</suite>");
writer.flush();
protected void finalize() {
stop();
}The XML output file looks like this
<?xml version="1.0" standalone="no"?>
<!DOCTYPE suite SYSTEM "../conf/suite.dtd">
<suite defaultHost="tiserver.com" defaultPort="8899" label="test">
<request path="/acfrs/loginP.jsp" label="Login">
<param>
<paramName>userId</paramName>
<paramValue>redfsdf</paramValue>
</param>
<param>
<paramName>passWord</paramName>
<paramValue>h1dffd3dfdf</paramValue>
</param>
<validate>
<regexp pattern="Invalid Login" cond="false" ignoreCase="true" label="Login Check"/>
</validate>
</request>
</session>
</suite>frs/left_frame.jsp" label="request1">
<validate>
<byteLength min="20" label="validation1"/>
</validate>
</request>
<request path="/acfrs/welcome.jsp" label="request2">
<validate>
<byteLength min="20" label="validation2"/>
</validate>
</session>
</suite>
If you closely observe the XML file "</session> </suite>" is written in the middle of the file too. Why does this happen? By the way, this code works perfectly on my windows desktop but on unix server the above problem turns up. Any clues??
Thanks

Answer 1

Ooops! The finalize() method in RequestRecorder is redundant. Mistakenly uncommnented it (finalize() method code ) while posting it here :-)