Category Archives: ColdFusion

Java Class.forName(String className) and JDBC

A reader asked a question via a comment a couple months ago that I didn’t really have an answer for (and had always kind of wondered the same thing). In the original post (which showed how to use JDBC with ColdFusion), I used the following snippet of code:

Connection con = DriverManager.getConnection(url,
  "myLogin", "myPassword");

and the reader wanted to know what the Class.forName(..) method did. The most common answer you’ll hear is that it loads the database driver, which, while technically true, is shallow. Where does it get loaded? How does it happen? And why?

To answer the question I started with the JavaDoc for the Class.forName() method. According to the documentation, the method:

… attempts to locate, load, and link the class or interface

I wasn’t perfectly clear on what “locate, load, and link” meant, so I did a little digging through the Java Language Specification. According to chapter 12 of the JLS:

Loading refers to the process of finding the binary form of a class or interface type with a particular name, perhaps by computing it on the fly, but more typically by retrieving a binary representation previously computed from source code by a compiler, and constructing, from that binary form, a Class object to represent the class or interface.

Next, again according to the JLS, it must be transformed from it’s binary representation to something the Java virtual machine can use, this process is called linking. Finally, the class is initialized, which is the process that executes the static initializer and the initializers for static fields declared in the class.

So then back to the original problem, when Class.forName() is called with an argument like this:


the classloader attempts to load and link the Driver class in the “” package and if successful, the static initializer is run. The MySQL Driver (download the source code) static initializer looks like this:

static {
  try {
    java.sql.DriverManager.registerDriver(new Driver());
  } catch (SQLException E) {
    throw new RuntimeException("Can't register driver!");

So it calls a static method in the java.sql.DriverManager class which apparently registers a copy of itself when it loads.

So now I understand the where and the how, what about why? To understand the why you have to look at the next line in the initial code example:

Connection con = DriverManager.getConnection(url,
  "myLogin", "myPassword");

The DriverManager class (view DriverManager source here) returns a database connection given a JDBC URL string, a username and a password. In order to create that connection, the DriverManager class has to know which database driver you want to use. It does that by iterating over the array (internally a Vector) of drivers that have registered with it (ie: the registerDriver(Driver driver) method illustrated above) and calls the acceptsURL(url)) method on each driver in the array, effectively asking the driver to tell it whether or not it can handle the JDBC URL.

So there you have it. Class.forName explained.

ColdFusion MX and java.sql

Last week a reader sent me an interesting problem. When deleting a record from a database using a standard <cfquery> tag you don’t get any indication back that let’s you know whether or not the row or rows in question actually existed, nor do you get back any indication as to how many rows might have been affected. He wanted to be able run a single query that deleted a record AND let him know whether or not the record existed. He thought (correctly) that there was a way to do this in Java and wondered if I could write a CFX tag to do it for him. I could, but it would be much easier to do it in <cfscript>. In Java, you would write this:

// replace the package/class name of your db driver
// replace w/ your server, database name, username & password
String conurl = "jdbc:mysql://server/db?user=u&password=p";
Connection con = DriverManager.getConnection(conurl);
PreparedStatement ps;
ps = con.prepareStatement("DELETE from table_name where id = 3045");
int result = ps.executeUpdate();

In short, you load the appropriate database driver (I’m using MySQL in the above example), obtain a connection to the database using the DriverManager class, create a PreparedStatement, and then call the executeUpdate() method. This method returns an int: “… either (1) the row count for INSERT, UPDATE, or DELETE statements or (2) 0 for SQL statements that return nothing.”

Using the above sample it’s pretty easy to do the same thing in ColdFusion using <cfscript>:

clazz = CreateObject("java", "java.lang.Class");
// replace the package/class name of your db driver
driverManager = CreateObject("java", "java.sql.DriverManager");
// replace w/ your server, database name, username & password
conurl = "jdbc:mysql://server/db?user=u&password=p";
connection = driverManager.getConnection(conurl);
query = "DELETE from category where id = 3045";
preparedStatement = connection.prepareStatement(query);
result = preparedStatement.executeUpdate();
WriteOutput("result = " & result);

Further, you can test the value of the result variable so that you can show a custom message to a end user or perform some other type of business logic:

if (result == "0") {
  WriteOutput("No records were deleted.");
} else if (result == "1") {
  WriteOutput("One record was deleted.");
} else {
  WriteOutput(result & " records were deleted.");

Using iText PDF & ColdFusion

Mike Steele sent me an email in reference to an article I wrote for the ColdFusion Developer’s Journal a year or so ago. In the email, he mentions that he is trying to use the iText Java-PDF library with ColdFusion MX:

… The getInstance method is static and according to your July 2003 CFDJ article, you can’t instantiate an object in CF this way.

