Get Entered Fields in the Servlet

You can use request.getParameter("field") to get values. If there is no value input, then this method returns null.

But How I can write query to seach the database?

You can use JDBC. What database are you using?

I know how to connect and excute query.. BUT

for example I have this form:

<form method="POST" action="action.do">
      <p>Name: <input type="text" name="name" size="20"></p>
      <p>Email:<input type="text" name="email" size="20"></p>
      <p>Company: <input type="text" name="company" size="20"></p>
      <p>&nbsp;</p>
      <p><input type="submit" value="Submit" name="B1"><input type="reset" value="Reset" name="B2"></p>
</form>

the user may want to search for person whose name is Jane and company is IBM. so he will enter two fields only ..

so in the servlet how I can get the name and company and make my query to search and find all person whose name is jane and company is IBM.

String p1 = request.getParameter("field1");
String p2 = request.getParameter("field2");
String p3 = request.getParameter("field3");
String p4 = request.getParameter("field4");
 
if(field1 == null) ; //report error
string query = "select * from table where field = " + field1;
if(field2 != null) query += " OR field = " + field2;
if(field3 != null) query += " OR field = " + field3;
if(field4 != null) query += " OR field = " + field4;

String p1 = request.getParameter("field1");
String p2 = request.getParameter("field2");
String p3 = request.getParameter("field3");

 
if(field1 == null && field2 == null && field3 == null) ; //report error
string query = "select * from table where ";
boolean first = true;
if(field1 != null) {
if(!first)query += " AND";
first = false;
query += " field1 = '" + field1 + "'";
}

if(field2 != null) {
if(!first)query += " AND";
first = false;
query += " field2 = '" + field2 + "'";
}

if(field3 != null) {
if(!first)query += " AND";
first = false;
query += " field3 = '" + field3 + "'";
}

Why should I report error if field1 is null?

it is optional .. may  he need to search for all person who work in IBM?

Thank u that what I need .. u deserve the points

Or if all are optional:

String f1 = request.getParameter("Field1");
String f2 = request.getParameter("Field2");
String f3 = request.getParameter("Field3");
String f4 = request.getParameter("Field4");

String sql = "";
String sql1 = "";

if (f1 == null && f2 == null && f3==null && f4 ==null)
   sql = "select * from yourtable";
else {
   sql += "where ";
   sql1 = "";
   if (f1 != null)
         sql1 = "field1 = '" + f1 + "'";
   
   if (f2 != null) {
        if ("".equals(sql1))
            sql1 = " field2 = '" + f2 + "'";
        else
             sql1 += " and field2 = '" + f2 + "'";
   }

   if (f3 != null) {
        if ("".equals(sql1))
            sql1 = " field3 = '" + f3 + "'";
        else
             sql1 += " and field3 = '" + f3 + "'";
   }

   if (f4 != null) {
        if ("".equals(sql1))
            sql1 = " field4 = '" + f4 + "'";
        else
             sql1 += " and field4 = '" + f4 + "'";
   }

   sql += sql1;
}

// your query