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Is it possible to reuse a connection statement without closing it? [duplicate]

I've been working at this for almost a day and a half now and I can't seem to work this error out. I don't know why the ResultSet is being closed. Maybe some of you can help me out.
MySQLDatabase:
package net.gielinor.network.sql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public abstract class MySQLDatabase {
private String host;
private String database;
private String username;
private String password;
private Connection connection = null;
private Statement statement;
public MySQLDatabase(String host, String database, String username, String password) {
this.host = host;
this.database = database;
this.username = username;
this.password = password;
}
public abstract void cycle() throws SQLException;
public abstract void ping();
public void connect() {
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(String.format("jdbc:mysql://%s/%s", host, database), username, password);
statement = connection.createStatement();
} catch (Exception e) {
e.printStackTrace();
}
}
public void ping(String table, String variable) {
try {
statement.executeQuery(String.format("SELECT * FROM `%s` WHERE `%s` = 'null'", table, variable));
} catch (Exception e) {
connect();
}
}
public ResultSet query(String query) throws SQLException {
if (query.toLowerCase().startsWith("select")) {
return statement.executeQuery(query);
} else {
statement.executeUpdate(query);
}
return null;
}
public Connection getConnection() {
return connection;
}
}
MySQLHandler
package net.gielinor.network.sql;
import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import net.gielinor.network.sql.impl.MySQLDonation;
public class MySQLHandler extends Thread {
private static final MySQLHandler mysqlHandler = new MySQLHandler();
public static MySQLHandler getMySQLHandler() {
return mysqlHandler;
}
private static List<MySQLDatabase> updateList;
private static String host;
private static String database;
private static String username;
private static String password;
#Override
public void run() {
while (true) {
for (MySQLDatabase database : updateList) {
try {
if (database.getConnection() == null) {
database.connect();
} else {
database.ping();
}
database.cycle();
} catch (Exception ex) {
ex.printStackTrace();
}
try {
Thread.sleep(10000);
} catch (Exception ex) {
}
}
}
}
private static void loadProperties() {
Properties p = new Properties();
try {
p.load(new FileInputStream("./sql.ini"));
host = p.getProperty("host");
database = p.getProperty("database");
username = p.getProperty("username");
password = p.getProperty("password");
} catch (Exception ex) {
System.out.println("Error loading MySQL properties.");
}
}
public static String getHost() {
return host;
}
static {
loadProperties();
updateList = new ArrayList<MySQLDatabase>();
updateList.add(new MySQLDonation(host, database, username, password));
}
}
MySQLDonation
package net.gielinor.network.sql.impl;
import java.sql.ResultSet;
import java.sql.SQLException;
import net.gielinor.game.model.player.Client;
import net.gielinor.game.model.player.PlayerHandler;
import net.gielinor.game.model.player.PlayerSave;
import net.gielinor.network.sql.MySQLDatabase;
public final class MySQLDonation extends MySQLDatabase {
public MySQLDonation(String host, String database, String username, String password) {
super(host, database, username, password);
}
#Override
public void cycle() throws SQLException {
ResultSet results = query("SELECT * FROM `gieli436_purchases`.`donations`");
if (results == null) {
return;
}
while (results.next()) {
String username = results.getString("username").replace("_", " ");
System.out.println("name=" + username);
Client client = (Client) PlayerHandler.getPlayer(username.toLowerCase());
System.out.println(client == null);
if (client != null && !client.disconnected) {
int creditamount = results.getInt("creditamount");
if (creditamount <= 0) {
continue;
}
handleDonation(client, creditamount);
query(String.format("DELETE FROM `gieli436_purchases`.`donations` WHERE `donations`.`username`='%s' LIMIT 1", client.playerName.replaceAll(" ", "_")));
}
}
}
#Override
public void ping() {
super.ping("donations", "username");
}
private void handleDonation(Client client, int creditamount) throws SQLException {
client.credits = (client.credits + creditamount);
client.sendMessage("Thank you for your purchase. You have received " + creditamount + " store credits.");
PlayerSave.save(client);
}
}
The exception occurs here: in the while loop within MySQLDonation and the actual stacktrace is this:
java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
at com.mysql.jdbc.ResultSetImpl.checkClosed(ResultSetImpl.java:794)
at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:7077)
at net.gielinor.network.sql.impl.MySQLDonation.cycle(Unknown Source)
at net.gielinor.network.sql.MySQLHandler.run(Unknown Source)
With this information let me say that this does work, I get my message and what not in-game but it repeats, like the user is never removed from the query so it gives them infinite rewards. If you need any more information feel free to ask.

