Techie Notes

Monday, February 16, 2009

Other Pointers

Weblogic Erroneous Handlers Error - this is caused by the jrockit version of jdk. To get the correct error message, use the Java jdk first. Source: http://ricksolutions.blogspot.hk/2009/03/fixing-erroneous-handlers-error.html
checking tables on db2
command for unzipping war files
Extracting the Contents a JAR File
The basic command to use for extracting the contents of a JAR file is:
```
jar xf jar-file [archived-file(s)] 
```
Let's look at the options and arguments in this command:
- The x option indicates that you want to extract files from the JAR archive.
- The f options indicates that the JAR file from which files are to be extracted is specified on the command line, rather than through stdin.
- The jar-file argument is the filename (or path and filename) of the JAR file from which to extract files.
- archived-file(s) is an optional argument consisting of a space-delimited list of the files to be extracted from the archive. If this argument is not present, the Jar tool will extract all the files in the archive.
character encoding - http://www.joelonsoftware.com/articles/Unicode.html
DB2 Timestamp to java.util.Date or java.sql.Timestamp
- DB2 format = yyyy-MM-dd HH:mm:ss.ZZZZZZ where Z = seconds since previos midnight (00000 - 86400), http://pic.dhe.ibm.com/infocenter/db2luw/v9r7/index.jsp?topic=%2Fcom.ibm.db2.luw.sql.ref.doc%2Fdoc%2Fr0007107.html
- java.sql.Timestamp = yyyy-mm-dd hh:mm:ss.fffffffff where f = nanoseconds
The ZZZZZZ part of DB2 timestamp is insignificant because it is just the total seconds since previos midnight.
To convert to java.util.Date, use
```
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(dateStr)
```
To convert to java.sql.Timestamp, use
```
resultSet.getTimestamp([column name or column index])
```

Ref:
http://technobuz.com/2011/04/run-commands-for-microsoft-applications/

Java Pointers / Links

strength and limitations of for each loop (for( : ))
http://today.java.net/article/2006/11/03/nuances-java-50-each-loop

Loading properties/configurationfiles

Java 5 New Features
http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html
http://java.sun.com/developer/technicalArticles/releases/j2se15/
http://download.oracle.com/javase/1.5.0/docs/guide/language/index.html

Increase Java Performance
http://java.sun.com/developer/technicalArticles/Programming/Performance/

Java Language Best Practices
http://docs.oracle.com/cd/A97688_16/generic.903/bp/java.htm

Code Conventions for the Java Programming Language
http://www.oracle.com/technetwork/java/codeconv-138413.html

ThreadLocal - http://java.dzone.com/articles/java-thread-local-%E2%80%93-how-use

String Concatenation
- use plus operator(+) only if all operands are constants
```
    1) String temp = “alpha” + “beta”;
         '-> String temp = “alphabeta”; (compile time translation)
    2) String temp = x + “beta”;
         '-> String temp = (new StringBuilder()).append(x).append(“beta”).toString();
```
- concat using plus operator uses StringBuilder and String behind the scenes:
```
    “alpha” + “beta” = new StringBuilder(String.toString(“alpha”)).append(“beta”).toString()
```
- use String.concat if concatenating only 2 or few strings
- use StringBuilder(unsynchronized)/StringBuffer(synchronized) for more than 2 strings, specially in a loop
- in a loop, SB is better than concat is better than +
- always initialize SB with initial capacity to greatly improve performance
```
new SB() has 16 char initial capacity by default
```
- best explanation is here: http://www.znetdevelopment.com/blogs/2009/04/06/java-string-concatenation/

character set conversion

String stringToConvert = bmText;
byte[] convertStringToByte = stringToConvert.getBytes("UTF-8");
bmText = new String(convertStringToByte, "ISO-8859-1");
options.add(new SelectOption(bmValue, new String(bmText)));

creating pdf

  public void doHeader() throws Exception {
      Image logoImage = PDFUO.getLogoImage();
      //logoImage.setAbsolutePosition(ReportConstantsIF.ITEXT_POINTS/2, length - ReportConstantsIF.ITEXT_POINTS);
      logoImage.setAlignment(Image.ALIGN_TOP | Image.TEXTWRAP);
    
      Paragraph p = new Paragraph();
      p.add(logoImage);
      p.add(new Phrase("BEAR, STEARNS SECURITIES CORP." + "\n\n", new Font(Font.TIMES_ROMAN, 6, Font.BOLD)));
p.add(new Phrase(
        "ONE METROTECH CENTER NORTH" + "\n" +
  "BROOKLYN, NEW YORK 11201-3859" + "\n" +
  "(212) 272-1000", smallFont));
      p.setLeading(9f);
    
