Category Archives: java

Apache Commons

If you are a Java developer, and you don’t know about Apache Commons, you should take a minute to check it out. A lot of times when you need to write some mundane code to do something, and you are thinking to yourself, “I’m sure a million other people have had to write this code”, you should take a quick look at commons to see if they did it. A lot of times they have it packaged up in a nice library. One of my favorites is the IOUtils class in commons-io, which can pull an InputStream into a String object in one line of code, but they have a bunch of other stuff that is useful as well.

Maven is like apt-get for Java

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When I first learned Linux, I used Slackware 3.0. In those days, if you wanted to install extra software, you pretty much had to compile it yourself. And they didn’t even have configure scripts back then, if I recall correctly. Eventually, Redhat took over, and software was easier to install via RPM packages. At first, RPMs weren’t available for everything, so you still had to compile some stuff, but eventually they became pretty ubiquitous. Dependencies could be a big pain though. You download one RPM you want, and you find out you need to download five more that it depends on. And those five each depend on five others. Remember rpmfind.net? Then came yum and apt-get, and those trouble were alleviated.

Now, building Java apps is almost like managing a Linux system. There are so many great third party libraries available, you can find ones to do almost any common task you need, saving lots of time when coding stuff. But, the people that write those libraries also use other libraries. Things like Hibernate have a lot of dependencies. Getting all of the jars for the libraries you need can be somewhat like the old RPM hunt. This is where Maven comes in. Just tell it you need Hibernate and it will make sure you have everything else you need. It’s pretty awesome, and it can completely eliminate those sessions where you waste a lot of time looking for jar files.

Spring JDBC is awesome

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I would like to just take a moment to express my love for Spring JDBC. I just deleted giant swaths of database connection handling code from an app I’m maintaining by replacing a DAO with a Spring JDBC version. If you haven’t taken the time to learn about it, check it out here.

Sometimes I feel like constructors should be removed from Java

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Sometimes constructors in Java are convenient. You can instantiate your class with all the data you need with a simple one-liner:

Car car = new Car(numberOfWheels, color, engine, doors);

That code is fairly readable and concise, but things can quickly spiral out of control. Unless you use really descriptive variable names like those above, it’s pretty easy to get lost. Eventually you end up with code like this (partially obfuscated to protect the innocent):

foo = new Bar(rs.getString(1),
rs.getString(2),
rs.getString(3),
rs.getString(4),
rs.getString(5),
rs.getString(6),
rs.getString(7),
rs.getString(8),
rs.getString(9),
rs.getString(10),
rs.getDate(11),
rs.getDate(12),
(“Y”.equals(rs.getString(13)) ? true : false),
(“Y”.equals(rs.getString(14)) ? true : false),
(“Y”.equals(rs.getString(15)) ? true : false),
(“Y”.equals(rs.getString(16)) ? true : false),
(“Y”.equals(rs.getString(17)) ? true : false),
(“Y”.equals(rs.getString(18)) ? true : false),
(“Y”.equals(rs.getString(19)) ? true : false),
rs.getTimestamp(20),
rs.getTimestamp(21),
rs.getString(22),
rs.getString(23),
rs.getString(24));

This is the point where I say you gotta just use a blank constructor and setter methods. Much more readable. And on a side note, when you are typing rs.getString(24), you should probably start thinking about how it might be more readable if you refer to your result set columns by name. That is all.

A recipe for trouble

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Dear the Internet,

Please never write this code:

if (value == null || value.equals(“”)) {
d = new Date(0);
} else {

This is what I like to call “bug hiding”. Rarely does a person really mean 12/31/1969 when they pass you a null or blank value. That is all.

JSP is still really bad

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I had to do some maintenance work recently on a JSP app. Normally, I avoid JSP like the plague because my (dated) experience with it has been mostly bad. The app I had to maintain was a stone age thing full of scriptlets, but I did a little research and used JSTL to do some of the work on the updates. I was pretty impressed with how cleanly you can do some flow control stuff now. So, I started some new development on a new project with JSP as a proof of concept to see if it is a tolerable programming environment now. It isn’t. For the real basics, there has been a lot of improvement, but some of the mechanisms for taglibs, dealing with variable between servlet/JSP, etc. are still very clunky. And today I encountered this. If you forget to put the return type when defining a function within your app, you get a super mysterious error.

