 Popup calendar using Linux cal commandContributed by Zsolt Kiss as part of the Win With NetBeans comptetition
The idea of this calendar came from one of my projects. Working for GE, Hungary, I had to build up an intranet application with a web GUI that had used calendar components on more pages. I developed a fairly elaborated one with lots of work using Date object of javascript. I had to do a few tricks to handle correctly leap years, to convert numbers representing months and days into localized Strings, not to mention the formatting works, that rendered my calendar in a stylish html table... The result was fine, finally I had had an own javascript Calendar class with dozens of methods... Today I would set off on a somewhat differing way. I would use the Linux cal command... The cal command displays the current calendar month if you call it without any input, or, if you specify the year and month, it displays any month in any year (the value of year can be a number between 1 and 9999 and the value of month can be between 1 and 12). Here you can see a calling and an output of cal command in a my Linux terminal window (my local settings are Hungarian):
:~> cal 12 2004
december 2004
v h k sz cs p sz
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31
:~>
No more need juggling with javascript's Date object, no more need conversion methods... We can simply use the output provided by Linux cal command to build up a cute, formatted calendar to display for our customers on the web. Supposing our web server runs on a Linux machine and it has access to run operating system commands. At my place these conditions are fulfilled. How it all worksBut how does a Linux command's output become an input of an html page? Fairly simple way. We have to use the exec() method of java.lang.Runtime class to start an external process (or program) outside the Java Virtual Machine. If you call exec() passing it the Linux cal command this way:
Process p = Runtime.getRuntime().exec("cal 12 2004");
you can read the output of the command - i.e. the displayed calendar - as an InputStream: BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream())); Now we have a Reader object that can be processed by a StreamTokenizer to filter spaces and not numeric values from the output. Focusing on numbers an arbitrary formed html table can be built. I created a CalBuilder class and a static build() method in it to format an output string that I would use in a servlet writing out the html. Here is the CalBuilder class:
public class CalBuilder {
private static final String spanBegin = "<span style=\"color:green;font-size:14px;\" onmouseover=\"this.style.color='red';\" onmouseout=\"this.style.color='green';\" onclick=\"Send(this);\">";
private static final String spanEnd = "</span>";
public CalBuilder() {
}
public static String build(String year, String month) throws IOException {
String line;
int token;
StringBuffer cmd = new StringBuffer("cal ").append(month).append(" ").append(year);
Process p = Runtime.getRuntime().exec(cmd.toString());
BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
StringBuffer sb = new StringBuffer("<th id=\"header\" align=\"center\" colspan=\"7\">");
StreamTokenizer st = new StreamTokenizer(br);
st.eolIsSignificant(true);
st.ordinaryChar(32);
int eolCounter = 1;
int line3Tokens = 0;
while((token = st.nextToken()) != StreamTokenizer.TT_EOF) {
System.out.println(st.toString());
if(eolCounter == 1 && token == StreamTokenizer.TT_WORD) {
sb.append(st.sval + " ");
}else if(eolCounter == 1 && token == StreamTokenizer.TT_NUMBER) {
sb.append((int)st.nval);
}else if(eolCounter == 1 && token == StreamTokenizer.TT_EOL) {
sb.append("</th><tr>");
}else if(eolCounter == 2 && token == StreamTokenizer.TT_WORD) {
sb.append("<td>" + st.sval + "</td>");
}else if(eolCounter == 2 && token == StreamTokenizer.TT_EOL) {
sb.append("</tr><tr>");
}else if(eolCounter == 3 && token == StreamTokenizer.TT_NUMBER) {
line3Tokens++;
}else if(eolCounter == 3 && token == StreamTokenizer.TT_EOL) {
sb.append(padding(line3Tokens));
sb.append("</tr><tr>");
}else if(eolCounter > 3 && token == StreamTokenizer.TT_NUMBER) {
sb.append("<td>" + spanBegin + (int)st.nval + spanEnd + "</td>");
}else if(eolCounter > 3 && token == StreamTokenizer.TT_EOL) {
sb.append("</tr><tr>");
}
if(token == StreamTokenizer.TT_EOL) {
eolCounter++;
}
}
return sb.toString();
}
private static String padding(int num) {
StringBuffer sb = new StringBuffer();
if(num > 0 && num < 8) {
int spaces = 7 - num;
for(int i=0;i<spaces;i++) {
sb.append("<td> </td>");
}
for(int i=1;i<=num;i++) {
sb.append("<td>" + spanBegin + i + spanEnd + "</td>");
}
}else {
for(int i=0;i<7;i++) {
sb.append("<td> </td>");
}
}
return sb.toString();
}
}
The static strings at the top of the class are used to set some style for cells where numbers will be put in the html, and, not least, to make them clickable for the user. The CalBuilder class will be called by a servlet, that will insert the formatted html text of calendar into its html output, namely into a <table></table> tag. The servlet also writes out a javascript sender function, named Send(), that is responsible for sending the user-clicked date back to the index.jsp page, from where the calendar component have been popped up. After sending back the date, the popup calendar window is closed. In the index.jsp there are two combo boxes only for sending some initial value the calendar. The popup window will be activated on a simple html button click (not Submit element, but a Button) that calls the standard javascript window.open() funtion. Here you can see the servlet:
public class ShowCalendar extends HttpServlet {
protected void processRequest(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
String year = "";
String month = "";
if(req.getParameter("initMonth") != null) {
month = req.getParameter("initMonth");
}
if(req.getParameter("initYear") != null) {
year = req.getParameter("initYear");
}
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("<html>");
out.println("<head>");
out.println("<title>Calendar set up with Linux cal command</title>");
out.println(sender());
out.println("</head>");
out.println("<body>");
out.println("<table border=\"1\">");
out.println(CalBuilder.build(year, month));
out.println("</table>");
out.println("</body>");
out.println("</html>");
out.close();
}
private static String sender() {
StringBuffer javascript = new StringBuffer();
javascript.append("<script type=\"text/javascript\">\n");
javascript.append("function Send(obj) {\n");
javascript.append("var winObj = window.opener;\n");
javascript.append("var docObj = winObj.document;\n");
javascript.append("if(docObj != null) {\n");
javascript.append("var cbYear = docObj.getElementById(\"cbYear\");\n");
javascript.append("var cbMonth = docObj.getElementById(\"cbMonth\");\n");
javascript.append("var year = cbYear.options[cbYear.selectedIndex].value;\n");
javascript.append("var month = cbMonth.options[cbMonth.selectedIndex].text;\n");
javascript.append("docObj.getElementById(\"selectedDate\").value = year + \" \" + month + \" \" + obj.firstChild.nodeValue;\n");
javascript.append("}\n");
javascript.append("window.close();");
javascript.append("}\n");
javascript.append("</script>\n");
return javascript.toString();
}
}
Developing the clickable calendar with NetBeans 4.0The following main steps I will walk you through:
Setting up a new web application with NetBeans IDE 4.0
Adding the ShowCalendar servlet to the project
Creating the CalBuilder class
Editing the index.jsp
Build and run the project
To build and run your project in the IDE first press Ctlr+F11 to Clean and Build. If it succeds then you can run the project with F6.
These functions can be triggered from the menu of NetBeans IDE certainly.
If your project is running then IDE's built-in Tomcat will be rendering the index.jsp
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