In the article I said this:

… using the CreateObject() function does not get you access to an instance of an object. In order to access a Java object, you must either a) first call the CreateObject() method and then the init() method, which in the above example, maps to the default constructor in Java, or b) call any nonstatic method on the object, which causes ColdFusion to then instantiate the object for you.

I guess this statement needs to be amended to include a third possible, but not always valid solution: call a static method on the class which returns an instance of the object in question. In this case the API designer included a static method ‘getInstance()’ on the PDFWriter class. Given that news, you can take the quick example that the author of the iText library gives here to create a PDF in a snap using ColdFusion:

// create a 'Document' object
document = CreateObject("java", "com.lowagie.text.Document");
// get an outputstream for the PDF Writer
fileIO = CreateObject("java", "");
// call the constructor, pass the location where you want
// the pdf to be created
// get a PDF Writer var
writer = CreateObject("java", "com.lowagie.text.pdf.PdfWriter");
// call the static 'getInstance' factory method
writer.getInstance(document, fileIO);
// open the document;
// create a new paragraph
paragraph = CreateObject("java", "com.lowagie.text.Paragraph");
paragraph.init("Hello World!");
// add the paragraph
// close the document (PDF Writer is listening and will automatically
// create the PDF for us

Copy that code into a cfml page and make sure you’ve downloaded the iText jar to the /lib/ directory of your ColdFusion server and you should be able to create PDF’s in a jiffy!

Full source code available here.

ColdFusion & log4j

Integrating log4j and CFMX - An open source Java project gives developers new capabilities The January issue of ColdFusion Developer’s Journal features an article I wrote on how to integrate ColdFusion and log4j entitled “Integrating log4j and CFMX – An open source Java project gives developers new capabilities”. You can read it here.

While not especially interesting for developers writing simple ColdFusion applications, I’m finding that log files are becoming especially useful in applications with multiple tiers and clients. Even if you don’t use log4j and ColdFusion, I’d suggest taking a long look at your application to find out where it might be helpful to make your application more transparent.

Instant Messenging with ColdFusion, Jabber and Smack

I noticed a couple different people wanting information on instant messenging with ColdFusion and then in another place instant messenging with Jabber and ColdFusion in the last couple days (for reasons beyond me) [first on cfguru, then on my blog, then on the jive software forums]. For those that care I put together a quick and ugly web-based instant messenging interface to Jabber using an open source Java library called Smack. You can download the source code at the end of this article or follow along as I describe the process.

Setup: 1) You need to download the Smack library and place the smack.jar and smackx.jar files into a directory acccesible to ColdFusion (commonly /WEB-INF/lib/). 2) You need to setup a couple Jabber accounts. You can either download, install and run your own jabber server or create a free account on (or one of the many other public jabber servers). 3) You need to get a Jabber client (I’m using Exodus).

There are 2 (technically 3) parts to the interface. The easiest is a standard Application.cfm that creates an application that enables us to use sessions. You need sessions because you need to be able to persist the Jabber chat and connection objects across requests.

The second part is composed of 2 documents: a) the default page that presents a form for sending a message and has an iframe to hold the conversation and then b) the iframe that holds the conversation and then initializes the Jabber connection and chat objects. I’ll show the iframe first.

The iframe is split up into 2 parts: initialization and display. The first thing it does is check to see if the connection object exists in session scope:

// if no connection exists, create one
if (NOT structKeyExists(session, "connection")) {

If the connection doesn’t exist, the following block of code is run:

// create a connection to the server
XMPPConnection = createObject("java", "org.jivesoftware.smack.XMPPConnection").init("");
// login to the jabber server
login = XMPPConnection.login("username", "password");
// create a chat w/ another user
chat = XMPPConnection.createChat("");
// store the connection and chat objects in session scope
session.connection = XMPPConnection; = chat;
// init an empty string to hold the conversation
session.conversation = "";

The block above creates a Smack XMPPConnection to the Jabber server (in this case I’m using ‘’, but you should change this to be whatever server you have an account on). Next I call the login(username,password) method to login to the Jabber server and then I create a Smack Chat object by called the createChat() method on the connection. Because I need the chat and the connection to persist (in order to chat with someone), I store both in session scope. Finally, I create a session variable called ‘conversation’ that will store the conversation between the 2 chatting clients.

