1. JDBC 概述
基本介绍
模拟 JDBC
接口:
public interface JdbcInterface {
//连接
public Object getConnection() ;
//crud
public void crud();
//关闭连接
public void close();
}
实现类:
public class MysqlJdbcImpl implements JdbcInterface{
@Override
public Object getConnection() {
System.out.println("得到 mysql 的连接");
return null;
}
@Override
public void crud() {
System.out.println("完成 mysql 增删改查");
}
@Override
public void close() {
System.out.println("关闭 mysql 的连接");
}
}
实现类:
public class OracleJdbcImpl implements JdbcInterface {
@Override
public Object getConnection() {
System.out.println("得到 oracle的连接 升级");
return null;
}
@Override
public void crud() {
System.out.println("完成 对oracle的增删改查");
}
@Override
public void close() {
System.out.println("关闭 oracle的连接");
}
}
main:
public class TestJDBC {
public static void main(String[] args) throws Exception {
//完成对mysql的操作
JdbcInterface jdbcInterface = new MysqlJdbcImpl();
jdbcInterface.getConnection(); //通过接口来调用实现类[动态绑定]
jdbcInterface.crud();
jdbcInterface.close();
//完成对oracle的操作
System.out.println("==============================");
jdbcInterface = new OracleJdbcImpl();
jdbcInterface.getConnection(); //通过接口来调用实现类[动态绑定]
jdbcInterface.crud();
jdbcInterface.close();
}
}
2. JDBC 快速入门
JDBC 程序编写步骤
JDBC 第一个程序
Create Table actor(
ID int PRIMARY KEY AUTO_IncremeNT,
NAME VARCHAR (32) not NULL DEFAULT '',
SEX CHAR(1) NOT NULL DEFAULT '女',
BORNDATE DATETIME ,
PHONE VARCHAR(12)
);
SELECT * FROM ACTOR
JDBC 第一个程序
public class Jdbc01 {
public static void main(String[] args) throws SQLException, ClassNotFoundException {
//前置工作: 在项目下创建一个文件夹比如 libs
// 将 mysql.jar 拷贝到该目录下,点击 add to project ..加入到项目中
//1. 注册驱动
//Driver driver = new Driver(); //创建driver对象
//加载类`com.mysql.jdbc.Driver'。 这已被弃用。 新的驱动程序类是`com.mysql.cj.jdbc.Driver'。 驱动通过SPI自动注册,一般不需要手动加载驱动类
Class.forName("com.mysql.cj.jdbc.Driver");
System.out.println("加载驱动成功");
//2. 得到连接
// 老师解读
//(1) jdbc:mysql:// 规定好表示协议,通过jdbc的方式连接mysql
//(2) localhost 主机,可以是ip地址
//(3) 3306 表示mysql监听的端口
//(4) student_management 连接到mysql dbms 的哪个数据库
//(5) mysql的连接本质就是前面学过的socket连接
String url = "jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "123456"); //密码
Connection connect = DriverManager.getConnection(url,properties);
//3. 执行sql
//String sql = "insert into actor values(null, '刘德华', '男', '1970-11-11', '110')";
//String sql = "update actor set name='周星驰' where id = 1";
String sql = "delete from actor where id = 1";
//statement 用于执行静态SQL语句并返回其生成的结果的对象
Statement statement = connect.createStatement();
int rows = statement.executeUpdate(sql); // 如果是 dml语句,返回的就是影响行数
System.out.println(rows > 0 ? "成功" : "失败");
//4. 关闭连接资源
statement.close();
connect.close();
}
}
3. 获取数据库连接 5 种方式
sql8以下版本
方式 1
//方式1
@Test
public void connect01() throws SQLException {
Driver driver = new Driver(); //创建driver对象
String url = "jdbc:mysql://localhost:3306/hsp_db02";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "hsp"); //密码
Connection connect = driver.connect(url, properties);
System.out.println(connect);
}
方式 2
//方式2
@Test
public void connect02() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {
//使用反射加载Driver类 , 动态加载,更加的灵活,减少依赖性
Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver)aClass.newInstance();
String url = "jdbc:mysql://localhost:3306/hsp_db02";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "root");// 用户
properties.setProperty("password", "hsp"); //密码
Connection connect = driver.connect(url, properties);
System.out.println("方式2=" + connect);
}
方式 3
//方式3 使用DriverManager 替代 driver 进行统一管理
@Test
public void connect03() throws IllegalAccessException, InstantiationException, ClassNotFoundException, SQLException {
//使用反射加载Driver
Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver) aClass.newInstance();
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
DriverManager.registerDriver(driver);//注册Driver驱动
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第三种方式=" + connection);
}
方式 4
//方式4: 使用Class.forName 自动完成注册驱动,简化代码
//这种方式获取连接是使用的最多,推荐使用
@Test
public void connect04() throws ClassNotFoundException, SQLException {
//使用反射加载了 Driver类
//在加载 Driver类时,完成注册
/*
源码: 1. 静态代码块,在类加载时,会执行一次.
