Java homework please help! :( - Overclock.net

patrickkkm · 12-19-07

I coded a script, Currently I can add and delete items to the database but I cannot edit the data. Here's my 3 paged script :

Christmasswishlist.java

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;

/**
* Servlet implementation class for Servlet: ChristmasWishlist
*
*/
public class ChristmasWishlist extends javax.servlet.http.HttpServlet implements
javax.servlet.Servlet
{
static final long serialVersionUID = 1L;

/*
* Connect to the database
*/

/*
* (non-Java-doc)
*
* @see javax.servlet.http.HttpServlet#HttpServlet()
*/
public ChristmasWishlist()
{
super();
}

/*
* (non-Java-doc)
*
* @see javax.servlet.http.HttpServlet#doGet(HttpServletRe quest request,
* HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
process(request, response);
}

/*
* (non-Java-doc)
*
* @see javax.servlet.http.HttpServlet#doPost(HttpServletR equest request,
* HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
process(request, response);
}

protected void process(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
out.println("<html><title>List of All Your Wishes</title><body>");

//check if you are getting the right values, comment out once the program is working
//line below will work only for java 5 up
java.util.Enumeration e = request.getParameterNames();
while (e.hasMoreElements())
{
String gift = e.nextElement().toString();
out.println("<br>" + gift + " - " + request.getParameter(gift));
}

if (request.getParameter("submit") != null)
{
if (!request.getParameter("submit").isEmpty())
{
if (request.getParameter("submit").equals("Add"))
{
if (!request.getParameter("gift").isEmpty())
{
out.println(addChristmasWishlist(request
.getParameter("gift")));
}
else
{
out.println("<p>Nothing to do");
}
}

else if(request.getParameter("submit").equals("Delete") )
{
delChristmasWishlist(Integer.parseInt(request.getP arameter("id")));
}
else if(request.getParameter("submit").equals("Delete") )
{
out.println("<p>Nothing to do");
}
}

} else
{
out.println("<p>empty");
}
out.println("<p><a href=wish.html>Add again</a>");

ResultSet rst = null;
try
{
rst = viewChristmasWishlist();
int count = 1;
out.println("<table><tr><th colspan=2>ChristmasWishlist</th></tr>");
while(rst.next())
{
out.println("<tr><td><b>"+count+".</b></td><td>"+rst.getString("gift")+"</td>" +
"<td><a href=ChristmasWishlist?id="+rst.getInt("id")+"&sub mit=Edit>Edit</a.</td>"+
"<td><a href=ChristmasWishlist?id="+rst.getInt("id")+"&sub mit=Delete>Delete</a.</td></tr>");
count++;
}
out.println("</table>");
}
catch(Exception e2)
{

}

out.println("</body></html>");

}

public String addChristmasWishlist(String wish)
{

try
{
ConnectionManager con = new ConnectionManager();
Statement stmt = con.logOn().createStatement();
String msg = "";
String sql = "insert into wishes set gift='" + wish.replaceAll("\'", "\\\'") + "'";
if (stmt.execute(sql))
{
msg = "Insert failed";
}
else
{
msg = "Added successfully";
}
con.logOff();
return msg;

}
catch (SQLException e)
{

return "Add failed. SQL error " + e.getMessage();
}
catch (java.lang.NullPointerException ne)
{

return "<?p>Null error: " + ne.getMessage();
}

}

public String delChristmasWishlist(int id)
{

try
{
ConnectionManager con = new ConnectionManager();
Statement stmt = con.logOn().createStatement();
String msg = "";
String sql = "delete from wishes where id="+id;
if (stmt.execute(sql))
{
msg = "Delete failed";
} else
{
msg = "Delete successfully";
}
con.logOff();
return msg;

} catch (SQLException e)
{

return "Add failed. SQL error " + e.getMessage();
} catch (java.lang.NullPointerException ne)
{

return "<p>Null error: " + ne.getMessage();
}

}

public String editChristmasWishlist(String wish)
{

try
{
ConnectionManager con = new ConnectionManager();
Statement stmt = con.logOn().createStatement();
String msg = "";
String sql = "update from wishes where gift="+wish;
if (stmt.execute(sql))
{
msg = "update failed";
} else
{
msg = "update successfully";
}
con.logOff();
return msg;

} catch (SQLException e)
{

return "Add failed. SQL error " + e.getMessage();
} catch (java.lang.NullPointerException ne)
{

return "<p>Null error: " + ne.getMessage();
}

}

public ResultSet viewChristmasWishlist()
{

ResultSet rst = null;
try
{
ConnectionManager con = new ConnectionManager();
Statement stmt = con.logOn().createStatement();
String msg = "";

String sql = "select * from wishes";
rst = stmt.executeQuery(sql);

} catch (SQLException e)
{

} catch (java.lang.NullPointerException ne)
{

}
return rst;
}

Connectionmanager.java

import java.sql.Connection;
import java.sql.DriverManager;

public class ConnectionManager {

protected Connection con;
protected String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/";
String database = "WishList";
String user = "root";
String password = "";

/** Creates a new instance of ConnectionManager */
public ConnectionManager() {

}
public Connection logOn(){
try {
Class.forName(driver).newInstance();
con = DriverManager.getConnection(url+database,user,pass word);

}
catch(Exception e){
System.out.print(e.getMessage());
}
return con;

}

public void logOff(){
try {
con.close();
}
catch(Exception e){
e.printStackTrace();
}
}

Wish.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Christmas Wishes</title>
</head>
<body>
<h3>Place Your Christmas Wishes Here</h3>
<form action="ChristmasWishlist" method=post>
<table>
<tr><th>Wish:</th><td><input type=text name=gift size=100></td></tr>
<tr><th>Amount:</th><td><input type=text name=amount size=10></td></tr>
<tr><th colspan=2><input type=submit name=submit value="Add"></th></tr>
</table>
</form>
</body>
</html>

xdaseinx · 12-19-07

I took a cursory glance at it thus far, so the following may not be your only issue.

Line: String sql = "update from wishes where gift="+wish;

Update statements do not incorporate a "from"

UPDATE <tableName>
SET <columnName> = <newValue>
WHERE <identityColumnName = <identityValue>

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Java homework please help! :(

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