Develop Reference

Connecting to different schemas using prepared statement

I have the following code running fine with one sql statement selectEmpShowDocs_SQL referring to schema1. In this scenario, I have hard coded the value of empID as 2 as shown in the sql below :
private String selectEmpShowDocs_SQL =
"SELECT " +
"emp_doc " +
"FROM " +
"schema1.emp_info " +
"WHERE " +
"doc_id = ? "+
"AND"+
"empID = 2";
Now, I have another sql statement which is retrieving the emp_id value and instead of hardcoding the value just like I did above for empID, I want to pass the value of emp_id obtained from the following sql statement to the above sql statement. This is the statement which is referring to schema2.
private String selectEmpIDSQL =
"SELECT " +
"emp_id " +
"FROM " +
"schema2.emp_id " +
"WHERE " +
"company_id = 435 "
I am wondering is it possible to connect with two different schemas with one prepared statement? Here someone mentioned that prepared statement is bound to a specific database and in that case if it's not possible, what would be the best approach for me?
Here is the full code that works fine for me using only the SQL query referring to schema1.
public List<EmployeeDocument> getEmployeeDocument(String docId, Integer employeeID) throws DaoException
{
StopWatch stopWatch = new StopWatch();
stopWatch.start();
DataSource ds = null;
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
List<EmployeeDocument> empShowDocs = new ArrayList<EmployeeDocument>();
try {
ds = jdbcTemplate.getDataSource();
conn = ds.getConnection();
pstmt = conn.prepareStatement(selectEmpShowDocs_SQL);
logger.debug("sql query :" + selectEmpShowDocs_SQL);
System.out.println(selectEmpShowDocs_SQL);
pstmt.setString(1, docId);
logger.debug("sql parameters, docId:" + docId);
rs = pstmt.executeQuery();
while(rs.next()) {
EmployeeDocument empShowDocRecord = new EmployeeDocument();
empShowDocRecord.setEmp_Content(rs.getString("emp_doc")));
empShowDocs.add(empShowDocRecord);
}
} catch(Throwable th) {
throw new DaoException(th.getMessage(), th);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
if (pstmt != null) {
try {
pstmt.close();
} catch(SQLException sqe) {
sqe.printStackTrace();
}
pstmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (SQLException sqle) {
sqle.printStackTrace();
}
conn = null;
}
if (ds != null) {
ds = null;
}
}
return empShowDocs;
}
private String selectEmpShowDocs_SQL =
"SELECT " +
"emp_doc " +
"FROM " +
"schema1.emp_info " +
"WHERE " +
"doc_id = ? "+
"AND"+
"empID = 2";
private String selectEmpIDSQL =
"SELECT " +
"emp_id " +
"FROM " +
"schema2.emp_id " +
"WHERE " +
"company_id = 435 "

Sending data by JDBC, strange case with StrictMode

My method working only with StrictMode, when i delete StrictMode, my app after the run this method loading in the infinity... and never stop.
I don't know why, somebody can explain it ?
public void sending() {
Connection co = null;
Statement st = null;
try {
StrictMode.ThreadPolicy po = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(po);
Class.forName("com.mysql.jdbc.Driver");
co = DriverManager.getConnection(url2, user2, pass2);
st = co.createStatement();
Double bb = latitude;
Double bb1 = longitude;
String sql2 = "INSERT table (tab1, tab2) VALUES('" + bb + "', '" + bb1 + "')";
st.executeUpdate(sql2);
} catch (SQLException se) {
se.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (st != null) {
co.close();
}
} catch (SQLException se) {
}
try {
if (co != null) {
co.close();
}
} catch (SQLException se) {
se.printStackTrace();
}
}
}

Your have a problem in your Query it should be :
"INSERT Into table (tab1, tab2) VALUES('" + bb + "', '" + bb1 + "')"
and not :
"INSERT table (tab1, tab2) VALUES('" + bb + "', '" + bb1 + "')"
You missed Into in your query.
Note
You can get syntax error or Sql injection with your way i suggest to use PreparedStatement it's more secure and more helpful like this :
PreparedStatement preparedStatement =
connection.prepareStatement("INSERT into table (tab1, tab2) VALUES(?, ?)");
preparedStatement.setString(1, bb);
preparedStatement.setString(2, bb1);

