42 Advanced Java Servlet Tutorial | Different Components of form page

Pubblicato il: 06 febbraio 2018
sul canale di: Programming

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#Advanced Java Servlet Tutorial #Different Components of form page:
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Reading values from different types of form compements of form page being from servlet program:

1) Text box:
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In Servlet Program : String name=request.getParameter("t1");

2) Password Box:
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In Servlet Program : String age=request.getParameter("tage");
int ageVal=Integer.parseInt(age);

3) TextArea:
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In Servlet Program : String addr=request.getParameter("taddrs");

4) Radio Button:
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We always work with multiple radio buttons by grouping them into single unit, for this we take multiple radio buttons having same logical name.

In form page : Gender :

In Servlet Program : String gen=request.getParameter("gender");

Gives 'M' when Male radio button is selected in the form page or gives 'F' when female radio button is selected in form page.

Note:
1) When radio button is selected in form page its label will not come to server as request parameter value but value kept in "value" attribute of that radio button input (value="M") comes to server as request parameter value.

2) Do not take single radio button in form page because once its selected there is no possibility of de-selection.

5) CheckBox:
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We can take single or multiple checkboxes.
We can group multiple checkbox into single unit by having same name, then also we can select or deselect our choice boxes.

Ex 1:
In Form Page:

In Servlet Program:
String marr=request.getParameter("ms");

When checkbox is selected the value "not_single" comes to server as request parameter value.

When check box is not selected no value will come to server as request parameter.

Ex 2:
In Form Page:
Hobbies :

Note : Here multiple checkboxs are grouped into single unit having same logical name as 'ch1'.

In Servlet: String hb[]=request.getParameter("ch1");

If first two checkboxes are selected the hb[] array will holds "reading", "tv" as element values.

Note: When checkbox is selecteed in form page the value kept in "value" attribute of that checkbox related input comes to server as request parameter value.

6) Choice/Combo Box: This component allows us to select only one item at a time.
In Form Page:
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Qualification:
In Servlet Program :
String quali=request.getParameter("qlfy");

Gives "engg" when BE/B.Tech item is selected.

Note: When item of select box is selected, the selected item label will not go to server a request parameter value but the value placed in attribute of option tag of select tag will go to server as request parameter value.

7) ListBox:
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In form page
Note : We can select multiple items from list box by holding "ctrl" key.

In servlet :
String crs[]=req.getParameter("crs");

When first & last items are selected the crs[] contains the java & oracle as element values.

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