文章目录
MySQL学习记录11JDBCstatement对象、SQL注入问题与PreparedStatement对象
11.1statement对象
Jdbc中的statement对象用于向数据库发送SQL语句,想完成对数据库的增删改查,只需要通过这个对象向数据库发送增删改查语句即可。
Statement对象的executeUpdate方法,用于向数据库发送增、删、改的sql语句,executeUpdate执行完后,将会返回一个整数(即受影响的行数)。
Statement.executeQuery方法用于向数据库发送查询语句,executeQuery方法返回代表查询结果的ResultSet对象。
CRUD操作-create
使用executeUpdate(String sql)方法完成数据添加操作,示例操作:
Statement statement = connection.createStatement();
String sql = "insert into user(... ) values(... . ) ";
int num = statement.executeUpdate(sql);
if (num > 0) {
System.out.println("插入成功!!! ");
}
CRUD操作-delete
使用executeUpdate(String sql)方法完成数据删除操作,示例操作:
Statement statement = connection.createStatement();
String sql = "delete from user where id = 1";
int num = statement.executeUpdate(sql);
if (num > 0) {
System.out.println("删除成功!!! ");
}
CRUD操作-update
使用executeUpdate(String sql)方法完成数据修改操作,示例操作:
Statement statement = connection.createStatement();
String sql = "update user set name = '' where name = '' ";
int num = statement.executeUpdate(sql);
if (num > 0) {
System.out.println("修改成功!!! ");
}
CRUD操作-read
使用executeUpdate(String sql)方法完成数据查询操作,示例操作:
Statement statement = connection.createStatement();
String sql = "select * from user where id = 1";
ResultSet resultSet = statement.executeUpdate(sql);
where(resultSet .next()){
//根据获取列的数据类型,分别调用resultSet的相应方法映射到java对象中
}
11.1.1代码实现(增删改查)
首先编写数据库配置文件:
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=123456
其次编写jdbc工具类:
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
public class JdbcUtils {
private static String driver = null;
private static String url = null;
private static String username = null;
private static String password = null;
static {
try {
InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(in);
//从db.properties中读取这四个信息
driver = properties.getProperty("driver");
url = properties.getProperty("url");
username = properties.getProperty("username");
password = properties.getProperty("password");
//1.驱动只用加载一次
Class.forName(driver);
} catch (Exception e) {
e.printStackTrace();
}
}
//获取连接
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, username, password);
}
//释放连接
public static void release(Connection conn, Statement st, ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (conn != null) {
conn.close();
}
}
}
插入测试:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestInsert {
public static void main(String[] args) throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
st = conn.createStatement(); //获得SQL的执行对象
String sql = "INSERT INTO users(id,`NAME`,`PASSWORD`,`email`,`birthday`)" +
"VALUES(4,'zhaoliu','123456','XXXX@qq.com','2020-01-01')";
int i = st.executeUpdate(sql); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("插入成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
查看数据库表中的结果:
插入成功!
既然插入的代码成功了,那么删除:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestDelete {
public static void main(String[] args) throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
st = conn.createStatement(); //获得SQL的执行对象
String sql = "DELETE FROM users WHERE id = 4";
int i = st.executeUpdate(sql); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("删除成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
运行代码:
查看数据库表数据:
删除成功!
再来一段更新:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestUpdate {
public static void main(String[] args) throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
st = conn.createStatement(); //获得SQL的执行对象
String sql = "UPDATE users SET `NAME`='madongmei',`email`='XXXXXX@qq.com' WHERE id = 1;";
int i = st.executeUpdate(sql); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("更新成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
更新成功!
