How to create a database deadlock using jdbc and JUNIT
- by Isawpalmetto
I am trying to create a database deadlock and I am using JUnit. I have two concurrent tests running which are both updating the same row in a table over and over again in a loop.
My idea is that you update say row A in Table A and then row B in Table B over and over again in one test. Then at the same time you update row B table B and then row A Table A over and over again. From my understanding this should eventually result in a deadlock.
Here is the code For the first test.
public static void testEditCC()
{
try{
int rows = 0;
int counter = 0;
int large=10000000;
Connection c=DataBase.getConnection();
while(counter<large)
{
int pid = 87855;
int cCode = 655;
String newCountry="Egypt";
int bpl = 0;
stmt = c.createStatement();
rows = stmt.executeUpdate("UPDATE main " + //create lock on main table
"SET BPL="+cCode+
"WHERE ID="+pid);
rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table
counter++;
}
assertTrue(rows == 1);
//rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')");
}
catch(SQLException ex)
{
ex.printStackTrace();
//ex.getMessage();
}
}
And here is the code for the second test.
public static void testEditCC()
{
try{
int rows = 0;
int counter = 0;
int large=10000000;
Connection c=DataBase.getConnection();
while(counter<large)
{
int pid = 87855;
int cCode = 655;
String newCountry="Jordan";
int bpl = 0;
stmt = c.createStatement();
//stmt.close();
rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table
rows = stmt.executeUpdate("UPDATE main " + //create lock on main table
"SET BPL="+cCode+
"WHERE ID="+pid);
counter++;
}
assertTrue(rows == 1);
//rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')");
}
catch(SQLException ex)
{
ex.printStackTrace();
}
}
I am running these two separate JUnit tests at the same time and am connecting to an apache Derby database that I am running in network mode within Eclipse. Can anyone help me figure out why a deadlock is not occurring? Perhaps I am using JUnit wrong.
