Java Servlet – Logging with Log4j Example

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.PrintWriter;
import java.io.IOException;
import org.apache.log4j.*;

public class LoggingServlet extends HttpServlet {

    private static Logger logger = Logger.getLogger(LoggingServlet.class);

    public void doPost(HttpServletRequest req, HttpServletResponse res)
            throws IOException, ServletException {
        logger.info("invoked the LoggingServlet...");
        PrintWriter writer = res.getWriter();
        writer.println("Check your web server console...");
        writer.flush();
        writer.close();
    }

}

Java – Generate Random alpha-numeric String

The code below show you how to use the apache commons RandomStringUtils class to generate some random string data.

import org.apache.commons.lang.RandomStringUtils;

public class RandomStringUtilsDemo {

	public static void main(String[] args) {
		//
		// Creates a 64 chars length random string of number.
		//
		String result = RandomStringUtils.random(64, false, true);
		System.out.println("random = " + result);

		//
		// Creates a 64 chars length of random alphabetic string.
		//
		result = RandomStringUtils.randomAlphabetic(64);
		System.out.println("random = " + result);

		//
		// Creates a 32 chars length of random ascii string.
		//
		result = RandomStringUtils.randomAscii(32);
		System.out.println("random = " + result);

		//
		// Creates a 32 chars length of string from the defined array of
		// characters including numeric and alphabetic characters.
		//
		result = RandomStringUtils.random(32, 0, 20, true, true, "qw32rfHIJk9iQ8Ud7h0X".toCharArray());
		System.out.println("random = " + result);
	}

}

Output:

random = 2377316738997278218735578855577798247976319451877477254850564896
random = wwqbLxlRynIdptAoxuSIfbABRoOFHLyKaFEscrUoBQjAHPOkcIqfHuMnhXVzaLCf
random = 6nQ0PJf<#VgIi=’&d`*`Ru#i_exMoHXb
random = ZGbelXYEiLrlLBXKroCIDJPrevZPIGkD

Java – Convert Array to Map using Commons ArrayUtils

This example use the Apache Commons lang’s ArrayUtils class to convert a two dimensional array to a Map object.

import java.util.Map;
import org.apache.commons.lang.ArrayUtils;

public class ArrayToMapExample {

	public static void main(String[] args) {
		//
		// A two dimensional array of countries capital.
		//
		String[][] countries = {{"United States", "New York"},
				{"United Kingdom", "London"},
				{"Netherlands", "Amsterdam"},
				{"Japan", "Tokyo"},
				{"France", "Paris"}};

		//
		// To convert an array to a Map each array elements must
		// be an array with at least two elements where the first
		// element will be the key and the second element will be
		// the value.
		//
		Map countryCapitals = ArrayUtils.toMap(countries);

		System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));
		System.out.println("Capital of France is " + countryCapitals.get("France"));
	}

}

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