java实现三种数据库连接完整的demo

都是源码直接复制过来的，可直接粘用


public class A {

public static Connection conn;

public static ResultSet rs = null ;

public static Statement st = null ;

public static void main(String[] args) {

getConnection("127.0.0.1", "3306", "ly", "root", "root", "c");

}

public static void getConnection(String ip,String port,String dbname,String user,String pwd,String type){

String url = "";

try {

//初始化驱动包

try {

//判断需要连接的数据库类型

if(type.equals("a")){

//sqlserver 连接

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

url = "jdbc:sqlserver://" + ip + ":" + port + ";databaseName=" + dbname;

}else if(type.equals("b")){

//oracle 连接

Class.forName("oracle.jdbc.driver.OracleDriver");

url = "jdbc:oracle:thin:@" + ip + ":" + port + ":" + dbname;

}else{

//mysql 连接

Class.forName("com.mysql.jdbc.Driver");

url = "jdbc:mysql://" + ip + ":" + port + "/" + dbname ;

}

} catch (ClassNotFoundException e) {

e.printStackTrace();

System.out.println("驱动类加载失败！");

}

//连接数据库

try {

conn=DriverManager.getConnection(url, user, pwd);

} catch (SQLException e) {

e.printStackTrace();

System.out.println("数据库连接失败！");

}

//查询

List<Map> list = new ArrayList<Map>();

st = conn.createStatement();

String sql = " select * from user ";

rs = st.executeQuery(sql);

while (rs.next()) {

Map<String,String> map = new HashMap<String,String>();

map.put("id", rs.getString("id"));

map.put("name", rs.getString("name"));

map.put("rolekey", rs.getString("rolekey"));

list.add(map);

}

System.out.println("2222222==="+list);

} catch (Exception e) {

e.printStackTrace();

}finally{

//关闭（必须有）

try {

if(rs!=null){

rs.close();

}

if(st!=null){

st.close();

}

if(conn!=null){

conn.close();

}

} catch (SQLException e) {

e.printStackTrace();

}

}

}

}