2. DriverManager.registerDriver(new Driver());
3. 因此注册driver的工作已经完成
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
*/
Class.forName("com.mysql.jdbc.Driver");
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/hsp_db02";
String user = "root";
String password = "hsp";
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第4种方式~ " + connection);
}
方式 5
//方式5 , 在方式4的基础上改进,增加配置文件,让连接mysql更加灵活
@Test
public void connect05() throws IOException, ClassNotFoundException, SQLException {
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
Class.forName(driver);//建议写上
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("方式5 " + connection);
}
sql8以上版本
MySQL 8.0 以上版本的数据库连接有所不同:
- 1、MySQL 8.0 以上版本驱动包版本 mysql-connector-java-8.0.16.jar。
- 2、com.mysql.jdbc.Driver 更换为 com.mysql.cj.jdbc.Driver。
- MySQL 8.0 以上版本不需要建立 SSL 连接的,需要显示关闭。
- allowPublicKeyRetrieval=true 允许客户端从服务器获取公钥。
- 最后还需要设置 CST。
加载驱动与连接数据库方式如下:
Class.forName("com.mysql.cj.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC","root","password");
方式一
//方式1
@Test
public void connect01() throws SQLException {
Driver driver = new Driver(); //创建driver对象
String url = "jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "zzb");// 用户
properties.setProperty("password", "123456"); //密码
Connection connect = DriverManager.getConnection(url, properties);
System.out.println(connect);
}
sql8以上 : Driver driver = new Driver(); //创建driver对象
这一行可以不用写,会自动创建对象
方式二
//方式2
@Test
public void connect02() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException, NoSuchMethodException, InvocationTargetException {
//使用反射加载Driver类 , 动态加载,更加的灵活,减少依赖性
Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance();
String url = "jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
//将 用户名和密码放入到Properties 对象
Properties properties = new Properties();
//说明 user 和 password 是规定好,后面的值根据实际情况写
properties.setProperty("user", "zzb");// 用户
properties.setProperty("password", "123456"); //密码
Connection connect = driver.connect(url, properties);
System.out.println("方式2=" + connect);
}
}
方式三
//方式3 使用DriverManager 替代 driver 进行统一管理
@Test
public void connect03() throws IllegalAccessException, InstantiationException, ClassNotFoundException, SQLException, NoSuchMethodException, InvocationTargetException {
//使用反射加载Driver
Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance();
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
String user = "zzb";
String password = "123456";
DriverManager.registerDriver(driver);//注册Driver驱动
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第三种方式=" + connection);
}
方式四
//方式4: 使用Class.forName 自动完成注册驱动,简化代码
//这种方式获取连接是使用的最多,推荐使用
@Test
public void connect04() throws ClassNotFoundException, SQLException {
//使用反射加载了 Driver类
//在加载 Driver类时,完成注册
/*
源码: 1. 静态代码块,在类加载时,会执行一次.
