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Drop down list is causing an error on the jsp page

I was trying to create the drop-down list to delete the booktag value by retrieving the data and using the remove function from the DAO class but it made this error: "java.lang.NumberFormatException: For input string: "isbn13" ". I have found out that the servlet must gain access to the name attribute so I inserted this code int isbn13ID = Integer.parseInt(request.getParameter("booktag"));. But the problem is that eclipse tells me that the variable is unused so I am not sure what else to do for the select tag to gain access to the servlet variable. Here is code:
JSP:
<!-- Header -->
<jsp:include page="header.jsp" />
<!-- JSTL includes -->
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%# taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<%# taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<header>
<div class="container">
<h1>PUBHUB <small>Add Booktag</small></h1>
<hr class="book-primary">
<form action="AddBookTag" method="post" class="form-horizontal">
<div class="form-group">
<label for="isbn13" class="col-sm-4 control-label">ISBN 13</label>
<div class="col-sm-5">
<input type="text" class="form-control" id="isbn13" name="isbn13" placeholder="ISBN 13" required="required" value="${param.isbn13 }" />
</div>
</div>
<div class="form-group">
<label for="nametag" class="col-sm-4 control-label">NameTag</label>
<div class="col-sm-5">
<input type="text" class="form-control" id="nametag" name="nametag" placeholder="NameTag" required="required" value="${param.nametag }" />
</div>
</div>
</form>
</div>
</header>
<section>
<div class="container">
<h1><small>Delete Booktag</small></h1>
<form action="DeleteBookTag" method="post" class="form-horizontal" >
<select name="booktag">
<c:forEach items="${booktags}" var="booktag">
<option value="${booktags.isbn13}">${booktags.isbn13}</option>
<option value="${booktags.nameTag}">${booktags.nameTag}</option>
</c:forEach>
</select>
</form>
</div>
</section>
<!-- Footer -->
<jsp:include page="footer.jsp" />
AddBookTag Servlet:
package examples.pubhub.servlets;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import examples.pubhub.model.BookTag;
import examples.pubhub.dao.BookTagDAO;
import examples.pubhub.utilities.DAOUtilities;
#WebServlet("/AddBookTag")
public class AddBookTagServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.getRequestDispatcher("").forward(request, response);
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//String isbn13 = req.getParameter("isbn13");
BookTagDAO database = DAOUtilities.getBookTagDAO();
BookTag bookTag = new BookTag();
bookTag.setIsbn13(req.getParameter("isbn13"));
bookTag.setNameTag(req.getParameter("nametag"));
boolean isSuccess = database.addNameTag(bookTag);
if(isSuccess){
req.getSession().setAttribute("message", "Book Tag successfully added");
req.getSession().setAttribute("messageClass", "alert-success");
// We use a redirect here instead of a forward, because we don't
// want request data to be saved. Otherwise, when
// a user clicks "refresh", their browser would send the data
// again!
// This would be bad data management, and it
// could result in duplicate rows in a database.
resp.sendRedirect(req.getContextPath() + "/AddBookTag");
}else {
req.getSession().setAttribute("message", "There was a problem publishing the book");
req.getSession().setAttribute("messageClass", "alert-danger");
req.getRequestDispatcher("bookTag.jsp").forward(req, resp);
}
}
}
BookTAG Servlet
package examples.pubhub.servlets;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import examples.pubhub.model.BookTag;
import examples.pubhub.dao.BookTagDAO;
import examples.pubhub.utilities.DAOUtilities;
#WebServlet("/BookTag")
public class BookTagServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//Populates the drop down list
BookTagDAO dao = DAOUtilities.getBookTagDAO();
List<BookTag>tagList = dao.getAllBookTags();
request.getSession().setAttribute("booktags", tagList);
request.getRequestDispatcher("bookTag.jsp").forward(request, response);
}
}
Delete BookTag Servlet
package examples.pubhub.servlets;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import examples.pubhub.model.BookTag;
import examples.pubhub.dao.BookTagDAO;
import examples.pubhub.utilities.DAOUtilities;
#WebServlet("/DeleteBookTag")
public class DeleteBookTagServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
boolean isSuccess = false;
String isbn13 = request.getParameter("isbn13");
String nameTag = request.getParameter("nametag");
BookTag booktag = new BookTag();
booktag.setIsbn13(isbn13);
booktag.setNameTag(nameTag);
BookTagDAO dao = DAOUtilities.getBookTagDAO();
isSuccess = dao.removeNameTag(booktag);
int isbn13ID = Integer.parseInt(request.getParameter("booktag"));
if(isSuccess){