How can I speed up the execution of a large amount of SQL updates in Java (JDBC)

I'm trying to code a system for a large IRC channel (Twitch Channel)
One of the things I'm trying to do is log every user and give them points for being in the chat. For all intents and purposes the chat is just a large IRC channel. I'm retrieving the users in a big list from the twitch API, I put all the usernames in a large Array and running the following timer with a while loop:
timer = new Timer(900000, new ActionListener() {
public void actionPerformed(ActionEvent evt) {
updating = true;
try {
Arraynumber = 0;
TwitchBot.getDate();
arrayused = false;
System.out.println("trying to save users if theres enough stuff");
while(Arraynumber < TwitchBot.words.length){
TwitchBot.CheckUpdateUserSQL(TwitchBot.words[Arraynumber]);
Arraynumber++;
System.out.println("updating database");
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
As you can see it's a simple timer that picks the name from a String[] and runs every name through the script individually.
The updateuser looks like such:
public static void CheckUpdateUserSQL(String sqluser) throws ClassNotFoundException{
selectSQL(sqluser);
if (id == "thisuserdoesntexistforsure"){
InsertSQL(sqluser);
}
else{
int progress = CurrentTime - lastlogin;
int totalprogress = progress + totaltime;
if(progress < 60 && progress > 0){
c15 = null;
Statement stmt = null;
if(isonline == 1) {
coins = progress / 4;
}
else{
coins = progress / 5;
}
int coinsincrease = (int) Math.ceil(coins);
int coinstotal = coinsamount + coinsincrease;
Class.forName("org.sqlite.JDBC");
try {
c15 = DriverManager.getConnection("jdbc:sqlite:users.db");
c15.setAutoCommit(false);
stmt = c15.createStatement();
String sql = "UPDATE USERS set TOTALTIME = " + totalprogress + " where NAME='" + sqluser + "';";
stmt.executeUpdate(sql);
c15.commit();
String sql2 = "UPDATE USERS set LASTLOGIN = " + CurrentTime + " where NAME='" + sqluser + "';";
stmt.executeUpdate(sql2);
c15.commit();
String sql3 = "UPDATE USERS set TOTALCOIN = " + coinstotal + " where NAME='" + sqluser + "';";
stmt.executeUpdate(sql3);
c15.commit();
String sql4 = "UPDATE USERS set ISONLINE = 0 where NAME='" + sqluser + "';";
stmt.executeUpdate(sql4);
c15.commit();
stmt.close();
c15.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
else {
Connection c = null;
Statement stmt = null;
try {
c = DriverManager.getConnection("jdbc:sqlite:users.db");
c.setAutoCommit(false);
stmt = c.createStatement();
String sql2 = "UPDATE USERS set LASTLOGIN = " + CurrentTime + " where NAME='" + sqluser + "';";
stmt.executeUpdate(sql2);
c.commit();
stmt.close();
c15.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
This code checks whether an user exists. (using the select method, which is as concise as I can get it, it only search for an username and returns the id, which will be 'thisuderdoesntexistforsure' if nothing returns)
If the user exists it will run the code to calculate their online time and the increase in online time and points since the last time they visited. Then updates the code. If they were not online or if the time somehow returns a negative value (or one that's too high) it will instead only update the timestamp and skip the rest of the updates. This makes sure that users who leave for a day don't just get 1.400 minutes of online time when they log on five minutes the next day.
Anyway. My question is; How can I trim it down? I'm running into an issue where it will take 6 minutes to update the entire userlist. having 2000 users online is not rare and it would take 2,000 loops through that while loop to update them all. The program is updating more often then not. I've tried cutting down the code to be as condensed as possible, but I have no idea where to start to speed things up.
Sorry if I'm coming over as moronic, I'm relatively new to SQL and this is my biggest project yet in JAVA.

