///幾個重要的語句
String insertSql="insert into Product(name,price) values('"+name+"',"+price+")";//price 為整型
String updateSql="update Product set  PName='"+name+"', PPrice="+price+" where PID='"+id+"'";
String sql="select * from Product where PName like '%"+key+"%'";
String sql = "delete  t_user  where userid="+userid;

JNDI方法一
/////////////////////////////////////////
記得導入6個.JAR包并在tomcat中的lib文件下也要導入這6個.JAR包
工具類

package util;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

import com.Admin;

/**
 * @author wsq
 * @version 1.0 07/10/20
 */
public class DBConnection {

 private static Connection con = null;

 private static Statement stmt = null;

 private static ResultSet rs = null;

 private static ArrayList<String[]> ArrayRs = null;

 /**
  *
  * 創建數據源
  *
  * @return Connection
  * @throws Exception
  */
 public static synchronized Connection getConnection() throws Exception {
  Context initCtx = new InitialContext(); // 從Context中lookup數據源。
  DataSource ds = (DataSource) initCtx.lookup("java:comp/env/jdbc/data"); // jdbc/data為下面Resource的name屬性
  return ds.getConnection();
 }

 /**
  *
  * 執行數據查詢操作
  *
  * @param sql
  * @return ResultSet
  */
 public static ArrayList executeQuery(String sql) {
  try {
   stmt = con.createStatement();
   rs = stmt.executeQuery(sql);
   ResultSetMetaData rsmd = rs.getMetaData(); // 獲取此 ResultSet 對象的列的編號、類型和屬性。
          
   int numberOfColumns = rsmd.getColumnCount();// 返回此 ResultSetMetaData對象中的列數。
              

   // 判斷是否為空
   if (!ArrayRs.isEmpty()) {
    ArrayRs.clear();
   }
   /*
    * 將每條記錄寫入數組 將數組放在ArrayList里
    */
   while (rs.next()) {
    String[] strArrayTemp = new String[numberOfColumns];
    for (int i = 0; i < numberOfColumns; i++) {
     if (rs.getObject(i + 1) == null) {
      strArrayTemp[i] = "";
     } else {
      strArrayTemp[i] = rs.getObject(i + 1).toString();// 以
            // Java
            // 編程語言中
            // Object
                  // 的形式獲取此
                  // ResultSet
                 // 對象的當前行中指定列的值;
             // 第一個列是1,第二個列是2,....
                  
      System.out.println(" test value    " + strArrayTemp[i]);

     }
    }
    ArrayRs.add(strArrayTemp);
   }
   System.out.println("executeQuery successfully!");

   return (ArrayList) ArrayRs.clone();
  } catch (SQLException ex) {
   System.out.println("query error:" + ex.getMessage());
  } finally {
   DBConnection.close();
  }
  return ArrayRs;
 }

 /**
  * @param executeInsert插入數據方法
  * @return 插入條數是否成功(boolean)
  */
 public static boolean executeInsert(String strSql) throws SQLException {
  rs = null;
  try {
   con = DBConnection.getConnection();
   stmt = con.createStatement();
   con.setAutoCommit(true);
   int i = stmt.executeUpdate(strSql);

   if (i == 1) {
    return (true);
   }
  } catch (Exception e) {
   System.out.println("Insert error:" + e.getMessage());
  } finally {
   DBConnection.close();
  }

  return (false);
 }

 /**
  * 執行數據更新操作
  *
  * @param sql
  * @return 更新是否成功 (int)
  * @throws Exception
  */
 public static int executeUpdate(String sql) throws Exception {
  int result = 0;
  con = DBConnection.getConnection();
  try {
   Statement stmt = con.createStatement();
   result = stmt.executeUpdate(sql);// 返回影響的行數
   con.commit(); // 提交

  } catch (SQLException ex) {
   try {
    con.rollback();// 回滾
   } catch (SQLException e) {
    System.out.println("update error:" + e.getMessage());
   }
   System.err.println(ex.getMessage());

  } finally {
   DBConnection.close();
  }
  return result;
 }

 /**
  * @param executeDelete刪除數據方法
  * @return 刪除數據數(int)
  */
 public static int executeDelete(String strSql) throws SQLException {
  rs = null;
  int j = 0;
  try {
   con = DBConnection.getConnection();
   stmt = con.createStatement();
   con.setAutoCommit(false);
   j = stmt.executeUpdate(strSql);

   if (j > 0) {
    con.commit();
   } else {
    con.rollback();
   }
  } catch (Exception e) {
   System.out.println("Delete error:" + e.getMessage());
  } finally {
   DBConnection.close();
  }
  return j;
 }

 /**
  *
  * 關閉連接，將連接送回連接池
  *
  */

 public static void close() {
  if (con != null) {
   try {
    con.close();
    con = null;
   } catch (SQLException ex) {
    System.err.println(ex.getMessage());
   }
  }
 }

}

在項目的...\WebRoot\META-INF下創建個context.xml或者在tomcat中的server.xml寫
  <Context path="/jndi" docBase="jndi" debug="0"  reloadable="true" crossContext="true">   
   <Resource name="jdbc/data"  auth="Container" type="javax.sql.DataSource"     
              driverClassName="com.microsoft.jdbc.sqlserver.SQLServerDriver"
              url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=dbs"        
              username="wsq" password="123"   maxIdle="20" maxWait="5000"   
              maxActive="100" removeAbandoned="true"
    removeAbandonedTimeout="60" logAbandoned="true"/>
</Context>