request.getSession().setAttribute("message", "Book successfully deleted");
request.getSession().setAttribute("messageClass", "alert-success");
response.sendRedirect("ViewBookDetails?isbn13=" + isbn13);
}else {
request.getSession().setAttribute("message", "There was a problem deleting this booktag");
request.getSession().setAttribute("messageClass", "alert-danger");
request.getRequestDispatcher("bookTag.jsp").forward(request, response);
}
}
}
BookTag DAO class
package examples.pubhub.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import examples.pubhub.model.BookTag;
import examples.pubhub.model.Book;
import examples.pubhub.utilities.DAOUtilities;
public class BookTagDAOImpl implements BookTagDAO {
Connection connection = null; // Our connection to the database
PreparedStatement stmt = null; // We use prepared statements to help protect against SQL injection
#Override
public List<BookTag>getAllBookTags(){
List<BookTag>bookTags = new ArrayList<>();
try {
connection = DAOUtilities.getConnection(); // Get our database connection from the manager
String sql = "SELECT * FROM book_tag"; // Our SQL query
stmt = connection.prepareStatement(sql); // Creates the prepared statement from the query
ResultSet rs = stmt.executeQuery(); // Queries the database
// So long as the ResultSet actually contains results...
while (rs.next()) {
// We need to populate a Book object with info for each row from our query result
BookTag bookTag = new BookTag();
// Each variable in our Book object maps to a column in a row from our results.
bookTag.setIsbn13(rs.getString("isbn_13"));
bookTag.setNameTag(rs.getString("name_tag"));
// Finally we add it to the list of Book objects returned by this query.
bookTags.add(bookTag);
}
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
// We need to make sure our statements and connections are closed,
// or else we could wind up with a memory leak
closeResources();
}
return bookTags;
}
#Override
public List<BookTag> getNameTagsByBook(String isbn13) {
List<BookTag> booktags = new ArrayList<>();
try {
connection = DAOUtilities.getConnection();
String sql = "SELECT * FROM book_tag WHERE isbn_13 = ?";
stmt = connection.prepareStatement(sql);
stmt.setString(1,isbn13);
ResultSet rs = stmt.executeQuery();
while(rs.next()) {
BookTag booktag = new BookTag();
booktag.setNameTag(rs.getString("name_tag"));
booktag.setIsbn13(rs.getString("isbn_13"));
booktags.add(booktag);
}
}
catch (SQLException e) {
e.printStackTrace();
} finally {
closeResources();
}
return booktags;
}
#Override
public List<Book> getBookByNameTag(String nameTag) {
List<Book> books = new ArrayList<>();
try {
connection = DAOUtilities.getConnection();
String sql = "SELECT * FROM books\r\n"
+ "LEFT JOIN book_tag ON books.isbn_13=book_tag.isbn_13\r\n"
+ "WHERE name_tag = ?";
stmt = connection.prepareStatement(sql);
stmt.setString(1, nameTag);
ResultSet rs = stmt.executeQuery();
while(rs.next()) {
//BookTag booktag = new BookTag();
Book book = new Book();
book.setIsbn13(rs.getString("isbn_13"));
book.setAuthor(rs.getString("author"));
book.setTitle(rs.getString("title"));
book.setPublishDate(rs.getDate("publish_date").toLocalDate());
book.setPrice(rs.getDouble("price"));
book.setContent(rs.getBytes("content"));
books.add(book);
//books.add(book);
}
}
catch (SQLException e) {
e.printStackTrace();
} finally {
closeResources();
}
return books;
}
#Override
public boolean addNameTag(BookTag booktag) {
try {
connection = DAOUtilities.getConnection();
String sql = "INSERT INTO book_tag VALUES (?, ?)"; // Were using a lot of ?'s here...
stmt = connection.prepareStatement(sql);
// But that's okay, we can set them all before we execute
stmt.setString(1, booktag.getNameTag());
stmt.setString(2, booktag.getIsbn13());
// If we were able to add our book to the DB, we want to return true.
// This if statement both executes our query, and looks at the return
// value to determine how many rows were changed
if (stmt.executeUpdate() != 0)
return true;
else
return false;
} catch (SQLException e) {
e.printStackTrace();
return false;
} finally {
closeResources();
}
}
#Override
public boolean removeNameTag(BookTag booktag) {
try {
connection = DAOUtilities.getConnection();
String sql = "DELETE book_tag WHERE name_tag=? AND isbn_13=?";
stmt = connection.prepareStatement(sql);
stmt.setString(1, booktag.getNameTag());
stmt.setString(2, booktag.getIsbn13());
if (stmt.executeUpdate() != 0)
return true;
else
return false;
} catch (SQLException e) {
e.printStackTrace();
return false;
} finally {
closeResources();
}
}
private void closeResources() {
try {
if (stmt != null)
stmt.close();
} catch (SQLException e) {
System.out.println("Could not close statement!");
e.printStackTrace();
}
try {
if (connection != null)
connection.close();
} catch (SQLException e) {
System.out.println("Could not close connection!");
e.printStackTrace();
}
}
}