I guess you could blame the implementation (Jasper), but what does anyone else use? Also, you can sort of tell from the screen shot of the editor, but the JSP editor in the current version of Eclipse is pretty awful. It displays some of your double quotes as single quotes, which is really awkward.

Miscellany

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Here’s a good example of some bad user interface design in my favorite IDE.

I know the Maven stuff is a plugin, so I’m guessing NetBeans allows plugins to install tabs under “Miscellaneous”. So what you end up with is a configuration screen that looks simple until you find out that there are really supposed to be 30 tabs instead of 7, but they are hiding out in the Miscellaneous section.

Tapestry 5 pain points

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I have been doing Tapestry 5 work for about a year now, and I’m definitely still learning, but I think I know my way around fairly well. I really (mostly) like it, and I think it is way easier to use than Tapestry 4, as well as many other frameworks. It also results in a nice clean code base which isn’t too difficult to approach. There are, however, a couple of areas that I really just find confusing. Some of them aren’t too bad once you get to know them, but they are hard to learn. I think it is important for most aspects of the framework to be easy to learn/use, because if people encounter pain during their initial impression stage, they will abandon the framework and use something else.

The first issue I have is with the way that the Select component works when you want to have a dynamic model for the list. I think this is a common requirement for applications, so it is something people will most likely encounter fairly quickly. For complex models, it is usually necessary to implement two interfaces: SelectModel and ValueEncoder. The interfaces make sense once you get to know them, but I think the learning curve is quite steep for such a common task. I’m not sure how this could be solved, but it seems like Tapestry 4 may have had a more simple system (though I’m sure it had some problems which led to it being redone).

The second issue I have is with page context. Often times in standalone web applications, I have created pages which take query string parameters. These can be referenced by external apps or pages, and used to link between pages of an app. Tapestry’s equivalent is the page context, which can be used to pass contextual data between pages. There are two problems that I’ve encountered with page context. First, it is limited in what data it can represent. It is generally just a list of nameless parameters. This makes it difficult to pass only certain parameters or parameters with names. Second, the format for the URL is not a part of the spec (correct me if I’m wrong), so it can only reliably be used via other Tapestry pages. This makes it difficult to pass data in to a Tapestry page from an external place.

So to sum it up, I’d like to reiterate that I really do like Tapestry 5 and hope for its widespread adoption, but it has a few points that are difficult to deal with. If these issues were addressed in a future version, I think it would help ease a new developer’s adoption of the framework.

Image submit in Tapestry 5.1

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This just took me a really long time to figure out, so I’m writing it down. Tapestry 5.1 adds support for submit buttons with an image (I think it was added in 5.1). In any case, you just use the normal tag, but you add an image attribute which is an “asset”. I added an Asset property to my page class and used @Inject and @Path to inject the asset. I used that property name in the image attribute, and it didn’t work. It turns out, you don’t need to declare the asset as a property in your page class. You just specify the path in the image attribute just like you would in the @Path annotation. So, it looks something like this:

<t:submit image=”context:images/submit.gif”/>

Much simpler than I was thinking. Sometimes I get really frustrated with these little Tapestry issues…

Tabs vs spaces in Netbeans

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I work with some people that like spaces and some people that like tabs in their code. I don’t really care, so I try to follow whatever the project is using. I ran into a big problem with Netbeans, though, in that it seems like getting it to use tabs only is impossible. It turns out they appear to be following a weird part of the Java Code Conventions spec:

Four spaces should be used as the unit of indentation. The exact construction of the indentation (spaces vs. tabs) is unspecified. Tabs must be set exactly every 8 spaces (not 4).

http://java.sun.com/docs/codeconv/html/CodeConventions.doc3.html#262

So, Netbeans sort of has two different “numbers” around tabs. There is a number that says how many spaces a tab should appear as, and a number that says how many spaces should be used when you indent something. By default a tab appears as 8 spaces, but a level of indentation is 4 (like the spec says above). As a result, it inserts four hard spaces when you indent one level, and a tab if you indent two levels. The solution is to set the two numbers to the same value. Just a wee bit confusing for a new user.

Here’s a bug report where someone describes it:

http://www.netbeans.org/issues/show_bug.cgi?id=52053