I am a student learning JSP, and I seem to have this issue in executing a method via an object of a DAO class. When the database connectivity and SQL query is given on the servlet itself it, it will work. But when given in the DAO class and a object is used, it doesn't work. Please help.
import dataaccessobjects.cartDAO1;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class addtoCartServ extends HttpServlet {
#Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
cartDAO1 newcart = new cartDAO1();
PrintWriter out = response.getWriter();
if (request.getParameter("submit") != null){
//out.println("added to cart");
try {
//out.println("submit not null");
String Uname = (String) request.getSession().getAttribute("Welcome");
String ino = request.getParameter("ino");
String iqnty = request.getParameter("quantity");
String iname = request.getParameter("iname");
if(newcart.addToCart(iname,Uname,ino,iqnty)){
out.println("added to cart");
}
} catch (SQLException ex) {
Logger.getLogger(addtoCartServ.class.getName()).log(Level.SEVERE, null, ex);
} catch (ClassNotFoundException ex) {
Logger.getLogger(addtoCartServ.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
The DAO class
public cartDAO1(){
}
public boolean addToCart(String iname,String username, String ino,String iqnty) throws SQLException, ClassNotFoundException{
boolean flag = false;
Class.forName("org.apache.derby.jdbc.ClientDriver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/styleomega","root","");
PreparedStatement ps = conn.prepareStatement("INSERT INTO cart(iname,uname,ino,iqnty) VALUES (?,?,?,?)");
// set the values for parameters
ps.setString(1,iname);
ps.setString(2,username);
ps.setString(3,ino);
ps.setString(4,iqnty);
int rs = ps.executeUpdate();
if (rs==1){
flag = true;
}
return flag;
}
}
You should be import the DAO class package in servlet then access it it will work like
import DAO.cartDao;
If you will not import then how to acces it
I don't understand exactly what is not working? But I have noticed, you're not closing statement and the database connection in your DAO class.
FYI: An example
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = // Retrieve connection
stmt = conn.prepareStatement(// Some SQL);
rs = stmt.executeQuery();
} catch(Exception e) {
// Error Handling
} finally {
try { if (rs != null) rs.close(); } catch (Exception e) {};
try { if (stmt != null) stmt.close(); } catch (Exception e) {};
try { if (conn != null) conn.close(); } catch (Exception e) {};
}
Related
I am attempting to write a JUnit test for a query which is retrieved via a textbox in an html form. The text retrieval has been tested and works but my unit test is failing. I am using 2 relevant classes: QueryController and QueryControllerTest. I have been playing around with when and what I am closing in these two classes and keep getting the error: Operation not allowed after ResultSet closed.
QueryControllerTest.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.junit.Test;
import static org.junit.Assert.*;
public class QueryControllerTest {
#Test
public void testQuery() {
ResultSet testRs = null;
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "GCImage";
conn = DriverManager.getConnection(connectionUrl,
connectionUser, connectionPassword);
Query testQuery = new Query();
testQuery
.setQuery("select * from service_request where FN_contact = 'Greg'");
testRs = QueryController.executeSelect(conn, testQuery);
assertEquals("Laughlin", testRs.getString("LN_contact"));
assertEquals("Hello World", testRs.getString("Notes"));
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
testRs.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
QueryController.java
import java.util.Map;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
#Controller
public class QueryController {
#RequestMapping(value = "/query")
public String processRegistration(#ModelAttribute("query") Query query,
Map<String, Object> model) {
String queryString = query.getQuery();
if (queryString != null && !queryString.isEmpty()) {
System.out.println("query (from controller): " + queryString);
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "GCImage";
conn = DriverManager.getConnection(connectionUrl,
connectionUser, connectionPassword);
if (queryString.toLowerCase().startsWith("select")) {
ResultSet rs = executeSelect(conn, query);
} else {
int rowsUpdated = executeUpdate(conn, query);
System.out.println(rowsUpdated + " rows updated");
}
} catch (Exception e) {
e.printStackTrace();
}
}
return "query";
}
public static ResultSet executeSelect(Connection conn, Query query) {
ResultSet rs = null;
Statement stmt = null;
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(query.getQuery());
while (rs.next()) {
String id = rs.getString("ID");
String firstName = rs.getString("FN_Contact");
String lastName = rs.getString("LN_Contact");
String notes = rs.getString("Notes");
System.out.println("ID: " + id + ", First Name: " + firstName
+ ", Last Name: " + lastName + ", Notes: " + notes);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(rs!=null){
rs.close();
}
if(stmt != null){
stmt.close();
}
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return rs;
}
}
QueryController.executeSelect is calling rs.close(), but then your assertEquals in QueryControllerTest.testQuery are calling methods on testRS. As executeSelect is returning the resultset, closing it first doesn't make sense. Further, executeSelect is being passed the connection, so it shouldn't be closing that either (what happens if the caller wants to do two different selects on the same connection?).
I think the problem is because you are creating two connections. Try to only instantiate the connection of QueryController class for your test. You will need to provide the connection. After you store it in a variable to run the query.
