Develop Reference

The conversion from UNKNOWN to UNKNOWN is unsupported exception (in Java program for migration)

I have a program to migrate data from an oracle database to a SQL Server database with the same structure.
private void migrateAllDataToMssql() throws Exception {
Connection connOracle = DBConnection.getConnection();
Connection connMssql = DBConnection.getConnectionToMsSql();
Statement selectAll = connOracle.createStatement();
ResultSet tableResultSet = selectAll.executeQuery("select table_name from dba_tables where owner= 'USER1'");
//insert to mssql db
while(tableResultSet.next()) {
String tableName = tableResultSet.getString("table_name");
if(tableName.equals("DATABASECHANGELOG_CORE") || tableName.equals("GLOBAL_PARAM") ||
tableName.equals("LOG") || tableName.equals("ORDERS") || tableName.equals("ORDER_BOOK")) {
System.out.println("do nothing");
}
else {
System.out.println(tableName);
try (PreparedStatement s1 = connOracle.prepareStatement("select * from " + tableName);
ResultSet rs = s1.executeQuery()) {
ResultSetMetaData meta = rs.getMetaData();
List<String> columns = new ArrayList<>();
for (int i = 1; i <= meta.getColumnCount(); i++)
columns.add(meta.getColumnName(i));
String identityInsertOn = "";
String sql = "INSERT INTO " + tableName + " ("
+ columns.stream().collect(Collectors.joining(", "))
+ ") VALUES ("
+ columns.stream().map(c -> "?").collect(Collectors.joining(", "))
+ ")";
String identityInsertOff = "";
if(tableName.equals("COMMODITY") || tableName.equals("DELIVERY_CODE") ||
tableName.equals("DELIVERY_CODE_ENUM") || tableName.equals("INS_CLASS") ||
tableName.equals("ORDER_TYPE") || tableName.equals("PRIVS_TO_ROLES") ||
tableName.equals("PROD_DEF_GROUP") || tableName.equals("RESULTS") ||
tableName.equals("ROLES")) {
identityInsertOn = "SET IDENTITY_INSERT " + tableName + " ON ";
identityInsertOff = " SET IDENTITY_INSERT " + tableName + " OFF ";
}
System.out.println(sql);
try (PreparedStatement s2 = connMssql.prepareStatement(
identityInsertOn +
sql +
identityInsertOff
)) {
while (rs.next()) {
for (int i = 1; i <= meta.getColumnCount(); i++) {
System.out.println(meta.getColumnType(i) + " " + i); //log which data type the column has
s2.setObject(i, rs.getObject(i));
}
s2.addBatch();
}
s2.executeBatch();
}
}
}}
}
It actually works fine but at some tables there occurs this SQLServerException:
Exception in thread "main" com.microsoft.sqlserver.jdbc.SQLServerException: The conversion from UNKNOWN to UNKNOWN is unsupported.
at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:234)
at com.microsoft.sqlserver.jdbc.DataTypes.throwConversionError(DataTypes.java:1094)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObject(SQLServerPreparedStatement.java:1595)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObjectNoType(SQLServerPreparedStatement.java:1493)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.setObject(SQLServerPreparedStatement.java:1502)
at test.DatabaseDataMigrator2.migrateAllDataToMssql(DatabaseDataMigrator2.java:179)
at test.DatabaseDataMigrator2.main(DatabaseDataMigrator2.java:36)
I have checked which data types the tables have and they have in common that there is a TIMESTAMP data type in each table of them but at some other tables where TIMESTAMP occurs as well, the exception does not appear. What could be the reason for this exception?

I just had to check if it was a timestamp column and if so then replace setObject with setDate
while (rs.next()) {
for (int i = 1; i <= meta.getColumnCount(); i++) {
System.out.println("Column type: " + meta.getColumnType(i) + " Iteration: " + i); //log which data type the column has
if(meta.getColumnType(i) == 93) {
s2.setDate(i, rs.getDate(i));
}else {
s2.setObject(i, rs.getObject(i));
}
}
According to the documentation columnType==93 means timestamp so that is what is checked in the if clause. After doing that the insert and set works fine.