Your Dao code for deletion seems ill-designed: it should take a single unique identifier for the BookTag to be deleted. You would use that as <option> value in your drop-down list.
Anyway, you can't pass 2 separate values from a <select> in a <form>. If you really need both the name and ISBN13 fields for deletion, then concatenate both in the <option> value attribute, and then split them apart in your DeleteBookTagServlet
JSP
<h1><small>Delete Booktag</small></h1>
<form action="DeleteBookTag" method="post" class="form-horizontal" >
<select name="booktag">
<c:forEach items="${booktags}" var="booktag">
<option value="${booktags.isbn13};<c:out value="${booktags.nameTag}" />">
${booktags.isbn13}
-
<c:out value="${booktags.nameTag}" />
</option>
</c:forEach>
</select>
</form>
DeleteBookTagServlet.java
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
...
final String selectedOption = request.getParameter("booktag");
if (selectedOption == null)
return; //TODO: Manage error
final String[] spl = selectedOption.trim().split("\\s*;\\s*", 2);
if (spl.length < 2)
return; //TODO: Manage error
final String isbn13 = spl[0];
final String nameTag = spl[1];
final BookTag booktag = new BookTag();
booktag.setIsbn13(isbn13);
booktag.setNameTag(nameTag);
//Perform deletion and redirect
...
}

login is not working in my servlet program

I have a MySQL database where I created a userid "mads" and password "mads". I would like to test through a JSP site and servlet if the user exist in the database. I think my code is correct, but I keep getting the wrong exception... that my user is not valid. So I guess my code is not correct :-/
The connection to my database is successful. Without knowing it, then I have a feeling of that my servlet looks at the last column in my database and not the first? I don't know if that have anything to do with it. Can anybody see what it is wrong?
Best Regards
Mads
My JSP page looks like this:
<title>Validation</title>
</head>
<body>
<br><br><br>
<center>
<h1>Please enter user name and password</h1>
<form name="frm" action="LoginValidation" method="post">
<input type="text" name="user">
<input type ="password" name="pass">
<input type="submit" value="Check">
</form>
</center>
</body>
and my Servlet here:
package jsp;
import java.io.*;
//import java.util.*;
import java.sql.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import javax.servlet.*;
#WebServlet(urlPatterns = {"/LoginValidation"})
public class Validation extends HttpServlet {
private static final long serialVersionUID = 1L;
private ServletConfig config;
public void init (ServletConfig config)
throws ServletException{
this.config = config;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException,IOException {
PrintWriter out = response.getWriter();
String connectionURL = "jdbc:mysql://localhost/dblogin";
Connection connection = null;
ResultSet rs;
String userid = new String("");
String password = new String("");
response.setContentType("text/html");
try {
// Load the database driver
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(connectionURL, "root", "");
//Add the data into the database
String sql = "SELECT userid, password FROM login";
Statement s = connection.createStatement();
s.executeQuery(sql);
rs = s.getResultSet();
while(rs.next()) {
userid = rs.getString("userid");
password = rs.getString("password");
}
rs.close();
s.close();
} catch(Exception e) {
System.out.println("Exception is: " + e);
}
if(userid.equals(request.getParameter("userid")) && password.equals(request.getParameter("password"))) {
out.println("The user is valid");
}
else {
out.println("You are not valid");
}
}
}