2. DriverManager.registerDriver(new Driver());
3. 因此注册driver的工作已经完成
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
*/
Class.forName("com.mysql.cj.jdbc.Driver");
//创建url 和 user 和 password
String url = "jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
String user = "zzb";
String password = "123456";
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第4种方式~ " + connection);
}
方式五
//方式5 , 在方式4的基础上改进,增加配置文件,让连接mysql更加灵活
@Test
public void connect05() throws IOException, ClassNotFoundException, SQLException {
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
Class.forName(driver);//建议写上
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("方式5 " + connection);
}
4. ResultSet[结果集]
基本介绍
应用实例
public class ResultSet_ {
public static void main(String[] args) throws Exception {
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到Statement
Statement statement = connection.createStatement();
//4. 组织SqL
String sql = "select id, name , sex, borndate from actor";
//执行给定的SQL语句,该语句返回单个 ResultSet对象
/*
+----+-----------+-----+---------------------+
| id | name | sex | borndate |
+----+-----------+-----+---------------------+
| 4 | 刘德华 | 男 | 1970-12-12 00:00:00 |
| 5 | jack | 男 | 1990-11-11 00:00:00 |
+----+-----------+-----+---------------------+
*/
/*
老韩阅读debug 代码 resultSet 对象的结构
*/
ResultSet resultSet = statement.executeQuery(sql);
//5. 使用while取出数据
while (resultSet.next()) { // 让光标向后移动,如果没有更多行,则返回false
int id = resultSet.getInt(1); //获取该行的第1列
//int id1 = resultSet.getInt("id"); 通过列名来获取值, 推荐
String name = resultSet.getString(2);//获取该行的第2列
String sex = resultSet.getString(3);
Date date = resultSet.getDate(4);
System.out.println(id + "\t" + name + "\t" + sex + "\t" + date);
}
//6. 关闭连接
resultSet.close();
statement.close();
connection.close();
}
}
5. Statement
基本介绍
-- 演示 sql 注入
-- 创建一张表
CREATE TABLE admin ( -- 管理员表
NAME VARCHAR(32) NOT NULL UNIQUE,
pwd VARCHAR(32) NOT NULL DEFAULT ''
) CHARACTER SET utf8;
-- 添加数据
INSERT INTO admin VALUES('tom', '123');
-- 查找某个管理是否存在
SELECT *
FROM admin
WHERE NAME = 'tom' AND pwd = '123'
-- SQL
-- 输入用户名 为 1' or
-- 输入万能密码 为 or '1'= '1
SELECT *
FROM admin
WHERE NAME = '1' OR' AND pwd = 'OR '1'= '1'
SELECT * FROM admin
应用实例
sql 创建表:
create table admin(
name varchar(32) not null unique,
pwd varchar(32) not null default "")
character set utf8;
insert into admin values('admin','123');
sql 注入:
public class Statement_ {
public static void main(String[] args) throws Exception {
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输入管理员的名字: "); //next(): 当接收到 空格或者 '就是表示结束 如果想看到sql注入需要用nextline():回车时才是结束
String admin_name = scanner.nextLine(); // 老师说明,如果希望看到SQL注入,这里需要用nextLine
System.out.print("请输入管理员的密码: ");
String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到Statement
Statement statement = connection.createStatement();
//4. 组织SqL
String sql = "select name , pwd from admin where name ='"
+ admin_name + "' and pwd = '" + admin_pwd + "'";
ResultSet resultSet = statement.executeQuery(sql);
if (resultSet.next()) { //如果查询到一条记录,则说明该管理员存在
System.out.println("恭喜, 登录成功");
} else {
System.out.println("对不起,登录失败");
}
//关闭连接
resultSet.close();
statement.close();
connection.close();
}
}
— 输入用户名 为 1’ or
— 输入万能密码 为 or ‘1’= ‘1
6. PreparedStatement
基本介绍
预处理好处
应用案例
public class PreparedStatement_ {
public static void main(String[] args) throws Exception {
//看 PreparedStatement类图
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输入管理员的名字: "); //next(): 当接收到 空格或者 '就是表示结束
String admin_name = scanner.nextLine(); // 老师说明,如果希望看到SQL注入,这里需要用nextLine
System.out.print("请输入管理员的密码: ");
String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到PreparedStatement
//3.1 组织SqL , Sql 语句的 ? 就相当于占位符
String sql = "select name , pwd from admin where name =? and pwd = ?";
//3.2 preparedStatement 对象实现了 PreparedStatement 接口的实现类的对象
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//3.3 给 ? 赋值
preparedStatement.setString(1, admin_name);
preparedStatement.setString(2, admin_pwd);
//4. 执行 select 语句使用 executeQuery
// 如果执行的是 dml(update, insert ,delete) executeUpdate()
// 这里执行 executeQuery ,不要在写 sql