You can use batching to perform your updates, but in your given code a simpler optimization would be to update the values with one update call (instead of 4). Also, you could use PreparedStatement and try-with-resources close. Something like,
public static void CheckUpdateUserSQL(String sqluser) throws ClassNotFoundException {
selectSQL(sqluser);
if (id.equals("thisuserdoesntexistforsure")) {
InsertSQL(sqluser);
} else {
String sql = "UPDATE USERS set TOTALTIME = ?, LASTLOGIN = ?, "
+ "TOTALCOIN = ?, ISONLINE = 0 where NAME = ?";
String sql2 = "UPDATE USERS set LASTLOGIN = ? where NAME=?";
int progress = CurrentTime - lastlogin;
int totalprogress = progress + totaltime;
if (progress < 60 && progress > 0) {
if (isonline == 1) {
coins = progress / 4;
} else {
coins = progress / 5;
}
int coinsincrease = (int) Math.ceil(coins);
int coinstotal = coinsamount + coinsincrease;
Class.forName("org.sqlite.JDBC");
try (Connection conn = DriverManager.getConnection("jdbc:sqlite:users.db");
PreparedStatement ps = conn.prepareStatement(sql)) {
ps.setInt(1, totalprogress);
ps.setInt(2, CurrentTime);
ps.setInt(3, coinstotal);
ps.setString(4, sqluser);
ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
} else {
Class.forName("org.sqlite.JDBC");
try (Connection conn = DriverManager.getConnection("jdbc:sqlite:users.db");
PreparedStatement ps = conn.prepareStatement(sql2)) {
ps.setInt(1, CurrentTime);
ps.setString(2, sqluser);
ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}

What you need is batchupdate. Some good tutorial can be found on the internet.
An example can be the following:
stm = db.prepareStatement("INSERT INTO ITEM (ID, TYPE, TITEL, UITGELEEND) VALUES (?, ?, ?, ?)");
db.setAutoCommit(false);
for (int n = 0; n < ItemLijst.getItems().size(); n++) {
Item huidigItem = ItemLijst.getItemObvIdx(n);
stm.setString(1, huidigItem.getID().toString());
stm.setString(2, huidigItem.getType().toString());
stm.setString(3, huidigItem.getTitel());
stm.setString(4,String.valueOf(huidigItem.isUitgeleend()));
stm.addBatch();
}
String SQL = "UPDATE Employees SET age = 35 " +
"WHERE id = 100";
// Add above SQL statement in the batch.
stm.addBatch(SQL);
stm.executeBatch();
db.commit();
Also try avoiding joining strings, instead use '?', otherwise it will be subjected to sql injection attacks.
http://tutorials.jenkov.com/jdbc/batchupdate.html
http://www.tutorialspoint.com/jdbc/jdbc-batch-processing.htm

Not able to run executeUpdate()