      HeaderFooter header = new HeaderFooter(p, false);
      header.setAlignment(Element.ALIGN_RIGHT);
      header.setBorder(PdfTable.NO_BORDER);

      document.setHeader(header);
  }

JSP Pointers

secure/nonsecure alerts on IE6 & 7

http://www.zorked.com/security/ie-mixed-content-secure-nonsecure-items/

no caching on browsers

  
< META HTTP-EQUIV="Expires" CONTENT="0"> - any # less than 1 means no cache
< META HTTP-EQUIV="Pragma" CONTENT="no-cache"> - for backward compatability
< META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> - for HTTP 1.1 spec

day in Date

function fnGetPrevDayDate(objDate){
 // 1 day = 86400000 ms 
 // var datPrevDate = new Date(objDate.getTime() - 86400000);
 // code above returns incorrect result when time changes from DST to standard time
 
 var datPrevDate = new Date(objDate);
 datPrevDate.setDate(datPrevDate.getDate() - 1);
 return datPrevDate;
}

html:checkbox

how to use indexId on logic:iterate

< logic:iterate id="entityRow" name="<%= DerivativeEntityConstantsIF.SEARCH_RESULT %>" scope="session" offset="<%= String.valueOf(offset)%>" length="<%= String.valueOf(maxLength)%>" indexId="indexNum">
  < html:select name="entityRow" property="linkageClassCode"
onchange='<%= "fnEditValue(this, " + indexNum + ")" %>' >...

html element default values - defaultValue/defaultSelectedd

if (frm["termDeal.accountNo"].value != frm["termDeal.accountNo"].defaultValue) return true;
if (fnIsSelectChanged(frm["termDeal.currency"])) return true;

function fnIsSelectChanged(selectObj) {
  var index = selectObj.selectedIndex;
  var selectedOption = selectObj.options[index];
  if (selectedOption.defaultSelected) return false; 
  return true;
}

use popUpCalendar.js

if (!document.layers){
var startDate = document.getElementById("personalInfoForm.dateOfBirth");
// use showCalendarWithHolidays if you want to show holidays
document.write("<[toRemove]a href='javascript:void(0)' onclick='showCalendarWithHolidays(this, startDate, \"mm-dd-yyyy\",null,1,-1,-1, true)'><[toRemove]img src='' border='0'/>");
}

regex of replace

.value.replace(/_|-/g, '')  --> replace _ and - with empty str

use of sessionScope

CL.isNewClient = ${sessionScope[ClientConstants.IS_NEW_CLIENT]} --> do not put semi colon at end (not sure if for AMS only)

The class Object's clone method only performs a shallow copy. This means that it creates a new instance of the object but the fields of both the new and original object end up referencing the same objects because only the reference of the fields is copied to the new object. To make deep copies of an object, we can use this class:


import java.io.IOException;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;

/**
 * Utility for making deep copies (vs. clone()'s shallow copies) of
 * objects. Objects are first serialized and then deserialized. Error
 * checking is fairly minimal in this implementation. If an object is
 * encountered that cannot be serialized (or that references an object
 * that cannot be serialized) an error is printed to System.err and
 * null is returned. Depending on your specific application, it might
 * make more sense to have copy(...) re-throw the exception.
 *
 * A later version of this class includes some minor optimizations.
 */
public class ObjectCloner {

    // so that nobody can accidentally create an ObjectCloner object
    private ObjectCloner() {
    }

    /**
     * Returns a copy of the object, or null if the object cannot
     * be serialized.
     */
    public static Object deepCopy(Object orig) {
        Object obj = null;
        try {
            // Write the object out to a byte array
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream out = new ObjectOutputStream(bos);
            out.writeObject(orig);
            out.flush();
            out.close();

            // Make an input stream from the byte array and read
            // a copy of the object back in.
            ObjectInputStream in = new ObjectInputStream(
                new ByteArrayInputStream(bos.toByteArray()));
            obj = in.readObject();
        }
        catch(IOException e) {
            e.printStackTrace();
        }
        catch(ClassNotFoundException cnfe) {
            cnfe.printStackTrace();
        }
        return obj;
    }
}

Sample call: Object clone = ObjectCloner.deepCopy(oldObject);
A more optimized version can be found here: http://javatechniques.com/blog/faster-deep-copies-of-java-objects/

