Buenos videos de Uncle Bob (Robert Martin, autor de Clean Code)

http://www.objectmentor.com/videos/video_index.html

Exceptions de jetty para retornar http status codes

Usando jetty, puedes arrojar un status code, con mensaje incluido, de la sgte manera:

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
  throws ServletException, IOException {
 throw new HttpException(404, "not found jeje");
}

Wrap your Exception as a RuntimeException when it is not of your method's business

A method is not required to declare in its throws clause any subclasses of RuntimeException that might be thrown during the execution of the method but not caught.

package exceptions;

public class RuntimeExceptionTest {

 public class TestException extends Exception {
  
 }
 
 public static void main(String[] args) {
  RuntimeExceptionTest test = new RuntimeExceptionTest();
  try {
   test.throwWrappedTestExceptionAsRuntimeException();
  } catch (Exception e) {
   System.out.println("exception catched:\n");
   e.printStackTrace();
  }
 }

 private void throwTestException() throws TestException {
  throw new TestException();
 }
 
 
 public void throwWrappedTestExceptionAsRuntimeException() {
  try {
   throwTestException();
  } catch (TestException e) {
   throw new RuntimeException(e);
  }
 }
}

Notification rather than logging

¿Te ha pasado que el log ensucia?:

Location location = tracker.getCurrentLocation();
for (Filter filter : filters) {
 filter. selectFor(location);
 if (logger. isInfoEnabled()) {
   logger. info("Filter " + filter.getName() + ", " + filter.getDate()
                + " selected for " + location.getName()
                + ", is current: " + tracker.isCurrent(location));
 }
}

Solución:

Location location = tracker.getCurrentLocation();
for (Filter filter : filters) {
 filter. selectFor(location);
 support.notifyFiltering(tracker, location, filter);
}

Otros beneficios:

• Mientras programas, no te preocupas de escribir un string concatenando objetos, déjalo para el final.
• El traspaso del software al área de soporte de tu empresa se complementará dándoles la clase Support, en ella están todos los monitoreos o alarmas que deben capturar.
• No debes inicializar un Logger de log4j en cada clase que creas (sino sólo en caso de que quieras hacer un log.debug mientras programas)
• Los logs dejan de ser un string que se escribe "a la rápida", pues deben ser pensados realmente como solución a un requerimiento implícito del departamento de operaciones de tu empresa.
• En cada método de support no sólo puedes poner un logger en disco, sino también un registro en BD o cualquier otra cosa, usa la encapsulación.

Ref:

• Growing Object-Oriented Software, Guided by Tests

• By: Steve Freeman; Nat Pryce

Cómo convertir encoding en java tipo iconv, ej: UTF-8 a latin1

import org.apache.commons.io.IOUtils;

public class Iconv {

 public static void iconv(InputStream in, OutputStream out, Charset inCharset, Charset outCharset) throws IOException {
  InputStreamReader reader = new InputStreamReader(in,inCharset);
  OutputStreamWriter writer = new OutputStreamWriter(out,outCharset);
  IOUtils.copy(reader,writer);
  writer.close();
 }

Cómo se usa:

 public static void main(String[] args) throws Exception {
  utf8ToLatin1();
  latin1ToUtf8();
 }

 private static void latin1ToUtf8() throws Exception  {
  FileInputStream in = new FileInputStream("/home/pablo/Desktop/workspace/test/files/textoLatin1.txt");
  FileOutputStream out = new FileOutputStream("/tmp/textoLatin1ToUTF8.txt");
  iconv(in, out, Charset.forName("latin1"), Charset.forName("UTF-8"));
  out.close();
 }

 private static void utf8ToLatin1() throws Exception {
  FileInputStream in = new FileInputStream("/home/pablo/Desktop/workspace/test/files/textoUTF8.txt");
  FileOutputStream out = new FileOutputStream("/tmp/textoUTF8ToLatin1.txt");
  iconv(in, out, Charset.forName("UTF-8"), Charset.forName("latin1"));
  out.close();
 }

Entrada:

pablo@pablo-desktop:~/Desktop/workspace/test/files$ file --mime texto*
textoLatin1.txt: text/plain; charset=iso-8859-1
textoUTF8.txt:   text/plain; charset=utf-8

Resultado:

pablo@pablo-desktop:~/Desktop/workspace/test/files$ file --mime /tmp/texto*
/tmp/textoLatin1ToUTF8.txt: text/plain; charset=utf-8
/tmp/textoUTF8ToLatin1.txt: text/plain; charset=iso-8859-1

Cómo ver el contenido de un jar para saber donde esta una clase que se deba incluir

pablo@pablo-desktop:~/bea/user_projects/workspaces/workSpaceStudio/TimerService$ jar -tf /home/pablo/bea/wlserver_10.0/server/lib/weblogic.jar | grep ApplicationException

com/sun/java/xml/ns/javaee/ApplicationExceptionType$1.class

com/sun/java/xml/ns/javaee/ApplicationExceptionType$Factory.class

com/sun/java/xml/ns/javaee/ApplicationExceptionType.class

com/sun/java/xml/ns/javaee/impl/ApplicationExceptionTypeImpl.class

schemacom_bea_xml/javaname/com/sun/java/xml/ns/javaee/ApplicationExceptionType.xsb

weblogic/application/ApplicationException.class

weblogic/j2ee/descriptor/ApplicationExceptionBean.class

weblogic/j2ee/descriptor/ApplicationExceptionBeanImpl$Helper.class

weblogic/j2ee/descriptor/ApplicationExceptionBeanImpl$SchemaHelper.class

weblogic/j2ee/descriptor/ApplicationExceptionBeanImpl$SchemaHelper2.class

weblogic/j2ee/descriptor/ApplicationExceptionBeanImpl.class

weblogic/j2ee/descriptor/ApplicationExceptionBeanImplBeanInfo.class

weblogic/management/ApplicationException.class

pablo@pablo-desktop:~/bea/user_projects/workspaces/workSpaceStudio/TimerService$

Difference between XML and HTML encoding

Ref: http://en.wikipedia.org/wiki/Character_encodings_in_HTML#XML_character_references