image showing my jFrame
I am making a frame which shows records in the sql table one-by-one using text fields as shown. While writing the code for the next button, I need to know the position of the result set to go to the next record. For this purpose, I used a do-while loop with an "if" condition. Following is my code:
try{
Connection conn=null;
Statement stmt=null;
ResultSet rs=null;
String url="jdbc:mysql://localhost/MYORG", userid="root", pwd="shreyansh";
conn=DriverManager.getConnection(url,userid,pwd);
stmt=conn.createStatement();
String query="select * from emp;";
rs=stmt.executeQuery(query);
String search=jTextField1.getText();
String search1=jTextField2.getText();
double search2=Double.parseDouble(jTextField3.getText());
String search3=jTextField3.getText();
rs.first();
do{
if(rs.equals(new Object[] {search, search1, search2, search3}))
break;
}while(rs.next());
rs.next();
String nm=rs.getString("Name");
String desg=rs.getString("Designation");
double pay=rs.getDouble("Pay");
String city=rs.getString("City");
jTextField1.setText(nm);
jTextField2.setText(desg);
jTextField3.setText(pay + "");
jTextField4.setText(city);
}catch(Exception e){
JOptionPane.showMessageDialog(null, e.getMessage());
}
But it shows an error "after end of Result Set".
Please help me with this.
Any suggestions to make my code better are also welcome.
Thanks in Advance!!
You can't use ResultSet.equals for this, because that is not what the Object.equals contract is for. It is for checking if an object is equal to another object of the same (or at least compatible) type. A ResultSet will therefor never be equal to an array of object values.
It looks like you want to select a single row from the emp table that matches your search values, in that case the correct solution is to ask the database for only that row. Selecting all rows and then filtering in your Java application is very inefficient, because the database has to send all rows to your application, while finding data is exactly what a database is good at.
Instead, you should use a where clause with a prepared statement:
try (Connection connection = DriverManager.getConnection(url, userid, pwd);
PreparedStatement pstmt = connection.prepareStatement(
"select * from emp where Name = ? and Designation = ? and Pay = ? and City = ?")) {
pstmt.setString(1, search);
pstmt.setString(2, search1);
pstmt.setDouble(3, search2);
pstmt.setString(4, search3);
try (ResultSet rs = pstmt.executeQuery()) {
if (rs.next() {
String nm = rs.getString("Name");
String desg = rs.getString("Designation");
double pay = rs.getDouble("Pay");
String city = rs.getString("City");
jTextField1.setText(nm);
jTextField2.setText(desg);
jTextField3.setText(String.valueOf(pay));
jTextField4.setText(city);
} else {
// handle not found case
}
}
}
Related
I would like to know if what am I lacking here, I can't compare the 'id' from the Textfield to the data from the database.
For example:
If TextField1 == to the data in the database.
Output: Swept by GSW.
Connection con = connect.getConnection();
String query = "SELECT * FROM item_list WHERE id = ?";
Statement st;
ResultSet rs;
int id;
try{
st = con.createStatement();
rs = st.executeQuery(query);
while(rs.next()){
id = rs.getInt("id");
if(Integer.parseInt(TF[0].getText()) == id){
System.out.println(id);
}
}
}catch(SQLException exc){
System.out.println("Not Found!");
}
Kindly Check the Image Output.
I attached the image file below.
Sample Output
Here are some mistake I see
You use a parameter in the query, "SELECT * FROM item_list WHERE id = ?";so use a PreparedStatement
Set the parameter to that PreparedStatement ps = connection.preparedStatement(query); with ps.setInt(1, Integer.parseInt(TF[0].getText()));
Don't catch the exception without logging it, here your query as a syntax error but you don't know it.
careful with uppercase in the database field name "Id"
This might not be everything ...
And of course, now that you get only the row with that ID, you can simply check if there is at least one row return to validate that it exists.
First of all, you need to log a stack trace of an exception that is thrown. At least you can use exc.printStackTrace() in your catch section.
Second, your issue is that you declared a parameter for your SQL query, but you have not put any value to it.
PreparedStatement p = con.prepareStatement("SELECT * FROM item_list WHERE id = ?");
p.setString(1, TF[0].getText() ); //VALUE_FROM_YOUR_TEXT_INPUT
You don't need to iterate over all result set to check if a user with such id exists. You can just check that result set is not empty.
you can use intValue() for Integer object obvious if your object is not null
while(rs.next()){
id = rs.getInt("id");
if(Integer.parseInt(TF[0].getText()).intValue() == id){
System.out.println(id);
}
}
You're not setting the value of the id parameter in the statement. Not familiar with Java but in C# it would be something like
statement.Parameters.AddWithValue("#id", id)
Thank You guys! I've been trying and reading all your suggestions, and I've found and debugged it. Thanks to the one said that I need to check what message I can get in the catch.
Appreciated all your help.