If the connection already exists in session scope, another block of code is run:

// get the connection & chat objects from the session
connection = session.connection;
chat =;
// retrieve the message using pollMessage() (which is nonblocking)
nextMessage = chat.pollMessage();
// if no message exists 'nextMessage' will be undefined (I think 'null' technicall)
if (IsDefined("nextMessage")) {
  // message does exist, add it to the conversation
  session.conversation = session.conversation & "<br /><strong><font color='blue'>" & chat.getParticipant() & "</font></strong> : " & nextMessage.getBody();

I retrieve the Smack XMPPConnection and Smack Chat objects from the session, and then call the pollMessage() method on the chat object. It’s important that I use the pollMessage() method instead of the nextMessage() method because the pollMessage method is non-blocking, it won’t wait until a message shows up from the person I’m chatting with, it returns immediately if no message exists. If the pollMessage() method returns a Smack Message object (which in Java will either return a Message or null), then I add the message to the conversation and finally display the conversation:

writeoutput("<META HTTP-EQUIV='Refresh' CONTENT='1'>");

You’ll notice that I’m having the iframe page refresh itself every 1 second, it would probably be better to use some JavaScript and a one pixel image to do the trick, but this works for now.

The last step is to create the page that holds the iframe and that presents the form for sending a message. The iframe is simple:

<iframe src="frame.cfm" name="chatwindow" id="chatwindow" width="800" height="500" marginwidth="5" marginheight="5"></iframe>

and then some code to handle a form post, retrieve the chat and connection objects from session scope, send the message to Jabber and then add the message to the conversation:

// if we have a form post
if (IsDefined("form.formPosted")) {
  // grab the connection and chat objects from the session
  connection = session.connection;
  chat =;
  // send the message via the chat object
  // append the message to the conversation
  session.conversation = session.conversation & "<br /><strong><font color='red'>" & connection.getUser() & "</font></strong> : " & form.message;

Finally, a short form for entering the message:

<form action="#cgi.script_name#" method="post">
<input type="text" name="message">
<input type="submit" name="newmessage" value="Send Message">
<input type="hidden" name="formPosted" value="1">

That’s all there is too it!

You can download the source code for my examples here:

source code

I’d love your feedback on the code (if you use it) and I’d love to hear how you’re using instant messenging with ColdFusion, if you’re so inclined.


Indexing Database Content with Lucene & ColdFusion

Terry emailed me a couple days ago wondering how he could use ColdFusion and Lucene to index and then search a database table. Since we’re completely socked in here in Boston, I had nothing better to do today that hack together a quick snippet that does just that:

<cfset an = CreateObject("java", "org.apache.lucene.analysis.StopAnalyzer")>
<cfset an.init()>
<cfset writer = CreateObject("java", "org.apache.lucene.index.IndexWriter")>
<cfset writer.init("C:\mysite\index\", an, "true")>
<cfquery name="contentIndex" datasource="sample">
select label, description, id
FROM product
<cfloop query="contentIndex">
  <cfset d = CreateObject("java", "org.apache.lucene.document.Document")>
  <cfset fld = CreateObject("java", "org.apache.lucene.document.Field")>
  <cfset content = contentIndex.description>
  <cfset title = contentIndex.label>
  <cfset urlpath = "/products/detail.cfm?id=" &>
  <cfset d.add(fld.Keyword("url", urlpath))>
  <cfset d.add(fld.Text("title", title))>
  <cfset d.add(fld.UnIndexed("summary", content))>
  <cfset d.add(fld.UnStored("body", content))>
  <cfset writer.addDocument(doc)>
<cfset writer.close()>

The only real change from the code that I wrote previously to index a document was that instead of looping over the file system looking for documents, I loop over a query and then indexed the text of a column from the database rather than the text of a document. (I would have written in in CFScript, but you can’t do queries from CFScript yet, unless you use a UDF to do the query)

You can download the source here, if you’re so inclined.

Why doesn’t ASP.NET include an <asp:query> tag?

Ray asked a great question a couple weeks ago that I meant to reply to but just never got around to it. He asked why ASP.NET doesn’t include an <asp:query> tag to enable developers to quickly embed SQL queries into an ASP.NET page. The responses seemed to agree with Ray’s assessment that the lack of an <asp:query> tag was shortcoming of ASP.NET, but I think it’s something more than that. If you look closely at the tags (oops! ‘controls’) that Microsoft chose to include in the System.Web.UI.WebControls namespace, you’ll notice that *none* of them give you the ability to declare variables, read a file, query a database, or send email. In fact, all of the controls are about outputting either form components (buttons, drop down lists, checkboxes, etc..) or regular HTML (like images, table cells, table rows, etc.) Microsoft didn’t leave it out because they didn’t have time or money to do it, they left it out because they don’t think you should be writing web applications using tags/controls. Using a code-behind class and controls leaves you with a much cleaner page, one that contains very little, if any scripting code and one where the design is truly separated from the logic. Not one to shy away from an example, compare these two blocks of code that create a drop down list in a form from a query. First in ColdFusion:

