Filter Data in Java

Question

am developing a screen on which user can see various details of an Employee. Details includes fields like Name, Date Of birth, Salary etc.
Server side code retrieves data for an employee using different data sources. Some fields are retrieved from the database using JDBC while other are retrieved from external system using API calls.
Now, application also allows end-user to configure different VIEW filters and end user can apply them while viewing the data. For ex: User can setup a filter as "Show Employee where firstname like 'A' and DOB > '2/2/2000'.
Issue is, how do I filter the dataset?
If user sets a filter on the attribute which is getting retrieved from JDBC, I can append this filter in the SQL string as WHERE clause (for ex: where emp.first_name like 'A%'). So no issues for SQL fields.
But how do I apply filter criteria which is set on the non SQL attributes?
One of the solution which I tried to implement is converting final dataset into XML and then applying filter using XPATH. But as I understand XPATH can be used only for String and numeric values. It can not be used for dates and filter criteria like "WHERE DEPTNAME IN A, B, C, D).
Any ideas?

Answer 1

I develope a filter for an html file that has wrong letters but my request object is null. I want to filter the response to show a clear page to the user.
THis is the java code.
public final class MacronFilter implements Filter{
     private FilterConfig filterConfig = null;
     private Vector browsers = new Vector();
     private static String browser = null;
     private boolean mode = false;
     public void init(FilterConfig filterConfig)
     throws ServletException
     this.filterConfig = filterConfig;
     public void destroy()
     this.filterConfig = null;
     public void doFilter(ServletRequest request,
                              ServletResponse response,
                              FilterChain chain)
     throws IOException, ServletException
          System.out.println("(FROZADOS) - in the filter class");
          if (filterConfig == null)
     return;
          PrintWriter writer = response.getWriter();
          System.out.println("(FROZADOS) - in the filter class 1");          
          CharResponseWrapper wrapper = new CharResponseWrapper((HttpServletResponse)response);
          System.out.println("(FROZADOS) - in the filter class 2");
          Pattern pattern = null;
          Matcher matcher = null;
          Hashtable paterns = new Hashtable();
          browsers.add("Win.*95");
          browsers.add("Win.*98");
          browsers.add("Mac");
          browsers.add("Opera.[345]");
          browsers.add("Elinks");
          browsers.add("Lynx");
          browsers.add("MSIE.[34]");
          browsers.add("Mozilla.[1234]");
          paterns.put("ā","a");
          paterns.put("ē","e");
          paterns.put("ī","i");
          paterns.put("ō","o");
          paterns.put("ū","u");
          paterns.put("Ā","A");
          paterns.put("Ē","E");
          paterns.put("Ī","I");
          paterns.put("Ō","O");
          paterns.put("Ū","U");
          System.out.println("(FROZADOS) - in the filter class 3:"+request.getContentType());
          Enumeration attributes = request.getAttributeNames();
     System.out.println("Printing attributes");
     while(attributes.hasMoreElements()){
          System.out.println(attributes.nextElement());
          if(("text/html").equals(wrapper.getContentType()))
          response.setContentType("text/html");
          browser = request.getAttribute("user-agent").toString();
          System.out.println("browser:"+browser);
          for(int i=0;i<browsers.size();i++)
               if(!browsers.elementAt(i).equals(browser))
                    mode = false;
     if(mode)
          CharArrayWriter caw = new CharArrayWriter();
          caw.write(wrapper.toString().substring(0,
          wrapper.toString().indexOf("</body>")-1));
          for(int i=0;i<caw.size();i++)
               for(Enumeration e=paterns.keys();e.hasMoreElements();)
                    String key = e.nextElement().toString();
                    pattern = Pattern.compile(key);
                    String regex = pattern.pattern();
                    boolean matches = pattern.matches(regex,caw.toCharArray().toString());
                    //boolean result = matcher.find();
                    while(matches)
                         matcher.replaceAll(paterns.get(key).toString());
                         //result = matcher.find();
          response.setContentLength(caw.toString().length());
          writer.write(caw.toString());
}else{
     writer.write(wrapper.toString());
     writer.close();
can you tell me, why the request object is null???.
thanks,
Federico