On Mon, Sep 30, 2002 at 12:02:41PM -0500, Jerry Jalenak wrote: > Yeah, already ran across the exceptions. Right now I'm trying > to decide how to handle them since all of this code is actually > in a custom Validator routine.....
Good Lord, people, why is reflection anything but the option of last resort here? You really do not want to be calling Class.forname(String) unless there is some class that cannot be loaded by the compiler. First, calling Class.forname is slow, and second, it perversely gets rid of the compile-time type-safety that you would have is you simply used MyClass.class. Reflection is a tool that's useful when you do not know at build time the classes with which you will be dealing. It's useful for discovery of APIs. Using reflection instead of a lookup table is needlessly obtuse and will cause your VM to do all sorts of work on which any programmer should not want to be wasting CPU cycles. 1. Using reflection here is fragile, especially if it's not wrapped within the class that defines your constants. Java is a strongly typed language so letting the compiler help you is encouraged. 2. Using reflection is slow. If you still think it's the way you want to go, I would strongly recommend limiting the times you call Class.forname, etc., such that you do not call it every time you validate the zip code. 3. Using reflection makes you check all sorts of exceptions for things that you as the programmer know should not occur, but only can be you are circumventing the type checking provided by the language. This is a clue that what should be a simple task is being made more complex than it needs to be. 4. I'm not sure what your application is, but using regexp strings to validate ZIP codes per state seems like a bad idea. The US post office makes new ZIP codes all the time, and unless you are getting a list from them every week, the most you may want your application to do is warn the user that the application doesn't recognize the ZIP code. 5. Tell your product managers that validating ZIP codes is not something you can do reliably without an often-updated list of ZIP codes that you would need to download from the Post Office on a regular schedule since your list of regexp string will become outdated. 6. Lookup tables implemented by arrays or HashMaps are orders of magnitude faster than the sequence of function calls and system calls that you have to do with reflection. I'm sorry I had to write this, but I am befuddled by the lack of outcry over using reflection instead of a simple lookup table. Cheers, John > > -----Original Message----- > > From: Taylor, Jason [mailto:[EMAIL PROTECTED]] > > Sent: Monday, September 30, 2002 11:57 AM > > To: 'Struts Users Mailing List' > > Subject: RE: [OT - Java] How can I do this in Java? > > > > > > good point-- you'd also want to printStackTrace() (if possible) before > > rethrowing InvocationTargetException, since it can be > > difficult to debug an > > ITE otherwise... > > > > -----Original Message----- > > From: Daniel Jaffa [mailto:[EMAIL PROTECTED]] > > Sent: Monday, September 30, 2002 9:49 AM > > To: Struts Users Mailing List > > Subject: Re: [OT - Java] How can I do this in Java? > > > > > > Make sure your code in a proper try and catch. Using > > reflection spits out > > nasty errors if anything is not right.:( > > > > ClassCastException > > IllegalAccessException > > NoSuchMethodException > > InvocationTargetException > > > > Daniel jaffa > > ----- Original Message ----- > > From: "Jerry Jalenak" <[EMAIL PROTECTED]> > > To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]> > > Sent: Monday, September 30, 2002 11:46 AM > > Subject: RE: [OT - Java] How can I do this in Java? > > > > > > > Jason - Thanks for the code snippet - worked like a charm > > first time! I > > > tend to get lost in JavaDoc sometimes, so this was a nice > > example to have > > on > > > how to wind my way through to the answer! Thanks again! > > > > > > John - Thanks for the suggestion on using the HashMap. I'm > > going to file > > it > > > away for now and use Jason's reflection method - but it > > never hurts to > > have > > > a couple of different methods to use on something like this! > > > > > > Thanks guys! > > > > > > Jerry > > > > > > > -----Original Message----- > > > > From: