Custom Tag - Beginning Java with WebSphere - page 391

Now when five states need to be added, the programmer must enter five if/else statements and ten start and
end OPTION tags. That's a lot of typing and, of course, this means mistakes can easily be made. To cut down on the
amount of “hard-coded” HTML, a String array will hold the state values and a for loop will:

1. Read each value in the array

2. Check if the array value is the selected value

Build the appropriate OPTION tags.

3.

Tutorial: Using an Array
Now let's use an array

In TNTStateDDM, add the following statements to create a class String array variable
called stateArray that has the following three values.

1.

String[] stateArray = {"FL", "GA", "OK"};
Notice that no size was specified for the array. An array can be assigned values, and the JVM will create an array
of the needed size - in this case three.

In TNTStateDDM, add the following statements to create class StringBuffer variables to
hold various “pieces” of the OPTION tags.

2.

StringBuffer optionTagStart = new StringBuffer("<OPTION value=\"");
StringBuffer optionSelected = new StringBuffer("\" selected>");
StringBuffer optionNotSelected = new StringBuffer("\">");
StringBuffer optionTagEnd = new StringBuffer("</OPTION>");
StringBuffer optionTags = new StringBuffer();
Because the HTML to define each option will be constantly changing in the loop, defining optionTags as a
StringBuffer is a more computer-efficient choice than defining it as a String . However, because only Strings can be
embedded into the JSP, we will need to convert the StringBuffer to a String t hereby adding a little extra code.
Notice that when a state is to be selected, only the start tag is different from a non-selected state. In other words,
the end tag never changes. Looking closer at the start tags, notice that non-selected and selected OPTION tags actually
begin the same. The difference is the characters that follow the value attribute in the start tag. If a value is not selected,
then the value in the start tag is simply followed by a double quote and a greater than sign. If the value is selected,
then it is followed by a double quote, a space, the keyword selected , and then the greater than sign. So, two strings
(optionSelected and optionNotSelected) were created to hold these two possible sets of characters.

3. In the doStartTag, between the two write statements, insert the following statements

for ( int ctr = 0; ctr < stateArray.length; ctr++) {
optionTags.append(optionTagStart).append(stateArray[ctr]);
if (stateArray[ctr] == this .selected) {
optionTags.append(optionSelected);
} else {
optionTags.append(optionNotSelected);
}
optionTags.append(stateArray[ctr]).append(optionTagEnd);
pageContext.getOut().write(String. valueOf (optionTags));
optionTags.delete(0,optionTags.length());
}