1.jdbc是什么
- JDBC（Java DataBase Connectivity,java数据库连接）是一种用于执行SQL语句的Java API，可以为多种关系数据库提供统一访问，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，据此可以构建更高级的工具和接口，使数据库开发人员能够编写数据库应用程序。(百度百科)
- jdbc经常用来连接数据库，创建sql或者mysql语句，使用相关的api去执行sql语句，从而操作数据库，达到查看或者修改数据库的目的。
- 学习jbbc要求对java编程有一定了解，并了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,我是直接装过wamp带有mysql数据库
2.使用eclipse开发
2.使用eclipse开发
2.1 创建数据库，数据表
数据库名字是test,数据表的名字是student，里面有四个字段，一个是id，也就是主键（自动递增），还有名字，年龄，成绩。最后先使用sql语句插入六个测试记录。
CREATE DATABASE `test` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci; 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 使用eclipse创建项目
打开eclipse–> File --> new -->Project ,创建java项目
输入项目的名字，然后点击Finish
代码的结构如下（一共创建了四个包，action是业务层，这里暂时写得与Test测试一样，去调用dao的方法，dao包下面是操作数据表的dao类，db包下面是封装好的db数据库连接工具类，model是与数据库表对应的model类，也就是模型层）：
Student.class
package model;/**
* student类，字段包括id,name,age,score
* 实现无参构造，带参构造，toString方法，以及get，set方法
* @author 秦怀
*/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();
= 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) {
= 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，获取数据库的连接
* @author 秦怀
*
*/public class DBUtil {
private static String URL="jdbc:mysql://127.0.0.1:3306/test";
private static String USER="root";
private static String PASSWROD ="123456";
private static Connection connection=null;
static{
try {
Class.forName("com.mysql.jdbc.Driver");
// 获取数据库连接
connection=DriverManager.getConnection(URL,USER,PASSWROD);
System.out.println("连接成功");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// 返回数据库连接
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
* 下面均使用预编译的方法
*/public class StudentDao {
//将连接定义为单例
private static Connection connection = DBUtil.getConnection();
// 添加新的学生
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);
// 下面把参数传进去
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("创建数据库连接失败");
}
}
// 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("连接数据库失败");
}
}
// 根据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();
}
}
// 根据id查询学生
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();
// 一条也只能使用resultset来接收
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;
}
// 查询所有学生，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在循环外面创建，要不list里面六个对象都是一样的，都是最后一个的值，
// 因为list add进去的都是引用
// 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("========================查询所有学生========================");
List<Student> students =studentDao.selectStudentList();
for(int i=0;i<students.size();i++){
System.out.println(students.get(i).toString());
}
System.out.println("========================修改学生信息========================");
Student stu2 = new Student("Jam",20,98.4);
stu2.setId(2);
studentDao.updateStudent(stu2);
System.out.println("========================通过id查询学生========================");
Student student = studentDao.selectStudent(2);
System.out.println(student.toString());
System.out.println("========================增加学生========================");
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("========================查询所有学生========================");
students =studentDao.selectStudentList();
for(int i=0;i<students.size();i++){
System.out.println(students.get(i).toString());
}
}}
执行的结果：