I have been trying to insert data into DB using prepared statement but not able to run stmt.executeUpdate() The query will insert the field from the array which is declared below,The statement will set the values from the array.
long[] array = new long[100];
int[] devreg = new int[10];
int count = 0, index = 0;
try
{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(Constants.DB_URL, Constants.USER, Constants.PASS);
// LogMgr.dblogger.info(name +" : Database connection established"); //connection passed
}
catch (Exception e)
{
LogMgr.dblogger.info("Cannot connect to database" + e.toString()); //connection failure
}
if (conn != null) //if connection passed or available
{ //checking device registration
String InsertQuery = " INSERT INTO `acc_dev_db`.`widhb` (`name`,`age`, `type`) VALUES ";
int needacomma = 0;
for (int i=0; i< noofMsg; i++)
{
long empid = array[(i*indexlength)+1];
try
{
Statement s = conn.createStatement ();
s.executeQuery ("SELECT `empid` FROM `acc_dev_db`.`ID` WHERE `widevid` = "+empid+";");
ResultSet rs = s.getResultSet ();
if (rs.next())
{
devstatus = true;
if(needacomma>0)
{
InsertQuery = InsertQuery + ",";
}
InsertQuery = InsertQuery + "(?,?,?,?)";
needacomma += 1;
devreg[j] = i;
j++;
LogMgr.dblogger.info("ID found registered : " + empid); //found device id in the device table. Known device
}
else
{
LogMgr.dblogger.info("ID found not registered : " + empid);
}
rs.close ();
s.close ();
}
catch (Exception e) {
LogMgr.dblogger.info("Database reading error \n" + e.toString() ); //database reading error
}
}
if (devstatus == true) //if device is registered or known device
{
InsertQuery = InsertQuery + ";";
java.sql.PreparedStatement stmt = conn.prepareStatement(InsertQuery);
int loc = 1;
for (count = 0;count < j; count++)
{
int position = (indexlength*devreg[count]);
stmt.setLong(loc, array[position]);
System.out.println( array[position]);
stmt.setDouble(loc + 1, array[position + 1]);
System.out.println( array[position+1]);
stmt.setTimestamp(loc + 2,dateconvert(2, array[position + 2]));
System.out.println( array[position+2]);
stmt.setLong(loc + 3, array[position + 3]);
System.out.println( array[position+3]);
loc += 4;
}
LogMgr.jmslogger.info(stmt.toString());
try{
stmt.executeUpdate();
LogMgr.dblogger.info(name +" : studentdata update successfull from dev : " + devaddress);
}
catch(SQLException e){
System.out.println("EXCEPTION MAN!!!");
}
conn.close ();
}
Current O/P:
12355419
3740073994
491504582
43690
EXCEPTION MAN!!!

You Should throw SqlException or use try-catch block and for manage SqlException

Getting SQL error 1078 Before start of result set in Java program [duplicate]

