I have to design an application for accessing excel application as database. My problem is I have to create multiple connection for each transaction and if I miss any of closing it, the excel is not being update.
I want to design pattern where i am able to access the excel. Any one help me in designing a common pattern through which i wont be having problem. I want something like this, but we are not able to use it to access excel.
Thanks in advance!
i have this method in utility class
static ResultSet getExcelData(String filePath,String sqlQuery){
ResultSet rs=null;
try{
conn = DriverManager.getConnection("jdbc:odbc:Driver={Microsoft Excel Driver (*.xls, *.xlsx, *.xlsm, *.xlsb)};DBQ="+filePath+";READONLY=false");
stmt= conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
rs=stmt.executeQuery( sqlQuery );
}catch (Exception e) {
e.printStackTrace();
return null;
// TODO: handle exception
}finally{
}
return rs;
}
and i am calling it this way
ResultSet rs=JdbcUtil.getExcelData("D:\\AB_demo\\AB_demo\\test.xls", "Select max(int(ID)) from [MAIN$] where HEADER_IND is not Null AND int(ID)<"+excelId);
int databaseId = 0;
if(rs.next())
{
databaseId=rs.getInt(1);
}
ResultSet rs1=JdbcUtil.getExcelData("D:\\AB_demo\\AB_demo\\test.xls", "SELECT * from [MAIN$] where id= '"+databaseId+"'or id='"+excelId+"'");
i am calling this method twice after which im updating the excel file by using
stmt.executeUpdate(sql);
its returning the integer 1 but its not reflecting in excel.when i use process explorer the file is still in use.i need a design pattern or come code to overcome his kind of problem.
I think more right way is generate Excel file from database. Otherwise you must create server side for ensure transactions and connections control.
Main problem of your task - Excel is
not database
not network database
Other words you must use other tools, other approach for your tasks.
Related
i created a kafka producer on java that works fine, now im trying to store the data produced in an mySQL database but i don't know how. i tried this code but it doesn't work
try {
String MyUrl = "jdbc:mysql://130.2.2.2/pfa";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(MyUrl, "root", "");
Statement stm = con.createStatement();
ResultSet rs = stm.executeQuery("select * from tmp");
while(rs.next()) {
producer.send(new ProducerRecord<String, String>("test",rs.getString(1)));
con.close();
}
}catch(Exception e) {System.out.println(e);}
any help is much appreciated about sending data to the database
I'm not sure I understand what you're expecting to happen from that code.
You're reading from the database, never inserting into it
You're closing the database connection after every loop iteration, meaning you'll get an exception that the database is already closed on the second loop, and therefore the resultset might terminate as well (I'm a little fuzzy on if those are lazy objects or not)
Might I suggest that you follow the Deep Dive on the JDBC connector? https://dev.to/rmoff/kafka-connect-jdbc-sink-tips-tricks-video-walkthrough-2egf
i copy pasted it literally becoz the writer said it worked
This will never be a good way to learn anything. You can read the code and type it all back out, explaining it to yourself as you go... But never blindly copy something that you assume solves your problem
Usually a SQLite db is read from a file. Each operation can require a file I/O operation if the db is large enough, and this can be slow.
However SQLite provides a way to load the db to memory - where it can be accessed using a JDBC url which looks something likejdbc:memory...
For example, this question describes how to achieve this using python: How to load existing db file to memory in Python sqlite3?
However I can't figure out how to achieve the same thing in Java or Scala using JDBC.
Any ideas?
