怎么封装jdbc连接外部数据库连接

写一个公共类，如下：

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import java.sql.*

public class ConnectDB {

//数据库用户名

String userName="sa"

//数据库密码

String userPassword="123456"

//数据库的URL，包括连接数据库所使用的编码格式

String url="jdbc:sqlserver://localhost:1433databaseName=stu"

//定义一个连接对象

Connection dbConn

//错误信息串

String errMes

public ConnectDB() {

//初始化 *** 作

errMes=""

dbConn=null

}

//连接数据库

public Connection getConn() {

try {

//声明所用的类包

Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver")

//获得数据库的连接对象

dbConn= DriverManager.getConnection(url,userName,userPassword)

} catch(Exception e) {

dbConn = null

errMes=e.toString()

}

return dbConn

}

//获取错误信息

public String getErrMes() {

return errMes

}

}

try{

class.forName(driver)

}

catch (ClassNotFoundException e)

{

e.printStackTrace()

}

错了，应该写在方法里面。。。

public Connection getConnection()

{

try{

class.forName(driver)

connection = DriverManager.getConnection(URL,username,password)

}

catch (SQLException e1)

{

e1.printStackTrace()

}

catch (ClassNotFoundException e)

{

e.printStackTrace()

}

return connection

}

或者把他放在构造方法里。

当然是：

Exception in thread "main" java.lang.Error: Unresolved compilation problems:

编译肯定不对。

用这个类吧.好的话,给我加加分.

import java.sql.*

/**

* @功能: 一个JDBC的本地化API连接类,封装了数据 *** 作方法,只用传一个SQL语句即可

* @作者: 李开欢

* @日期: 2007/

*/

public class ConnectionDemo {

/*

* 这里可以将常量全部放入另一个类中,以方便修改

*/

private static Connection conn

private static Statement ps

private static ResultSet rs

private static final String DRIVER = "com.microsoft.jdbc.sqlserver.SQLServerDriver"

private static final String URL = "jdbc:microsoft:sqlserver://localhost:1433DatabaseName=mydb"

private static final String USER ="sa"

private static final String PASS = "sa"

public ConnectionDemo() {

// TODO Auto-generated constructor stub

ConnectionDemo.getConnection()

}

public static Connection getConnection(){

System.out.println("连接中...")

try {

Class.forName(ConnectionDemo.DRIVER)

conn = DriverManager.getConnection(ConnectionDemo.URL, ConnectionDemo.USER, ConnectionDemo.PASS)

System.out.println("成功连接")

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace()

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

return conn

}

public static Statement getStatement(String sql){

System.out.println("执行SQL语句中...")

try {

ps = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE)

if(sql.substring(0, 6).equals("select")){

rs = ps.executeQuery(sql)

System.out.println("执行完查询 *** 作,结果已返回ResultSet集合")

}else if(sql.substring(0, 6).equals("delete")){

ps.executeUpdate(sql)

System.out.println("已执行完毕删除 *** 作")

}else if(sql.substring(0, 6).equals("insert")){

ps.executeUpdate(sql)

System.out.println("已执行完毕增加 *** 作")

}else{

ps.executeUpdate(sql)

System.out.println("已执行完毕更新 *** 作")

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

return ps

}

public static ResultSet getResultSet(){

System.out.println("查询结果为:")

return rs

}

public static void closeConnection(){

System.out.println("关闭连接中...")

try {

if (rs != null) {

rs.close()

System.out.println("已关闭ResultSet")

}

if (ps != null) {

ps.close()

System.out.println("已关闭Statement")

}

if (conn != null) {

conn.close()

System.out.println("已关闭Connection")

}

} catch (Exception e) {

// TODO: handle exception

}

}

public static void main(String[] args) {

// TODO Auto-generated method stub

ConnectionDemo.getConnection()

String sql = "delete from type where id = 1"

ConnectionDemo.getStatement(sql)

String sql2 = "insert into type values(1,'教学设备')"

ConnectionDemo.getStatement(sql2)

String sql1 = "select * from type"

ConnectionDemo.getStatement(sql1)

ResultSet rs = ConnectionDemo.getResultSet()

System.out.println("编号 "+"类型")

try {

while(rs.next()){

System.out.print(" "+rs.getInt(1)+" ")

System.out.println(rs.getString(2))

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

ConnectionDemo.closeConnection()

}

}

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