In this code you are comparing user input values with table's last row'data....write compare code inside the while loop to compare all values....and make redirection if any value match with database values........
package jsp;
import java.io.*;
//import java.util.*;
import java.sql.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import javax.servlet.*;
#WebServlet(urlPatterns = {"/LoginValidation"})
public class Validation extends HttpServlet {
private static final long serialVersionUID = 1L;
private ServletConfig config;
public void init (ServletConfig config)
throws ServletException{
this.config = config;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException,IOException {
PrintWriter out = response.getWriter();
String connectionURL = "jdbc:mysql://localhost/dblogin";
Connection connection = null;
ResultSet rs;
String userid = new String("");
String password = new String("");
response.setContentType("text/html");
try {
// Load the database driver
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(connectionURL, "root", "");
//Add the data into the database
String sql = "SELECT userid, password FROM login";
Statement s = connection.createStatement();
s.executeQuery(sql);
rs = s.getResultSet();
while(rs.next()) {
userid = rs.getString("userid");
password = rs.getString("password");
if(userid.equals(request.getParameter("userid")) && password.equals(request.getParameter("password")))
{
out.println("The user is valid");
//Write exit program code or rediraction code here
}
}
rs.close();
s.close();
} catch(Exception e) {
System.out.println("Exception is: " + e);
}
}
}
//I think it is not efficent way to make login........but i just gave you problem solution in your type login.........

Best way to handle Resultsets and other data fteched from HTML in a servlet

Ok so for our Uni project we are making a website to store information about churches (I know super interesting right -.-).
Basicly it just needs to have church information in a database and when a user clicks or searchs for a church it needs to pull the church information along with user comments from the database.
So far I have a HTML form that delivers a comment to the servlet/database and outputs it using a resultset. I was just wondering what the best method would be for handling multiple information as now that I'm trying to deliver both comments and the church information I'm kinda lost as to how to store it.
Thanks in advance!
Ow and here is my code for reference:
HTML
<form method="get" action="dbtest" id="form1">
<fieldset>
<p>Please enter you're Name:</p>
<input type="text" name="author" size="10" id="name"/><br />
<p>Please enter you're Email here:</p>
<input type="text" name="author_email" size="10" id="email"/><br />
<p>Please enter you're comment here:</p>
<input type="text" name="comment_text" size="10" id="comment"/><br />
<p>
<input type="submit" value="Submit" name="submit_button" />
</p>
</fieldset>
</form>
Servlet
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
*
* #author mxk12ycu
*/
public class dbtest extends HttpServlet {
/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* #param request servlet request
* #param response servlet response
* #throws ServletException if a servlet-specific error occurs
* #throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String authorName = request.getParameter("author");
String authorEmail = request.getParameter("author_email");
String commentText = request.getParameter("comment_text");
try {
//Holding SQL statement
String SQL;
String insertSQL;
//insertSQL = "INSERT INTO comments VALUES('0002')" + authorName + authorEmail + commentText + ("('29 Nov 2012','002')");
//insertSQL = "INSERT INTO comments VALUES (default,'Ryan H','Test#hotmail.com','TestComments','29 Nov 2012','1')";
//insertSQL = "INSERT INTO comments (author, author_email, comment_text, comment_date, church_id) VALUES ('" + authorName + "'," + "'" + authorEmail + "'," + "'" + commentText + "', '29 Nov 2012', '1')";
//insertSQL = "INSERT INTO comments VALUES ('Ryan Holder', 'test#hotmail.com', 'Comment here', '30 Nov 2012', 'default', '1')";
insertSQL = "INSERT INTO comments VALUES (default, " + "'" + authorName + "'," + "'" + authorEmail + "'," + "'" + commentText + "', '29 Nov 2012', '1')";
SQL = "SELECT * FROM churches, comments";
Class.forName("org.postgresql.Driver");
Connection connection = DriverManager.getConnection(
"jdbc:postgresql:ChurchSearch",
"postgres",
"*****");
Statement statement = connection.createStatement();
statement.executeUpdate(insertSQL);
ResultSet resultSet = statement.executeQuery(SQL);
/* TODO output your page here. You may use following sample code. */
out.println("<html>");
out.println("<head>");
out.println("<title>Test Comment Servlet</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Servlet test at " + request.getContextPath() + "</h1>");
out.println("<h2>Comment Form</h2>");
while (resultSet.next()) {
out.println("<p>");
out.println(resultSet.getString("author"));
out.println("</p>");
out.println("<p>");
out.println(resultSet.getString("author_email"));
out.println("</p>");
out.println("<p>");
out.println(resultSet.getString("comment_text"));
out.println("</p>");
}
out.println("</body>");
out.println("</html>");
connection.close();
}
catch (Exception e) {
System.err.println("Error: " + e);
}
finally {
out.close();
}
}