When you run the Delete query, you use the same Statement that was used in the Select query. When you re-execute on the same Statement, the previous ResultSet gets closed.
To avoid this, you should create a new Statement everytime you execute a query. So remove statement = connection.createStatement(); from the connect() method in MySQLDatabase class, and replace all statement in that class to connection.createStatement(). You may also choose to delete the private variable statement altogether.
You can read more about it here.

this error is some time occur when we use same statement object for diff. types
check Statement objectsss;

not able to write onto a file

I have written this code to read from a table and write onto a file, but I am unable to write to a file. The file gets created, but its empty. I don't have a mysql problem tried to insert comments and debug. Code compiles fine, but has a problem in creating a file:
import java.io.File;
import java.io.FileNotFoundException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Formatter;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
public class tabletocsv {
public static void main(String[] args) {
System.out.println("enter the table name");
Scanner input = new Scanner(System.in);
String table = input.next();
System.out.println("enter number of columns");
int columns = input.nextInt();
createcsv(table, columns);
System.out.print(" csv created");
displaycsv(table, columns);
}
static void displaycsv(String table, int count) {
Scanner file123;
try {
file123 = new Scanner(new File("/Users/Tannishk/Documents/csv/" + table + ".csv"));
//System.out.printf("reading");
while (file123.hasNext()) {
System.out.println("going inside");
for (int i = 1; i <= count; i++) {
String a = file123.next();
System.out.print(a + " ");
}
System.out.println();
}
} catch (FileNotFoundException ex) {
Logger.getLogger(tabletocsv.class.getName()).log(Level.SEVERE, null, ex);
}
}
static void createcsv(String table, int count) {
Formatter x;
Connection connection;
Statement st;
try {
x = new Formatter("/Users/Tannishk/Documents/csv/" + table + ".csv");
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db", "root", "password");
st = connection.createStatement();
ResultSet rs = st.executeQuery("select * from " + table + ";");
while (rs.next()) {
for (int i = 1; i <= count; i++) {
String a = rs.getString(i);
x.format("%s ", a);
// System.out.print(a);
}
x.format("\n");
}
} catch (Exception e) {
} finally {
}
}
}

Try flushing and closing the formatter

I think you have missed to flush the file.
static void createcsv(String table,int count)
{
Formatter x = null;
Connection connection;
Statement st;
try{
x = new Formatter("/Users/Tannishk/Documents/csv/"+table+".csv");
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","password");
st = connection.createStatement();
ResultSet rs= st.executeQuery("select * from "+table+";");
while(rs.next())
{
for(int i=1;i<=count;i++)
{
String a = rs.getString(i);
x.format("%s ",a);
// System.out.print(a);
}
x.format("\n");
}
}
catch(Exception e)
{
}
finally
{
try {
x.flush();
x.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Try this ...

You need to close the output stream that you're using to write to the file. For example if you're using a FileWriter object named fout to write to the file, you'll have to do fout.close() to actually have anything written to the file as otherwise it would just be in memory.

