PreparedStatement实现数据表的操作

一、基本操作

//3.获取连接
con = DriverManager.getConnection(url, user, password);
 //4.预编译sql语句，返回PreparedStatement的实例
String sql = "insert into customers(name,email,birth)value(?,?,?)";//?:占位符
ps = con.prepareStatement(sql);

//5.填充占位符
ps.setString(1, "娜扎");
ps.setString(2, "[email protected]");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
java.util.Date date = sdf.parse("2000-01-01");
ps.setDate(3, new java.sql.Date(parse.getTime()));

//6.执行操作
ps.execute();

//7.资源的关闭
ps.close();
con.close();

 二、封装连接类

public class JDBCUtil {
    /**
     * 获取数据库的链接
     * @return
     * @throws Exception
     */
    public static Connection getConnection() throws Exception {
        //1.读取配置文件中的四个基本信息
        //1)将配置文件转换成字符流
        InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("jdbc.properties");
        //2)将资源加载
        Properties pros = new Properties();
        pros.load(is);
        //3)分别接收四个基本信息
        String user = pros.getProperty("user");
        String password = pros.getProperty("password");
        String url = pros.getProperty("url");
        String driver = pros.getProperty("driver");

        //2.加载驱动
        Class.forName(driver);

        //3.获取连接
        Connection con = DriverManager.getConnection(url, user, password);
        return con;
    }

    /**
     * 关闭连接和Statement的操作
     * @param con
     * @param ps
     */
    public static void closeResource(Connection con, PreparedStatement ps) {
        //7.资源的关闭
        try {
            if (ps != null) {
                ps.close();
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        try {
            if (con != null) {
                con.close();
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    
}

三、数据表的修改

import com.zjds.util.JDBCUtil;
import org.junit.Test;

import java.sql.Connection;
import java.sql.PreparedStatement;

public class PreparedStatementUpdateTest {
    @Test
    public void testUpdate() throws Exception {
        //1.获取连接
        Connection conn = JDBCUtil.getConnection();

        //2.预编译sql语句，返回PreparedStatement的实例
        String sql = "update cistomers set name = ? where id = ?";
        PreparedStatement ps = conn.prepareStatement(sql);
        
        //3.填充占位符
        ps.setString(1, "古力娜扎");
        ps.setString(2, "18");
        
        //4.执行
        ps.execute();
        
        //5.资源的关闭
        JDBCUtil.closeResource(conn, ps);
    }
}

抛异常 

import com.zjds.util.JDBCUtil;
import org.junit.Test;

import java.sql.Connection;
import java.sql.PreparedStatement;

public class PreparedStatementUpdateTest {
    @Test
    public void testUpdate() throws Exception {
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            //1.获取连接
            conn = JDBCUtil.getConnection();

            //2.预编译sql语句，返回PreparedStatement的实例
            String sql = "update cistomers set name = ? where id = ?";
            ps = conn.prepareStatement(sql);

            //3.填充占位符
            ps.setString(1, "古力娜扎");
            ps.setString(2, "18");

            //4.执行
            ps.execute();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //5.资源的关闭
            JDBCUtil.closeResource(conn, ps);
        }

    }
}

四、通用的增删改操作 

import com.zjds.util.JDBCUtil;
import jdk.nashorn.internal.scripts.JD;
import org.junit.Test;

import java.sql.Connection;
import java.sql.PreparedStatement;

public class PreparedStatementUpdateTest {
    //通用的增删改操作
    public void update(String sql, Object ...args) {
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            //1.获取连接
            conn = JDBCUtil.getConnection();

            //2.预编译
            ps = conn.prepareStatement(sql);

            //3.填充占位符
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);
            }

            //4.执行操作
            ps.execute();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //5.资源关闭
            JDBCUtil.closeResource(conn, ps);
        }

    }

    @Test
    public void testUpdate() {
        String sql = "update `order` set order_name = ? where order_id = ?";
        update(sql, "DD", "2");
    }
}

五、查询操作

import org.junit.jupiter.api.Test;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;

public class StuForQuery {

    public Student queryForStu(String sql, Object ...args) throws Exception {
        //1.获取连接
        Connection conn = JDBCUtil.getConnection();
        //2.预编译
        PreparedStatement ps = conn.prepareStatement(sql);
        //3.填充占位符
        for (int i = 0; i < args.length; i++) {
            ps.setObject(i + 1, args[i]);
        }

        //4.获取结果集
        ResultSet rs = ps.executeQuery();
        // 1）获取结果集里的元数据
        ResultSetMetaData rsmd = rs.getMetaData();
        // 2）通过ResultMetaData获取结果集中的列数
        int columnCount = rsmd.getColumnCount();
        if (rs.next()) {
            Student stu = new Student();
            for (int i = 0; i < columnCount; i++) {
                //获取列值
                Object columnValue = rs.getObject(i + 1);
               //获取每个列的列名
                String columnName = rsmd.getColumnName(i + 1);
                //给stu对象指定的columnName属性，赋值columnValue，通过反射
                Field field = Student.class.getDeclaredField(columnName);
                field.setAccessible(true);
                field.set(stu, columnValue);
            }
            return stu;
        }
        JDBCUtil.closeResult(conn, ps, rs);
        return null;
    }
    @Test
    public void testQueryForStu() throws Exception {
        String sql = "select * from Stu where id = ?";
        Student Stu = queryForStu(sql, 1);
        System.out.println(Stu);
    }
}