补充下
常见数据库驱动记录
| 驱动jar | 具体驱动类 | 连接字符串 | |
|---|---|---|---|
| Oracle | ojdbc-x.jar | oracle.jdbc.OracleDriver | jdbc:oracle:thin:@localhost:1521:数据库实例名 |
| – | – | – | – |
| MySQL | mysql-connector-java-x.jar | com.mysql.jdbc.Driver | jdbc:mysql://localhost:3306/数据库实例名 |
| – | – | – | – |
| SqlServer | sqljdbc-x.jar | com.microsoft.sqlserver.jdbc.SQLServerDriver | jdbc:microsoft:sqlserver:localhost:1433;databasename=数据库实例名 |
1.比较
（1）Statement操作数据库：
增删改：executeUpdate()
查询：executeQuery();
（2）PreparedStatement操作数据库：
public interface PreparedStatement extends Statement
因此
增删改：executeUpdate()
查询：executeQuery();
–此外
赋值操作 setXxx();
2.推荐PreparedStatement，
（1）编码更加简便（避免了字符串的拼接）
String name = “zs” ;
int age = 23 ;
stmt:
String sql =" insert into student(stuno,stuname) values(’"+name+"’, “+age+” ) " ;
stmt.executeUpdate(sql);
pstmt:
String sql =" insert into student(stuno,stuname) values(?,?) " ;
pstmt = connection.prepareStatement(sql);//预编译SQL
pstmt.setString(1,name);
pstmt.setInt(2,age);
（2）提高性能(因为 有预编译操作，预编译只需要执行一次)
需要重复增加100条数
stmt:
String sql =" insert into student(stuno,stuname) values(’"+name+"’, “+age+” ) " ;
for(100)
stmt.executeUpdate(sql);
pstmt:
String sql =" insert into student(stuno,stuname) values(?,?) " ;
pstmt = connection.prepareStatement(sql);//预编译SQL
pstmt.setString(1,name);
pstmt.setInt(2,age);
for( 100){
pstmt.executeUpdate();
}
（3）安全（可以有效防止sql注入）
sql注入： 将客户输入的内容 和 开发人员的SQL语句 混为一体
stmt:存在被sql注入的风险
(例如输入 用户名：任意值 ’ or 1=1 –
密码：任意值)
分析：
select count() from login where uname=‘任意值 ’ or 1=1 --’ and upwd =‘任意值’ ;
select count() from login where uname='任意值 ’ or 1=1 ;
select count(*) from login ;
select count(*) from login where uname=’"+name+"’ and upwd =’"+pwd+"’
pstmt:有效防止sql注入
3.两种方式代码实现（代码有点混乱，看懂意思就好）
（1）Statement方式
public class JDBCDemo {
private static final String URL = "jdbc:oracle:thin:@localhost:1521:ORCL";
private static final String USERNAME = "scott";
private static final String PWD = "tiger";
public static void update() {// 增删改
Connection connection = null;
Statement stmt = null;
try {
// a.导入驱动，加载具体的驱动类
Class.forName("oracle.jdbc.OracleDriver");// 加载具体的驱动类
// b.与数据库建立连接
connection = DriverManager.getConnection(URL, USERNAME, PWD);
// c.发送sql，执行(增删改、查)
stmt = connection.createStatement();
//String sql = "insert into student values(1,'zs',23,'s1')";
// String sql = "update student set STUNAME='ls' where stuno=1";
String sql = "delete from student where stuno=1";
// 执行SQL
int count = stmt.executeUpdate(sql); // 返回值表示 增删改 几条数据
// d.处理结果
if (count > 0) {
System.out.println("操作成功！");
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
}
finally {
try {
if(stmt!=null) stmt.close();// 对象.方法
if(connection!=null)connection.close();
}catch(SQLException e) {
e.printStackTrace();
}
}
}
（2）PreparedStatement方式
public class JDBCPreparedStatementDemo {
private static final String URL = "jdbc:oracle:thin:@localhost:1521:ORCL";
private static final String USERNAME = "scott";
private static final String PWD = "tiger";
public static void update() {// 增删改
Connection connection = null;
PreparedStatement pstmt = null;
try {
// a.导入驱动，加载具体的驱动类
Class.forName("oracle.jdbc.OracleDriver");// 加载具体的驱动类
// b.与数据库建立连接
connection = DriverManager.getConnection(URL, USERNAME, PWD);
/* Statement
// c.发送sql，执行(增删改、查)
stmt = connection.createStatement();
//String sql = "insert into student values(1,'zs',23,'s1')";
// String sql = "update student set STUNAME='ls' where stuno=1";
String sql = "delete from student where stuno=1";
// 执行SQL
int count = stmt.executeUpdate(sql); // 返回值表示 增删改 几条数据
*/
//PreparedStatement
String sql = "insert into student values(?,?,?,?)";
pstmt = connection.prepareStatement(sql);//预编译
pstmt.setInt(1, 36);
pstmt.setString(2, "zhangsan");
pstmt.setInt(3, 56);
pstmt.setString(4, "s3");
int count =pstmt.executeUpdate() ;
// d.处理结果
if (count > 0) {
System.out.println("操作成功！");
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
}
finally {
try {
if(pstmt!=null) pstmt.close();// 对象.方法
if(connection!=null)connection.close();
}catch(SQLException e) {
e.printStackTrace();
}
}
}
public static void query() {
Connection connection = null;
PreparedStatement pstmt = null;
ResultSet rs = null ;
try {
// a.导入驱动，加载具体的驱动类
Class.forName("oracle.jdbc.OracleDriver");// 加载具体的驱动类
// b.与数据库建立连接
connection = DriverManager.getConnection(URL, USERNAME, PWD);
// c.发送sql，执行(增删改、【查】)
Scanner input= new Scanner(System.in);
System.out.println("请输入用户名：");
String name = input.nextLine() ;
System.out.println("请输入密码：");
String pwd = input.nextLine() ;
// String sql = "select * from student where stuname like '%"+name+"%'";
// String sql = "select * from student where stuname like ?";
String sql ="select count(*) from login where uname= ? and upwd =?";
pstmt = connection.prepareStatement(sql) ;
pstmt.setString(1, name);
pstmt.setString(2, pwd);
// String sql = "select stuno,stuname from student";
// 执行SQL(增删改executeUpdate()，查询executeQuery())
rs = pstmt.executeQuery(); // 返回值表示 增删改 几条数据
// d.处理结果
// while(rs.next()) {
// int sno = rs.getInt( "stuno") ;
// String sname = rs.getString("stuname") ;
//// int sno = rs.getInt(1) ; //下标：从1开始计数
//// String sname = rs.getString(2) ;
// System.out.println(sno+"--"+sname);
// }
int count = -1;
if(rs.next()) {
count = rs.getInt(1) ;
}
if(count>0) {
System.out.println("登陆成功！");
}else {
System.out.println("登陆失败！");
}
} catch (ClassNotFoundException e) {
System.out.println("111");
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
}
finally {
try {
if(rs!=null) rs.close();
if(pstmt!=null) pstmt.close();// 对象.方法
if(connection!=null)connection.close();
}catch(SQLException e) {
e.printStackTrace();
}catch(Exception e) {
e.printStackTrace();
}
}
}