This question already has answers here:
ResultSet exception - before start of result set
(6 answers)
Closed 5 years ago.
I have a Java method that is supposed to get column values from one MySQL row and create a string with the values. When run, it generates a SQL error 1078 "Before start of result set."
Here is the the class in which the error is occuring (Problem is in listPosesInSection method:
/** Class used to access the database */
import java.sql.*;
import java.util.ArrayList;
import javax.swing.JOptionPane;
public class YogaDatabaseAccess {
String dbUrl = "jdbc:mysql://localhost/yoga";
private Connection connection;
private ResultSet rset;
private ResultSetMetaData rsMetaData;
private Statement statement;
private PreparedStatement pStatementAll = null;
private PreparedStatement pStatementPartial = null;
// Strings for queries and updates
String strListPosesNotPrimary;
String strInsertNewClass;
String strInsertNewSection;
String strInsertNewPose;
String strUpdateClass;
String strUpdateSection;
String strUpdatePose;
String strArrangePoseOrder;
private String[] poseArray;
// Constructor
YogaDatabaseAccess() {
connectToDatabase();
}
// Method that connects to database
private void connectToDatabase() {
try {
connection = DriverManager.getConnection(dbUrl, "Kyle", "Kullerstrand#2");
System.out.println("Database connected");
}
catch(SQLException e) {
System.out.println(e.getMessage());
}
}
// Query that returns lists to be used with combo boxes
public String listForBoxes(String listName) {
// List to be returned
String strList = "";
// Determine name of the database table for this list
String listTableName;
if (listName == "pose")
listTableName = listName + "s";
else if (listName == "class")
listTableName = listName + "es";
else
listTableName = listName;
// Determine the database column name for this list
String listColumnName = listName + "_name";
// Run the query
try {
statement = connection.createStatement();
rset = statement.executeQuery("SELECT DISTINCT " + listColumnName + " FROM " + listTableName +
" ORDER BY " + listColumnName);
while (rset.next()){
strList = strList + rset.getString(listColumnName) + ", ";
}
} catch (SQLException e) {
e.printStackTrace();
}
return strList;
}
// Query that returns list of primary poses for a section
public String listPrimaryPoses(String sectionName) {
// List to be returned
String strList = "";
// Run the query
try {
statement = connection.createStatement();
rset = statement.executeQuery("SELECT DISTINCT pose_name FROM poses WHERE primarily_suitable_for = '" + sectionName +
"' OR primarily_suitable_for = 'Anything' ORDER BY pose_name");
while (rset.next()){
strList = strList + rset.getString("pose_name") + ", ";
}
} catch (SQLException e) {
e.printStackTrace();
}
return strList;
}
// Query that returns list of secondary poses for a section
public String listSecondaryPoses(String sectionName) {
// List to be returned
String strList = "";
// Run the query
try {
statement = connection.createStatement();
rset = statement.executeQuery("SELECT DISTINCT pose_name FROM poses WHERE sometimes_suitable_for = '" + sectionName + "' ORDER BY pose_name");
while (rset.next()){
strList = strList + rset.getString("pose_name") + ", ";
}
} catch (SQLException e) {
e.printStackTrace();
}
return strList;
}
// Query that returns the poses within a specific section
public String listPosesInSection(String tableName, String sectionName) {
String strList;
StringBuilder strBuilderList = new StringBuilder("");
// Run the query
try {
statement = connection.createStatement();
// Query will collect all columns from one specific row
rset = statement.executeQuery("SELECT * FROM " + tableName + " WHERE " + tableName + "_name = '" + sectionName + "'");
while (rset.next()) {
for (int i = 2; i <= countColumnsInTable(tableName); i++) // First value (0) is always null, skip section name (1)
if (rset.getString(i) != null) // If column has a value
strBuilderList.append(rset.getString(i) + "\n");
}
} catch (SQLException e) {
e.printStackTrace();
}
strList = strBuilderList.toString();
return strList.replaceAll(", $",""); // Strips off the trailing comma
}
// Insert statement that inserts a new class into the classes table
public void insertNewClass(String className) {
/** String insert = "INSERT INTO poses (pose_name, primarily_suitable_for, sometimes_suitable_for) values(?, ?, ?)";
System.out.println("About to create the prepared statement");
// Run the insert
try {
pStatement = connection.prepareStatement(insert);
// statement.execute("INSERT IGNORE INTO poses VALUES ('" + poseName + "', '" + suitableFor + "', '" + suitableForSometimes + "')");
pStatement.setString(1, poseName);
pStatement.setString(2, suitableFor);
pStatement.setString(3, suitableForSometimes);
System.out.println("Created the prepared statement");
// execute query, and return number of rows created
pStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} */
}
// Insert statement that inserts a new pose into poses table
public void insertNewPose(String poseName, String suitableFor, String suitableForSometimes) {
String insertAll = "INSERT INTO poses (pose_name, primarily_suitable_for, sometimes_suitable_for) values(?, ?, ?)";
String insertPartial = "INSERT INTO poses (pose_name, primarily_suitable_for) values(?, ?)";