<cfquery name="users" datasource="#mydatasource#">
select id,username FROM users
<select name="userid">
<cfloop query="users">
<cfoutput><option value="#userid#">#username#</option></cfoutput>

and then in ASP.NET:

// in code behind class, MyDBWrapper.Query returns a DataSet object
DataSet users = MyDBWrapper.Query("select id, username FROM users");
userid.DataSource = users;

<!--- page --->
<asp:dropdownlist id="userid" runat="server">

That’s a pretty lame example, but the main takeaway from it is that all of the ASP.NET controls can be manipulated from the code behind class, which is something you cannot do in ColdFusion. You can declare a drop down list in your code behind, bind it to a datasource, modify the selected value, toggle it’s visibility, or modify any of the other 20 or so properties that exist for a drop down list. To me this provides true separation of presentation from logic. Page designers can drop in ASP.NET controls and I can sit in a dark room and modify anything and everything on those controls from my codebehind. You can’t do that in ColdFusion.

Does this mean that ASP.NET is better than ColdFusion? Nope. Notice that I have to create a code behind (technically I could write my code in a <script runat=”server”> block) and that I have to create my own database wrapper class. ASP.NET takes a little bit more work. ColdFusion is much faster to develop in but arguably encourages you to intermingle code with display. ASP.NET takes a bit longer, but developed correctly, encourages you to separate your logic and display code.


CFX_Lucene updates

Couple people have written me in the last couple days with updates they’ve done to the Lucene and ColdFusion tags I wrote a couple months ago.

First, Nick Burch from Torchbox updated the CFX tag so that it “… behaves better under error conditions and … the command line debug now works.” I also read here that they (torchbox) are hoping to release an open source package written in Java “… to convert file
types to plain text and a CF custom tag to interface to Lucence which will
search them.

Today, Scott piped in with a nice addition that adds the score to the query returned to the calling tag:

// Define column indexes
String[] columns = { "URL", "TITLE", "SUMMARY", "SCORE" } ;

// loop over all the results, add each to the query
for (int i = 0; i
For those of you like Scott who want to index PDF and Office documents, I'd suggest you start taking a look at these JGURU FAQ's:

Java Guru: How can I index PDF documents?

Java Guru: How can I index Word documents?


Fail-Safe Amazon Image… using Java, C# & ColdFusion

Paul of fame (and the fabulous SnapGallery tool) wrote an article for the O’Reilly Network recently that (I think) was an excerpt of his recently released book “Amazon Hacks“. Anyway, he shows how you can check to see if an image exists on using ASP, Perl, and PHP and I thought it would be fun to show how to do the same thing in Java, C# and ColdFusion. His examples were all functions of the form:

Function hasImage(imageUrl)

so I’m following that style. In Java you’d end up with something like this:

public static boolean hasImage(String url) {
boolean result = false;
  try {
    URL iurl = new URL(url);
    HttpURLConnection uc = (HttpURLConnection)iurl.openConnection();
    if (uc.getContentType().equalsIgnoreCase("image/jpeg")) {
      result = true;
  } catch (Exception e) {
  return result;

In C#, almost the exact same thing:

public static Boolean HasImage(String url) {
  Boolean result = false;
  try {
    HttpWebRequest webreq = (HttpWebRequest)WebRequest.Create(url);
    WebResponse res = webreq.GetResponse();
    if (res.ContentType == "image/jpeg") {
      result = true;
  } catch {
  return result;

and then in ColdFusion:

<cffunction name="hasImage" returntype="boolean" output="no">
  <cfargument name="imageUrl" type="string" required="yes">
  <cfhttp url="#imageURL#" method="GET">
  <cfif cfhttp.responseHeader["Content-Type"] EQ "image/jpeg">
    <cfreturn true>
    <cfreturn false>

The full source for all these examples are available:

· Amazon.cs
· amazon.cfm


Migrating from ColdFusion to ASP.NET

Microsoft has put together an extensive article for developers migrating from CFMX to ASP.NET, including a pretty fair feature comparison chart. Probably the most obvious thing that the feature comparison table lacks is the mention of the close integration of Java with CFMX, in fact it says this:

It can also access Java class libraries with some extra work.

which is true and false… it requires extra work in the same way that it requires extra work to compile a C# file to an assembly, place the assembly in the /bin/ folder of the application and then import that assemblies namespace into an ASP.NET page.

Nonetheless, check it out if you have worked with CFMX before and are just getting started with ASP.NET.