97 Things Every Java Programmer Should Know

Chapter 57. Make Your Java Groovier

Ken Kousen

The screen was the color of a cyberpunk novel opened to the first line. I stared at it, worried I would never finish tonight. There was a knock on the wall of my cubicle. My boss stood there, waiting.

“How’s it going?” she said.

“Java is so verbose,” I sighed. “I just want to download some data from a service and save it to a database. I’m swimming in builders, factories, library code, try/catch blocks…”

“Just add Groovy.”

“Huh? How would that help?”

She sat down. “Mind if I drive?”

“Please.”

“Let me give you a quick demo.” She opened a command prompt and typed groovyConsole. A simple GUI appeared on the screen. “Say you want to know how many astronauts are in space at the moment. There’s a service at Open Notify that gives you that.”

She executed the following in the Groovy console:

def jsonTxt = 'http://api.open-notify.org/astros.json'.toURL().text

The JSON response came back with the number of astronauts, a status message, and nested objects relating each astronaut to a craft.

“Groovy adds toURL to String to generate a java.net.URL, and getText to URL to retrieve the data, which you access as text.”

“Sweet,” I said. “Now I have to map that to Java classes and use a library like Gson or Jackson—”

“Nah. If all you want is the number of people in space, just use a JsonSlurper.”

“A what?”

She typed:

 def number = new JsonSlurper().parseText(jsonTxt).number ...