Parameterized runner class with 2 arguments in constructor

I wish to use a Parameterized Junit class to read from a .csv file. I want to:-
Read a 'placeID' (a String) and append it to a base url to form a webpage
Assert that the Place name 'name' (a String) is as I expect it to be for the place
The tab delimited .csv file contains 2 records as follows (will have 100's records eventually):
132
The Big House
I'm currently getting an Illegal argument exception. What's a slicker way of achieving this? I guess having the relative URL and then test data in seperate files would be better.
My code:
#RunWith(Parameterized.class)
public class PlaceTest {
public static WebDriver driver;
private String placeId;
private String name;
private PropertyPage propertyPage;
public PlaceTest(String page, String name) {
this.placeId = page;
this.name = name;
}
#Parameterized.Parameters
public static Collection data() {
return csvFileAsCollectionOfStringArrays(
System.getProperty("user.dir") +
"/src/test/resources/" +
"place_ids.csv");
}
private static Collection<String[]> csvFileAsCollectionOfStringArrays(String csvFileName) {
List<String[]> csvRows = new ArrayList<String[]>();
String rawCSVRow;
BufferedReader csvFileReader = null;
String delimiter = "\t";
System.out.println("Reading data from " + csvFileName);
try {
csvFileReader = new BufferedReader(new FileReader(csvFileName));
} catch (FileNotFoundException e) {
System.out.println("Could not find file " + csvFileName);
e.printStackTrace();
}
int rowNumber = 1;
try {
if (csvFileReader != null) {
while ((rawCSVRow = csvFileReader.readLine()) != null) {
String delimitedItems[] = rawCSVRow.split(delimiter);
csvRows.add(delimitedItems);
rowNumber++;
}
}
} catch (IOException e) {
System.out.println("Error reading row number " + rowNumber);
e.printStackTrace();
}
try {
assert csvFileReader != null;
csvFileReader.close();
} catch (IOException e) {
System.out.println("Error closing file " + e.getMessage());
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
}
return csvRows;
}
#BeforeClass
public static void startDriver() {
driver = Driver.get();
}
#Before
public void getNextPage() {
propertyPage = new PropertyPage(driver);
driver.get(TestWebApp.getURL() + this.placeId);
}
#Test
public void checkNamePresent() {
WebElement placeName = propertyPage.checkName();
assertEquals("Expected match on name", this.name, placeName.getText());
}
#AfterClass
public static void quitDriver() {
driver.quit();
}
}

Try this:
import static org.junit.Assert.assertEquals;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import au.com.bytecode.opencsv.CSVReader;
#RunWith(Parameterized.class)
public class PlaceTest {
private String placeId;
private String name;
public PlaceTest(String page, String name) {
this.placeId = page;
this.name = name;
}
#Parameterized.Parameters
public static Collection<String[]> data() {
CSVReader reader = new CSVReader(new InputStreamReader(PlaceTest.class.getResourceAsStream("place_ids.csv")));
List<String[]> lines;
try {
lines = reader.readAll();
return lines;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return new ArrayList<String[]>();
}
#Test
public void checkNamePresent() {
System.out.println(this.placeId + " " + this.name);
}
}
The place_ids.csv has to be in: \src\test\resources\<your package>\place_ids.csv
Update your pom with CSVReader dependency:
<dependency>
<groupId>net.sf.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>2.3</version>
</dependency>
Update:
csv file:
132, Some text
133, Other text
Your example above has one word per line. The code above was compile and tested.