You can to use the MVC pattern. On the other hand, you must be sure to close the connection to the database.
Connection conn = null;
try {
conn = // get connection;
// do database operations
} catch (final SQLException e) {
throw new DAOException(e);
} finally {
if (conn != null) {
try {
conn.close();
} catch (final SQLException ex) {
LOG.warning("message warning to log");
}
}
}
This releases all resources used by the connection.
About MVC, you can find more information in Integrating Servlets and JSP: The Model View Controller (MVC) Architecture. You can also use a framework like Struts, Spring MVC.

Create A DAO(database access objects) class ..Handle connections.
public class DAO {
static private Connection conn = null;
static private String URL = "jdbc:mysql://localhost/<databse name>";
static private String USERNAME = "root";
static private String PASSWORD = "root";
static private String DRIVER = "com.mysql.jdbc.Driver";
private static Connection getConnection() throws ClassNotFoundException,
SQLException {
if (conn == null) {
Class.forName(DRIVER);
System.out.println("Driver Initailizing");
conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
}
return conn;
}
public static ResultSet selectQuery(String query) throws SQLException,
ClassNotFoundException {
//Read the query from the servlet class only SQL query
System.out.println(query);
ResultSet rs = DAO.getConnection().createStatement().executeQuery(query);
//return the result set back to servlet class
return rs;
}
Thanks,
Pavan

