Creating Web Applications from Scratch

Archy is a useful tool I came across which can be used to create blank web applications.

http://code.google.com/p/archy/

This tool becomes extremely handy as it includes all the necessary web.xml configuration and some sample code to start with.

And its very easy to use also. I recommend all starters to use this tool to create their application base.

Maven: See deprecated API usage warnings; commandline

Maven command line option to see the warnings for deprecated code usage.

mvn clean compile -Dmaven.compiler.showDeprecation=true

http://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html

ArrayList ClassCastException

When trying to typecast Object array to the Actual array type, a runtime ClassCastException is thrown.

ArrayList lst = new ArrayList();
lst.add("String 1");
lst.add("String 2");
lst.add("String 3");

String[] strArr = (String[])lst.toArray();


Solution for this is to use the toArray method with argument.

String[] strArr = new String[0];
strArr = (String[]) lst.toArray(strArr);


Time Zones in Java

Here is a complete list of Java TimeZone codes and their details.

Java Timezones Complete List

To get java.util.TimeZone instance for EST, following code can be used.


TimeZone estZone = TimeZone.getTimeZone("America/New_York");


To create a Calendar object with EST Timezone, following code can be used.


Calendar cal = GregorianCalendar.getInstance(TimeZone.getTimeZone("America/New_York"));


Image Resize

Following is sample Java code for reading an Image dimensions and to Resize image while preserving aspect ratio.

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;

import javax.imageio.ImageIO;

public class ImageTest {
  public static void main(String[] args) {
      try {
          System.out.println("Before reading...");
          BufferedImage bi = readImage("D:\\temp\\itsecurity.jpg");
          System.out.println("After reading...");

          printImageProperties(bi);

          BufferedImage scaledBufImg = scaleImageToWidth(bi, 200);

          System.out.println("Writing new img...");
          File modImg = new File("D:\\temp\\itsecurity_mod.jpg");
          ImageIO.write(scaledBufImg, "jpeg", modImg);

      } catch (Exception e) {
          e.printStackTrace();
      }
  }

  public static BufferedImage scaleImageToWidth(BufferedImage bi, int newWidth) throws Exception {
      int iw = bi.getWidth();
      int ih = bi.getHeight();
      // Getting aspect ratio
      double ratio = (double) iw / (double) ih;
      // Calculate new height
      int newheight = (int) (newWidth / ratio);
      System.out.println("Scaling... " + newWidth + " X " + newheight);
   
      // Get Scaled image
      Image scaledImg = bi.getScaledInstance(newWidth, newheight, Image.SCALE_SMOOTH);
   
      // Create new writable Image
      BufferedImage scaledBufImg = new BufferedImage(newWidth, newheight, BufferedImage.TYPE_INT_RGB);
      scaledBufImg.getGraphics().drawImage(scaledImg, 0, 0, null);
      return scaledBufImg;
  }

  public static void printImageProperties(BufferedImage bi) throws Exception {
      System.out.println("Dimensions(WxH):" + bi.getWidth() + " X " + bi.getHeight());
      System.out.println("MinX:" + bi.getMinX() + ", MinY:" + bi.getMinY());
  }

  public static BufferedImage readImage(String path) throws Exception {
      File imageFile = new File(path);
      InputStream is = new FileInputStream(imageFile);
      BufferedImage bi = ImageIO.read(is);
      return bi;
  }

  public static BufferedImage readImage(byte[] bytes) throws Exception {
      ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
      BufferedImage bi = ImageIO.read(bis);
      return bi;
  }
}