ResultSet resultSet = preparedStatement.executeQuery(sql);
if (resultSet.next()) { //如果查询到一条记录,则说明该管理存在
System.out.println("恭喜, 登录成功");
} else {
System.out.println("对不起,登录失败");
}
//关闭连接
resultSet.close();
preparedStatement.close();
connection.close();
}
}
DML:
public class PreparedStatementDML_ {
public static void main(String[] args) throws Exception {
//看 PreparedStatement类图
Scanner scanner = new Scanner(System.in);
//让用户输入管理员名和密码
System.out.print("请输删除管理员的名字: "); //next(): 当接收到 空格或者 '就是表示结束
String admin_name = scanner.nextLine(); // 老师说明,如果希望看到SQL注入,这里需要用nextLine
// System.out.print("请输入管理员的新密码: ");
// String admin_pwd = scanner.nextLine();
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
Class.forName(driver);//建议写上
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
//3. 得到PreparedStatement
//3.1 组织SqL , Sql 语句的 ? 就相当于占位符
//添加记录
//String sql = "insert into admin values(?, ?)";
//String sql = "update admin set pwd = ? where name = ?";
String sql = "delete from admin where name = ?";
//3.2 preparedStatement 对象实现了 PreparedStatement 接口的实现类的对象
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//3.3 给 ? 赋值
preparedStatement.setString(1, admin_name);
//preparedStatement.setString(2, admin_name);
//4. 执行 dml 语句使用 executeUpdate
int rows = preparedStatement.executeUpdate();
System.out.println(rows > 0 ? "执行成功" : "执行失败");
//关闭连接
preparedStatement.close();
connection.close();
}
}
课堂练习
public class PreparedStatementPractise {
public static void main(String[] args) throws IOException, ClassNotFoundException, SQLException {
/*
创建admin表
使用PreparedStatement添加5条数据
修改tom的记录,将name改成king
删除 一条 的记录
查询全部记录并显示在控制台
*/
Scanner scanner = new Scanner(System.in);
//通过Properties对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//获取相关的值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
String url = properties.getProperty("url");
//1. 注册驱动
// 建议写上
Class.forName(driver);
//2. 得到连接
Connection connection = DriverManager.getConnection(url, user, password);
PreparedStatement preparedStatement = null;
//使用PreparedStatement添加5条数据
for (int i = 0; i < 5; i++) {
//让用户输入管理员名和密码
System.out.print("请输入管理员的名字: ");
String admin_name = scanner.nextLine();
System.out.print("请输入管理员的密码: ");
String admin_pwd = scanner.nextLine();
String sql = "insert into admin values (?,?)";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, admin_name);
preparedStatement.setString(2, admin_pwd);
int rows = preparedStatement.executeUpdate();
System.out.println(rows > 0 ? "执行成功" : "执行失败");
}
//修改tom的记录,将name改成king
preparedStatement = connection.prepareStatement("update admin set name = ? where name = ?");
preparedStatement.setString(1,"king");
preparedStatement.setString(2,"tom");
int rows = preparedStatement.executeUpdate();
System.out.println(rows > 0 ? "执行成功" : "执行失败");
//删除 一条 的记录
preparedStatement = connection.prepareStatement("delete from admin where name = ?");
preparedStatement.setString(1,"json");
rows = preparedStatement.executeUpdate();
System.out.println(rows > 0 ? "执行成功" : "执行失败");
//查询全部记录并显示在控制台
preparedStatement = connection.prepareStatement("select * from admin");
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()){
String name = resultSet.getString(1);
int pwd = resultSet.getInt(2);
System.out.println(name + "\t" + pwd);
}
//关闭连接
preparedStatement.close();
connection.close();
resultSet.close();
}
}
7. JDBC 的相关 API 小结
8. 封装 JDBCUtils 【关闭连接, 得到连接】
说明
代码实现
public class JDBCUtils {
//定义相关的属性(4个), 因为只需要一份,因此,我们做出static
private static String user; //用户名
private static String password; //密码
private static String url; //url
private static String driver; //驱动名
//在static代码块去初始化
static {
try {
Properties properties = new Properties();
InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("mysql.properties");
properties.load(in);
//读取相关的属性值
user = properties.getProperty("user");
password = properties.getProperty("password");
url = properties.getProperty("url");
driver = properties.getProperty("driver");
} catch (IOException e) {
//在实际开发中,我们可以这样处理
//1. 将编译异常转成 运行异常
//2. 调用者,可以选择捕获该异常,也可以选择默认处理该异常,比较方便.
