jdbc案例
一、jdbc使用的案例
1.工具类
package com;
import java.io.FileInputStream;
import java.sql.*;
import java.util.Properties;
//1.获取连接对象 2.关闭连接对象---取代单元测试中的 @Before 和 @After
public class JdbcUtil {
private static Properties p;
static {
//1.读取jdbc.properties文件
try{
FileInputStream is = new FileInputStream("D:\\java0104\\jdbc--day05\\src\\jdbc.properties");
p = new Properties();
p.load(is);
}catch (Exception e){
e.printStackTrace();
}
}
//1.获取连接对象
public static Connection getCon(){
try{
return DriverManager.getConnection(p.getProperty("url"),p);
}catch (Exception e){
e.printStackTrace();
}
return null;
}
//2.释放资源
public static void close(ResultSet rs, Statement state,Connection con){
if (rs!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (state!=null){
try {
state.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (con!=null){
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
System.out.println(getCon());
}
}
2.查询一个表中所有的数据，得到一个结果集，封装结果集到list集合，并在控制台输出
package lei;
import java.sql.Date;
public class Emp {
private int id;
private String name;
private String gender;
private double salary;
private Date join_date;
private int dept_id;
public Emp() {
}
@Override
public String toString() {
return "Emp{" +
"id=" + id +
", name='" + name + '\'' +
", gender='" + gender + '\'' +
", salary=" + salary +
", join_date=" + join_date +
", dept_id=" + dept_id +
'}';
}
public Emp(int id, String name, String gender, double salary, Date join_date, int dept_id) {
this.id = id;
this.name = name;
this.gender = gender;
this.salary = salary;
this.join_date = join_date;
this.dept_id = dept_id;
}
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 String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public Date getJoin_date() {
return join_date;
}
public void setJoin_date(Date join_date) {
this.join_date = join_date;
}
public int getDept_id() {
return dept_id;
}
public void setDept_id(int dept_id) {
this.dept_id = dept_id;
}
}
package com;
import lei.Emp;
import org.junit.Before;
import org.junit.Test;
import java.sql.*;
import java.util.ArrayList;
public class Hello2 {
private Connection con=null;
private Statement state=null;
private ResultSet rs=null;
@Before//获得连接对象
public void init(){
try {
//1.注册驱动 Driver
Class.forName("com.mysql.cj.jdbc.Driver");
//2.DriverManager获取连接数据库对象
String url="jdbc:mysql:///db3?useSSL=false&serverTimezone=UTC";
con= DriverManager.getConnection(url,"root","123456");
} catch (Exception e) {
e.printStackTrace();
}
}
@Test//查询
public void test1(){
try {
//1.定义sql
String sql="select * from emp";
//2.创建执行sql的对象
state=con.createStatement();
//3.执行sql,返回一个结果rs--集合+迭代器
rs = state.executeQuery(sql);
ArrayList<Emp> emps = new ArrayList<>();
while(rs.next()){
int id = rs.getInt("id");
String name = rs.getString("name");
String gender = rs.getString("gender");
double salary = rs.getDouble("salary");
Date join_date = rs.getDate("join_date");
int dept_id = rs.getInt("dept_id");
//调用有参构造
Emp emp = new Emp(id,name,gender,salary,join_date,dept_id);
emps.add(emp);
}
System.out.println(emps);
} catch (SQLException e) {
e.printStackTrace();
}finally {
//释放资源
if (rs!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (state!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (con!=null){
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
3.用statement去实现登录案例
package com;
import java.sql.*;
import java.util.Scanner;
public class Hello1 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("请输入您的用户名：");
String name = sc.nextLine();
System.out.println("请输入您的密码：");
String psw = sc.nextLine();
boolean isLogin=login(name,psw);
System.out.println(isLogin);
}
//登陆方法
private static boolean login(String name, String psw) {
//1.获取连接对象
Connection con = JdbcUtil.getCon();
//2.定义sql
String sql="select * from users where name= '"+name+"' and psw= '"+psw+"'";
Statement state=null;
ResultSet rs = null;
try{
//3.获取执行sql的对象
state = con.createStatement();
//4.执行sql
rs=state.executeQuery(sql);
return rs.next();
}catch (Exception e){
e.printStackTrace();
}finally {
JdbcUtil.close(rs,state,con);
}
return false;
}
}
4.用子接口preparedstatement去优化登录案例
package com;
import java.sql.*;
import java.util.Scanner;
public class Hello2 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("请输入您的用户名：");
String name = sc.nextLine();
System.out.println("请输入您的密码：");
String psw = sc.nextLine();
boolean isLogin=login2(name,psw);
System.out.println(isLogin);
}
//登陆方法--改进版
private static boolean login2(String name, String psw) {
//1.获取连接对象
Connection con = JdbcUtil.getCon();
//2.定义sql
String sql="select * from users where name= ? and psw= ? ";
PreparedStatement pstm=null;
ResultSet rs = null;
try{
//3.获取执行sql的对象
pstm=con.prepareStatement(sql);
pstm.setString(1,name);
pstm.setString(2,psw);
//4.执行sql
rs=pstm.executeQuery();
return rs.next();
}catch (Exception e){
e.printStackTrace();
}finally {
JdbcUtil.close(rs,pstm,con);
}
return false;
}
}
5.事务–转账案例
package com;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
public class Hello2 {
public static void main(String[] args) {
//1.获取连接对象
Connection con = JdbcUtil.getCon();
//2.定义sql
String sql1="update account set balance=balance-? where id=?";
String sql2="update account set balance=balance+? where id=?";
PreparedStatement pstm1=null;
PreparedStatement pstm2=null;
try {
//开启事物--设置手动提交
con.setAutoCommit(false);
//3.获取执行sql的对象
pstm1=con.prepareStatement(sql1);
pstm2=con.prepareStatement(sql2);
//4.给占位符赋值
pstm1.setDouble(1,500);
pstm1.setInt(2,1);
pstm2.setDouble(1,500);
pstm2.setInt(2,2);
//5.执行sql
pstm1.executeUpdate();
int i=6/0;//主动制造异常
pstm2.executeUpdate();
//提交事务
con.commit();
} catch (SQLException e) {
try {
//回滚事务
con.rollback();
} catch (SQLException ex) {
ex.printStackTrace();
}finally {
JdbcUtil.close(null,pstm1,con);
}
}
}
}
总结
以上就是jdbc使用的具体案例的全部内容,主要是利用jdbc连接数据库从而达到实现。