JDBC数据库编程——基础、封装
JDBC：（java database connectivity）是java运行平台的核心类库中的一部分，提供了访问数据库中的API，由一些类和接口组成。
使用JDBC提的API操作数据库：应用程序，使用JDBC，来连接数据库。
1、数据库新建表，插入数据：
新建数据库：名字为school
列民（表头）
注意：auto_increment代表自增。只对于int型
插入数据：
查看表：
将sql语句存在工程中：
建Folder，名字为sql
建File，名字为 数据库ming.sql 。例如：school.sql
打开复制进去sql语句：
例如：
INSERT into student VALUES (1, ‘abc’, 20);
INSERT INTO student(name, age) VALUES (‘zs’, 20);
INSERT INTO student VALUES (null, ‘abb’, 20);
程序：
查询： 通过列名
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Main{
public static void main(String[] args) throws ClassNotFoundException, SQLException{
//1加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2获得数据库的连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/school", "root", "");//协议+数据库+端口号+数据库名---------用户名--------密码为空
// System.out.println(con);
//3准备执行语句
String sql = "select * from student";
PreparedStatement pst = con.prepareStatement(sql);
//4执行
ResultSet rs = pst.executeQuery();//结果集为一个二维表
while(rs.next()){//返回true，代表有数据可以读取
int id = rs.getInt("id");//参数字段名称为数据库的表头(列的名称)
String name = rs.getString("name");
int age = rs.getInt("age");
System.out.println(id + "--" + name + "--" + age);
}
//5关闭资源，关闭连接
rs.close();
pst.close();
con.close();
}
}输出：
1–abc–20
2–张三–20
3–abc–20
查询的改进： 通过列的序号
//4执行
ResultSet rs = pst.executeQuery();//结果集为一个二维表
while(rs.next()){//返回true，代表有数据可以读取
int id = rs.getInt(1);//列是从1开始的
String name = rs.getString(2);
int age = rs.getInt(3);
System.out.println(id + "--" + name + "--" + age);
}输出结果同上
增删改：
增：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Main{
public static void main(String[] args) throws ClassNotFoundException, SQLException{
//1加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2获得数据库的连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8", "root", "");//协议+数据库+端口号+数据库名---------用户名--------密码为空
//为了插入汉字，所以需要?useUnicode=true&characterEncoding=utf-8
//3insert
//有未知数，用？占位
String insertSQL = "insert into student values(null, ?, ?)";//准备sql语句
PreparedStatement pst1 = con.prepareStatement(insertSQL);//准备sql语句的对象
//给？赋值
pst1.setString(1, "李四");
pst1.setInt(2, 25);
int result = pst1.executeUpdate();//对于增删改用update，返回类型为int型
if(result == 1){
System.out.println("插入记录成功！");
}
//4delete
//5update
String sql = "select * from student";
PreparedStatement pst = con.prepareStatement(sql);
//6查询
ResultSet rs = pst.executeQuery();//对于查询用Query，返回类型为二维表
while(rs.next()){//返回true，代表有数据可以读取
int id = rs.getInt(1);//列是从1开始的
String name = rs.getString(2);
int age = rs.getInt(3);
System.out.println(id + "--" + name + "--" + age);
}
//7关闭资源，关闭连接
rs.close();
pst.close();
con.close();
}
}输出：
插入记录成功！
1–abc–20
2–张三–20
3–abc–20
4–李四–25
删：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Main{
public static void main(String[] args) throws ClassNotFoundException, SQLException{
//1加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2获得数据库的连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8", "root", "");//协议+数据库+端口号+数据库名---------用户名--------密码为空
/* //3insert
String insertSQL = "insert into student values(null, ?, ?)";//准备sql语句
PreparedStatement pst1 = con.prepareStatement(insertSQL);//准备sql语句的对象
//给？赋值
pst1.setString(1, "李四");
pst1.setInt(2, 25);
int result = pst1.executeUpdate();
if(result == 1){
System.out.println("插入记录成功！");
}*/
//4delete
String deleteSQL = "delete from student where id=?";//准备要执行sql语句
PreparedStatement pst2 = con.prepareStatement(deleteSQL);//准备sql语句的对象
pst2.setInt(1, 1);
int result1 = pst2.executeUpdate();
if(result1 == 1){
System.out.println("删除记录成功！");
}
//5update
//6查询所有记录
String sql = "select * from student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();//结果集为一个二维表
while(rs.next()){//返回true，代表有数据可以读取
int id = rs.getInt(1);//列是从1开始的
String name = rs.getString(2);
int age = rs.getInt(3);
System.out.println(id + "--" + name + "--" + age);
}
//7关闭资源，关闭连接
rs.close();
pst.close();
con.close();
}
}输出：
删除记录成功！
2–张三–20
3–abc–20
11–李四–25
改（更新）：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Main{
public static void main(String[] args) throws ClassNotFoundException, SQLException{
//1加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2获得数据库的连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8", "root", "");//协议+数据库+端口号+数据库名---------用户名--------密码为空
/* //3insert
String insertSQL = "insert into student values(null, ?, ?)";//准备sql语句
PreparedStatement pst1 = con.prepareStatement(insertSQL);//准备sql语句的对象
//给？赋值
pst1.setString(1, "李四");
pst1.setInt(2, 25);
int result = pst1.executeUpdate();
if(result == 1){
System.out.println("插入记录成功！");
}*/
/*//4delete
String deleteSQL = "delete from student where id=?";//准备要执行sql语句
