I'm trying to get some data from Oracle 11.2 using java and jdbc driver.
My goal is to get data from database using CallableStatement, but with no luck - I'm not able to put table name as parameter. I would like to have configurable table name in query. However, it would be good to keep it sanitized.
Here is an example..
public void getData() throws SQLException {
Connection conn = Config.getSQLConnection();
String query = "SELECT * FROM ?";
PreparedStatement st = conn.prepareStatement(query);
st.setString(1, Config.DATATABLE_NAME);
ResultSet rs = st.executeQuery();
if (rs.next()) {
System.out.println("SUCCESS");
System.out.println("ID:" + rs.getString("ID"));
} else {
System.out.println("FAILURE");
}
}
Is this the way it should work? Or am I missing something, or misused it?
A CallableStatement is used to make call to stored procedures.
From javadoc:
The interface used to execute SQL stored procedures
Use a PreparedStament instead for a normal select.
As an additional note don't pass the name of the table as parameter.
Create the query using concatenation.
Instead of
String query = "SELECT * FROM ?";
use
String query = "SELECT * FROM " + Config.DATATABLE_NAME;
You should use PreparedStatement instead of CallableStatement.
CallableStatement is an interface which is used to call stored procedures.
Related
The query inside MySQL is working:
DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'
I can delete data inside MySQL, but the problem is whenever I try to remove the account_tags from my Java application, it throws an error:
java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELETE FROM f9.yoo
WHERE account_tags = '#8GGGJPUR9'' at line 2
Here's my Java SQL query:
Statement statement = dbConnection.createStatement();
String sql = "SELECT * FROM "+databaseName+"."+tableName+";\n" +
"DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = '"+AccountTag+"';";
statement.executeQuery(sql);
The error isn't giving me much to work with, so I really have no idea what is wrong with the program.
Did you add the allowMultiQueries=true
If not then you can add that while you sending the connecting request to your database. So you need to append the allowMultiQueries=true in your to database URL.
Like this:
String dbUrl = "jdbc:mysql:///test?allowMultiQueries=true";
String sql = "DELETE FROM "+databaseName+"."+tableName+"\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
int updateCount = statement.executeUpdate();
System.out.printf("%s: %d records deleted.%n", tableName, updateCount);
}
The only thing used is the DELETE, for which one should use executeUpdate.
One definitely should use a PreparedStatement as many code checkers will give alarms otherwise. It escapes things like ', handles types of the arguments, and possible conversions, and especially is a security feature against SQL injection.
The System.out usage is bad style, better would be using a logger.
try-with-resources automatically closes the PreparedStatement even with a raised exception or break/return.
When doing both database operations, it seems better to use two (prepared) statements, as the first returns a ResultSet.
So:
String sql = SELECT * FROM "+databaseName+"."+tableName + "\n" +
"WHERE account_tags = ?";
try (PreparedStatement statement = dbConnection.prepareStatement(sq)) {
statement.setString(1, AccountTag);
try (ResultSet rs = statement.executeQuery()) {
...
}
}
Better to separate statements with an If condition :
String sql1="SELECT * FROM "+databaseName+"."+tableName;
String sql2="DELETE FROM "+databaseName+"."+tableName+" "+
"WHERE account_tags = '"+AccountTag+"';
statement.executeQuery(sql1);
statement.executeUpdate(sql2);
i have created prepared statement object .
now i want to get the result of multiple queries . is it possible to do using single prepared statement object/ find the piece code below
PreparedStatement ps = null;
String moviedirectorQry = "SELECT movie_director FROM movies WHERE movie_title= ?";
ps = dbConnection.prepareStatement(moviedirectorQry);
ps.setString(1, "Twilight");
ResultSet rs=null;
rs = ps.executeQuery(moviedirectorQry);
while (rs.next()) {
String director_name = rs.getString("movie_director");
System.out.println("director name : " + director_name);
}
now i want to run another query.. how to do
If the idea is to use the same PreparedStatement for different queries of the same type with only parameters' value that change, yes it is possible, simply call clearParameters() first to clear the parameters in case you want to reuse it before setting the new parameters' value.
The code could be something like that:
if (ps == null) {
// The PreparedStatement has not yet been initialized so we create it
String moviedirectorQry = "SELECT movie_director FROM movies WHERE movie_title= ?";
ps = dbConnection.prepareStatement(moviedirectorQry);
} else {
// The PreparedStatement has already been initialized so we clear the parameters' value
ps.clearParameters();
}
ps.setString(1, someValue);
ResultSet rs = ps.executeQuery();
NB: You are supposed to use executeQuery() not ps.executeQuery(moviedirectorQry) otherwise the provided parameters' value will be ignored such that the query will fail.
A security scan made by AppScan source flags that the input has to be validated (Validation.Required) on the line uprs.updateString in the code below:
PreparedStatement statement =
conn.prepareStatement (query, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
...
ResultSet uprs = statement.executeQuery ();
...
// Update DB ColumnA with input coming from client
uprs.updateString ('ColumnA', unvalidatedUserInput);
...
// Updates the underlying database
uprs.updateRow();
I assume that the intention behind this is to avoid SQL injection attacks, but I'm not sure whether that is possible in that scenario.
Questions: Are SQL Injection attacks possible through these JDBC methods? How does JDBC implements this under the scenes? Would this be another false positive reported by AppScan?
