jdbc的连接

Statement，会出现SQL注入：

import java.sql.*;

public class JdbcFirstDemo {
public static void main(String[] args) throws SQLException, ClassNotFoundException {

//加载驱动
Class.forName("com.mysql.jdbc.Driver");//固定写法
//获取用户ID 信息
//jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf8&useSSL=true
String url = "jdbc:mysql://localhost:3306/jdbc";
String username = "root";
String password = "321";
//连接成功，Connection代表数据库
Connection connection = DriverManager.getConnection(url,username,password);
//执行sql的对象 Statement 执行SQL的对象
Statement statement = connection.createStatement();
//调用执行SQL的对象去执行SQL，可能存在结果，产看返回结果集
String sql = "SELECT * FROM user";

//返回的结果集，结果集中封装了我们的全部查询出来的结果
ResultSet resultSet = statement.executeQuery(sql);

while(resultSet.next()){
System.out.println("id"+resultSet.getObject("id"));
System.out.println("name"+resultSet.getObject("name"));
System.out.println("password"+resultSet.getObject("password"));
}

resultSet.close();
statement.close();
connection.close();
}
}

预编译，不会出现SQL注入：

import java.sql.*;

public class JdbcFirstDemo {
public static void main(String[] args) throws SQLException, ClassNotFoundException {

//加载驱动
Class.forName("com.mysql.jdbc.Driver");//固定写法
//获取用户ID 信息
//jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf8&useSSL=true
String url = "jdbc:mysql://localhost:3306/jdbc";
String username = "root";
String password = "321";
//连接成功，Connection代表数据库
Connection connection = DriverManager.getConnection(url,username,password);

//调用执行SQL的对象去执行SQL，可能存在结果，产看返回结果集
String sql = "SELECT * FROM user";

//执行sql的对象 Statement 执行SQL的对象
PreparedStatement ps = connection.PreparedStatement(sql);

//返回的结果集，结果集中封装了我们的全部查询出来的结果
ResultSet resultSet = statement.executeQuery();

while(resultSet.next()){
System.out.println("id"+resultSet.getObject("id"));
System.out.println("name"+resultSet.getObject("name"));
System.out.println("password"+resultSet.getObject("password"));
}

resultSet.close();
statement.close();
connection.close();
}
}