PreparedStatement pst2 = con.prepareStatement(deleteSQL);//准备sql语句的对象
pst2.setInt(1, 1);
int result1 = pst2.executeUpdate();
if(result1 == 1){
System.out.println("删除记录成功！");
}
*/
//5update
String updateSQL = "update student set name = ?,age = ? where id = ?";
//?的意思是：待输入的值
PreparedStatement pst3 = con.prepareStatement(updateSQL);
pst3.setString(1, "吴振浩");
pst3.setInt(2, 55);
pst3.setInt(3, 2);
int result2 = pst3.executeUpdate();
if(result2 == 1){
System.out.println("修改记录成功！");
}
//6查询所有记录
String sql = "select * from student";
PreparedStatement pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();//结果集为一个二维表
while(rs.next()){//返回true，代表有数据可以读取
int id = rs.getInt(1);//列是从1开始的
String name = rs.getString(2);
int age = rs.getInt(3);
System.out.println(id + "--" + name + "--" + age);
}
//7关闭资源，关闭连接
rs.close();
pst.close();
con.close();
}
}输出：
修改记录成功！
2–吴振浩–55
3–abc–20
11–李四–25
在navicat可视化里面，新的数据库为：
封装：
学生类：Sdutent.java
public class Student {
private int id;
private String name;
private int age;
public Student(int id, String name, int age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
public Student() {
super();
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
}
//因为三个属性是私有的，所有可以通过get和set方法取值，赋值
//变量设置成私有的，方法设置成公开的！-----类的封装
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;
}
}
学生表操作类：StudentDao.java
package pp;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
public class StudentDao {
Connection con;
PreparedStatement pst;
public Connection getConn() throws SQLException, ClassNotFoundException{
//1加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2获得数据库的连接
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/school?useUnicode=true&characterEncoding=utf-8", "root", "");//协议+数据库+端口号+数据库名---------用户名--------密码为空
return con;
}
//增
public int addStudent(Student student) throws ClassNotFoundException, SQLException{
con = getConn();
String insertSQL = "insert into student values(null, ?, ?)";//准备sql语句
pst = con.prepareStatement(insertSQL);//准备sql语句的对象
//给？赋值
pst.setString(1, student.getName());
pst.setInt(2, student.getAge());
int result = pst.executeUpdate();
pst.close();
con.close();
return result;
}
//删
public int deleteStudent(int id) throws ClassNotFoundException, SQLException{
con = getConn();
String sql = "delete from student where id=?";//准备sql语句
pst = con.prepareStatement(sql);//准备sql语句的对象
//给？赋值
pst.setInt(1, id);
int result = pst.executeUpdate();
pst.close();
con.close();
return result;
}
//改
public int updateStudent(Student student) throws ClassNotFoundException, SQLException{
con = getConn();
String sql = "update student set name = ?,age = ? where id = ?";//准备sql语句
pst = con.prepareStatement(sql);//准备sql语句的对象
//给？赋值
pst.setString(1, student.getName());
pst.setInt(2, student.getAge());
pst.setInt(3, student.getId());
int result = pst.executeUpdate();
pst.close();
con.close();
return result;
}
//查询所有记录
public List queryAll() throws ClassNotFoundException, SQLException{
con = getConn();
String sql = "select * from student";
pst = con.prepareStatement(sql);
rs = pst.executeQuery();
List list = new ArrayList();//创建链表容器来存放数据
while(rs.next()) {
/*int id = rs.getInt(1);//列是从1开始的
String name = rs.getString(2);
int age = rs.getInt(3);
Student stu = new Student(id, name, age);*/
// Student stu = new Student(rs.getInt(1), rs.getString(2), rs.getInt(3));
Student stu = new Student();
stu.setId(rs.getInt(1));
stu.setName(rs.getString(2));
stu.setAge(rs.getInt(3));
list.add(stu);
}
return list;
}
//根据主键查询记录
public Student queryById(int id) throws ClassNotFoundException, SQLException{
con = getConn();
String sql = "select * from student where id = ?";
pst = con.prepareStatement(sql);
ResultSet rs = pst.executeQuery();
pst.setInt(1, id);
//查到或者没查到
Student stu = null;
if(rs.next()){
stu = new Student(rs.getInt(1), rs.getString(2), rs.getInt(3));
}
return stu;
} 测试类：Main.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
public class Main {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
StudentDao dao=new StudentDao();
Student stu1=new Student(1,"系统",22);
/*int result = dao.addStudent(stu1);
if(result==1)
{
System.out.println("插入记录成功！");
}*/
/* int result2 = dao.delStudent(1);
if(result2==1)
{
System.out.println("删除记录成功！");
}*/
Student stu2=new Student(3,"李四",32);
int result3 = dao.updateStudent(stu2);
if(result3==1)
{
System.out.println("修改记录成功！");
}
List stuList=dao.queryAll();
for(Student stu:stuList)
{
System.out.println(stu);
}
System.out.println("=======");
Student stu = dao.queryById(100);
System.out.println(stu);
}
}