java当中JDBC当中请给出一个SQLServer DataSource and SingleTon例子

[学习笔记]

5.sqlserver datasource and singleton：

import net.sourceforge.jtds.jdbcx.*;
import java.sql.*;
import javax.sql.*;

public class sqlserversingletondatasource {
static private jtdsdatasource ds;
private connection con;
private sqlserversingletondatasource() {

try {
ds = new jtdsdatasource();
ds.setservername("localhost");
ds.setdatabasename("pubs");
ds.setuser("sa");
ds.setpassword("");
}
catch (exception e) {
}
}

public static connection getconnection() throws exception {
if (ds == null) {
new sqlserversingletondatasource();
}
connection con =null;
try {
con = ds.getconnection();
} catch (sqlexception ex) {
}

return con;
}
}

测试程序：

/*when you use single step to debug the program, you can find that singleton only
is executed once.*/
import java.sql.*;
import javax.sql.*;

public class testsqlserversingletondatasource {

public static void main(string args[]) {
connection con;

try {
con = sqlserversingletondatasource.getconnection();
statement stmt = con.createstatement();
resultset rs = stmt.executequery("select * from authors");
while (rs.next()) {
system.out.print(rs.getstring("au_id") + " ");
system.out.println(rs.getstring("au_lname"));
}

}
catch (exception e) {
}

system.out.println("the following is the second time ");

try {
con = sqlserversingletondatasource.getconnection();
statement stmt = con.createstatement();
resultset rs = stmt.executequery("select * from authors");
while (rs.next()) {
system.out.print(rs.getstring("au_id") + " ");
system.out.println(rs.getstring("au_lname"));
}

}
catch (exception e) {
}

}

}

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