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 "

Get a result from First SQL Query to use it at Second SQL Query which is inside First

How to make this one work? Obviously I don't know some very basic staff about SQL queries inside other SQL queries in Java but searching around didn't help!
Thank you in advance
try (Connection con = L2DatabaseFactory.getInstance().getConnection())
{
PreparedStatement stm = con.prepareStatement("SELECT count,owner_id FROM items WHERE item_id=57 order by count desc limit 10");
ResultSet rSet = stm.executeQuery();
while (rSet.next())
{
int owner_id = rSet.getInt("owner_id");
int count = rSet.getInt("count");
if (count == 0)
{
continue;
}
PreparedStatement stm1 = con.prepareStatement("SELECT char_name,accesslevel,online FROM characters WHERE obj_Id=" + owner_id);
ResultSet rSet1 = stm1.executeQuery();
while (rSet1.next())
{
int accessLevel = rSet.getInt("accesslevel");
if (accessLevel > 0)
{
continue;
}
String pl = rSet.getString("char_name");
int online = rSet.getInt("online");
String status = online == 1 ? "<font color=\"00FF00\">Online</font>" : "<font color=\"FF0000\">Offline</font>";
sb.append("<tr><td>"+ pl +"</td><td>"+ count +"</td><td>"+ status +"</td></tr>");
}
}
}
catch (Exception e)
{
_log.log(Level.SEVERE, "Error", e);
}

It looks like you are trying to join two tables using Java code. This is not such a great idea and not good for performance. Let the database do the joins for you - it is an expert at that. Do not code "inner joins" in Java.
Apart from that: the prepared statements are not being closed and this will sooner or later cause you trouble with OS resources.
My suggestion would be to create one single query with an inner join or a select in statement and also close all prepared statements using try with resources. Something along these lines:
private String test() throws SQLException {
StringBuilder sb = new StringBuilder();
int count = 0;
try (Connection con = L2DatabaseFactory.getInstance().getConnection()) {
try (PreparedStatement stm1 = con.prepareStatement(
"SELECT char_name,accesslevel,online FROM characters WHERE obj_Id in (SELECT owner_id FROM items WHERE item_id=57 order by count desc limit 10)")) {
ResultSet rSet = stm1.executeQuery();
while (rSet.next()) {
count++;
int accessLevel = rSet.getInt("accesslevel");
if (accessLevel > 0) {
continue;
}
String pl = rSet.getString("char_name");
int online = rSet.getInt("online");
String status = online == 1 ? "<font color=\"00FF00\">Online</font>" : "<font color=\"FF0000\">Offline</font>";
sb.append("<tr><td>" + pl + "</td><td>" + count + "</td><td>" + status + "</td></tr>");
}
}
} catch (Exception e) {
Logger.getLogger("test").log(Level.SEVERE, "Error", e);
}
return sb.toString();
}

Resultset always empty when doing executeQuery

I am currently writing a simple Java app that reads information from an XLS file and then enters it in the database. Since that XLS does have duplicated records, I do a simple check if the entry in the XLS file already exists in the database. Here is my code:
public static void addResult(ArrayList<ArrayList<String>> listResults)
{
try
{
openDatabase();
stmt = c.createStatement();
for (int i = 0; i < listResults.size(); i++)
{
PreparedStatement stm = c.prepareStatement("SELECT player_name FROM results WHERE player_name=?;");
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
System.out.println(stm);
ResultSet rs = stm.executeQuery();
if (rs.getRow() <= 0)
{
String typeOfPlay = new String();
if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
{
typeOfPlay = "single";
}
else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
{
typeOfPlay = "double";
}
stm = c.prepareStatement("INSERT INTO results (player_name, school_id, " + typeOfPlay + ", tournament_id) "
+ "VALUES(?,?,?,?);");
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
stm.setString(2, listResults.get(i).get(ReadResultsFile.SCHOOL_ID));
stm.setInt(3, Integer.parseInt(listResults.get(i).get(ReadResultsFile.SCORE)));
stm.setString(4, "1");
stm.executeUpdate();
}
else
{
String typeOfPlay = new String();
if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
{
typeOfPlay = "single";
}
else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
{
typeOfPlay = "double";
}
stm = c.prepareStatement("UPDATE results SET " + typeOfPlay + "=? WHERE player_name=?;");
stm.setString(1, typeOfPlay);
stm.setString(2, listResults.get(i).get(ReadResultsFile.SCORE));
stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
System.out.println(stm);
stm.executeUpdate();
}
}
closeDatabase();
}
catch (Exception e)
{
System.err.println(e.getClass().getName() + ": " + e.getMessage());
System.exit(0);
}
}
The problem that arises is that the rs.getRow() function always returns -1. I tried running the SELECT query directly in the database tool and the query returns the player_name column if there is already a similar entry existing. It unfortunately do the same in Java.
I am unsure what to do at this point.
Thank you for any hint!

getRow will not work as per the javadocs
Retrieves the current row number. The first row is number 1, the second number 2, and so on.
and
A ResultSet cursor is initially positioned before the first row; the
first call to the method next makes the first row the current row
Usually use
while (rs.next ()) {....

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