Wednesday, February 11, 2009

NYAOS (NYACUS,NYADOS,NYAOS-II)

- Nihongo Yet Another Open Shell
- an enhanced commandline shell for Windows,DOS,OS/2
- advantages include filename autocomplete, built-in color, history, etc.
- support and downloads: http://nyaos.org/

1) Download and unzip
2) create env.bat with:
set MAVEN_HOME=S:\commons\apache-maven-2.0.10
set ANT_HOME=S:\commons\apache-ant-1.7.0
set JAVA_HOME=R:\commons\bea\jrockit_150_15
set path=%JAVA_HOME%\bin\;%MAVEN_HOME%\bin;%ANT_HOME%\bin;%PATH%;S:\commons\scripts;D:\Program Files\Rational\clearcase\ClearCase\bin;s:\commons\firefox
mvn -version
3) use nyacus as your cmd with the env properties by creating mycmd.bat with:
nyacus -r env.bat (means that you are loading the script file env.bat instead of _nya)
4) can start other apps by creating start command like eclipse.bat:
set path=R:\commons\bea\jrockit_150_15\bin\;%PATH%;
cmd /C start R:\commons\eclipse -data R:\bel\workspace\workspace33 -vmargs -Xms40m -Xmx512m -XX:MaxPermSize=256m
5) launch mycmd.bat
6) start other apps by calling filename of .cmd

Monday, January 5, 2009

Understanding Web Service

Web Service

- a software system designed to support interoperable machine-to-machine interaction over a network.
- makes software functionality available over the Internet so that programs like PHP, ASP, JSP, JavaBeans, the COM object, and all our other favorite widgets can make a request to a program running on another server (a web service) and use that program’s response in a website, WAP service, or other application.
- describes a standardized way of integrating Web-based applications using the XML, SOAP, WSDL and UDDI open standards over an Internet protocol backbone.

2 Types of Web Service

SOAP (Simple Object Access Protocol)
- a lightweight XML-based messaging protocol used to encode the information in Web service request and response messages before sending them over a network.
- SOAP messages are formatted in XML and are typically sent using HTTP but can be also transported using a variety of Internet protocols, including SMTP and MIME.
- older type, successor of XML-RPC
- uses JAX-WS specification
REST
- is simpler and more light weighted than SOAP
- can send and receive data as JSON, XML or even plain text
- uses JAX-RS specification

Related Terms

XML (Extensible Markup Language)
- a general-purpose specification for creating custom markup languages developed by the W3C.
- is a markup language much like HTML. A markup language is a mechanism to identify structures in a document.
- allows designers to create their own customized tags, enabling the definition, transmission, validation, and interpretation of data between applications and between organizations.

WSDL (Web Services Description Language)
- an XML-formatted language used to describe a Web service's capabilities as collections of communication endpoints capable of exchanging messages. WSDL is the language that UDDI uses, developed jointly by Microsoft and IBM.
- describes the interface of Web services

UDDI (Universal Description, Discovery and Integration)
- it is a Web-based distributed directory that enables businesses to list themselves on the Internet and discover each other, similar to a traditional phone book's yellow and white pages.

SEI (Service Endpoint Interface)
- is a Java interface class that defines the methods to be exposed as a Web service
- coverts the web service call including the (Java, C++, etc.) objects to a SOAP message

Protocol
- is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two.

References:
http://www.alistapart.com/articles/webservices
http://en.wikipedia.org
http://www.webopedia.com/TERM/W/Web_services.html
http://www.webopedia.com/DidYouKnow/Computer_Science/2005/web_services.asp
http://www.ibm.com/developerworks/library/ws-intwsdl
http://www.ibm.com/developerworks/library/ws-intwsdl2

Wednesday, August 20, 2008

Tutorial Links

J2EE 1.3 tutorial
http://java.sun.com/j2ee/tutorial/1_3-fcs/index.html

Java Tutorial
http://java.sun.com/docs/books/tutorial/

DWR
http://directwebremoting.org/dwr/getstarted

Java Generics
http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf

Spring Overview
http://www.theserverside.com/tt/articles/article.tss?l=SpringFramework

Spring MVC step by step tutorial
http://static.springframework.org/docs/Spring-MVC-step-by-step/

ExtJS 2.0
http://extjs.com/learn/Tutorial:Introduction_to_Ext_2.0

WSDL
http://www.w3.org/TR/wsdl

Apache Tomcat
http://tomcat.apache.org/

Java Itext Tables
http://tutorials.jenkov.com/java-itext/table.html