Mark Gregory Turansky

Jason McDonald’s printable design pattern reference cards were printed by DZone as part of their “RefCardz” iniative.

You can find Jason’s cards here and you can find other useful design patterns stuff here.

Using the batched statement capability of your JDBC driver can give you 7-8X throughput gains. Not only is batching significantly faster, it’ll save database CPU cycles and be easier on the network, too.

The graph below shows elapsed time (in milliseconds) by batch size. For each data point, 1K rows were inserted into a simple table in MySQL. The benchmarking code I used can be found here.

Why is batching so much faster?

First, depending on how much PreparedStatement caching your driver is doing, your database may be spending a lot of time parsing and compiling statements. After the statement is parsed and compiled, bind variables are applied. In our example, the data base will parse and compile the statement once as opposed to 1,000 times. This reduces the work your database performs and saves CPU.

Second, all bind variables are passed to the database in a single network call instead of 1,000 separate out-of-process, across-the-network calls. This helps reduce network traffic.

Third, depending on the internal architecture of your code, single statements may return the connection to a pool after every use. Multiply that by 1,000 and run a profiler and you’ll see yourself calling take/put methods a lot. Many pools also verify the connection on check-in and check-out. “select 1 from dual” is a common check for a pool to use. Your 1,000 uses of a connection may also be incurring the cost of 2,000 “select 1 from dual” statements!

When should you use batching?

Batching is particularly useful in importing scenarios where you need to get lots of data into your application quickly, but it can be used even when executing a few similar statements. Check out the example source code provided to see if batching is right for you. Fiddle with the numbers to see the gains for batching just 10 similar statements. It may not be 8X big, but trumpeting 25% gains to management is still a win for you and your team.

Use JDBC Batching!

JDBC batching can give you dramatic throughput gains while simultaneously being less abusive to your hardware. Overall, if you have the opportunity to use batch inserts and updates, you should seize that opportunity. Look at your application’s internal architecture to see if batching is right for you.

Don’t make me think. That’s how I feel about your code.

Or as Martin Fowler puts it:

“Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” -Martin Fowler, Refactoring: Improving the Design of Existing Code

You’ve reached a whole new level of mastery when you write for simplicity, elegance, and maintainability. This is done on purpose, and it’s hard to get right. Deadlines, schedules, pressure, and stress all encourage us to cut corners and adopt a “Git ‘er done!” mentality. But Abandonment of planning under pressure is one of software’s classic mistakes. It’s a cardinal sin.

How do you write simple and maintainable code? I’ve got a 3-step program for you:

Step 1: Admit that simple isn’t easy

Designing simple software is hard. It has to be done on purpose. You can’t accidentally find yourself with well-written code and an elegant solution, it has to be written that way on purpose.

This admission is a bedrock principle required for designing great software and products. If you can’t admit that simple is Hard Work™, you haven’t hit rock bottom yet by having to maintain code that would make readers of The Daily WTF blush.

Step 2: Read “Don’t Make Me Think”

Steve Krug’s excellent book “Don’t Make Me Think” is about website usability, yet it changed how I look at my code.

Why? Because Steve applied the same principles in his book to his book! And if it works in those two mediums, I thought it just might work for me, too, in my medium (code).

“Don’t Make Me Think” is very easily absorbed because he’s feeding you information in a readily accessible way. He wrote it simply on purpose, and I’m certain it took many more hours to edit than it did to write. Simple is hard.

Step 3: Practice simple everyday

There are innumerable decisions you make everyday that affect your project for better or worse. You need to recognize these as the opportunities they are. Here are a few things you can do every day:

dao.findCustomerBy(order);

Or what about this if statement?

if(admin.hasPermission(Permissions.VIEWFILE)){
   // allow...
}

or better yet…

if(admin.hasViewFilePermission()){
   // allow...
}

The pretty method on the Admin class looks like this:

public boolean hasViewFilePermission(){
   return hasPermission(Permissions.VIEWFILE);
}

Date dt = march(28, 1973);

When I’m reading through unit tests, I’d much rather see the above statement to create a date than the equivalent Java:

Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, Calendar.MARCH);
cal.set(Calendar.DATE, 28);
cal.set(Calendar.YEAR, 1973);
Date dt = cal.getTime();

You can find those convenient date methods here: dates.java (it’s Free software). Use Java 5’s static imports to make the short date seen above.

That’s it. Three steps to better code. Putting it into practice won’t be easy, but if you want to be a master of your craft you’ll embrace the challenge and write things simply on purpose. The people who follow you and maintain your code will appreciate it.