查询:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestSelect {
public static void main(String[] args) throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
st = conn.createStatement(); //获得SQL的执行对象
String sql = "select * from users where id = 1";
rs = st.executeQuery(sql); //查询完毕会返回一个结果集
while (rs.next()) {
System.out.println(rs.getString("NAME"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
11.1.2SQL注入问题
SQL注入即是指web应用程序对用户输入数据的合法性没有判断或过滤不严,攻击者可以在web应用程序中事先定义好的查询语句的结尾上添加额外的SQL语句,在管理员不知情的情况下实现非法操作,以此来实现欺骗数据库服务器执行非授权的任意查询,从而进一步得到相应的数据信息。
SQL注入是比较常见的网络攻击方式之一,它不是利用操作系统的BUG来实现攻击,而是针对程序员编写时的疏忽,通过SQL语句,实现无账号登录,甚至篡改数据库。
11.1.2.1SQL注入攻击的总体思路
- 寻找到SQL注入的位置
- 判断服务器类型和后台数据库类型
- 针对不同的服务器和数据库特点进行SQL注入攻击
案例:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class SqlInjection {
public static void main(String[] args) {
login("madongei", "123456");
}
public static void login(String username, String password) {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
st = conn.createStatement(); //获得SQL的执行对象
String sql = "select * from users where `NAME`='" + username + "' AND `PASSWORD` = '" + password + "'";
rs = st.executeQuery(sql); //查询完毕会返回一个结果集
while (rs.next()) {
System.out.println(rs.getString("NAME"));
System.out.println(rs.getString("PASSWORD"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
JdbcUtils.release(conn, st, rs);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
如果能正常登录,则应输出用户名、密码的结果
但:
如果将上述代码中login("madongei", "123456");
改为login("'or '1=1","123456");
所有的用户名和密码都被盗取。
11.2PreparedStatement对象
防止sql注入且效率更高
1、新增
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.*;
import java.util.Date;
public class TestInsert {
public static void main(String[] args) throws SQLException {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
//区别 使用?占位符代替参数
String sql = "INSERT INTO users(id,`NAME`,`PASSWORD`,`email`,`birthday`)" + "VALUES(?,?,?,?,?)";
st = conn.prepareStatement(sql);//预编译sql,先写sql,不执行
//手动给参数赋值
st.setInt(1, 4);
st.setString(2, "haha");
st.setString(3, "123456");
st.setString(4, "ssss@qq.com");
//注意点 sql.Date
// util.Date
st.setDate(5, new java.sql.Date(new Date().getTime()));
//执行
int i = st.executeUpdate(); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("插入成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
2、删除
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
public class TestDelete {
public static void main(String[] args) throws SQLException {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
//区别 使用?占位符代替参数
String sql = "delete from users where id = ?";
st = conn.prepareStatement(sql);//预编译sql,先写sql,不执行
//手动给参数赋值
st.setInt(1,4);
//执行
int i = st.executeUpdate(); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("删除成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
3、更新
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class TestUpdate {
public static void main(String[] args) throws SQLException {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
//区别 使用?占位符代替参数
String sql = "update users set `NAME` = ? where id = ?;";
st = conn.prepareStatement(sql);//预编译sql,先写sql,不执行
//手动给参数赋值
st.setString(1, "xialuo");
st.setInt(2, 1);
//执行
int i = st.executeUpdate(); //把sql语句丢进去执行,i是受影响的行数
if (i > 0) {
System.out.println("更新成功!");
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
4、查询
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.*;
public class TestSelect {
public static void main(String[] args) throws SQLException {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
//区别 使用?占位符代替参数
String sql = "select * from users where id = ?";
st = conn.prepareStatement(sql);//预编译sql,先写sql,不执行
//手动给参数赋值
st.setInt(1, 1);
//执行
rs = st.executeQuery(); //把sql语句丢进去执行,i是受影响的行数
if (rs.next()) {
System.out.println(rs.getString("NAME"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtils.release(conn, st, rs);
}
}
}
5、防止sql注入
正常业务:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.*;
public class SqlInjection {
public static void main(String[] args) {
login("xialuo", "123456");
//login("'or '1=1","123456");
}
public static void login(String username, String password) {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
String sql = "select * from users where `NAME`=? AND `PASSWORD`=?";
st = conn.prepareStatement(sql); //预编译sql
st.setString(1,username);
st.setString(2,password);
rs = st.executeQuery(); //查询完毕会返回一个结果集
while (rs.next()) {
System.out.println(rs.getString("NAME"));
System.out.println(rs.getString("PASSWORD"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
JdbcUtils.release(conn, st, rs);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
拼接sql:
import com.jatine.lesson02.utils.JdbcUtils;
import java.sql.*;
public class SqlInjection {
public static void main(String[] args) {
//login("xialuo", "123456");
login("''or 1=1","123456");
}
public static void login(String username, String password) {
Connection conn = null;
PreparedStatement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection(); //获取数据库连接,这样就连接上了,不用再写那些配置了
String sql = "select * from users where `NAME`=? AND `PASSWORD`=?";
st = conn.prepareStatement(sql); //预编译sql
st.setString(1,username);
st.setString(2,password);
rs = st.executeQuery(); //查询完毕会返回一个结果集
while (rs.next()) {
System.out.println(rs.getString("NAME"));
System.out.println(rs.getString("PASSWORD"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
JdbcUtils.release(conn, st, rs);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
没有结果,也没有报错