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Mustang Must-Haves: What's Cool in Java SE 6

The just-released Java SE 6 boasts many neat new features, such as integrated scripting, enhanced JDBC features, better Web service support, and much more. Here are few personal favorites from a seasoned Java developer and architect.

he long-awaited Java SE 6 is upon us. This latest version of the Java SE environment brings a number of new features and enhancements, such as integrated support for scripting languages and Web services, improved JDBC features, and an integrated Derby database (in the SDK release), as well as some nice management features and enhanced performance.

Writing a single article that details all the additional features and enhancements would be a difficult proposition. Instead, this article just highlights a few of my personal favorites in enough detail to be useful. In particular, it examines each of the following features in turn:

  • Scripting language support
  • JDBC 4 support
  • Monitoring and management
  • File system management

Support for Scripting Languages
Most developers have heard of, and possibly used, scripting languages such as PHP, Ruby, JavaScript, and Python. These dynamic languages are enjoying a resurgence in popularity, largely because of their flexibility and simplicity, and the productivity gains they promise.

Java 6 comes with built-in support for scripting languages. You can embed scripts in various scripting languages into your Java applications, passing parameters, evaluating expressions, and retrieving results. And you can do it all pretty seamlessly.

First of all, you obtain a new ScriptEngine object from a ScriptEngineManager, as shown here:

        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");

Each scripting language has its own unique identifier. The "js" here means you're dealing with JavaScript.

Now you can start having some fun. Interacting with a script is easy and intuitive. You can assign scripting variables using the put() method and evaluate the script using the eval() method,. which returns the most recently evaluated expression processed by the script. And that pretty much covers the essentials. Here's an example that puts it all together:

        engine.put("cost", 1000);
        String decision = (String) engine.eval(
            "if ( cost >= 100){ " +
            "    decision = 'Ask the boss'; " +
            "} else {" +
            "    decision = 'Buy it'; " +
        assert ("Ask the boss".equals(decision));

You can do more than just pass variables to your scripts— you can also invoke Java classes from within your scripts. Using the importPackage() function enables you to import Java packages, as shown here:

        engine.eval("importPackage(java.util); " +
                    "today = new Date(); " +
                    "print('Today is ' + today);");

Another cool feature is the Invocable interface, which lets you invoke a function by name within a script. This lets you write libraries in scripting languages, which you can use by calling key functions from your Java application. You just pass the name of the function you want to call, an array of Objects for the parameters, and you're done! Here's an example:

            "function calculateInsurancePremium(age) {...}");
        Invocable invocable = (Invocable) engine;
        Object result 
          = invocable.invokeFunction("calculateInsurancePremium",
                                     new Object[] {37});

You actually can do a fair bit more than what I've shown here. For example, you can pass a Reader object to the eval() method, which makes it easy to store scripts in external files, or bind several Java objects to JavaScript variables using a Map-like Binding object. You can also compile some scripting languages to speed up processing. But you probably get the idea that the integration with Java is smooth and well thought-out.

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