Connection con = QueryController.getConnection ();
I was trying to connect mysql database in my servlet. Then I'm getting an exception.But when I am testing the database connection from a usual Java class the connection is ok and I getting the data from the database.The exception I'm getting on tomcat server console is:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver .
The code of my DatabaseHandler.java is:
import java.sql.*;
public class DatabaseHandler {
private Statement stmt;
private Connection con;
String username = "root";
String password = "thunder";
String dbname = "bidderboy";
public DatabaseHandler()
{
this.createConnection();
}
private void createConnection()
{
//create the connection for first time
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
con = DriverManager.getConnection("jdbc:mysql://localhost/"+dbname , username , password);
stmt = con.createStatement();
} catch (Exception ex) {
System.out.println(ex.toString());
}
}
public int executeUpdate(String sql)
{
int result = 0;
//before update checks if connection is open
try {
if(con.isClosed()) {
Class.forName("com.mysql.jdbc.Driver").newInstance();
con = DriverManager.getConnection("jdbc:mysql://localhost/"+dbname , username , password);
stmt = con.createStatement();
}
} catch (Exception ex) {
System.out.println(ex.toString());
}
//try to executeUpdate the sql command
try{
result = stmt.executeUpdate(sql);
}
catch(Exception ex){
System.out.println("Couldn't executeUpdate sql command");
}
return result;
}
public ResultSet executeQuery(String sql)
{
ResultSet rs = null;
//before Query checks if connection is open
try {
if(con.isClosed()) {
Class.forName("com.mysql.jdbc.Driver").newInstance();
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+dbname , username , password);
stmt = con.createStatement();
}
} catch (Exception ex) {
System.out.println(ex.toString());
}
//try to executeQuery the sql command
try{
rs = stmt.executeQuery(sql);
}
catch(Exception ex){
System.out.println("Couldn't executeQuery sql command");
}
return rs;
}
public void closeConnection()
{
//if connection is open try to close the connection
try {
if(!con.isClosed()) {
con.close();
}
} catch (SQLException ex) {
System.out.println("Failed to close database connection");
}
}
}
The code of my servlet is:
import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
#SuppressWarnings("serial")
public class UserLogin extends HttpServlet{
public UserLogin()
{
}
#Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
}
#Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doPost(req, resp);
}
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
DatabaseHandler dbh = new DatabaseHandler();
String username="mamun";
String password="1234";
String dbusername="";
String dbpassword="";
String sql = "select * from users where username='"+username+"' and password='"+password+"'";
ResultSet rs = dbh.executeQuery(sql);
try {
while(rs.next())
{
dbusername = rs.getNString(1);
dbpassword = rs.getNString(2);
}
} catch (SQLException e) {}
System.out.println(dbusername+" "+dbpassword);
}
}
And the Code of normal java class from which I'm getting my data is:
import java.sql.ResultSet;
import java.sql.SQLException;
public class DatabaseConnectionTest {
public static void main(String[] args) {
String sql = "Select * from users";
DatabaseHandler dbh = new DatabaseHandler();
ResultSet rs = dbh.executeQuery(sql);
try {
while(rs.next())
{
String n = rs.getNString(1);
String c = rs.getNString(2);
System.out.println("Name: "+n+" Contact: "+c);
}
} catch (SQLException ex) {
System.out.println(ex.toString());
}
}
}
Anybody please explain why I'm getting this class not found exception and What can be the solution. Thanks in advance.
Adding mysql-connector-java-5.1.11-bin.jar file to WEB-INF/lib folder fixed my problem.
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from java.sql.Statement to com.mysql.jdbc.Statement
i am a beginner in java i am trying to use mysql database i have downloaded mysql-connector-java-5.1.23-bin.jar file from mysql.com and i have added this jar file to in my build path of my project but there is an error in the following code
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from java.sql.Statement to com.mysql.jdbc.Statement
package com.example.demo;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
public class DBConnect
{
private static final String userName = "root";
private static final String userpwd = "sverma";
private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db";
public static void main(String[] args) throws SQLException
{
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try
{
DriverManager.getConnection(CONN_STR, userName, userpwd);
st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = st.executeQuery("select * from user");
rs.last();
System.out.println("No of rows: " + rs.getRow());
// System.out.println("Connected Successfully...");
}
catch (SQLException e)
{
System.err.println(e);
}
finally
{
if (rs != null)
{
rs.close();
}
if (st != null)
{
st.close();
}
if (conn != null)
{
conn.close();
}
}
}
}
Wrong classes
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
should be
import java.sql.Connection;
import java.sql.Statement;
In fact, java decouples everything from a specific database engine. One never should need an import of MySQL (or ProgressSQL or ...) classes.
To have those classes available at run-time, the first thing after the try, before getting the connection would be:
Class.forName("com.mysql.jdbc.Driver");
This technique would allow reading all strings from a configuration file, and writing database independent code.
