JAVA

程序的主入口jdbc.JDBCTest13.class

package com.snailxq.jdbc;

import com.snailxq.jdbc.utils.DBUtil;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


public class JDBC_Test13 {
    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            // 获取连接
            conn = DBUtil.getConnection();
            // 获取预编译的数据库操作对象

            // 错误的写法
            

            String sql = "select ename from emp where ename like ?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, "_A%");
            rs = ps.executeQuery();
            while(rs.next()){
                System.out.println(rs.getString("ename"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            // 释放资源
            DBUtil.close(conn, ps, rs);
        }

    }
}

实习工具类的包装jdbc.utils.JDUtil.class

package com.snailxq.jdbc.utils;

import javax.smartcardio.CommandAPDU;
import java.sql.*;


public class DBUtil {

    
    private DBUtil() {
    }

    // 静态代码块在类加载时执行，并且只执行一次。
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }


    
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection("jdbc:mysql://localhost:3306/everours", "root", "333");
    }

    
    public static void close(Connection conn, Statement ps, ResultSet rs){
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(ps != null){
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

执行结果：

WARD
MARTIN
JAMES

Process finished with exit code 0