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A href command not working

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posted 19 years ago

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i have a text box and a submit button. once a user enters the name and click on the submit button that user info is displayed in the table which is firstname, lastname, username and password. Now in that table i have a link to deleteservlet by the name of delete and updateservlet by the name of update. For some reason my update and delete is not showing in the table any idea?.

this statement is not executing. Thanks for any help.

package testing;
 
import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
 
/**
 * Servlet implementation class for Servlet: SearchServlet
 *
 */
 public class SearchServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
 
  private String keyword = "";
 
public SearchServlet() {
super();
}   
public void init() {
    try {
      Class.forName("org.apache.derby.jdbc.ClientDriver");
      System.out.println("JDBC driver loaded");
    }
    catch (ClassNotFoundException e) {
      System.out.println(e.toString());
    }
  }
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
sendPageHeader(response);
    sendSearchForm(response);
    sendPageFooter(response);
}

/* (non-Java-doc)
 * @see javax.servlet.http.HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
keyword = request.getParameter("keyword");
    sendPageHeader(response);
    sendSearchForm(response);
    sendSearchResult(response);
    sendPageFooter(response);
}

void sendSearchResult(HttpServletResponse response)
    throws IOException {
    PrintWriter out = response.getWriter();
    try {
      Connection con = DriverManager.getConnection("jdbc :mrgreen: erby://localhost:1527/sample");
      System.out.println("got connection");
 
      Statement s = con.createStatement();
 
      out.println("<TABLE>");
      out.println("<TR>");
      out.println("<TH>First Name</TH>");
      out.println("<TH>Last Name</TH>");
      out.println("<TH>User Name</TH>");
      out.println("<TH>Password</TH>");
      out.println("</TR>");
      String sql = "SELECT FirstName, LastName, UserName, Password" +
        " FROM USERS.posts" +
        " WHERE FirstName LIKE '%" + fixSqlFieldValue(keyword) + "%'" +
        " OR LastName LIKE '%" +fixSqlFieldValue(keyword) + "%'";
      ResultSet rs = s.executeQuery(sql);
      while (rs.next()) {
      String id = rs.getString(1);
        out.println("<TR>");
        out.println("<TD>" + encodeHtmlTag(rs.getString(2)) + "</TD>");
        out.println("<TD>" + encodeHtmlTag(rs.getString(3)) + "</TD>");
        out.println("<TD>" + encodeHtmlTag(rs.getString(4)) + "</TD>");
        out.println("<TD>" + encodeHtmlTag(rs.getString(5)) + "</TD>");
        out.println("<TD><A HREF=DeleteServlet?id=" + id + ">Delete</A></TD>"); 
        out.println("<TD><A HREF=UpdateServlet?id=" + id + ">Update</A></TD>");
        out.println("</TR>");
      }
      s.close();
      con.close();
    }
    catch (SQLException e) {
    }
    catch (Exception e) {
    }
    out.println("</TABLE>");
  }
 
  /**
   * Send the HTML page header, including the title
   * and the <BODY> tag
   */
  private void sendPageHeader(HttpServletResponse response)
    throws ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println("<HTML>");
    out.println("<HEAD>");
    out.println("<TITLE>Displaying Selected Record(s)</TITLE>");
    out.println("</HEAD>");
    out.println("<BODY>");
    out.println("<CENTER>");
  }
 
  /**
   * Send the HTML page footer, i.e. the </BODY>
   * and the </HTML>
   */
  private void sendPageFooter(HttpServletResponse response)
    throws ServletException, IOException {
    PrintWriter out = response.getWriter();
    out.println("</CENTER>");
    out.println("</BODY>");
    out.println("</HTML>");
  }
 
  /**Send the form where the user can type in
   * the details for a new user
   */
  private void sendSearchForm(HttpServletResponse response)
    throws IOException {
 
    PrintWriter out = response.getWriter();
    out.println("<BR><H2>Search Form</H2>");
    out.println("<BR>Please enter the first name, last name or part of any.");
    out.println("<BR>");
    out.println("<BR><FORM METHOD=POST>");
    out.print("Name: <INPUT TYPE=TEXT Name=keyword");
  //  out.println(" VALUE=\"" + encodeHtmlTag(keyword) + "\"");
    out.println(">");
    out.println("<INPUT TYPE=SUBMIT>");
    out.println("</FORM>");
    out.println("<BR>");
    out.println("<BR>");
  }
  
  public static String encodeHtmlTag(String tag) {
    if (tag==null)
      return null;
    int length = tag.length();
    StringBuffer encodedTag = new StringBuffer(2 * length);
    for (int i=0; i<length; i++) {
      char c = tag.charAt(i);
      if (c=='<')
        encodedTag.append("<");
      else if (c=='>')
        encodedTag.append(">");
      else if (c=='&')
        encodedTag.append("&");
      else if (c=='"')
        encodedTag.append(""");  //when trying to output text as tag's value as in
        // values="???".
      else if (c==' ')
        encodedTag.append(" ");
      else
        encodedTag.append(c);
 