throw new RuntimeException(e);
}
}
//连接数据库, 返回Connection
public static Connection getConnection() {
try {
//1、注册JDBC驱动
Class.forName(driver);
/* 2、获取数据库连接 */
return DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
//1. 将编译异常转成 运行异常
//2. 调用者,可以选择捕获该异常,也可以选择默认处理该异常,比较方便.
throw new RuntimeException(e);
}
}
//关闭相关资源
/*
1. ResultSet 结果集
2. Statement 或者 PreparedStatement
3. Connection
4. 如果需要关闭资源,就传入对象,否则传入 null
*/
public static void close(ResultSet set, Statement statement, Connection connection) {
//判断是否为null
try {
if (set != null) {
set.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
//将编译异常转成运行异常抛出
throw new RuntimeException(e);
}
}
}
package net.jdbc.utils;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
import java.util.ResourceBundle;
public class JDBCUtils {
//数据库url、用户名和密码
private static String driver;//Ctrl+Alt+F抽取全局静态变量
private static String url;
private static String username;
private static String password;
/*读取属性文件,获取jdbc信息*/
static{
ResourceBundle bundle = ResourceBundle.getBundle("db");
driver = bundle.getString("driver");
url = bundle.getString("url");
username = bundle.getString("username");
password = bundle.getString("password");
}
public static Connection getConnection() {
Connection connection = null;
try {
//1、注册JDBC驱动
Class.forName(driver);
/* 2、获取数据库连接 */
connection = DriverManager.getConnection(url,username,password);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
/*关闭结果集、数据库操作对象、数据库连接*/
public static void release(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {
if(resultSet!=null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(preparedStatement!=null) {
try {
preparedStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(connection!=null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
实际使用使用工具类 JDBCUtils
public class JDBCUtils_Use {
@Test
public void testSelect() {
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "select * from actor where id = ?";
PreparedStatement preparedStatement = null;
ResultSet set = null;
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtils.getConnection();
System.out.println(connection.getClass()); //com.mysql.jdbc.JDBC4Connection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 5);//给?号赋值
//执行, 得到结果集
set = preparedStatement.executeQuery();
//遍历该结果集
while (set.next()) {
int id = set.getInt("id");
String name = set.getString("name");
String sex = set.getString("sex");
Date borndate = set.getDate("borndate");
String phone = set.getString("phone");
System.out.println(id + "\t" + name + "\t" + sex + "\t" + borndate + "\t" + phone);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
JDBCUtils.close(set, preparedStatement, connection);
}
}
@Test
public void testDML() {//insert , update, delete
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "update actor set name = ? where id = ?";
// 测试 delete 和 insert ,自己玩.
PreparedStatement preparedStatement = null;
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
//给占位符赋值
preparedStatement.setString(1, "周星驰");
preparedStatement.setInt(2, 4);
//执行
preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
JDBCUtils.close(null, preparedStatement, connection);
}
}
}
9. 事务
基本介绍
应用实例
模拟经典的转账业务
不使用事务可能出现的问题模拟-模拟经典的转账业务
使用事务解决上述问题-模拟经典的转账业务
public class Transaction_ {
//没有使用事务.