Connection con = connect.getConnection();
String query = "SELECT * FROM item_list";
Statement st;
ResultSet rs;
int id;
try{
st = con.createStatement();
rs = st.executeQuery(query);
while(rs.next()){
id = rs.getInt("id");
if(Integer.parseInt(TF[0].getText()) == id){
System.out.println(id);
JOptionPane.showMessageDialog(null, "FOUND!");
}
else{
JOptionPane.showMessageDialog(null, "Not Found!");
}
}
}catch(SQLException exc){
JOptionPane.showMessageDialog(null, exc.getMessage());
}
ID Found!
I have a strange problem. I have a database and I want to change the values of a column. The values are safed in an Arraylist (timelist).
In order to write the values in the right row, I have a second Arrylist (namelist). So I want to read the first row in my Database, than I check the namelist and find the name. Than i take the matching value out of the timelist and write it into the database into the column "follows_date" in the row, matching to the name.
And than I read the next row of the Database, until there are no more entries.
So the strange thing is, if I change nothing in the database, the while(rs.next()) part works.
For example:
ResultSet rs = statement.executeQuery("SELECT username FROM users");
while(rs.next()){
// read the result set
String name = rs.getString("username");
System.out.println("username = " + name); //liest die namen
}
}
This would print me every name after name. But when I change the table, the while loop ends after that. (no error, the program just finishes)
ResultSet rs = statement.executeQuery("SELECT username FROM users");
while(rs.next()){
// read the result set
String name = rs.getString("username");
System.out.println("username = " + name); //writes the name
//look, if name is in Arraylist "namelist"). if yes, than write the matching date from "timelist" into the database.
if (namelist.contains(name)){
System.out.println("name found: "+ name);
int listIndizi = namelist.indexOf(name); //get index
Long indiziDatum = (long) timelist.get(listIndizi); //get date from same Index
System.out.println(indiziDatum); // print date so i can see it is correct (which it is)
statement.executeUpdate("UPDATE users SET follows_date ="+ indiziDatum +" WHERE username = '"+name+"'"); //updates the follows_date column
}
}
Everything works fine, except that now, the while loop doesn't continues after the first passage, but ends.
The resultSet of a statement is closed and will not return further results if you execute another statement. Create a new separate statement object for the update and everything should work as excepted.
Statement statement1 = connection.createStatement();
Statement statement2 = connection.createStatement();
ResultSet resultSet1 = statement1.executeQuery("SELECT username FROM users");
while(resultSet1.next()){
...
statement2.executeUpdate("UPDATE users ..."));
}
As to Why it happens:
Here is the explanation from the official documentation:
A ResultSet object is automatically closed when the Statement object that generated it is closed, re-executed, or used to retrieve the next result from a sequence of multiple results.
Alternative Approach:
From your sample, it seems you are trying to update the "same" row in your resultSet, you should consider using an Updatable ResultSet.
Sample code from the official documentation:
public void modifyPrices(float percentage) throws SQLException {
Statement stmt = null;
try {
stmt = con.createStatement();
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_UPDATABLE);
ResultSet uprs = stmt.executeQuery(
"SELECT * FROM " + dbName + ".COFFEES");
while (uprs.next()) {
float f = uprs.getFloat("PRICE");
uprs.updateFloat( "PRICE", f * percentage);
uprs.updateRow();
}
} catch (SQLException e ) {
JDBCTutorialUtilities.printSQLException(e);
} finally {
if (stmt != null) { stmt.close(); }
}
}
Well I was wondering if there is any other way to get data from a SQL Query.
What I mean is that the "main" code that I always find is
Connection con = (connect to db)
PreparedStatement st = con.prepareStatement(....);
ResultSet rs = ps.executeQuery();
while (rs.next())
{
//do something
}
But if I want to retrieve specific data for example lets assume that my query is
Connection con = L2DatabaseFactory.getInstance().getConnection();
PreparedStatement ps = con.prepareStatement("SELECT login,email FROM accounts WHERE login=?");
ps.setString(1, account);
ResultSet rs = ps.executeQuery();
while (rs.next())
{
if (rs.getString("login").equals(account))
{
email = rs.getString("email");
break;
}
}
Is there any other way except that while loop to retrieve data?
The if condition inside the while loop is completely redundant - the where clause takes care of it and assures that any data returned from this query would have a login field that's equal to the value of account.
If you're sure there's no more than one row like this (e.g., the login column is a unique identifier in your table), you could just replace the while loop with an if:
// Check that such a logic exists
if (rs.next()) {
email = rs.getString("email");
}
// for good measures, just double check there isn't more than one
// of these logins:
if (rs.next()) {
throw new Exception ("This cannot be!"); // Or something more sensible
}
I have a mysql table user which is consisted of id, name, password and email columns.
Is there a way to create some sort of query or java code that will print in my message dialog window all of the users names.
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/mydb","root","");
String sql = "select * from user;";
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(sql);
if (rs.next()) {
val1 = rs.getString(2);
val2 = rs.getString(3);
}
value = val1 + " " + val2;
JOptionPane.showMessageDialog(null,value);
}catch(SQLException e){
JOptionPane.showMessageDialog(null, e);
}
}
This only prints the name and the surname of the first user from the table :(
I want to print them all one below another!