    }
    return encodedTag.toString();
  }
  
  public static String fixSqlFieldValue(String value) {
    if (value==null)
      return null;
    int length = value.length();
    StringBuffer fixedValue = new StringBuffer((int) (length * 1.1));
 
    for (int i=0; i<length; i++) {
      char c = value.charAt(i);
      if (c=='\'')
        fixedValue.append("''");
      else
        fixedValue.append(c);
    }
    return fixedValue.toString();
  }

}

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Baseet Ahmed

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posted 19 years ago

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Hi,

Can you tell us what error message are you getting(stack trace of error)
while running your application.

***********************************
Tip: Modesty is all virtue.
***********************************

Suleman zia

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posted 19 years ago

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No there is no error. My page is running good in tomcat. I can enter a name in the textbox and click on submit button and that person information is displayed in the table. The only problem i am having is that i cannot see the links for update and delete right beside the information of the user in the table. so then if a user wants to click on update it should go to my updateservlet page and a form is displayed, same thing goes for deleteServlet also.

My <A href> thing is not working. Since the id is a primary key and auto incremented i would like to show the id number also when a user clicks on delete or update.

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David O'Meara

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posted 19 years ago

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does the code show up when you view the source for the page?

Suleman zia

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posted 19 years ago

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Sorry Sherrif. what do you mean by the code show up?

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Suleman zia

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oh you mean when i do the view source for my searchservlet page?

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Ulf Dittmer

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posted 19 years ago

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This may or may not have anything to do with the problem, but this:

catch (SQLException e) {
}
catch (Exception e) {
}

is not a good idea. How will you ever know that there was a problem?

What does the HTML look like that gets generated?

Suleman zia

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posted 19 years ago

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this is when i load my searchservlet page

and this is how it looks like when the information is displayed.

But there is no error. i was just trying to create a url beside the information table for each user so he have an option to update or delete. But for some reason its not showing. i think the problem is in this statement. i need to have variable id in order to recognize which id was deleted from my database.

[code]

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Rajnish Ojha

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posted 19 years ago

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Hi Suleman

There is no error in your code except in a method

public static String encodeHtmlTag(String tag) {       
        if (tag==null)       
            return null;      
        int length = tag.length();     
        StringBuffer encodedTag = new StringBuffer(2 * length);    
        for (int i=0; i<length; i++) {        
            char c = tag.charAt(i);        
            if (c=='<')           
                encodedTag.append("<");       
            else if (c=='>')         
                encodedTag.append(">");      
            else if (c=='&')          
                encodedTag.append("&");       
            else if (c=='"')     
                //ERROR :  encodedTag.append("""); 
                encodedTag.append("\"");  
            //when trying to output text as tag's value as in          
            // values="???".          
            else if (c==' ')          
                encodedTag.append(" ");       
            else          
                encodedTag.append(c);       
            }       
        return encodedTag.toString();     
        }

indicated by ERROR: .And it working fine with satisfying your requirement.

Herman Schelti

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posted 19 years ago

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hi Suleman,

Hope this helps, look at your code:
String id = rs.getString(1); //gets FirstName
String id = rs.getString(2); //gets LastName
String id = rs.getString(3); //gets UserName
String id = rs.getString(4); //gets Password
String id = rs.getString(5); //gets ??

I think your last line will throw SQLException, but you swallow those (don't do that).
So better remove that line.

Herman
PS Your servlet is all in one: model, view and controller.
That's usually considered as bad, hard to test etc.

Suleman zia

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posted 19 years ago

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rangish my method for encodedhtml is running fine. i have tested in other applications also.

Herman hmmmm. Ok for instance in my sql i have a table by the name of USERS.posts which contains

There is a specific id for each user. in my URL for deleteservlet i would like to pass ID numebr also, so we know which user was deleted. now if i do this

Now it does not display any information + does not display the links also.