I just tried with Xerial's sqlite-jdbc-3.27.2.1.jar and it appears that they let us restore from a native (binary) SQLite database file into a :memory: database like so:
try (Connection conn = DriverManager.getConnection("jdbc:sqlite::memory:")) {
try (Statement st = conn.createStatement()) {
st.execute("restore from C:\\__tmp\\thing.sqlite");
// let's see if we can read one of the tables
ResultSet rs = st.executeQuery("SELECT * FROM Table1");
while (rs.next()) {
System.out.println(rs.getString(1));
}
}
} catch (Throwable e) {
e.printStackTrace(System.err);
}
So, for a school project, I am building a discord bot. One of the features that I have built in is that he can retrieve gif links from a MySQL database, and send them in a message. Now, my issue is that I am only able to retrieve one record from my database, and no other records. If I put the query that I use into MySQL workbench and run it, it will retrieve those records.
This is the method for retrieving the gifs
public static ArrayList<Gif> GetGifsFromDB(String msg){
ArrayList<Gif> gifs = new ArrayList<>();
try(Connection conn = (Connection)DriverManager.getConnection(url, userName, password)){
Class.forName("com.mysql.jdbc.Driver").newInstance();
Statement stmnt = conn.createStatement();
String sql = "Select * from gif WHERE Type = '" + msg + "'";
stmnt.execute(sql);
try(ResultSet rs = stmnt.getResultSet()){
while(rs.next()){
Gif g = new Gif();
g.setID(rs.getInt("GifID"));
g.setURL(rs.getString("GifURL"));
System.out.println(g.getID() + g.getURL());
gifs.add(g);
}
rs.close();
conn.close();
}
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
catch(Exception ex){
System.err.println(ex.getMessage());
}
return gifs;
}
The "Type" in the database it just a category. With the test data I have in there, the 3 types are no, surprised and lonely. Only no returns a gif.
Remove closing ResultSet and Connection lines:
rs.close();
conn.close();
You are already closing it using try-with-resources
Issue ended up being with MySql not committing records to the database. Once workbench was refreshed, the added records disappeared. Rather strange that even though the records weren't in the database, they could be retrieve.
Most likely your msg is not exactly matching with any of the values for the database Type column.
Test by running
SELECT COUNT(*) FROM gif WHERE Type = '... put msg content here ...'
Do this manually directly on the database.
You can also try to put following line of code at the end:
System.out.println("Number of Selected Gifs: "+gifs.size());
If either of those results zero, then it means that msg was not exactly matched with Type. Maybe uppercase/lowercase issue?
Also to avoid SQL Injection, and other issues, please strongly consider using bind variables using a PreparedStatement.
I am new to using Derby and databses in eclipse, and I have become a tad lost and in need to a bit of help. I have established a database connection, created a new database, and a new schema, within which I have some tables containing some test data. I don't have any problem with the sql queries to select the relevant data. The problem I have is getting to a point where I can use queries. I am trying to create a class which connects to the database, and for testing purposes, uses a simple query to select some data. This is what I have so far:
public void getExerciseInfo() {
try {
Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
connect = DriverManager.getConnection("jdbc:derby://localhost/c:/TestDatabase");
PreparedStatement statement = connect.prepareStatement("SELECT * from TESTSCHEMA.TESTTABLE");
resultSet = statement.executeQuery();
while (resultSet.next()) {
String name= resultSet.getString("NAME");
String type = resultSet.getString("TYPE");
System.out.println(name);
System.out.println(type);
}
} catch (Exception e) {
} finally {
close();
}
}
All I am trying to do is output the data in the table to the console, but I cant even do this simple task :( Im guessing my connection url is invalid, is it supposed to be the file path to the database folder in my eclipse workspace?
Anyhow, I am very lost, and any help would be greatly appreciated.
Did you take a look over: http://db.apache.org/derby/integrate/plugin_help/derby_app.html ? You seem to be using the network server but your db URL is wrong.
If you are not running the Derby server, you can establish an embedded database connection or use an EmbeddedDataSource, shown here.
I am working a Airsoft application.
