public class IsolationIrumTest {
Connection conn1;
Connection conn2;
//our connnection to the db - presist for life of program
// we dont want this garbage collected until we are done
public IsolationIrumTest(String db_file_name_prefix) throws Exception { // note more general exception
// Load the HSQL Database Engine JDBC driver
// hsqldb.jar should be in the class path or made part of the current jar
Class.forName("org.hsqldb.jdbcDriver");
conn1 = DriverManager.getConnection("jdbc:hsqldb:"
+ db_file_name_prefix, // filenames
"sa", //
username
"");
conn2 = DriverManager.getConnection("jdbc:hsqldb:"
+ db_file_name_prefix, // filenames
"sa", // username
"");
conn1.setAutoCommit(false);
conn2.setAutoCommit(false);
}
public void shutdown() throws SQLException {
update1("SHUTDOWN");
conn1.close(); // if there are no other open connection
conn2.close();
//
}
public synchronized void query1(String _expression_) throws SQLException {
Statement st = null;
ResultSet rs = null;
st = conn1.createStatement(); // statement objects can be reused with
// repeated calls to execute but we
// choose to make a new one each time
rs = st.executeQuery(_expression_); // run the query
// do something with the result set.
dump(rs);
st.close(); // NOTE!! if you close a statement the associated ResultSet is
// closed too
// so you should copy the contents to some other object.
// the result set is invalidated also if you recycle an Statement
// and try to execute some other query before the result set has been
// completely examined.
}
public synchronized void query2(String _expression_) throws SQLException {
Statement st = null;
ResultSet rs = null;
st = conn2.createStatement(); // statement objects can be reused with
// repeated calls to execute but we
// choose to make a new one each time
rs = st.executeQuery(_expression_); // run the query
// do something with the result set.
dump(rs);
st.close(); // NOTE!! if you close a statement the associated ResultSet is
}
public synchronized void update1(String _expression_) throws SQLException {
Statement st = null;
st = conn1.createStatement(); // statements
int i = st.executeUpdate(_expression_); // run the query
if (i == -1) {
System.out.println("db error : " + _expression_);
}
st.close();
} // void update()
public synchronized void update2(String _expression_) throws SQLException {
Statement st = null;
st = conn2.createStatement(); // statements
int i = st.executeUpdate(_expression_); // run the query
if (i == -1) {
System.out.println("db error : " + _expression_);
}
st.close();
} // void update()
public static void dump(ResultSet rs) throws SQLException {
// the order of the rows in a cursor
// are implementation dependent unless you use the SQL ORDER statement
ResultSetMetaData meta = rs.getMetaData();
int colmax = meta.getColumnCount();
int i;
Object o = null;
// the result set is a cursor into the data. You can only
// point to one row at a time
// assume we are pointing to BEFORE the first row
// rs.next() points to next row and returns true
// or false if there is no next row, which breaks the loop
for (; rs.next(); ) {
for (i = 0; i < colmax; ++i) {
o = rs.getObject(i + 1); // Is SQL the first column is indexed
// with 1 not 0
System.out.print(o.toString() + " ");
}
System.out.println(" ");
}
} //void dump( ResultSet rs )
public static void main(String[] args) {
IsolationIrumTest db = null;
try {
db = new IsolationIrumTest("db_file");
} catch (Exception ex1) {
ex1.printStackTrace(); // could not start db
return; // bye bye
}
try {
//FROM CONNECTION 1
db.update1(
"CREATE TABLE sample_table ( id INTEGER IDENTITY, str_col VARCHAR(256), num_col INTEGER, num_col2 INTEGER)");
} catch (SQLException ex2) {
//ignore
//ex2.printStackTrace(); // second time we run program
// should throw execption since table
// already there
//
// this will have no effect on the db
}
try {
// add some rows - will create duplicates if run more then once
// the id column is automatically generated
db.update1(
"INSERT INTO sample_table(str_col,num_col, num_col2) VALUES('Ford', 100, 50)");
// do a query
db.query1("SELECT * FROM sample_table");
//NOW UPDATE THROUGH CONNECTION1
db.update1("UPDATE sample_table SET num_col = '34' WHERE str_col = 'Ford'");
System.out.println("From connection1: ");
db.query1("SELECT * FROM sample_table");
//now update throught connection2.
db.update2("UPDATE sample_table SET num_col = '36' WHERE str_col = 'Ford'");
System.out.println("From connection2: ");
db.query2("SELECT * FROM sample_table");
// at end of program
db.shutdown();
} catch (SQLException ex3) {
ex3.printStackTrace();
}
} // main()
} // class Testdb
My Test Results are:
0 Ford 100 50
From connection1:
0 Ford 34 50
From connection2:
0 Ford 36 50
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