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Suleman zia

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posted 19 years ago

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Now if i remove my String = id; and do this

it works fine. perfect no problem. so now my question is when a user clicks on delete it is suppose to delete the requested information. with no variable id how can i do that? this is my deleteservlet

package testing;
 
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
 
public class DeleteServlet extends HttpServlet {
  /**Process the HTTP Get request*/
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException {
    int recordAffected = 0;
    try {
      String id = request.getParameter("id");
      String sql = "DELETE FROM USERS.posts WHERE Id=" + id;
      Connection con =
        DriverManager.getConnection("jdbc :mrgreen: erby://localhost:1527/sample");
 
      Statement s = con.createStatement();
      recordAffected = s.executeUpdate(sql);
      s.close();
      con.close();
    }
    catch (SQLException e) {
    }
    catch (Exception e) {
    }
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println("<HTML>");
    out.println("<HEAD>");
    out.println("<TITLE>Deleting A Record</TITLE>");
    out.println("</HEAD>");
    out.println("<BODY>");
    out.println("<CENTER>");
    if (recordAffected==1)
      out.println("<P>Record deleted.</P>");
    else
      out.println("<P>Error deleting record.</P>");
    out.println("<A HREF=SearchServlet>Go back</A> to the Search page");
  }
}

Thanks for the help

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Suleman zia

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posted 19 years ago

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ID seems perfect so for the time being just to make the program work i updated my sql to delete the record based on the first name of the user.

Sorry i am new to sql. but it still displays me the else statement part which says "error in details" and this is what i see on my url when i click on delete

http://localhost:8080/chapter4/DeleteServlet?firstName=

That means firstName is null. if its null then no record will be deleted. hope i make sense. sorry

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Ulf Dittmer

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posted 19 years ago

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You're still ignoring exceptions.

Herman Schelti

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posted 19 years ago

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hi there,

-sql-parameters start at 1 ("rs.getString(0)" won't work), but since you swallow your sql-exceptions, you won't know (like Ulf said).

-rs.getString(2) will retrieve the 2nd column in your sql-statement
(which maybe the same column as in your table, but that depends on your sql-statement)

-try this:

and

Herman

Suleman zia

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posted 19 years ago

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ok thanks herman. i figured that post_id part earlier. Now everything works fine except when i click on delete my else statement always executes in deleteservlet.

package testing;
 
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
 
public class DeleteServlet extends HttpServlet {
  /**Process the HTTP Get request*/
  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException {
    int recordAffected = 0;
    try {
      String id = request.getParameter("id");
      String sql = "DELETE FROM USERS.posts WHERE post_id = '" + id + "'";
     // String sql = "DELETE FROM Users WHERE Id=" + id;
      Connection con =
        DriverManager.getConnection("jdbc :mrgreen: erby://localhost:1527/sample");
 
      Statement s = con.createStatement();
      System.out.println(sql);
      recordAffected = s.executeUpdate(sql);
      s.close();
      con.close();
    }
    catch (SQLException e) {
    System.out.println(e.getMessage());
    }
    catch (Exception e) {
     System.out.println(e.getMessage());
    }
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println("<HTML>");
    out.println("<HEAD>");
    out.println("<TITLE>Deleting A Record</TITLE>");
    out.println("</HEAD>");
    out.println("<BODY>");
    out.println("<CENTER>");
    if (recordAffected==1)
      out.println("<P>Record deleted.</P>");
    else
      out.println("<P>Error deleting record.</P>");
    out.println("<A HREF=SearchServlet>Go back</A> to the Search page");
  }
}

if i use this statement

the stack trace prints

Now if i do this

i get this

my sql statement looks fine.

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Ulf Dittmer

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posted 19 years ago

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In both examples you show it looks as if the value of 'id' is empty.

Suleman zia

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yes exactly bartender. but i printed the post_id on my searchpage, so i can see all the id, username, firstname, lastname and password. for some reason when i pass that id to my deletservlet page it seems like id was never read or id was empty when it was passed to deleteservlet.

I debugged it for a long time still not successful. i think i can do this by having the option of deleting by the user firstName but still its not relevant and not a good idea to delete through the firstname, who knows there might be bunch of people with the same firstName.

Any ideas ?

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Ulf Dittmer

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posted 19 years ago

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yes exactly bartender.

My name is Ulf.

I'd suggest to make sure that the correct id is submitted by the browser (using a tool like the LiveHTTPHeaders Firefox extension), and that it gets to the server (by looking at the access logs).

Suleman zia

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Well sorry. i am learning servlets and i am new to it. So will definitely check the documentation on livehttp.

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