Freemarker 表达语言在 java class 中使用

Question

I'm a junior and got a task. I need to write simple app to test performance of Freemarker expression.

Map<String, Object> data = new HashMap<String, Object>();
data.put("firstString", "13");
data.put("secondString", "17");

Condition: ${(firstString + secondString)?number};

The goal is repeat the process 100.000 times (parse template, set variables, evaluate template) and evaluate performance in milliseconds of the process.

public static void main(String[] args) throws IOException {

Configuration cfg = new Configuration();
   try {
        long startTime = System.nanoTime();
        // Connect to Freemarker template
        Template template = cfg.getTemplate("src/concatenation.ftl");

        // Create data to use in expresion String to number = ${(firstString + secondString)?number}
        Map<String, Object> data = new HashMap<String, Object>();
        data.put("firstString", "13");
        data.put("secondString", "17");


        for (int i = 0; i < 100_000 ; i++) {
            // Console output
            Writer out = new OutputStreamWriter(System.out);
            template.process(data, out);
            out.flush();
        }

        // Measure performance time
        long endTime = System.nanoTime();
        long duration = (endTime - startTime);
        System.out.println();
        System.out.println("Parse template for 100.000 objects completed in " + duration / 1000000 + " milliseconds");

    } catch (IOException e) {
        e.printStackTrace();
    } catch (TemplateException e) {
        e.printStackTrace();
    }
}

Need help to figure out how to use Freemarker expression in main class, to prevent reading from external file to be more precisely in performance test.

Would be glad to hear all your recommendations.

ps We are gonna to build a big app, that would be work with a big data. And we planning to use Freemarker to handle this data.

Answer 1

It's critical to decide which phases you really want to measure, and with what weight. Above you are measuring loading the template once, and executing the already parsed template for 100000 times. If you don't want to measure template loading and parsing, then just put the long startTime =... line after the getTemplate line.

Some further notes:

• What the templates write into can matter, sometimes a lot. You re writing to the console, but the real application will not. If you just want to rule out that factor, then use freemarker.template.utility.NullWriter.INSTANCE for the output.

• You should do some "warm up", so that the JIT can do its work. So maybe run the whole test for some hundreds of times before starting the actual measurement.

• The data model ( data ) will be wrapped 100000 times as well. If lot of small templates will read the same data, then it's maybe a good idea to pre-wrap it via TemplateHashModel wrappedData = (TemplateHashModel) config.getObjectWrapper().wrap(data) , and then pass wrappedData to the process calls of different templates later.