Servlets Jsp And Null Pointers

Hi all I have a website where a Lecturer assigns a tutor to a lab, Currently I have a list of tutors where I can click assign and then it takes the user to another page where there is a drop down box and they can select which lab they would like the tutor to teach. It's supposed to submit the id of the lab and the id of the user to the database.
Currently When a user gets the tutor list, they click a link called 'assign' which puts the tutors id up in the url, then they have a list of tutes they can select, once I've selected the tute and click submit I get the following error.
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Unknown Source)
java.lang.Integer.parseInt(Unknown Source)
TutorAssign.doPost(TutorAssign.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
the sendBack method is running but the doPost is not and it's pointing to the line where I get the request parameter as being null - int user_id = Integer.parseInt(request.getParameter("id"));
how can i fix this? I'll include the entirety of my servlet for better clarification
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class TutorAssign
*/
#WebServlet("/TutorAssign")
public class TutorAssign extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
public TutorAssign() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
sendBack(request, response);
}
private void sendBack(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession(true);
//Set data you want to send back to the request (will be forwarded to the page)
//Can set string, int, list, array etc.
int user_id = Integer.parseInt((String)request.getParameter("id"));
String sql = "SELECT l.id,s.name,l.day,l.time,l.room" +
" FROM subject s, lab l " +
" WHERE s.user_id="+(Integer)session.getAttribute("id");
try{
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("got a hj");
System.out.println(session.getAttribute("id"));
Statement stmt = con.createStatement();
ResultSet res = stmt.executeQuery(sql);
System.out.println(res);
ArrayList<String> list1 = new ArrayList<String>();
ArrayList<String> list2 = new ArrayList<String>();
if (res.next()){
do{
list1.add(res.getString(1));
list2.add(res.getString(2)+" "+res.getString(3)+" "+res.getString(4)+" "+res.getString(5));
}while(res.next());
System.out.println("Outside");
String[] arr1 = list1.toArray(new String[list1.size()]);
String[] arr2 = list2.toArray(new String[list2.size()]);
System.out.println(list1);
request.setAttribute("res1", arr1);
request.setAttribute("res2", arr2);
request.setAttribute("user_id", user_id);
}
}catch (SQLException e) {
}
catch (Exception e) {
}
//Decides what page to send the request data to
RequestDispatcher view = request.getRequestDispatcher("TutorAssign.jsp");
//Forward to the page and pass the request and response information
view.forward(request, response);
}
/**
* #see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int user_id = Integer.parseInt((String)request.getParameter("id"));
System.out.println(user_id);
int lab_id = 0;
System.out.println("I got a blow job");
String message = null;
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("got connection");
System.out.println(user_id);
Statement s = con.createStatement();
String sql = "INSERT INTO user_lab" +
" (user_id, lab_id)" +
" VALUES" +
" ('" + user_id + "'," +
" '" + lab_id + "')";
System.out.println(sql);
int i = s.executeUpdate(sql);
if (i==1) {
message = "Successfully assigned a tutor.";
response.sendRedirect("Lecturer_labs");
}
s.close();
con.close();
}
catch (SQLException e) {
message = "Error." + e.toString();
boolean error = true;
}
catch (Exception e) {
message = "Error." + e.toString();
boolean error = true;
}
if (message!=null) {
PrintWriter out = response.getWriter();
out.println("<B>" + message + "</B><BR>");
out.println("<HR><BR>");
}
}
// TODO Auto-generated method stub
}
here is my jsp code
<form name ="TutorAssign" ACTION="TutorAssign" method="post">
<input type="hidden" name="user_id" value="user_id"/>
<select name="lab_id">
<%
for(int i=0; i<list1.length;i++)
{
out.println("<option value="+list1[i]+"> "+list2[i]+" </option>");
} %>
</select>
<input type=SUBMIT value="Submit" name="Submit" />
</form>

It appears that id is not being passed into your servlet when a HTTP POST occurs. You could guard against this by adding a suitable guard statement:
if (request.getParameter("id") == null) {
// handle non existance of id
}
The reason that id is not being passed in is that you don't have any input field in your JSP form to pass in this value. This would look like:
<input type="hidden" name="id" value="your_id_here"/>

The problem is here:
<form name ="TutorAssign" ACTION="TutorAssign" method="post">
<select name="labs">
<%
for(int i=0; i<list1.length;i++)
{
out.println("<option value="+list1[i]+"> "+list2[i]+" </option>");
} %>
</select>
More specifically:
<select name="labs">
If you would either change the name to id OR use request.getParameter("labs"), you will probably get what you want.

