[TOC]
1.jdbc是什么
JDBC（Java DataBase Connectivity,java数据库连贯）是一种用于执行SQL语句的Java API，能够为多种关系数据库提供对立拜访，它由一组用Java语言编写的类和接口组成。JDBC提供了一种基准，据此能够构建更高级的工具和接口，使数据库开发人员可能编写数据库应用程序。(百度百科)jdbc常常用来连贯数据库，创立sql或者mysql语句，应用相干的api去执行sql语句，从而操作数据库，达到查看或者批改数据库的目标。- 学习jbbc要求对java编程有肯定理解，并理解一种数据库系统以及
sql语句。- 环境要求：
1.本地装好
jdk，并且装好mysql数据库,我是间接装过wamp带有mysql数据库/docker中装置的mysql。
2.应用IDEA开发
2.应用IDEA开发
2.1 创立数据库，数据表
我的mysql是应用docker创立的，如果是windows环境能够应用wamp较为不便。
数据库名字是test,数据表的名字是student，外面有四个字段，一个是id，也就是主键（主动递增），还有名字，年龄，问题。最初先应用sql语句插入六个测试记录。
CREATE DATABASE `test` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;USE test;CREATE TABLE `student` ( `id` INT NOT NULL AUTO_INCREMENT , `name` VARCHAR(20) NOT NULL , `age` INT NOT NULL , `score` DOUBLE NOT NULL , PRIMARY KEY (`id`)) ENGINE = MyISAM; INSERT INTO `student` VALUES (1, '小红', 26, 83);INSERT INTO `student` VALUES (2, '小白', 23, 93);INSERT INTO `student` VALUES (3, '小明', 34, 45);INSERT INTO `student` VALUES (4, '张三', 12, 78);INSERT INTO `student` VALUES (5, '李四', 33, 96);INSERT INTO `student` VALUES (6, '魏红', 23, 46);2.2 应用IDEA创立我的项目
我应用maven工程形式，我的项目目录：
Student.class
package model;/** * student类，字段包含id,name,age,score * 实现无参结构，带参结构，toString办法，以及get，set办法 */public class Student { private int id; private String name; private int age; private double score; public Student() { super(); // TODO Auto-generated constructor stub } public Student(String name, int age, double score) { super(); this.name = name; this.age = age; this.score = score; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public double getScore() { return score; } public void setScore(double score) { this.score = score; } @Override public String toString() { return "Student [id=" + id + ", name=" + name + ", age=" + age + ", score=" + score + "]"; } }DBUtil.class
package db;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;/** * 工具类，获取数据库的连贯 * @author 秦怀 * */public class DBUtil { private static String URL="jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf-8&serverTimezone=UTC"; private static String USER="root"; private static String PASSWROD ="123456"; private static Connection connection=null; static{ try { Class.forName("com.mysql.jdbc.Driver"); // 获取数据库连贯 connection=DriverManager.getConnection(URL,USER,PASSWROD); System.out.println("连贯胜利"); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } // 返回数据库连贯 public static Connection getConnection(){ return connection; }}StudentDao.class
package dao;import model.Student;import java.util.ArrayList;import java.util.List;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import db.DBUtil;/** * 操作学生表的dao类 * @author 秦怀 * 上面均应用预编译的办法 */public class StudentDao { //将连贯定义为单例 private static Connection connection = DBUtil.getConnection(); // 增加新的学生 public void addStudent(Student student){ String sql ="insert into student(name,age,score) "+ "values(?,?,?)"; boolean result = false; try { // 将sql传进去预编译 PreparedStatement preparedstatement = connection.prepareStatement(sql); // 上面把参数传进去 preparedstatement.setString(1, student.getName()); preparedstatement.setInt(2, student.getAge()); preparedstatement.setDouble(3, student.getScore()); preparedstatement.execute(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.println("创立数据库连贯失败"); } } // 更新学生信息 public void updateStudent(Student student){ String sql = "update student set name = ? ,age =?,score = ? where id = ? "; boolean result = false; try { PreparedStatement preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, student.getName()); preparedStatement.setInt(2, student.getAge()); preparedStatement.setDouble(3, student.getScore()); preparedStatement.setInt(4, student.getId()); preparedStatement.