Taylor, Jason [mailto:[EMAIL PROTECTED]] > > > > Sent: Monday, September 30, 2002 10:28 AM > > > > To: 'Struts Users Mailing List' > > > > Subject: RE: [OT - Java] How can I do this in Java? > > > > > > > > > > > > I don't happen to have any sample code that does exactly what > > > > you're doing, > > > > but off the top of my head (with a little help from sun's > > > > javadoc) I'd say > > > > it's something like: > > > > > > > > import java.lang.reflect.Field; > > > > > > > > String stateCode = "AK"; > > > > Class constantClass = > > > > Class.forName("com.yourdomain.yourapp.Constants"); > > > > Field stateField = constantClass.getDeclaredField(stateCode); > > > > String stateRegExp = (String) stateField.get(constantClass); > > > > System.err.println("regexp for "+stateCode+": "+stateRegExp); > > > > > > > > I don't really know any more about reflection than you, I > > > > just followed the > > > > trail from java.lang.Class to java.lang.reflect.Field. Once > > > > you've done it > > > > once, you see it's no mystery-- you're just doing runtime > > compiling. > > > > > > > > HTH-- This is just how I'd start, as I haven't tested or used > > > > this code. If > > > > I'm wrong, I'm sure you can figure out what I missed by > > > > studying the API > > > > docs. If, on the other hand, you don't like reading javadocs > > > > and generating > > > > your own test cases, LOL! > > > > > > > > -JT > > > > > > > > -----Original Message----- > > > > From: Jerry Jalenak [mailto:[EMAIL PROTECTED]] > > > > Sent: Monday, September 30, 2002 8:05 AM > > > > To: 'Struts Users Mailing List' > > > > Subject: RE: [OT - Java] How can I do this in Java? > > > > > > > > > > > > Jason, > > > > > > > > Thanks for the quick reply. I just took at look at the > > > > API's, but don't yet > > > > understand enough about reflection to know how to > > implement it. Just > > > > looking at the methods I don't see a way to do what I want - > > > > any chance that > > > > you'd have some sample code laying about? > > > > > > > > Jerry > > > > > > > > > -----Original Message----- > > > > > From: Taylor, Jason [mailto:[EMAIL PROTECTED]] > > > > > Sent: Monday, September 30, 2002 9:59 AM > > > > > To: 'Struts Users Mailing List' > > > > > Subject: RE: [OT - Java] How can I do this in Java? > > > > > > > > > > > > > > > sounds like a job for reflection (java.lang.reflect.*;) Have > > > > > you looked at > > > > > java.lang.Class and java.lang.reflect.Field? > > > > > > > > > > -----Original Message----- > > > > > From: Jerry Jalenak [mailto:[EMAIL PROTECTED]] > > > > > Sent: Monday, September 30, 2002 7:50 AM > > > > > To: '[EMAIL PROTECTED]' > > > > > Subject: [OT - Java] How can I do this in Java? > > > > > > > > > > > > > > > OK - off topic, but Sun's java forum sucks, and there are an > > > > > incredible > > > > > number of Java guru's on this list, so I thought I'd throw > > > > > this out here. > > > > > (That and I am using this in a custom validation routine > > > > > :-)) Any help > > > > > would be GREATLY appreciated! > > > > > > > > > > Here's the scenario - I've got a series of static constants > > > > > that represent > > > > > Java regular expressions. These RE's are used to validate > > > > > driver license > > > > > formats for the 50 states + DC. The strings look like this: > > > > > > > > > > public static final String AK = "^[0-9]{1,7}$"; > > > > > public static final String AL = "^[0-9]{7}$"; > > > > > public static final String AR = "^[0-9]{8,9}$"; > > > > > public static final String AZ = > > > > > "^[0-9ABDY][0-9]{8}$|^[A-Z][0-9]{3,6}$|^[A-Z]{2}[0-9]{3,5}$"; > > > > > public static final String CA = "^[A-Z][0-9]{4,7}$"; > > > > > public static final String CO = > > > > > "^[A-Z][0-9]{1,6}$|^[A-Z]{2}[0-9]{1,6}$|^[0-9]{9}$"; > > > > > etc. etc. etc. > > > > > > > > > > On my form I have a drop-down box of states, and a field for > > > > > the license > > > > > number. In my custom validator routine, I pick up the value > > > > > of the state, > > > > > and build a string to represent the constant - i.e. > > > > > > > > > > private static boolean validateDriversLicenseNumber(String > > > > > licenseState, String licenseNumber) > > > > > { > > > > > String licenseConstant = "Constants." + licenseState; > > > > > > > > > > I then want to use "licenseConstant" in a Pattern / Match: > > > > > > > > > > Pattern p = Pattern.compile(licenseConstant, > > > > > Pattern.CASE_INSENSITIVE); > > > > > Match m = p.matcher(licenseNumber); > > > > > return (m.find()); > > > > > } > > > > > > > > > > Obviously the line "String licenseConstant = "Constants." + > > > > > licenseState;" > > > > > does not give me the value of Constant.