Re: soooo many questions!

soldier.coder wrote:
Hello kind professional java programmers!

I am a former soldier trying to re-establish himself in the civilian
world and I have so many questions. First of all, what does it really
take to create a java bean that does anything? A friend of mine who
is exploring servlets was very shocked to discover how much work it
takes to create a dropdown HTML menu in Java, so I thought I would
have a go at it.

I thought my javabean should have properties for the:
name of the HTML dropdown menu,
a default <option> tag (to handle when user selects nothing),
a size,
and an SQL statement that when executed would yield 2 columns, the
first being the non-zero id of the row we got from the
database(for the "value" part of an option tag), and the second column
being the displayed part of the
option tag.

Anyway, I haven not handled getting the data from database yet, but
what else must i do or include to make it a bean, and how then would I
use it for a bean inside a JSP page?

/
*******************************************************************************************************************
*
* DropDownHTML
*
* This code creates a serializable object (that might someday
become a Java Bean) that, given an SQL statement,
* and a connection to the appropriate database, will produce a
dropdown menu in HTML, as a string via the toString
* method.
*******************************************************************************************************************/


import java.io.*; // we will support serialization


public class DropDownHTML implements Serializable
{
private String SqlStatement; // SQL for 2 columns: first column is
value part, second column is display part
private String Name; // html name for the the drop down menu
private String HandleNoChoice; // if they choose nothing, this will
be displayed -- always has 0 value
private int Size; // size of the display in rows, not the
number of actual rows
private boolean SelectMoreThanOne; // can user choose more than one?
transient int nRows;

public DropDownHTML()
{
this.SqlStatement = new String("select * from categories");
this.Name = new String("example_drop_down");
this.HandleNoChoice = new String("<option selected value=\"0\">No
selection has been choosen</option>");
this.Size = 4;
this.SelectMoreThanOne = false;
}

public DropDownHTML(String mySQLStatement,String myDropDownName, int
size,boolean single )
{
this.SqlStatement = new String(mySQLStatement);
this.Name = new String(myDropDownName);
this.HandleNoChoice = new String("<option selected value=\"0\">No
selection has been choosen</option>");
this.Size = size;
this.SelectMoreThanOne = single;
}

public String toString()
{
String selectMoreThanOne = new String ((this.SelectMoreThanOne) ?
"MULTIPLE " : "SINGLE ");

String selectHTML = new String("<SELECT ") + selectMoreThanOne +
"SIZE=\'" + this.Size + "\' name=\'" + this.Name + "\'>";
String endSelectHTML = new String("</SELECT>");
return selectHTML + endSelectHTML;
}

}

Hi Soldier

it seems like you've got the wrong approach on what Java can do for you in terms of Web Application.

What you're producing in your code is almost not maintainable and secondly it should rather be part of a servlet than a bean. Have a look in the internet what you can find about MVC (Model, View, Controller). There are some very good frameworks out there (JSF, Struts etc) that will help you create HTML content without having to struggle putting and assembling html strings together.

The fundamentals of MVC is actually to separate the View (JSP) from the Model (Data) and the Logic (Controller). What again means that your Controller will access - through JAVA - the Data on the one side and provide it to the View (JSP)on the other side.

In this context the mentioned JavaBeans will be used to translate as example the data from a database to a Java Object. Which again will be used in the JSP to display the data.

The separation makes pretty much sense since we also reached the age of web 2.0. Per se, the age of designing pages completely with CSS (Cascaded Style Sheets). Imagine a project where the designer doesn't need to be aware of any programing language, and on the counter part the developer doesn't need to know anything about design. While again the DB administrator doesn't need to be an expert in either of the previous mentioned skills... That's what MVC is for...

Wish you a lot of success re-establishing yourself as a developer...

Vince

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