Missing: conn = ...
conn = DriverManager.getConnection(CONN_STR, userName, userpwd);
package com.example.demo;
import java.sql.*;
public class DBConnect
{
private static final String userName = "root";
private static final String userpwd = "sverma";
private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db";
public static void main(String[] args) throws SQLException
{
Connection conn;
Statement st;
ResultSet rs;
try
{
Class.forName("com.mysql.jdbc.Driver");
DriverManager.getConnection(CONN_STR, userName, userpwd);
st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = st.executeQuery("select * from user");
rs.last();
System.out.println("No of rows: " + rs.getRow());
// System.out.println("Connected Successfully...");
}
catch (SQLException e)
{
System.err.println(e);
}
finally
{
if (rs != null)
{
rs.close();
}
if (st != null)
{
st.close();
}
if (conn != null)
{
conn.close();
}
}
}
The following is a servlet for getting parameter from a jsp page.
I am trying to run following code --
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.swing.JFrame;
public class oneServlet extends HttpServlet {
public static Connection getConnection() throws Exception {
String driver = "org.postgresql.Driver";
String url = "jdbc:postgresql://10.1.11.112:5432/pack";
String username = "pack";
String password = "pack";
Class.forName(driver);
Connection conn = DriverManager.getConnection(url, username, password);
return conn;
}
public static void main(String[] args) throws Exception {
String user=request.getParameter("t1");
String pass=request.getParameter("t2");
Connection conn = null;
PreparedStatement pstmt = null;
try {
conn = getConnection();
String queryTest = "select username,password from login";
pstmt = conn.prepareStatement(queryTest);
ResultSet rs = pstmt.executeQuery();
while (rs.next()) {
String username=rs.getString(1);
String password=rs.getString(2);
if(user.equals(username) && pass.equals(password))
{
JFrame frame = new JFrame("/LoginSuccess.jsp");
}
else
{
System.out.println("Login Failed,Please try Againe");
}
}}
catch (Exception e) {
e.printStackTrace();
} finally {
pstmt.close();
conn.close();
}
}
}
It's showing error in request.getParameter that " request cannot be resolved. Can anyone help me resolve this.
When you extends HttpServlet, you need to override doGet and doPost() which take HttpServletRequest and HttpServletResponse as parameters.
Example:
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
.......
String user=request.getParameter("t1"); //Use request variable to do get...
}
Read more here and here
Servlets doesnt have main() , they are executed by SelvletContainer or Webserver (like tomcat)
In your scenario.
public void doGet(){
String user=request.getParameter("t1");
String pass=request.getParameter("t2");
Connection conn = null;
PreparedStatement pstmt = null;
try {
conn = getConnection();
String queryTest = "select username,password from login";
pstmt = conn.prepareStatement(queryTest);
ResultSet rs = pstmt.executeQuery();
while (rs.next()) {
String username=rs.getString(1);
String password=rs.getString(2);
if(user.equals(username) && pass.equals(password))
{
//JFrame frame = new JFrame("/LoginSuccess.jsp");
request.getRequestDispatcher().redirect("/LoginSuccess.jsp");
}
else
{
System.out.println("Login Failed,Please try Againe");//This will print at the console
}
}}
catch (Exception e) {
e.printStackTrace();
} finally {
pstmt.close();
conn.close();
}
Learn more about servlets
This is my CreateQuery.java class .
package DbConnect;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class CreateQuery {
Connection conn;
public CreateQuery() throws ClassNotFoundException, SQLException, IOException {
conn=new DbAccess().returnDatabaseConnection();
}
public int addNewLayertoDB(){
try {
PreparedStatement statement = null;
//String table_name = feature_name + "_" + shape;
String query = "SELECT the_geom from bbmp ";
statement = conn.prepareStatement(query);
//statement.setString(1, feature_name);
ResultSet rs = statement.executeQuery();
rs.close();
return 1;
} catch (SQLException ex) {
System.out.println("Sql exception");
return 0;
}
}
public void closeConn() throws SQLException {
if (conn != null) {
this.conn.close();
}
}
public static void main(String args[]) throws FileNotFoundException, IOException, ClassNotFoundException, SQLException{
CreateQuery cq = new CreateQuery();
cq.addNewLayertoDB();
cq.closeConn();
}
}
This is my DbConnect class
package DbConnect;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;
public class DbAccess{
public static void main(String[] argv) {
System.out.println("-------- PostgreSQL " +
"JDBC Connection Testing ------------");
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your PostgreSQL JDBC Driver? " +
"Include in your library path!");
e.printStackTrace();
return;
}
System.out.println("PostgreSQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection(
"jdbc:postgresql://127.0.0.1:5432/Ethermap","postgres", "*******");
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
return;
}
if (connection != null){
System.out.println("You made it, take control your database now!");
}else{
System.out.println("Failed to make connection!");
}
}
public Connection returnDatabaseConnection() {
System.out.println("DB not connected");
return null;
}
}
The error I am getting when I run CreateQuery is
DB not connected
Exception in thread "main" java.lang.NullPointerException
at DbConnect.CreateQuery.addNewLayertoDB(CreateQuery.java:24)
at DbConnect.CreateQuery.main(CreateQuery.java:45)
What is the error ? And How do I debug it ?
The method returnDatabaseConnection() that you call in the constructor of CreateQuery always returns null, so it's not a surprise that your connection object is null.