I'm trying to add records to a MS Access Database via SQL in Java. I have established a link to the database, with the following:
try
{
//String Driver = "sun.java.odbc.JdbcOdbcDriver";
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn = DriverManager.getConnection("jdbc:ucanaccess://" + URL,"","");
Statement stmt = conn.createStatement();
System.out.println("Connection Established!");
ResultSet rs = stmt.executeQuery("SELECT * FROM AirsoftGunRentals");
tblRent.setModel(DbUtils.resultSetToTableModel(rs));
}
catch(Exception ex)
{
JOptionPane.showMessageDialog(null, "Error");
}
I am using Ucanaccess to access my MS database. It is reading the database and is displaying to a JTable. However, I need to create three JButtons to add, delete and update the table. I have tried to code the add button, and I have tried to add a record, but it crashes and gives me errors.
try
{
//String Driver = "sun.java.odbc.JdbcOdbcDriver";
Class.forName("net.ucanaccess.jdbc.UcanaccessDriver");
Connection conn = DriverManager.getConnection("jdbc:ucanaccess://" + URL,"","");
Statement stmt = conn.createStatement();
System.out.println("Connection Established!");
String Query= "INSERT INTO AirsoftGunRentals(NameOfGun, Brand, TypeOfGuns, NumberOfMagazines,Extras,NumberAvailable,UnitRent)"+
"VALUES('"+pName+"','"+pBrand+"','"+pTypeOfGun+"','"+pNumMags+"','"+pExtras+"','"+pNumberAvail+"','"+pRent+"');";
ResultSet rs = stmt.executeQuery(Query);
JOptionPane.showMessageDialog(null, "Success!");
}
catch(Exception ex)
{
JOptionPane.showMessageDialog(null, "Error");
}
I have attempted all three, hoping for a result. But am still getting big errors. The only difference between the buttons is that one adds, one deletes and one updates the table. Other then that, the code is the same, minus variables.
As Brahim mentionned it, you should use stmt.executeUpdate(Query) whenever you update / insert or delete data. Also with this particular query, given your String concatenation (see end of line), there is no space between the ")" and the "VALUES" which probably causes a malformed query.
However, I can see from your code that you are not very experienced with such use-cases, and I'd like to add some pointers before all hell breaks loose in your project :
Use PreparedStatement instead of Statement and replace variables by placeholders to prevent SQL Injection.
The code that you are using here is extremely prone to SQL injection - if any user has any control over any of the variables, this could lead to a full database dump (theft), destruction of data (vandalism), or even in machine takeover if other conditions are met.
A good advice is to never use the Statement class, better be safe than sorry :)
Respect Java Conventions (or be coherent).
In your example you define the String Query, while all the other variables start with lower-case (as in Java Conventions), instead of String query. Overtime, such little mistakes (that won't break a build) will lead to bugs due to mistaking variables with classnames etc :)
Good luck on your road to mastering this wonderful language ! :)
First add a space before the quotation marks like this :
String Query= "INSERT INTO AirsoftGunRentals(NameOfGun, Brand, TypeOfGuns, NumberOfMagazines,Extras,NumberAvailable,UnitRent) "+
" VALUES('"+pName+"','"+pBrand+"','"+pTypeOfGun+"','"+pNumMags+"','"+pExtras+"','"+pNumberAvail+"','"+pRent+"');";
And use stmt.executeUpdate(Query); instead of : stmt.executeQuery(Query);in your insert, update and delete queries. For select queries you can keep it.
I managed to find an answer on how to add, delete and update records to a MS Access DB. This is what I found, after I declared the connection, and the prepped statement. I will try to explain to the best I can. I had to add values individually using this:
(pstmt = Prepped Statement Variable)
pstmt.setWhatever(1,Variable);
And it works fine now. I use the same method to delete and update records.
This is the basic query format:
String SQLInsert = "INSERT INTO Tbl VALUES(NULL,?,?,?,?)";
The NULL in the statement is the autonumber in the table. and .setWhatever() clause replaces the question marks with the data types. Thus manipulating the database.
Thank you everyone for all your contributions. It helped a lot, and made this section a lot more understandable.