@Test
public void noTransaction() {
//操作转账的业务
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "update account set balance = balance - 100 where id = 1";
String sql2 = "update account set balance = balance + 100 where id = 2";
PreparedStatement preparedStatement = null;
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtils.getConnection(); // 在默认情况下,connection是默认自动提交
preparedStatement = connection.prepareStatement(sql);
preparedStatement.executeUpdate(); // 执行第1条sql
int i = 1 / 0; //抛出异常
preparedStatement = connection.prepareStatement(sql2);
preparedStatement.executeUpdate(); // 执行第3条sql
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
JDBCUtils.close(null, preparedStatement, connection);
}
}
//事务来解决
@Test
public void useTransaction() {
//操作转账的业务
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "update account set balance = balance - 100 where id = 1";
String sql2 = "update account set balance = balance + 100 where id = 2";
PreparedStatement preparedStatement = null;
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtils.getConnection(); // 在默认情况下,connection是默认自动提交
//将 connection 设置为不自动提交
connection.setAutoCommit(false); //开启了事务
preparedStatement = connection.prepareStatement(sql);
preparedStatement.executeUpdate(); // 执行第1条sql
int i = 1 / 0; //抛出异常
preparedStatement = connection.prepareStatement(sql2);
preparedStatement.executeUpdate(); // 执行第3条sql
//这里提交事务
connection.commit();
} catch (SQLException e) {
//这里我们可以进行回滚,即撤销执行的SQL
//默认回滚到事务开始的状态.
System.out.println("执行发生了异常,撤销执行的sql");
try {
connection.rollback();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
e.printStackTrace();
} finally {
//关闭资源
JDBCUtils.close(null, preparedStatement, connection);
}
}
}
10. 批处理
基本介绍
应用实例
传统方式
public class Batch_ {
//传统方法,添加5000条数据到admin2
@Test
public void noBatch() throws Exception {
Connection connection = JDBCUtils.getConnection();
String sql = "insert into admin2 values(null, ?, ?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
System.out.println("开始执行");
long start = System.currentTimeMillis();//开始时间
for (int i = 0; i < 5000; i++) {//5000执行
preparedStatement.setString(1, "jack" + i);
preparedStatement.setString(2, "666");
preparedStatement.executeUpdate();
}
long end = System.currentTimeMillis();
System.out.println("传统的方式 耗时=" + (end - start));//传统的方式 耗时=10702
//关闭连接
JDBCUtils.close(null, preparedStatement, connection);
}
批处理
//使用批量方式添加数据
@Test
public void batch() throws Exception {
Connection connection = JDBCUtils.getConnection();
String sql = "insert into admin2 values(null, ?, ?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
System.out.println("开始执行");
long start = System.currentTimeMillis();//开始时间
for (int i = 0; i < 5000; i++) {//5000执行
preparedStatement.setString(1, "jack" + i);
preparedStatement.setString(2, "666");
//将sql 语句加入到批处理包中 -> 看源码
/*
//1. //第一就创建 ArrayList - elementData => Object[]
//2. elementData => Object[] 就会存放我们预处理的sql语句
//3. 当elementData满后,就按照1.5扩容
//4. 当添加到指定的值后,就executeBatch
//5. 批量处理会减少我们发送sql语句的网络开销,而且减少编译次数,因此效率提高
public void addBatch() throws SQLException {
synchronized(this.checkClosed().getConnectionMutex()) {
if (this.batchedArgs == null) {
this.batchedArgs = new ArrayList();
}
for(int i = 0; i < this.parameterValues.length; ++i) {
this.checkAllParametersSet(this.parameterValues[i], this.parameterStreams[i], i);
}
this.batchedArgs.add(new PreparedStatement.BatchParams(this.parameterValues, this.parameterStreams, this.isStream, this.streamLengths, this.isNull));
}
}
*/
preparedStatement.addBatch();
//当有1000条记录时,在批量执行
if((i + 1) % 1000 == 0) {//满1000条sql
preparedStatement.executeBatch();
//清空一把
preparedStatement.clearBatch();
}
}
long end = System.currentTimeMillis();
System.out.println("批量方式 耗时=" + (end - start));//批量方式 耗时=108
//关闭连接
JDBCUtils.close(null, preparedStatement, connection);
}
}
1.5倍扩容
11. 数据库连接池
5k 次连接数据库问题
public class ConQuestion {
//代码 连接mysql 5000次
@Test
public void testCon() {
//看看连接-关闭 connection 会耗用多久
long start = System.currentTimeMillis();
System.out.println("开始连接.....");
for (int i = 0; i < 5000; i++) {
//使用传统的jdbc方式,得到连接
Connection connection = JDBCUtils.getConnection();
//做一些工作,比如得到PreparedStatement ,发送sql
//..........
