JDBC 学习笔记
学习参考视频：
[1] JDBC从入门到精通视频教程-JDBC实战精讲
[2] 尚硅谷JDBC核心技术视频教程（康师傅带你一站式搞定jdbc）
代码总结：
testConnection1（）方法介绍了数据库连接的6个步骤：
1.注册JDBC驱动，告诉Java程序将要连接什么数据库；
2.Java程序连接数据库；
3.由连接对象创建操作SQL的对象；
4.执行SQL语句；
5.获取结果集；
6.JVM进程与数据库进程的通信是重量级的，因此需关闭资源。
后续方法都对上述步骤作了不同的优化，在方法上有说明。.
代码如下：
package com.bjpowernode;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
/**
* @author: sjmp1573
* @date: 2022/6/22 17:19
* @description:
*/
public class JDBC01 {
/**
* 1.注册JDBC驱动，告诉Java程序将要连接什么数据库；
* 2.Java程序连接数据库；
* 3.由连接对象创建操作SQL的对象；
* 4.执行SQL语句；
* 5.获取结果集；
* 6.JVM进程与数据库进程的通信是重量级的，因此需关闭资源。
*/
@Test
public void jdbcTest01() {
Connection connection = null;
Statement statement = null;
try {
Driver driver = new com.mysql.jdbc.Driver();
DriverManager.registerDriver(driver);
connection = DriverManager.getConnection("jdbc:mysql://ip:port/database", "xxx", "xxx");
statement = connection.createStatement();
String sql = "INSERT INTO `t_student`(`name`,`gender`) VALUE('小绿',1),('小黄',0);";
// 返回值 i 表示：i行受到影响
int i = statement.executeUpdate(sql);
System.out.println(i);
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 优化 JDBC 驱动的注册过程：
* 由于 com.mysql.jdbc 包中的 Driver 类已经的静态代码块中包含了驱动的注册过程;
* 所以只需要通过反射加载该 Driver 类，即可完成驱动的注册；
*/
@Test
public void jdbcTest02() {
Connection connection = null;
Statement statement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://ip:port/database", "xxx", "xxx");
statement = connection.createStatement();
String sql = "DELETE FROM `t_student` WHERE `name` = '小黄';";
int i = statement.executeUpdate(sql);
System.out.println(i);
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 将数据库的访问信息抽取到配置文件
*/
@Test
public void jdbcTest03() {
InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
try {
properties.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
String driverClass = properties.getProperty("driverClass");
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
Connection connection = null;
Statement statement = null;
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, user, password);
statement = connection.createStatement();
String sql = "INSERT INTO `t_student`(`name`,`gender`) VALUE('小绿',1),('小黄',0);";
// 返回值 i 表示：i行受到影响
int i = statement.executeUpdate(sql);
System.out.println(i);
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 使用 ResultSet 获取结果集，使用 statement.executeQuery() 执行查询操作。
*/
@Test
public void jdbcTest04() {
InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
try {
properties.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
String driverClass = properties.getProperty("driverClass");
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, user, password);
statement = connection.createStatement();
String sql = "SELECT * FROM `t_student`;";
// 返回值 i 表示：i行受到影响,注意：由于是查询
resultSet = statement.executeQuery(sql);
while (resultSet.next()) {
String name = resultSet.getString("name");
String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
System.out.format("姓名：%s，性别：%s", name, gender);
System.out.println();
}
} catch (SQLException | ClassNotFoundException e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* SQL 注入是利用某些系统没有对用户输入的数据进行充分的检查，而在用户输入数据中注入
* 非法的SQL语句段或命令（如：
* String sql = "select * from t_user where loginName = '" + loginName + "'and loginPwd='" + loginPwd +"'";
* loginName = fdsa
* loginPwd = fdsa' or '1'='1;
* select * from t_user where loginName = 'fdsa' and loginPwd='fdsa' or '1'='1';
* 由此引起的安全问题称为SQL注入；
* 解决方案：PreparedStatement 提供的预编译功能,使用 ? 作为占位符，同时提高了语句查询的效率。
*/
@Test
public void jdbcTest05() {
InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
try {
properties.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
String driverClass = properties.getProperty("driverClass");
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, user, password);
String sql = "SELECT * FROM `t_user` where loginName = ? and loginPwd = ?;";
statement = connection.prepareStatement(sql);
statement.setString(1, "sjmp");
statement.setString(2, "666666");
// 返回值 i 表示：i行受到影响,注意：由于是查询
resultSet = statement.executeQuery(sql);
while (resultSet.next()) {
String name = resultSet.getString("name");
String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
System.out.format("姓名：%s，性别：%s", name, gender);
System.out.println();
}
} catch (SQLException | ClassNotFoundException e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (resultSet != null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 设置事务
* 1.取消事务自动提交功能 connection.setAutoCommit(false);
* 2.没有出现异常，全部提交 connection.commit();
* 3.出现异常，开始回滚 connection.rollback();
*/
@Test
public void jdbcTest06() {
InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
try {
properties.load(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
String driverClass = properties.getProperty("driverClass");
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
Connection connection = null;
PreparedStatement statement = null;
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, user, password);
// 1.取消事务自动提交功能
connection.setAutoCommit(false);
// 事务逻辑代码，几个sql语句要么都执行，要么都不执行...
//2.没有出现异常，全部提交
connection.commit();
} catch (SQLException | ClassNotFoundException e) {
//3.出现异常，开始回滚
try {
connection.rollback();
} catch (SQLException ex) {
ex.printStackTrace();
}
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 使用数据库连接池获取数据库连接 druid
*/
@Test
public void jdbcTest07() {
InputStream inputStream = getClass().getClassLoader().getResourceAsStream("jdbc.properties");
Properties properties = new Properties();
DataSource dataSource = null;
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
properties.load(inputStream);
dataSource = DruidDataSourceFactory.createDataSource(properties);
connection = dataSource.getConnection();
String sql = "SELECT * FROM `t_student` ;";
statement = connection.prepareStatement(sql);
resultSet = statement.executeQuery();
while (resultSet.next()){
String name = resultSet.getString("name");
String gender = resultSet.getInt("gender") == 0 ? "女" : "男";
System.out.format("姓名：%s，性别：%s", name, gender);
System.out.println();
}
} catch (Exception e) {
e.printStackTrace();
}finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}