HTTP Status 500 - An exception occurred processing JSP page /home/index.jsp at line 54

Question

I am having trouble with this exception:

type Exception report

message An exception occurred processing JSP page /home/index.jsp at line 54

description The server encountered an internal error that prevented it from fulfilling this   request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /home/index.jsp at line 54

51:     <link rel="shortcut icon" href="../assets/ico/favicon.png"> 
52:     <style type="text/css"> 
53:     <%  
54:         HashMap<String,Object> background = com.controlj.green.definitions.Utilities.getBackground();
55:             String background_image = "";
56:             if(!background.isEmpty()){
57:                 background_image = "data:image/png;base64," + background.get("bytes").toString();


Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
com.controlj.green.servlets.Index.doGet(Index.java:51)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

root cause

javax.servlet.ServletException: java.lang.IncompatibleClassChangeError: Found class   com.mysql.jdbc.Statement, but interface was expected
 org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:912)
 org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:841)
 org.apache.jsp.home.index_jsp._jspService(index_jsp.java:83)
 org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
 org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
 org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
 com.controlj.green.servlets.Index.doGet(Index.java:51)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

 root cause

 java.lang.IncompatibleClassChangeError: Found class com.mysql.jdbc.Statement, but interface was expected
 com.controlj.green.definitions.Utilities.getBackground(Utilities.java:172)    org.apache.jsp.home.index_jsp._jspService(index_jsp.java:68)
 org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
 org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
 org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
 com.controlj.green.servlets.Index.doGet(Index.java:51)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

 note The full stack trace of the root cause is available in the Apache Tomcat/7.0.42 logs.
 Apache Tomcat/7.0.42

I really don't know what's wrong in line 54.

It is apparently calling this : com.controlj.green.definitions.Utilities.getBackground();

which is :

    import java.util.*;

    public static HashMap<String,Object> getBackground() throws SQLException, ClassNotFoundException, IOException {
    if(establishConnection()){

        Statement st = (Statement) con.createStatement();
        rs = st.executeQuery("select bytes from connection_string");

        ResultSetMetaData md = (ResultSetMetaData) rs.getMetaData();
        int columns = md.getColumnCount();
        HashMap<String,Object> list = new HashMap<String,Object>();

        if (rs.next()) {
            for(int i=1; i<=columns; ++i){
                list.put(md.getColumnName(i),rs.getObject(i));
                }
            }    
        return list;
    }else{
        return null;
    }

}

What could be wrong in this?

Thanks.

Answer 1

From the stacktrace,

root cause javax.servlet.ServletException: java.lang.IncompatibleClassChangeError: Found class
com.mysql.jdbc.Statement, but interface was expected

Why have you cast the statement class here ,

Statement st = (Statement) con.createStatement();

it needs to be,

Statement st =con.createStatement();

Expecting con to be connection object

Update:

As per the error you have shared its the wrong imports ,

Wrong classes

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;

should be

import java.sql.Connection;
import java.sql.Statement;

Hope this helps

Answer 2

I dont think we need casting as you did here

Statement st = (Statement) con.createStatement();

as long as con is an object of type java.sql.Connection

or may be you are using some older version of mysql-connector.jar trying replacing it with some newer version and import the connection statements again

Answer 3

From where are you getting the connection?. Global variable?, I would try to changes your prepared statement for something like this. I dont know if you´re controlling the exception in some point to close the connection by the way.

PreparedStatement ps = null;

try{
    ps = conn.prepareStatement("select bytes from connection_string");
    ps.executeQuery();
} catch(Exception ex){
    System.out.println("");
} finally {
   try{
       if(ps!=null){
           ps.close();
       }
       if(conn!=null){
           conn.close();
       }
   } catch(Exception ex){
       System.out.println("");
   }
}

Answer 4

What is con in Statement st = (Statement) con.createStatement();
Where does is come from. And anyway you donot need a cast to Statement.