I'm not sure about bluemix-app-scan, but I'm providing my explanation here. (This is my assumption based on the below tests and code pasted)
I ran a test code to check this (in H2 DB)
value of testName String : (select 'sqlInjection' from dual)
Using createStatement (Not-Safe):
String query = "update TEST_TABLE set TEST_CHAR = " + testName + " where ID = 1";
Statement statement = connection.createStatement();
statement.executeUpdate(query);
Output: TEST_CHAR in DB was sqlInjection.
Using ResultSet of createStatement (Safe in H2 DB):
String query = "select * from TEST_TABLE where ID = 1";
Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
ResultSet executeQuery = statement.executeQuery(query);
executeQuery.next();
executeQuery.updateString("TEST_CHAR", testName);
executeQuery.updateRow();
Output: Surprisingly TEST_CHAR in DB was (select 'sqlInjection' from dual).
Using PreparedStatement (Safe):
String query = "update TEST_TABLE set TEST_CHAR = ? where ID = 1";
PreparedStatement statement = connection.prepareStatement(query);
statement.setString(1, testName);
statement.executeUpdate();
Output: Expected - TEST_CHAR in DB was (select 'sqlInjection' from dual).
Using ResultSet of prepareStatement (Safe in H2 DB):
String query = "select * from TEST_TABLE where ID = 1";
PreparedStatement statement = connection.prepareStatement(query, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
ResultSet uprs = statement.executeQuery();
uprs.next();
uprs.updateString("TEST_CHAR", testName);
uprs.updateRow();
Output: Expected - TEST_CHAR in DB was (select 'sqlInjection' from dual).
Back to Questions:
Are SQL Injection attacks possible through these JDBC methods?
Maybe. It depends on the database driver that you're using.
How? :
The reason SQL Injection failed in my result set update was because H2 database internally uses PreparedStatement to update the row when ResultSet.updateRow() is invoked.
public void updateRow(Value[] current, Value[] updateRow) throws SQLException {
StatementBuilder buff = new StatementBuilder("UPDATE ");
...
buff.append(" SET ");
appendColumnList(buff, true);
...
appendKeyCondition(buff);
PreparedStatement prep = conn.prepareStatement(buff.toString());
...
for (int i = 0; i < columnCount; i++) {
...
v.set(prep, j++);
}
setKey(prep, j, current);
int count = prep.executeUpdate();
...
}
I'm not sure if all DB drivers in java implemented updateRow() method using preparedStatement or not. However it's clear that this is left to the driver and if bluemix is suggesting you to add a validation here, I suggest you follow that :)
How does JDBC implements this under the scenes?
Well, as shown above this is driver specific. However there is a good explanation on how PreparedStatement handles it over here.
Would this be another false positive reported by AppScan?
I don't think this is false positive (but in cases like H2 DB it is) but you'll never know if all database drivers implemented this securely.
Edit -
Even PostgreSQL and MySQL use PreparedStatement to handle this.
public synchronized void updateRow() throws SQLException
{
...
updateStatement = ((java.sql.Connection) connection).prepareStatement(updateSQL.toString());
...
updateStatement.executeUpdate();
...
}
why we use setInt with select query instead of using getInt when value is already there in database?
try {
conn = getConnection();
ps = conn.prepareStatement("SELECT * FROM circle where id =?");
ps.setInt(1, circleId);
Circle circle = null;
rs = ps.executeQuery();
if (rs.next()) {
//String s = rs.getString(circleId);
circle = new Circle(circleId, rs.getString("name"));
}
You're setting the value of the parameter to be used in the query. The ? in the SQL represents the parameter, and here you're giving it a value.
When you call getString() later, that's getting a value from the results of the query, which are very different from the parameters sent as part of the query.
Parameterized SQL allows safe inclusion of values into queries, without needing to escape them to prevent SQL injection attacks, or worrying about data type conversions. You should read the JDBC PreparedStatement tutorial for more details.
Im trying to write sample stored functions in postgresql and call them using the CallableStatement offered by JDBC.
Here's some my test code
Consumer bean =new Consumer();
CallableStatement pstmt = null;
try {
con.setAutoCommit(false);
String query = "{ ? = call getData( ? ) }";
pstmt = con.prepareCall(query);
pstmt.registerOutParameter(1, Types.OTHER);
pstmt.setInt(2,5);
pstmt.execute(); // execute update statement
bean=(Consumer)pstmt.getObject(1);
System.out.println("bean"+bean.getConsumer_name());
And my Stored function is of the form .
CREATE FUNCTION getData(int) RETURNS SETOF db_consumer AS $$
SELECT * FROM db_consumer WHERE consumer_id = $1;
$$ LANGUAGE SQL;
However, I'm getting the following error when I try to run the code .
org.postgresql.util.PSQLException: A CallableStatement was executed with an invalid number of parameters .
Any idea why this could be happening?
I don't think you need a CallableStatement as you should be able to run select * from getData(5) directly:
PreparedStatement pstmt = con.prepareStatement("select * from getData(?)")
pstmt.setInt(1,5);
ResultSet rs = pstmt.execute();
while (rs.next()) {
System.out.println(rs.getString(1));
}
You are trying to call a SETOFF function via a Callable Statement. That's not going to happen! You'll always get an error.
PostgreSQL's stored functions can return results in two different ways. The function may return either a refcursor value or a SETOF some datatype. Depending on which of these return methods are used determines how the function should be called.
Functions that return data as a set should not be called via the CallableStatement interface, but instead should use the normal Statement or PreparedStatement interfaces.