另：准备工作
电脑安装MySQL，安装MySQL可视化操作工具Workbench，创建好数据库。
一：连接数据库
--1--导入mysql相关jar包 ：mysql-connector-jar(手动导包过程在另一文章)
--2--加载驱动
--3--通过Connection类，填写待连接数据库的基本信息
package jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
* Created by Seadragon on 2019-12-26.
*/
public class JdbcConnect {
public static void main(String[] args) throws ClassNotFoundException {
Connection connection = null;
Statement statement = null;
try {
//初始化驱动，加载驱动
Class.forName("com.mysql.jdbc.Driver");
//Connection对象的连接，填写待连接数据库的信息。连接相关数据库
connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?characterEncoding=UTF-8",
"root","root");
System.out.println("连接成功:"+connection.toString());
//创建sql语句相关对象 Statement
statement = connection.createStatement();
System.out.println("获取sql语句对象:"+statement);
//准备相关sql语句
//自增主键的位置用NULL代替即可
String sql = "INSERT INTO hero VALUES (NULL ,'男枪', 3150)";
int i = 100;
while (i!=0) {
statement.execute(sql);
i--;
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
//关闭连接，释放资源
//先关statement,再关Connection
if(statement!=null){
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection!=null)
{
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
System.out.println("关闭："+statement+"----"+connection);
}
}
}
二：数据库操作
Connection对象用于连接数据库
--1--调用方法为调用mysql驱动类，DriverManager.getConnection(url)
Statement对象用于对sql语句操作,
--1--创建：connection.createStatement
--2--执行：executeQuery()【执行查询，返回的是ResultSet对象】；execute【增删更新，可以通过getResultSet进行查询，返回的是Boolean】；executeUpdate【不可查询，返回数据是受影响的数据条数】
ps：sql语句中自增长用null代替即可
PreparedStatement为Statement的升级版，sql的语句可简写，预编译机制速度快，可以预防sql注入式攻击
--1--sql注入攻击：改变sql语句结构，例如：拼接 "sql"+"or 1=1"，使得语句无限次执行
--2--PreparedStatement只可设置值，分为预编译和执行两个阶段，且不可改变sql结构，故能防御注入
package jdbc;
import java.sql.*;
/**
* Created by Seadragon on 2019-12-26.
*/
public class JdbcPreparedStatemen {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = null;
Statement statement = null;
String sql_preState = "insert into hero values(null,?,?)";
String sql_state = "insert into hero VALUES (null,"+"'提莫',"+12+")";
//执行sql语句的两种方式
connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?","root","root");
statement = connection.createStatement();
PreparedStatement preparedStatement = connection.prepareStatement(sql_preState);
statement.execute(sql_state);
preparedStatement.setString(1,"提莫pre");
preparedStatement.setInt(2,1233);
preparedStatement.execute();
}
}
三：数据库元数据
即数据库名称，有哪些表等一些的基本数据，通过DatabaseMetaData对象获取，调用getMetaData方法
package jdbc;
import java.sql.*;
/**
* Created by Seadragon on 2019-12-27.
*/
public class getMetaData {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?","root","root");
DatabaseMetaData databaseMetaData = connection.getMetaData();
System.out.println(databaseMetaData.getDatabaseProductName());
System.out.println(databaseMetaData.getDatabaseProductVersion());
}
}
四：事务
即把几个sql语句的执行打包在一起，若全都成功执行才执行，若有一条失败则全都不执行。处理方法为关闭自动提交改为手动提交。
--1---
connection.setAutoCommit(false)
{sql}
connection.commit()
package jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
* Created by Seadragon on 2019-12-27.
*/
public class JdbcTransaction {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?","root","root");
Statement statement = connection.createStatement();
connection.setAutoCommit(false);
String sql = "insert into user values(NULL,"+"'kkk',"+"'12345'"+")";
String sql_false = "insert into rrrr values(NULL,"+"'kkk',"+"'12345'"+")";
statement.execute(sql);
statement.execute(sql_false);
connection.commit();
System.out.println("你是否要删除该数据");
}
}
五：ORM
对象映射数据，即把数据库的每条数据与一对象映射，我愿理解为数据库在java中的封装
package jdbc;
import hero.Hero;
import jdbc.*;
import java.security.PublicKey;
import java.sql.*;
/**
* Created by Seadragon on 2019-12-27.
*/
public class JdbcORM {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
Hero hero = get(3);
Hero hero_add = new Hero("男枪",12);
add(hero_add);
delete("男枪");
update(1);
System.out.println(hero.getName()+":"+hero.getPrice());
}
public static Connection connectMysql() throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?","root","root");
return connection;
}
//ID查询
public static Hero get(int id) throws ClassNotFoundException, SQLException {
Hero hero = null;
Connection connection = connectMysql();
Statement statement = connection.createStatement();
String sql = "select * from hero where idHero = "+id;
ResultSet resultSet = statement.executeQuery(sql);
while (resultSet.next()){
hero = new Hero();
String name = resultSet.getString("name");
int price = resultSet.getInt("price");
hero.setName(name);
hero.setPrice(price);
}
return hero;
}
//add方法
public static void add(Hero hero) throws ClassNotFoundException, SQLException {
Connection connection = connectMysql();
String sql = "insert into hero values(null,?,?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1,hero.getName());
preparedStatement.setInt(2,hero.getPrice());
preparedStatement.execute();
}
//delete方法
public static void delete(String heroname) throws SQLException, ClassNotFoundException {
Connection connection = connectMysql();
String sql = "DELETE FROM hero WHERE NAME = ?";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1,heroname);
preparedStatement.execute();
}
//update
public static void update(int id) throws SQLException, ClassNotFoundException {
Connection connection = connectMysql();
String sql = "UPDATE hero SET name = ?,price = ? WHERE idHero = ?";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1,"修改的英雄名称");
preparedStatement.setInt(2,1234);
preparedStatement.setInt(3,id);
preparedStatement.execute();
}
}
六：连接池
减少创建数据库创建连接和关闭连接的时间，创建连接池，里面开启n条连接永不关闭。
若需要连接数据库，则往连接池中申请，若连接池有空闲连接，则给它；使用完连接后不直接关闭而是返还到连接池中处于空闲状态。
涉及多线程相关
package jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Seadragon on 2019-12-28.
*/
public class JdbcConnectionPool {
List<Connection> connections = new ArrayList<Connection>();
int size;
public JdbcConnectionPool(int size) throws SQLException, ClassNotFoundException {
this.size=size;
init();
}
public void init() throws ClassNotFoundException, SQLException {
Class.forName("com.mysql.jdbc.Driver");
for (int i = 0;i<size;i++) {
Connection connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/ksea?", "root", "root");
connections.add(connection);
}
}
public synchronized Connection getConnection() throws InterruptedException {
while (connections.isEmpty()){
this.wait();
}
Connection connection = connections.remove(0);
return connection;
}
public synchronized void returnConnection(Connection connection){
connections.add(connection);
this.notifyAll();
}
}
来源：https://www.cnblogs.com/KSea/p/12095970.html