方法二
Struts（1.2）
/////////////////////////
連接池在struts-cionfig.xml中的配置（sql2000）
 <data-sources>
    <data-source type="org.apache.commons.dbcp.BasicDataSource" key="data'>
      <set-property property="driverClassName"value="com.microsoft.jdbc.sqlserver.SQLServerDriver" />//記得要Name
 <set-property property="url"value="jdbc:microsoft:sqlserver://localhost:1433;databasename=dbs" />
 <set-property property="username" value="wsq" />//記得要name
 <set-property property="password" value="123" />
 <set-property property="maxActive" value="10" />
 <set-property property="maxWait" value="5000" />
 <set-property property="defaultAutoCommit" value="false" />//記得在false的情況（插入和更新時要con.commit）
 <set-property property="defaultReadOnly" value="false" />
   </data-source>
</data-sources>
/////////////////////////////////////////////////////////
                      輔助類
package tools;

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

import javax.sql.DataSource;

public class DBUtil {
 Connection con=null;
 ResultSet rs = null;
 
 public DBUtil(DataSource dataSource)
 {
  try {
   con=dataSource.getConnection();
  } catch (SQLException e) {
   
   e.printStackTrace();
  }
 }
////在數據庫中執行查詢操作
 public ResultSet executeQuery(String sql) {
  try {
   Statement stmt = con.createStatement();
   rs = stmt.executeQuery(sql);
  }
  catch(SQLException ex) {
   ex.printStackTrace();
  }
  return rs;
 }
// 在數據庫中執行數據更新的方法
 public int executeUpdate(String sql) {
  int result = 0;
  try {
   Statement stmt = con.createStatement();
   
   //返回影響的行數
   result = stmt.executeUpdate(sql);
  }
  catch(SQLException ex) {
   try {
    con.rollback();                       //回滾
   } catch (SQLException e) {
    // TODO 自動生成 catch 塊
    e.printStackTrace();
   }
   System.err.println(ex.getMessage());
   
  }
  return result;
 }
// 關閉數據源
 public void close(){
  if(con!=null){
   try{
    con.close();
    con = null; 
   }catch(SQLException ex) {
    System.err.println(ex.getMessage());
   }
  } 
 }

}
//////////////////////////////////////////////////////////////////////////////////////
                      （不利用輔助類時）
在xxxAction.java中的execute()方法中
  try{
      DataSource dataSource=getDataSource(request,"data");//得到數據源
                                 //得到數據源ServletContext context=servlet.getServletContext();
                                 // DataSource dataSource=(DataSource) context.getAttribute("data");
      Connetion con=dataSource.getConnection();
      PreparedStatement pstm=con.prepareStatement("insert into userone (name,password) values(?,?)");
      pstm.setString(1,name);
      pstm.setString(2,password);
      pstm.executUpadate();
      con.commit();/////記得寫上(在插入或更新時一定要記得加上)正確是提交事務
      } catch (SQLException e) {
    con.rollback();//失敗時回滾
    e.printStackTrace();
   }
   
   finally{
    pstm.close();
    con.close();

      }

方法三（最原始的）直接連
**********************
1. MySQL(http://www.mysql.com)mm.mysql-2.0.2-bin.jar/
Class.forName( "org.gjt.mm.mysql.Driver" );
cn = DriverManager.getConnection(
"jdbc:mysql://MyDbComputerNameOrIP:3306/myDatabaseName", sUsr, sPwd );

2. PostgreSQL(http://www.de.postgresql.org)pgjdbc2.jar/
Class.forName( "org.postgresql.Driver" );
cn = DriverManager.getConnection(
"jdbc:postgresql://MyDbComputerNameOrIP/myDatabaseName", sUsr, sPwd );

3. Oracle(http://www.oracle.com/ip/deploy/database/oracle9i/)classes12.zip
Class.forName( "oracle.jdbc.driver.OracleDriver" );
cn = DriverManager.getConnection(
"jdbc:oracle:thin:@MyDbComputerNameOrIP:1521:ORCL", sUsr, sPwd );

4. Sybase(http://jtds.sourceforge.net)jconn2.jar/
Class.forName( "com.sybase.jdbc2.jdbc.SybDriver" );
cn = DriverManager.getConnection(
"jdbc:sybase:Tds:MyDbComputerNameOrIP:2638", sUsr, sPwd );
//(Default-Username/Password: "dba"/"sql")

5. Microsoft SQLServer(http://jtds.sourceforge.net/)
Class.forName( "net.sourceforge.jtds.jdbc.Driver" );
cn = DriverManager.getConnection(
"jdbc:jtds:sqlserver://MyDbComputerNameOrIP:1433/master", sUsr, sPwd );

6. Microsoft SQLServer(http://www.microsoft.com/)
Class.forName( "com.microsoft.jdbc.sqlserver.SQLServerDriver" );
cn = DriverManager.getConnection(
"jdbc:microsoft:sqlserver://localhost:1433;databaseName=dbs", sUsr, sPwd );

7. ODBC
Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
Connection cn = DriverManager.getConnection( "jdbc:odbc:" + sDsn, sUsr, sPwd
);

 
select @@version 是查看你的MSSQL版本  看補丁打沒打
///////////////////////////////////////////////////////////////////////////////////

String insertSql="insert into Product values('"+id+"','"+name+"',"+price+")";
String updateSql="update Product set  PName='"+name+"', PPrice="+price+" where PID='"+id+"'";
String sql="select * from Product where PName like '%"+key+"%'";
String sql = "delete  t_user  where userid="+userid;

////////////////////////////////////////////////////////