//关闭
JDBCUtils.close(null, null, connection);
}
long end = System.currentTimeMillis();
System.out.println("传统方式5000次 耗时=" + (end - start));//传统方式5000次 耗时=7099
}
}
传统获取 Connection 问题分析
数据库连接池
数据库连接池示意图
数据库连接池种类
C3P0 应用实例
文档: https://www.oschina.net/p/c3p0
[https://www.mchange.com/projects/c3p0/#installation](https://www.mchange.com/projects/c3p0/#installation)
c3p0-config.xml
<c3p0-config>
<!-- 数据源名称代表连接池 -->
<named-config name="hsp">
<!-- 驱动类 -->
<property name="driverClass">com.mysql.cj.jdbc.Driver</property>
<!-- url-->
<property name="jdbcUrl">jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&serverTimezone=GMT%2B8</property>
<!-- 用户名 -->
<property name="user">zzb</property>
<!-- 密码 -->
<property name="password">123456</property>
<!-- 每次增长的连接数-->
<property name="acquireIncrement">5</property>
<!-- 初始的连接数 -->
<property name="initialPoolSize">10</property>
<!-- 最小连接数 -->
<property name="minPoolSize">5</property>
<!-- 最大连接数 -->
<property name="maxPoolSize">50</property>
<!-- 可连接的最多的命令对象数 -->
<property name="maxStatements">5</property>
<!-- 每个连接对象可连接的最多的命令对象数 -->
<property name="maxStatementsPerConnection">2</property>
</named-config>
</c3p0-config>
c3p0
public class C3P0_ {
//方式1: 相关参数,在程序中指定user, url , password等
@Test
public void testC3P0_01() throws Exception {
//1. 创建一个数据源对象
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
//2. 通过配置文件mysql.properties 获取相关连接的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\\mysql.properties"));
//读取相关的属性值
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String url = properties.getProperty("url");
String driver = properties.getProperty("driver");
//给数据源 comboPooledDataSource 设置相关的参数
//注意:连接管理是由 comboPooledDataSource 来管理
comboPooledDataSource.setDriverClass(driver);
comboPooledDataSource.setJdbcUrl(url);
comboPooledDataSource.setUser(user);
comboPooledDataSource.setPassword(password);
//设置初始化连接数
comboPooledDataSource.setInitialPoolSize(10);
//最大连接数
comboPooledDataSource.setMaxPoolSize(50);
//测试连接池的效率, 测试对mysql 5000次操作
long start = System.currentTimeMillis();
for (int i = 0; i < 5000; i++) {
Connection connection = comboPooledDataSource.getConnection(); //这个方法就是从 DataSource 接口实现的
//System.out.println("连接OK");
connection.close();
}
long end = System.currentTimeMillis();
//c3p0 5000连接mysql 耗时=391
System.out.println("c3p0 5000连接mysql 耗时=" + (end - start));
}
//第二种方式 使用配置文件模板来完成
//1. 将c3p0 提供的 c3p0.config.xml 拷贝到 src目录下
//2. 该文件指定了连接数据库和连接池的相关参数
@Test
public void testC3P0_02() throws SQLException {
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource("hsp");
System.out.println(comboPooledDataSource);
//测试5000次连接mysql
long start = System.currentTimeMillis();
System.out.println("开始执行....");
for (int i = 0; i < 500000; i++) {
Connection connection = comboPooledDataSource.getConnection();
// System.out.println("连接OK~");
connection.close();
}
long end = System.currentTimeMillis();
//c3p0的第二种方式 耗时=413
System.out.println("c3p0的第二种方式(500000) 耗时=" + (end - start));//1917
}
}
Druid(德鲁伊)应用实例
druid.propertise
#key=value
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/student_management?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC&rewriteBatchedStatements=true
username=zzb
password=123456
#initial connection Size 初始化连接数
initialSize=10
#min idle connecton size 最小连接数