// Run the insert
try {
if (suitableForSometimes == "NULL") { // Insert statement contains a null value for sometimes suitable column
pStatementPartial = connection.prepareStatement(insertPartial);
pStatementPartial.setString(1, poseName);
pStatementPartial.setString(2, suitableFor);
pStatementPartial.executeUpdate();
} else { // Insert statement contains values for all three columns
pStatementAll = connection.prepareStatement(insertAll);
pStatementAll.setString(1, poseName);
pStatementAll.setString(2, suitableFor);
pStatementAll.setString(3, suitableForSometimes);
pStatementAll.executeUpdate();
}
} catch (SQLException e) {
System.err.println("SQLException: " + e.getMessage() + ":" + e.getSQLState());
JOptionPane.showMessageDialog(null, "This pose already exists.");
} finally {
SQLWarning w;
try {
for (w = connection.getWarnings(); w != null; w = w.getNextWarning())
System.err.println("WARNING: " + w.getMessage() + ":" + w.getSQLState());
} catch (SQLException e) {
e.printStackTrace();
JOptionPane.showMessageDialog(null, "An unknown error in the yoga design program has occurred.");
}
}
}
// Insert statement that inserts a new section into warmup, work or restore sections
public void insertNewSection(String sectionType, String sectionName, ArrayList<String> poses) {
System.out.println("insertNewSection method was called");
int maxColumns = countColumnsInTable(sectionType);
poseArray = new String[poses.size()];
poseArray = poses.toArray(poseArray);
if (poseArray.length == 0)
JOptionPane.showMessageDialog(null, "There are no poses in this section. Please add poses.");
// Create a list of columns of the table for the INSERT statement
StringBuilder columns = new StringBuilder(sectionType + "_name");
for (int c = 1; c < maxColumns; c++)
columns.append(", pose_" + c);
// Create a string list of poses, separated by commas, from the array
StringBuilder values = new StringBuilder();
values.append("'" + poseArray[0] + "'");
for (int v = 1; v < poseArray.length - 1; v++)
values.append(", '" + poseArray[v] + "'");
// make sure query uses correct number of columns by padding the query with NULL
for (int i = poseArray.length; i < maxColumns; i++)
values.append(", NULL");
String posesToAddToSection = values.toString();
// The string containing the entire insert statement
String insert = "INSERT INTO " + sectionType + " (" + columns + ") VALUES ('" + sectionName + "', " + posesToAddToSection + ")";
// Run the insert
try {
statement = connection.createStatement();
statement.executeUpdate(insert);
} catch (SQLException e) {
System.err.println("SQLException: " + e.getMessage() + ":" + e.getSQLState());
JOptionPane.showMessageDialog(null, "An error in the yoga design program has occurred. SQLException: " +
e.getMessage() + ":" + e.getSQLState());
} finally {
SQLWarning w;
try {
for (w = connection.getWarnings(); w != null; w = w.getNextWarning())
System.err.println("WARNING: " + w.getMessage() + ":" + w.getSQLState());
} catch (SQLException e) {
e.printStackTrace();
JOptionPane.showMessageDialog(null, "An unknown error in the yoga design program has occurred.");
}
}
}
// Statement that deletes rows from tables
public void deleteRow(String tableName, String columnName, String rowName) {
String delete = "DELETE FROM " + tableName + " WHERE " + columnName + " = '" + rowName + "'";
// Run the insert
try {
statement = connection.createStatement();
statement.executeUpdate(delete);
System.out.println("Delete statement was run on Java's end.");
} catch (SQLException e) {
System.err.println("SQLException: " + e.getMessage() + ":" + e.getSQLState());
JOptionPane.showMessageDialog(null, "Sorry, something went wrong: SQLException: " +
e.getMessage() + ":" + e.getSQLState());
} finally {
SQLWarning w;
try {
for (w = connection.getWarnings(); w != null; w = w.getNextWarning())
System.err.println("WARNING: " + w.getMessage() + ":" + w.getSQLState());
} catch (SQLException e) {
e.printStackTrace();
}
}
}
// Method for getting the number of columns in a table using metadata
public int countColumnsInTable(String sectionType) {
int count = 16;
try {
// System.out.println(sectionType);
statement = connection.createStatement();
rset = statement.executeQuery("SELECT * FROM " + sectionType);
rsMetaData = rset.getMetaData();
count = rsMetaData.getColumnCount();
// System.out.println("Column count is " + count);
} catch (SQLException e) {
e.printStackTrace();
}
return count;
}
// Close the database and release resources
public void closeDatabase() {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
And here is the beginning of the error list:
java.sql.SQLException: Before start of result set
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1078)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:920)
at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:855)
at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5773)
at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5693)
at YogaDatabaseAccess.listPosesInSection(YogaDatabaseAccess.java:125)
at YogaSectionDesigner$5.actionPerformed(YogaSectionDesigner.java:229)

May be you can check this out:
ResultSet exception - before start of result set
Had the same Problem. Solved it that way.