How to make semicolon (;) as delimiter in java

I made a program that can parse .csv file to database,
I want to make semicolon as delimiter but I got some trouble here ~
This is my code CSVLoader.java
package id.co.lolo.coreservice;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.util.Date;
import org.apache.commons.lang.StringUtils;
import au.com.bytecode.opencsv.CSVReader;
public class CSVLoader {
private static final String SQL_INSERT = "INSERT INTO ${table}(${keys}) VALUES(${values})";
private static final String TABLE_REGEX = "\\$\\{table\\}";
private static final String KEYS_REGEX = "\\$\\{keys\\}";
private static final String VALUES_REGEX = "\\$\\{values\\}";
private Connection connection;
private char seprator;
/**
* Public constructor to build CSVLoader object with Connection details. The
* connection is closed on success or failure.
*
* #param connection
*/
public CSVLoader(Connection connection) {
this.connection = connection;
// Set default separator
this.seprator = ',';
}
/**
* Parse CSV file using OpenCSV library and load in given database table.
*
* #param csvFile
* Input CSV file
* #param tableName
* Database table name to import data
* #param truncateBeforeLoad
* Truncate the table before inserting new records.
* #throws Exception
*/
#SuppressWarnings("resource")
public void loadCSV(String csvFile, String tableName,
boolean truncateBeforeLoad) throws Exception {
CSVReader csvReader = null;
if (null == this.connection) {
throw new Exception("Not a valid connection.");
}
try {
csvReader = new CSVReader(new FileReader(csvFile), this.seprator);
} catch (Exception e) {
e.printStackTrace();
throw new Exception("Error occured while executing file. "
+ e.getMessage());
}
String[] headerRow = csvReader.readNext();
if (null == headerRow) {
throw new FileNotFoundException(
"No columns defined in given CSV file."
+ "Please check the CSV file format.");
}
String questionmarks = StringUtils.repeat("?,", headerRow.length);
questionmarks = (String) questionmarks.subSequence(0,
questionmarks.length() - 1);
String query = SQL_INSERT.replaceFirst(TABLE_REGEX, tableName);
query = query
.replaceFirst(KEYS_REGEX, StringUtils.join(headerRow, ","));
query = query.replaceFirst(VALUES_REGEX, questionmarks);
System.out.println("Query: " + query);
String[] nextLine;
Connection con = null;
PreparedStatement ps = null;
try {
con = this.connection;
con.setAutoCommit(false);
ps = con.prepareStatement(query);
if (truncateBeforeLoad) {
// delete data from table before loading csv
con.createStatement().execute("DELETE FROM " + tableName);
}
final int batchSize = 1000;
int count = 0;
Date date = null;
while ((nextLine = csvReader.readNext()) != null) {
if (null != nextLine) {
int index = 1;
for (String string : nextLine) {
date = DateUtil.convertToDate(string);
if (null != date) {
ps.setDate(index++,
new java.sql.Date(date.getTime()));
} else {
ps.setString(index++, string);
}
}
ps.addBatch();
}
if (++count % batchSize == 0) {
ps.executeBatch();
}
}
ps.executeBatch(); // insert remaining records
con.commit();
} catch (Exception e) {
con.rollback();
e.printStackTrace();
throw new Exception(
"Error occured while loading data from file to database."
+ e.getMessage());
} finally {
if (null != ps)
ps.close();
if (null != con)
con.close();
csvReader.close();
}
}
public char getSeprator() {
return seprator;
}
public void setSeprator(char seprator) {
this.seprator = seprator;
}
}
this is Main.java
package id.co.lolo.coreservice;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class Main {
#SuppressWarnings("unused")
private static String JDBC_CONNECTION_URL =
"jdbc:mysql://localhost:3306/bni";
public static void main(String[] args) {
try {
CSVLoader loader = new CSVLoader(getCon());
loader.setSeprator(';');
loader.loadCSV("C:\\Log\\Logtima.csv", "coreservice", true);
} catch (Exception e) {
e.printStackTrace();
}
}
private static Connection getCon() {
Connection connection = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/bni","root","shikamaru");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
}
I got this Error,
Query: INSERT INTO coreservice(MODULE_NAME,SERVICE_NAME,COUNTER,LOG_DATE,UPDATE_DATE) VALUES(?)
java.sql.BatchUpdateException: Column count doesn't match value count at row 1
at com.mysql.jdbc.PreparedStatement.executeBatchSerially(PreparedStatement.java:1693)
at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:1108)
at id.co.bni.coreservice.CSVLoader.loadCSV(CSVLoader.java:118)
at id.co.bni.coreservice.Main.main(Main.java:20)
java.lang.Exception: Error occured while loading data from file to database.Column count doesn't match value count at row 1
at id.co.bni.coreservice.CSVLoader.loadCSV(CSVLoader.java:123)
at id.co.bni.coreservice.Main.main(Main.java:20)

How to access and ArrayList inside another class inside multiple try's?