If I set rs.getString(5); - it gives me an error: column index out of range.
I suggest you avoid JOptionPane for this kind of code. Better to use some Frame (Swing) and display all of the users into a separate window.
The problem with your code is that variable value is lyiong outside of the loop (which must be btw while loop, as spencer said).
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/mydb","root","");
String sql = "select * from user;";
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(sql);
while (rs.next()) {
val = rs.getString(2) + " " + rs.getString(3);
value += val + " ";
}
JOptionPane.showMessageDialog(null,value);
}catch(SQLException e){
JOptionPane.showMessageDialog(null, e);
}
}
Try to avoid this type of code, use ArrayList and save in the array all of the users credentials. Then easily label it wherever you want.
You're only fetching the first row from the resultset. It sounds like you want a loop, and process every row from the resultset.
while (rs.next()) {
}
UPDATE
Q: It only gives me now the last user. Probably because it overwrites the val1 and val2 variable. I suppose somehow this should also goes into the loop..
A: Yes, it should go inside the loop. But I'd be populating a collection, rather than concatenating a String.
As a performance and maintenance note, you can avoid the messiness of the string concatenation in the Java by doing the concatenation in the SQL statement. I wouldn't use SELECT * and rely on the positions of two particular columns in the resultset.
I'd use a SQL statement like this:
SELECT CONCAT(u.first_name,' ',u.last_name) AS user_name FROM users
If I wasn't populating a collection, and I needed to concatenate a honkous string, I'd use a StringBuffer, e.g.
val = new StringBuffer(4096));
while (rs.next()) {
val.append(rs.getString("user_name"));
}
value = val.toString;
I have been searching and trying different stuff for awhile, but have not found an answer. I'm trying to make a connection to sql using JDBC from eclipse. I am having trouble when I need to select a string in the database. If I use:
Select name from data where title = 'mr';
That works with terminal/command line but when I try to use eclipse where I use
statement sp = connection.createstatement();
resultset rs = sp.executequery("select name from data where title = '" + "mr" + "'");
It does not give me anything while the terminal input does. What did I do wrong in the eclipse? Thanks
Heres a part of the code. Sorry, its a bit messy, been trying different things.
private boolean loginChecker(String cid, String password) throws SQLException{
boolean check = false;
PreparedStatement pstatment = null;
Statement stmt = null;
//String query = "SELECT 'cat' FROM customer";
String query = "select '"+cid+"' from customer where password = '"+password+"'";
try {
System.out.println("in try......");
//stmt = con.createStatement();
//ResultSet rs = stmt.executeQuery(query);
PreparedStatement prepStmt = con.prepareStatement(query);
ResultSet rs = prepStmt.executeQuery();
//System.out.print(rs.getString("cid"));
while(rs.next()){
check = true;
System.out.print(rs.getString("cid"));
}
} catch (SQLException e ) {
e.printStackTrace();
} finally {
if (stmt != null) {
//stmt.close();
}
}
return check;
}
Second try on a simpler query:
public List<Object> showTable() {
List<Object> result = new ArrayList<Object>();
String name = "bob";
try
{
PreparedStatement preStatement = con.prepareStatement("select total from test where name = ?");
preStatement.setString(1, name);
ResultSet rs1 = preStatement.executeQuery();
while(rs1.next()){
System.out.println("there");
System.out.println(rs1.getInt("total"));
}
}
catch (SQLException ex)
{
System.out.print("Message: " + ex.getMessage());
}
return result;
}
Remove the quotes around the column name.
String query = "select "+cid+" from customer where password = '"+password+"'";
You've not mentioned which database you're working with but many databases like Oracle change the column case to upper case unless they're quoted. So, you only quote table columns if that's how you had created them. For example, if you had created a table like
CREATE TABLE some_table ( 'DoNotChangeToUpperCase' VARCHAR2 );
Then you would have to select the column with quotes as well
SELECT 'DoNotChangeToUpperCase' FROM some_table
But, if you didn't create the table using quotes you shouldn't be using them with your SELECTs either.
Make sure you are not closing the ResultSet before you are trying to use it. This can happen when you return a ResultSet and try to use it elsewhere. If you want to return the data like this, use CachedRowSet:
CachedRowSet crs = new CachedRowSetImpl();
crs.populate(ResultSet);
CachedRowSet is "special in that it can operate without being connected to its data source, that is, it is a disconnected RowSet object"
Edit: Saw you posted code so I thought I add some thoughts. If that is your ACTUAL code than the reason you are not getting anything is because the query is probably not returning anything.
String query = "select '"+cid+"' from customer where password = '"+password+"'";
This is wrong, for two reasons. 1) If you are using prepared statements you should replace all input with '?' so it should look like the following:
String query = "select name from customer where password = ?";
Then:
PreparedStatement prepStmt = con.prepareStatement(query);
prepStmt.setString(1, password);
ResultSet rs = prepStmt.executeQuery();
2)
System.out.print(rs.getString("cid"));
Here are are trying to get the column named "cid", when it should be the name stored in cid. You should actually never be letting the user decide what columns to get, this should be hardcoded in.