一个简单封装类DBUtil

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBUtil {

private static Connection con = null;
private Statement statement;
private PreparedStatement preparedStatement;

public static final String URL = "jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=mydb;SelectMethod=cursor";
public static final String DRIVERNAME = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
private final static String USERNAME = "sa";
private final static String PASSWORD = "";

private DBUtil() {
   con = getConnection();
}

public static synchronized DBUtil getDBInstance() {
   return new DBUtil();
}

public static synchronized Connection getConnection() {

   // 直接连接数据库

   try {
    Class.forName(DRIVERNAME).newInstance();
    con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
    con.setAutoCommit(true);
   } catch (Exception ex) {
    System.out.println("数据库加载失败!");
   }

   return con;
}

public Statement getStatement() {
   try {
    con = getConnection();
    statement = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
      ResultSet.CONCUR_READ_ONLY);
   } catch (Exception e) {
    System.out.println("getStatement Exception");
    System.out.println(e.getMessage());
   }
   return statement;
}

public PreparedStatement getPreparedStatement(String sql) {
   try {
    con = getConnection();
    preparedStatement = con.prepareStatement(sql);
   } catch (Exception e) {
    System.out.println("getPstmt");
    System.out.println(e.getMessage());
   }
   return preparedStatement;
}

// 关闭数据库

public void closeConnection() {
   // System.out.println("---------------开始关闭数据库连接------------------");
   try {
    if (statement != null)
     statement.close();
   } catch (Exception e) {
    System.err.println("statement关闭出现异常！");
   }
   try {
    if (preparedStatement != null)
     preparedStatement.close();
   } catch (Exception e) {
    System.err.println("preparedStatement关闭出现异常！");
   }
   if (con != null) {
    try {
     con.close();
    } catch (SQLException e) {
     e.printStackTrace();
    } finally {
     con = null;
    }
   }
   // System.out.println("----------------关闭数据库连接成功！---------------------");
}
public static void main(String[] args) {
   new DBUtil();
}

}