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.println("连贯数据库失败"); } } // 依据id删除一个学生 public void deleteStudent(int id){ String sql = "delete from student where id = ?"; boolean result = false; try { PreparedStatement preparedStatement = connection.prepareStatement(sql); preparedStatement.setInt(1, id); result=preparedStatement.execute(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } // 依据id查问学生 public Student selectStudent(int id){ String sql ="select * from student where id =?"; try { PreparedStatement preparedStatement = connection.prepareStatement(sql); preparedStatement.setInt(1, id); ResultSet resultSet = preparedStatement.executeQuery(); Student student = new Student(); // 一条也只能应用resultset来接管 while(resultSet.next()){ student.setId(resultSet.getInt("id")); student.setName(resultSet.getString("name")); student.setAge(resultSet.getInt("age")); student.setScore(resultSet.getDouble("score")); } return student; } catch (SQLException e) { // TODO: handle exception } return null; } // 查问所有学生，返回List public List<Student> selectStudentList(){ List<Student>students = new ArrayList<Student>(); String sql ="select * from student "; try { PreparedStatement preparedStatement = DBUtil.getConnection().prepareStatement(sql); ResultSet resultSet = preparedStatement.executeQuery(); // 不能把student在循环里面创立，要不list外面六个对象都是一样的，都是最初一个的值， // 因为list add进去的都是援用 // Student student = new Student(); while(resultSet.next()){ Student student = new Student(); student.setId(resultSet.getInt(1)); student.setName(resultSet.getString(2)); student.setAge(resultSet.getInt(3)); student.setScore(resultSet.getDouble(4)); students.add(student); } } catch (SQLException e) { // TODO: handle exception } return students; }}StudentAction.class
package action;import java.util.List;import dao.StudentDao;import model.Student;public class StudentAction { /** * @param args */ public static void main(String[] args) { StudentDao studentDao = new StudentDao(); // TODO Auto-generated method stub System.out.println("========================查问所有学生========================"); List<Student> students =studentDao.selectStudentList(); for(int i=0;i<students.size();i++){ System.out.println(students.get(i).toString()); } System.out.println("========================批改学生信息========================"); Student stu2 = new Student("Jam",20,98.4); stu2.setId(2); studentDao.updateStudent(stu2); System.out.println("========================通过id查问学生========================"); Student student = studentDao.selectStudent(2); System.out.println(student.toString()); System.out.println("========================减少学生========================"); Student stu = new Student("new name",20,98.4); studentDao.addStudent(stu); System.out.println("========================删除学生信息========================"); studentDao.deleteStudent(4); System.out.println("========================查问所有学生========================"); students =studentDao.selectStudentList(); for(int i=0;i<students.size();i++){ System.out.println(students.get(i).toString()); } }}执行的后果：
须要留神的点：
- 创立数据库之后须要赋予用户增删改查的权限
- 如果不是应用maven形式导入包，须要将依赖的包复制进来，并且add to path
- 以上代码应用的是预编译的形式，这样能够进步代码的可读性与维护性，还有就是很大水平上避免了sql注入的问题
- 如果不是用预编译，那么就须要拼接sql语句，很容易出错，而且预编译的作用是sql编译过后，放在缓存中，这样速度会更快。
- 应用拼接形式参考上面这段代码：
sql = "select * from table where name= '" + name + "' and password= '" + password+"'";Statement statement = connection.createStatement();ResultSet resultset = statement.executeQuery(sql);pom文件应用到的依赖,必须和本人的数据库版本匹配，要不会连贯失败
<dependencies> <!-- mysql驱动包 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.21</version> </dependency> </dependencies>此文章仅代表本人（本菜鸟）学习积攒记录，或者学习笔记，如有侵权，请分割作者删除。人无完人，文章也一样，文笔稚嫩，在下不才，勿喷，如果有谬误之处，还望指出，感激不尽~
技术之路不在一时，山高水长，纵使迟缓，驰而不息。
公众号：秦怀杂货店