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Useful Tools - 12. page

Useful tools: the catch all email address

When working on a web application that requires authentication, email address is often chosen as a username. It’s guaranteed to be unique, it’s something that the user knows rather than another username they have to remember, and communication to the user is built in–if they’re having trouble, just have send them an email.

However, when developing the initial registration portion of a site that depends on email address for the username, you often run through many email addresses as you tackle development and bugs. Now, it is certainly easy enough to get more email addresses through Yahoo or hotmail. But that’s a tedious process, and you’re probably violating their terms of service.

Two other alternatives arise: you can delete the emails you want to reuse from the web application’s database. This is unsavory for a number of reasons. One is that mucking around in a database when you’re in the middle of testing registration is likely to distract you. Of course, if you have a the deletes scripted, it’s less of an issue. You’ll need to spend some time ensuring you’ve reset the state back to a true pure place; I’ve spent time debugging issues that arose for anomalous user state that could never be achieved without access to the back end.

Which is why I favor the other option. If you own your own domain name and have the catch all key set, all email for your domain that does not have a specified user goes to the catch all account. (I wasn’t able to find out much of hose this is set up, other than this offhanded reference to the /etc/mail/virtusertable file.)

I find having this available tremendously useful. You have an infinite number (well, perhaps not infinite, but very large) of addresses to throw away. At times, the hardest part is remembering which address I actually used, which is why having a system of some kind is useful. For example, for my dev database on my current project, I start all users with foo and then a number. For the stage database, I start all users with bar and then a number.

In addition to helping with development, it’s useful to have these throwaway email addresses when you are signing up for other web applications or posting on the web. For example, my jaas@mooreds.com account, which was posted on my JAAS and Struts paper, is hopelessly spammed. If I had put my real address on that paper, I would have much more spam than I do now, as jaas@mooreds.com simply goes to /dev/null courtesy of procmail. I’ve also used distinctive email addresses for blog comments and for subscribing to various mailling lists; this way I can find out if everyone really keeps their data as private as they say they will. Of course, there are free services out there that let you have throwaway email addresses but having your own domain gives you a bit more security and longevity.

All in all, I find that having a catch all email address set up for a given domain is a very useful development tool, as well as a useful general web browsing technique.

Programming Useful Tools | moore |

Useful tools: javap

javap lets you examine java class files and jar files in a number of ways. See this web page for more information. For me, it’s an API reference. I use it in two ways:

1. When I’m coding, and I need to know the exact syntax of a method, I shell out: javap java.util.StringTokenizer. (Yes, I know that any modern IDE will do this for you without shelling out, but javap will work anywhere java is installed and with any editing tool. You trade portability for convenience.) One large catch is that inherited methods are not shown:

$ javap java.io.BufferedReader
Compiled from "BufferedReader.java"
public class java.io.BufferedReader extends java.io.Reader{
public int read();
throws java/io/IOException
static {};
public void close();
throws java/io/IOException
public void reset();
throws java/io/IOException
public boolean markSupported();
public boolean ready();
throws java/io/IOException
public void mark(int);
throws java/io/IOException
public long skip(long);
throws java/io/IOException
public int read(char[],int,int);
throws java/io/IOException
public java.io.BufferedReader(java.io.Reader);
public java.io.BufferedReader(java.io.Reader,int);
public java.lang.String readLine();
throws java/io/IOException
java.lang.String readLine(boolean);
throws java/io/IOException
}

Running javap on java.io.BufferedReader does not show the method read(char[]), inherited from java.io.Reader. (This example is from the J2SE 1.4 libraries.)

2. Sometimes, the javadoc is too up-to-date (or your jar files are too old) to answer questions about an API. For example, I’m working on a project with Jetspeed which depends on Turbine version 2.2. Unfortunately, this is an extremely old version of Turbine (release 16-Aug-2003), and the javadoc doesn’t appear to be available. (Updated Dec 11: It looks like the Turbine 2.2 javadoc is indeed online. Whoops.) Generating the javadoc with ant is certainly an possibility, and if I found myself going time and again to verify the API of Turbine 2.2, I’d do that. But for a quick one- or two-off question about an API that no web search turns up, javap can be very handy.

In short, if you have a quick question about an API, javap can help you out.

Java Programming Useful Tools | moore |

Useful tools: p6spy

This entry kicks off a series of entries where I’ll examine some of my favorite tools for development. Some of them will be long, some short, but all of them will highlight software I use to make my life a bit easier.

A large, large chunk of the development I do is taking data from a relational database to a an HTML screen, and back again. Often there are business rules for transforming the data, or validation rules, but making sure the data is stored safely and consistently is a high priority, and that means a relational database.

However, I do much of my work in java, which means that the relational-OO impedance mismatch is a common problem. One common way to deal with it is to use an OR tool–something like OJB or JDO. These tools provide object models of your database tables, usually with some help from you. You then have the freedom to pretend like your database doesn’t exist, and use these objects in your application. The OR framework takes care of the dirty work like SQL updates and caching.

Every convenience has its price, however, and OR mapping tools are no exception. The same abstraction that lets you pretend that you’re simply dealing with objects means that you cannot easily examine the SQL that is generated. In addition, the way that you’re using the objects may cause performance issues, because you’re treating the data as objects, rather than rows.

It’s much the same issue as calling methods over the network via RMI or accesing files via NFS: the abstraction is great and means that programmers don’t have to think about the consequences of remote access. But the failure of the abstraction can be catastrophic, all the more so because the programmer was not expecting to have to deal with the grotty details under the abstraction (that’s the whole point, right?).

OR tools do not fail often, or have many catastrophic failure modes, but they sure can be slow. With open source software, you can dig around and see how SQL is being generated, but that’s tedious and time consuming. With commercial products, you don’t even have that option. (Some OR tools may have their own ‘Show me the SQL’ switch–I haven’t run into them.)

Enter p6spy. p6spy can be used in place of any JDBC driver. You point it to the the real driver and it passes on any configuration or SQL calls to that driver. But p6spy logs every SQL statement passed to it and every result set passed back. (A fine non object oriented example of the Decorator pattern.)

It took me about 15 minutes to figure out how to use p6spy, the software is open source with decent documentation, the latest version has data source support, and it scratches an itch that most, if not all, java developers will have at some time. With p6spy, you can find out what that OR tool is doing under the covers–it’s an easy way to peel back some of the abstraction if needed.

Java Programming Useful Tools | moore |