I have a homework to retrieve a myqsl query and save it to a ArrayList , and then to link it to another class and then serialize it and send it through http,
In a scheme it would be
class Server{static class a {try{try{ try{arraylist1} }}}}
class b {var1,var2,link_to(arraylist1)}
then serialize class b and send it
i managed to take the sql query and save the objects in the ArrayList (objects created from class "Personat") through
if (rs != null) {
List<Personat> perList = new ArrayList<Personat>();
while (rs.next()) {
Personat per = new Personat();
per.setID(rs.getInt("var1"));
per.setName(rs.getString("var2"));
per.setAmount(rs.getInt("var3"));
perList.add(per);
}
}
Where rs=ResultSet object
but i cant access the ArrayList from class b so i can serialize it. I have tried to make it static (nothing ,it cant be linked).I have tried to make a getter (yet nothing eclipse wont let me as i automatically generate them).
So i don't know what i should do ! Can someone help me ? Or does anyone have any idea?
i have tried to search google for this but as you can see is a little too specific so no results until now ....
here is my Server.java
package server2;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.net.InetSocketAddress;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
public class Server {
private static List<Personat> perList = new ArrayList<Personat>();
//need to access this in the SendRes class
public List<Personat> getPerList() {
return perList;
}
public static void main(String[] args) throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(3333), 0);
server.createContext("/", new MyHandler());
server.setExecutor(null);
server.start();
}
static public class MyHandler implements HttpHandler {
public void handle(HttpExchange t) throws IOException {
ObjectInputStream ios = new ObjectInputStream(t.getRequestBody());
//
final String url = "jdbc:mysql://localhost/httpServer";
final String user = "root";
final String password = "";
try {
Send oin = (Send) ios.readObject();
int id = oin.getId();
String emri = oin.getName();
int amount = oin.getAmount();
int paid = oin.getPaid();
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(url, user,
password);
try {
PreparedStatement s = con
.prepareStatement("INSERT INTO person(ID,Name,Amount,Paid) VALUES (?,?,?,?)");
s.setInt(1, id);
s.setString(2, emri);
s.setInt(3, amount);
s.setInt(4, paid);
s.executeUpdate();
ResultSet rs = s.executeQuery("SELECT * "
+ "from personat ORDER BY EmpId");
if (rs != null) {
while (rs.next()) {
Personat per = new Personat();
per.setID(rs.getInt("ID"));
per.setName(rs.getString("Name"));
per.setAmount(rs.getInt("Amount"));
perList.add(per);
}
}
//here i need to send an SendRes object with the ArrayList inside it
} catch (Exception e) {
e.printStackTrace();
} finally {
if (con != null) {
con.close();
}
}
} catch (Exception e) {
e.printStackTrace();
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
}
class SendResponse implements Serializable {
String gabim;
String gabimNr;
//link the arraylist from class server here
}
class Personat {
int ID;
public int getID() {
return ID;
}
public void setID(int iD) {
ID = iD;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public int getAmount() {
return Amount;
}
public void setAmount(int amount) {
Amount = amount;
}
String Name;
int Amount;
}

Objects of type B can only access the public members of type A. To get access to your list you need to make it a public member of A. The typical way to do this is to use a private field and a public getter.
class A
{
private List<Personat> personList;
public List<Personat> getPersonList() { return personList; }
public void handle(HttpExchange t) throws IOException
{
// ...
personList = ...;
// ...
}
}
Note that by giving public access to your list you are also allowing clients to modify the contents of the list. You may prefer to give them a copy of the list if this is not desirable.
On a slightly unrelated note, if you three nested try blocks in a single method then that method is probably too complex and should be refactored into smaller methods.