JDBC连接mysql数据库

一、创建java项目，导入jar包，配置properties文件(src路径下)

druid-1.2.8.jar
mysql-connector-java-8.0.25.jar

#   ????key-value???
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/数据库名
username=数据库用户名
password=数据库用户密码
# init size
initialSize=5
# max size
maxActive=10
maxWait=3000

二、根据数据库建好的表创建实体类（如：Student）

package day2.Test;import java.util.Date;public class Student {private int id;private String name;private int age;private Date birthday;@Overridepublic String toString() {return "Student{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", birthday=" + birthday +'}';}public Student(String name, int age, Date birthday) {this.name = name;this.age = age;this.birthday = birthday;}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 Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public Student() {}public Student(int id, String name, int age, Date birthday) {this.id = id;this.name = name;this.age = age;this.birthday = birthday;}
}

三、创建数据库连接工具类JDBCUtil

package day2.Test;import com.alibaba.druid.pool.DruidDataSourceFactory;import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;public class JDBCUtil {//  全局定义动态变量private static Connection conn = null;private static PreparedStatement ps = null;private static ResultSet rs = null;private static DataSource dataSource = null;//  加载驱动static{Properties prop = new Properties();InputStream ress = JDBCUtil.class.getClassLoader().getResourceAsStream("druid.properties");try {prop.load(ress);dataSource = DruidDataSourceFactory.createDataSource(prop);} catch (IOException e) {throw new RuntimeException(e);} catch (Exception e) {throw new RuntimeException(e);}}//  建立数据库连接public static void getConnection() {try {conn = dataSource.getConnection();} catch (SQLException e) {throw new RuntimeException(e);}}//  创建sql对象//  增删改public static int update(String sql,Object obj[]) {//  连接数据库getConnection();try {//  创建sql对象ps = conn.prepareStatement(sql);//  注入数据for (int i = 0; i < obj.length; i++) {ps.setObject(i+1, obj[i]);}//  执行sql语句int num = ps.executeUpdate();return num;} catch (SQLException e) {throw new RuntimeException(e);}finally {close();}}//  查public static ResultSet query(String sql,Object obj[]) {getConnection();try {ps = conn.prepareStatement(sql);for (int i = 0; i < obj.length; i++) {ps.setObject(i+1, obj[i]);}rs = ps.executeQuery();return rs;} catch (SQLException e) {throw new RuntimeException(e);}}//  释放资源public static void close() {if(rs!=null){   //  防止空指针异常try {rs.close();} catch (SQLException e) {throw new RuntimeException(e);}}if(ps!=null){try {ps.close();} catch (SQLException e) {throw new RuntimeException(e);}}if(conn!=null){try {conn.close();} catch (SQLException e) {throw new RuntimeException(e);}}}}

四、创建StudentDao类根据自身需求编写不同sql语句

package day2.Test;import day2.Test.JDBCUtil;import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;public class StudentDao {//  增public int addStudent(Student student){String sql = "insert into student values(null,?,?,?)";Object obj[] = {student.getName(),student.getAge(),student.getBirthday()};int num = JDBCUtil.update(sql,obj);return num;}//  改public int updateStudent(Student student){String sql = "update student set name=?,age=?,birthday=? where id=?";Object obj[] = {student.getName(),student.getAge(),student.getBirthday(),student.getId()};int num = JDBCUtil.update(sql,obj);return num ; //}//  删public int deleteStudent(int id){String sql ="delete from student where id = ?";Object obj[] = {id};int num = JDBCUtil.update(sql,obj);return num;}//  查public List<Student> findStudents(){String sql = "select * from student";Object obj[] = {};List<Student> list = new ArrayList<>();ResultSet res = JDBCUtil.query(sql, obj);while(true){try {if(!res.next()){break;}int id = res.getInt(1);String name = res.getString(2);int age = res.getInt(3);Date birthday = res.getDate(4);list.add(new Student(id,name,age,birthday));} catch (SQLException e) {throw new RuntimeException(e);}}JDBCUtil.close();return list;}
}

五、创建测试类测试查询方法

public class TestDao {public static void main(String[] args) {List<Student> list= new StudentDao().findStudents();for (Student student: list) {System.out.println(student);}}
}

文件目录样式（不包含StudentUI）