Tutorials : Working with files and directories in Java :

Now for some HTML output

Outputting results to System.out is not actually cutting edge technology, so let's consider showing the directory structure in some other formats. In the first one we'll present the output as an HTML "unordered list" using the UL- and LI-tags. The idea is this:

start by opening an unordered list
for every directory you show its name as a list item and then open a new unordered list
for every directory you must also close the unordered list when all its contents have been written out
for every file you show its name as a list item
as the last step close the first unordered list

This is accomplished by simply subclassing MyFileStructure and implementing new output-methods:

package hansen.playground;

public class MyFileStructureUL extends MyFileStructure {

  protected void outFile(MyFile f, int level) {
    String name = f.getName();
    result += "<li>" + name + "</li>\n";
  }  
  
  protected void outDir(MyDir d, int level) {
    String name = d.getName();
    result += "<ul>\n<li>" + name + "</li>\n";
  }  
  
  protected void outEndDir() {
    result += "</ul>\n";
  }  
  
  public String getResult() {
    return "<ul>\n" + super.getResult() + "</ul>";
  }
}

To test this bean we write a simple jsp-file:

<jsp:useBean id="file" 
 class="hansen.playground.MyFileStructureUL" 
 scope="session" />
    
<%
file.setDirname("c:\\Dir-A");
file.build();
file.list();
out.println(file.getResult());
%>

Entering the name of this file in a browser will give this result:

- Figure 2 -

It's a rather simple matter to make the file names appear as hyperlinks if this is useful. Files like Word documents, simple text-files, gif's and jpeg's--and of course html-files--can be displayed in most browsers. You will, however, need to place the top directory in a place where the web server can reach it.

I'll also give you a word of warning: if you plan to put an application like this on the Internet, then be careful only to show files that you want others to see, and never give the user any possibility to specify the name of the top directory. Hackers have been exploiting test programs doing exactly this.

Ready for another type of output? OK, here we go.

Next step: XML

I think it's very tempting to output the results in XML format--the syntax of an HTML unordered list has some resemblance to the XML-format. So we'll define a "directory" and "file" element, both with a "name" attribute. The directory element looks like this:

<directory>
<directory-name>Dir-A</directory-name>
</directory>

And this is the file element:

<file>
<file-name>File C.txt</file-name>
</file>

We need a new subclass to create the XML output:

package hansen.playground;

public class MyFileStructureXML extends MyFileStructure {

  protected void outFile(MyFile f, int level) {
    String name = f.getName();
    result += 	"<file>\n<file-name>" + name + "</file-name>\n</file>\n";
  }  
  
  protected void outDir(MyDir d, int level) {
    String name = d.getName();
    result += "<directory>\n<directory-name>" + name + "</directory-name>\n";
  }  
  
  protected void outEndDir() {
    result += "</directory>\n";
  }  
  
}

To test this format, we again write a small jsp-file. Note that the first line says that the output is in xml format:

<?xml version="1.0"?>

<jsp:useBean id="fileXML" 
  class="hansen.playground.MyFileStructureXML" 
  scope="session" />
     
<%

fileXML.setDirname("c:\\Dir-A");
fileXML.build();
fileXML.list();
out.println(fileXML.getResult());

%>

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