Statement 简单操作数据库

使用Statement的弊端：需要拼写sql语句，并且存在SQL注入的问题

解决办法：只要使用PreparedStatement（从Statement扩展而来）取代Statement

mysql配置 : jdbc.properties

#mysql配置
user=root
password=root
url=jdbc:mysql://localhost:3306/java?serverTimezone=Asia/Shanghai
driverClass=com.mysql.cj.jdbc.Driver

JDBCUtils链接数据库

package JDBCUtil;

import JDBCTest.PreperdStatementUpdateTest;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
 * @Author HLY
 * @Create 2019-12-05 12:55
 */
public class JDBCUtils {

    public static Connection getConnection() throws IOException, ClassNotFoundException, SQLException {
        InputStream inputStream= JDBCUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties=new Properties();
        properties.load(inputStream);

        String user=properties.getProperty("user");
        String password=properties.getProperty("password");
        String url=properties.getProperty("url");
        String driverClass=properties.getProperty("driverClass");
        //加载驱动
        Class.forName(driverClass);
        //获取链接
        Connection connection = DriverManager.getConnection(url, user, password);
        return connection;
    }

    public void closeResource(Connection connection, Statement preparedStatement) throws SQLException {
        //资源关闭
        if (connection!=null){
            connection.close();
        }
        if (preparedStatement!=null){
            preparedStatement.close();
        }
    }

}

 User对象

package JDBCStatement;

/**
 * @Author HLY
 * @Create 2019-12-17 11:39
 */
public class User {

    private String user;
    private String password;

    public User (){

    }

    public User (String user,String password){
        this.user=user;
        this.password=password;
    }


    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{user:"+user
                +"password:"+password+"}";
    }

}

StatementTest

package JDBCStatement;
import JDBCUtil.JDBCUtils;
import org.junit.Test;

import java.io.IOException;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.Scanner;

/**
 * @Author HLY
 * @Create 2019-12-17 11:39
 */
public class StatementTest {


    public static void main(String[] args) {

        test();

    }


    public static void test(){

        System.out.println("请输入用户名：");
        Scanner input=new Scanner(System.in);
        //接受String类型
        String str=input.next();
        System.out.println("请输入密码：");
        String ps=input.next();
        String sql="SELECT user,password FROM user_login WHERE user='"+str+"' AND PASSWORD='"+ps+"'";
        try {
            User user1 = get(sql, User.class);
            System.out.print(user1.toString());
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
    }


    public static <T> T get(String sql, Class clazz) throws SQLException, IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {

        T t=null;
        Connection connection = JDBCUtils.getConnection();
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        ResultSetMetaData resultSetMetaData=resultSet.getMetaData();
        int columnCount=resultSetMetaData.getColumnCount();
        if (resultSet.next()){
            t= (T) clazz.newInstance();
            for (int i=0;i<columnCount;i++){
                String name=resultSetMetaData.getColumnLabel(i+1);

                Object val=resultSet.getObject(name);
                Field field= null;
                try {
                    field = clazz.getDeclaredField(name);
                } catch (NoSuchFieldException e) {
                    e.printStackTrace();
                }
                field.setAccessible(true);
                field.set(t,val);
            }

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

            return t;
        }
        return null;
    }

}

问题：在单元测试中使用Scanner ，控制台不能输入

希望大神留言解释

代码如下：

package JDBCStatement;
import JDBCUtil.JDBCUtils;
import org.junit.Test;

import java.io.IOException;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.Scanner;

/**
 * @Author HLY
 * @Create 2019-12-17 11:39
 */
public class StatementTest {
    

    @Test
    public  void test(){

        System.out.println("请输入用户名：");
        Scanner input=new Scanner(System.in);
        //接受String类型
        String str=input.next();
        System.out.println("请输入密码：");
        String ps=input.next();
        String sql="SELECT user,password FROM user_login WHERE user='"+str+"' AND PASSWORD='"+ps+"'";
        try {
            User user1 = get(sql, User.class);
            System.out.print(user1.toString());
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        }
    }


    public <T> T get(String sql, Class clazz) throws SQLException, IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {

        T t=null;
        Connection connection = JDBCUtils.getConnection();
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        ResultSetMetaData resultSetMetaData=resultSet.getMetaData();
        int columnCount=resultSetMetaData.getColumnCount();
        if (resultSet.next()){
            t= (T) clazz.newInstance();
            for (int i=0;i<columnCount;i++){
                String name=resultSetMetaData.getColumnLabel(i+1);

                Object val=resultSet.getObject(name);
                Field field= null;
                try {
                    field = clazz.getDeclaredField(name);
                } catch (NoSuchFieldException e) {
                    e.printStackTrace();
                }
                field.setAccessible(true);
                field.set(t,val);
            }

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

            return t;
        }
        return null;
    }

}