<state name>; the > > > > > question I have is, > > > > > is there a method (or something) that will allow me to build > > > > > such a string, > > > > > and return the value (i.e. the regular expression)? Or is > > > > > there a better > > > > > way of doing this? > > > > > > > > > > TIA! > > > > > > > > > > Jerry Jalenak > > > > > Web Publishing > > > > > LabOne, Inc. > > > > > 10101 Renner Blvd. > > > > > Lenexa, KS 66219 > > > > > (913) 577-1496 > > > > > [EMAIL PROTECTED] > > > > > > > > > > > > > > > This transmission (and any information attached to it) may be > > > > > confidential > > > > > and is intended solely for the use of the individual or > > > > > entity to which it > > > > > is addressed. If you are not the intended recipient or > > the person > > > > > responsible for delivering the transmission to the intended > > > > > recipient, be > > > > > advised that you have received this transmission in error and > > > > > that any use, > > > > > dissemination, forwarding, printing, or copying of this > > > > information is > > > > > strictly prohibited. If you have received this transmission > > > > > in error, please > > > > > immediately notify LabOne at (800)388-4675. > > > > > > > > > > > > > > > > > > > > -- > > > > > To unsubscribe, e-mail: > > > > > <mailto:[EMAIL PROTECTED]> > > > > > For additional commands, e-mail: > > > > > <mailto:[EMAIL PROTECTED]> > > > > > > > > > > > > > This transmission (and any information attached to it) may be > > > > confidential > > > > and is intended solely for the use of the individual or > > > > entity to which it > > > > is addressed. If you are not the intended recipient or the person > > > > responsible for delivering the transmission to the intended > > > > recipient, be > > > > advised that you have received this transmission in error and > > > > that any use, > > > > dissemination, forwarding, printing, or copying of this > > information is > > > > strictly prohibited. If you have received this transmission > > > > in error, please > > > > immediately notify LabOne at (800)388-4675. > > > > > > > > > > > > > > > > -- > > > > To unsubscribe, e-mail: > > > > <mailto:[EMAIL PROTECTED]> > > > > For additional commands, e-mail: > > > > <mailto:[EMAIL PROTECTED]> > > > > > > > > > > This transmission (and any information attached to it) may > > be confidential > > and is intended solely for the use of the individual or > > entity to which it > > is addressed. If you are not the intended recipient or the person > > responsible for delivering the transmission to the intended > > recipient, be > > advised that you have received this transmission in error and > > that any use, > > dissemination, forwarding, printing, or copying of this information is > > strictly prohibited. If you have received this transmission > > in error, please > > immediately notify LabOne at (800)388-4675. > > > > > > > > > > > > -- > > > To unsubscribe, e-mail: > > <mailto:[EMAIL PROTECTED]> > > > For additional commands, e-mail: > > <mailto:[EMAIL PROTECTED]> > > > > > > > > > -- > > To unsubscribe, e-mail: > > <mailto:[EMAIL PROTECTED]> > > For additional commands, e-mail: > > <mailto:[EMAIL PROTECTED]> > > > > This transmission (and any information attached to it) may be confidential and is >intended solely for the use of the individual or entity to which it is addressed. If >you are not the intended recipient or the person responsible for delivering the >transmission to the intended recipient, be advised that you have received this >transmission in error and that any use, dissemination, forwarding, printing, or >copying of this information is strictly prohibited. If you have received this >transmission in error, please immediately notify LabOne at (800)388-4675. > > > > -- > To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- end of line -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