Searching from PostgreSQL using Java Servlet. Cannot get any result to show

When I search by Name or Latname, it does not return anything. It returns values only if date of birth is given. Another question is if date of birth is left blank I get
null value in column "birthyear" violates not-null constraint error.
import java.util.*;
import java.sql.*;
import java.io.*;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class searchfromdatabase
*/
public class searchfromdatabase extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* #see HttpServlet#HttpServlet()
*/
public searchfromdatabase() {
super();
// TODO Auto-generated constructor stub
}
/**
* #see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
System.out.println("command: " + request.getParameter("command"));
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
out.println("<html><head>");
out.println("<title>Search form</title></head><body>");
out.println("<h2>Artist details.</h2><tr>");
// HTMl Customer Input
out.println("<form method=\"post\" action =\""
+ request.getContextPath() + "/searchfromdatabase\" >");
out.println("<table border='0' width='300' align='center' bgcolor='#CDFFFF'>");
out.println("<tr><td colspan=2 style='font-size:12pt;color:#00000;' align='center'><h3>Search Artist</h3></td></tr>");
out.println("<tr><td ><b>Artist Name</b></td><td>: <input type='text' name='givenname' id='givenname'></td></tr>");
out.println("<tr><td ><b>Artist Last Name</b></td><td>: <input type='text' name='familyname' id='familyname'></td></tr>");
out.println("<tr><td ><b>Date of Birth</b></td><td>: <input type='text' name='birthyear' id='birthyear'></td></tr>");
out.println("<tr><td colspan=2 align='center'><input type='submit' name='submit' value='Submit'></td></tr></table>");
out.println("</form>");
out.println("</body></html>");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
java.io.PrintWriter out = response.getWriter();
Connection conn = null;{
try {
Class.forName("org.postgresql.Driver");
conn = DriverManager.getConnection(
"jdbc:postgresql://localhost:5432/caglar", "postgres",
"abracadabra");
System.out.println("Connected to the database");
String agent_name = request.getParameter("givenname");
String agent_lastname = request.getParameter("familyname");
String dob = request.getParameter("birthyear");
//if dob is left blank
if (request.getParameter("birthyear").equals("")) {
dob = null;
// otherwise, get the exact number and define it as variable
} else {
dob = request.getParameter("birthyear");
}
//
ArrayList al=null;
ArrayList agent_list =new ArrayList();
//Problem 1: If dob is not given, it is not searching by name or lastname.
String query = "select * from agent where givenname='"+agent_name+"' or familyname='"+agent_lastname+"' or birthyear='"+dob+"' order by givenname";
System.out.println("query" + query);
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery(query);
while(rs.next())
{
al = new ArrayList();
al.add(rs.getString(1));
al.add(rs.getString(2));
al.add(rs.getString(3));
al.add(rs.getString(4));
System.out.println("al :: "+al);
agent_list.add(al);
}
request.setAttribute("agentList",agent_list);
System.out.println("agentList " + agent_list);
// out.println("agent_list " + agent_list);
// HTML results
response.setContentType("text/html");
//java.io.PrintWriter out = response.getWriter();
out.println("<html><head>");
out.println("<title>Final Results</title></head><body>");
out.println("<table width='700px' align='center' style='border:1px solid #000000;'><tr><td colspan=8 align='center' style='background-color:ffeeff'><b>Artist Record</b></td>");
out.println("</tr><tr style='background-color:efefef;'><td><b>Artist ID</b></td><td><b>Date of Birth</b></td><td><b>Artist First Name</b></td><td><b>Artist Last Name</b></td></tr>");
int count=0;
String color = "#F9EBB3";
if(request.getAttribute("agentList")!=null)
{
al=(ArrayList)request.getAttribute("agentList");
Iterator itr = al.iterator();
while(itr.hasNext())
{
if((count%2)==0)
{
color = "#eeffee";
}
else
{
color = "#F9EBB3";
}
count++;
ArrayList agentList = (ArrayList)itr.next();
out.println("<tr style='background-color:"+color+";'>");
out.println("<td>"+agentList.get(0)+"</td>");
out.println("<td>"+agentList.get(1)+"</td>");
out.println("<td>"+agentList.get(2)+"</td>");
out.println("<td>"+agentList.get(3)+"</td></tr>");
}
}
if(count==0)
{
out.println("<tr><td colspan=8 align='center' style='background-color:eeffee'><b>No Record</b></td></tr>");
}
conn.close();
System.out.println("Disconnected from database");
} catch (Exception e) {
e.printStackTrace();
}
out.println("</table></body></html>");
}
}
}

String query = "select * from agent where givenname='"+agent_name+"' or familyname='"+agent_lastname+"' ";
if(dob!=null && !"".equals(dob))
query = query + " or birthyear='"+dob+"'";
query = query+ "order by givenname";
User conditional statement to construct a query.