minIdle=5
#max active connection size 最大连接数
maxActive=50
#max wait time (5000 mil seconds) 最大等待时间
maxWait=5000
Druid
public class Druid_ {
@Test
public void testDruid() throws Exception {
//1. 加入 Druid jar包
//2. 加入 配置文件 druid.properties , 将该文件拷贝项目的src目录
//3. 创建Properties对象, 读取配置文件
Properties properties = new Properties();
properties.load(new FileInputStream("src\\druid.properties"));
//4. 创建一个指定参数的数据库连接池, Druid连接池
DataSource dataSource =
DruidDataSourceFactory.createDataSource(properties);
long start = System.currentTimeMillis();
for (int i = 0; i < 500000; i++) {
Connection connection = dataSource.getConnection();
System.out.println(connection.getClass());
//System.out.println("连接成功!");
connection.close();
}
long end = System.currentTimeMillis();
//druid连接池 操作5000 耗时=412
System.out.println("druid连接池 操作500000 耗时=" + (end - start));//539
}
}
将 JDBCUtils 工具类改成 Druid(德鲁伊)实现
JDBCUtilsByDruid
public class JDBCUtilsByDruid {
private static DataSource ds;
//在静态代码块完成 ds初始化
static {
Properties properties = new Properties();
try {
properties.load(new FileInputStream("src\\druid.properties"));
ds = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
e.printStackTrace();
}
}
//编写getConnection方法
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
//关闭连接, 老师再次强调: 在数据库连接池技术中,close 不是真的断掉连接
//而是把使用的Connection对象放回连接池
public static void close(ResultSet resultSet, Statement statement, Connection connection) {
try {
if (resultSet != null) {
resultSet.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
JDBCUtils 工具类使用
public class JDBCUtilsByDruid_USE {
@Test
public void testSelect() {
System.out.println("使用 druid方式完成");
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "select * from actor where id >= ?";
PreparedStatement preparedStatement = null;
ResultSet set = null;
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtilsByDruid.getConnection();
System.out.println(connection.getClass());//运行类型 com.alibaba.druid.pool.DruidPooledConnection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 1);//给?号赋值
//执行, 得到结果集
set = preparedStatement.executeQuery();
//遍历该结果集
while (set.next()) {
int id = set.getInt("id");
String name = set.getString("name");//getName()
String sex = set.getString("sex");//getSex()
Date borndate = set.getDate("borndate");
String phone = set.getString("phone");
System.out.println(id + "\t" + name + "\t" + sex + "\t" + borndate + "\t" + phone);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
JDBCUtilsByDruid.close(set, preparedStatement, connection);
}
}
//使用老师的土方法来解决ResultSet =封装=> Arraylist
@Test
public void testSelectToArrayList() {
System.out.println("使用 druid方式完成");
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "select * from actor where id >= ?";
PreparedStatement preparedStatement = null;
ResultSet set = null;
ArrayList<Actor> list = new ArrayList<>();//创建ArrayList对象,存放actor对象
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtilsByDruid.getConnection();
//连接
System.out.println(connection.getClass());//运行类型 com.alibaba.druid.pool.DruidPooledConnection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 1);//给?号赋值
//执行, 得到结果集
set = preparedStatement.executeQuery();
//遍历该结果集
while (set.next()) {
int id = set.getInt("id");
String name = set.getString("name");//getName()
String sex = set.getString("sex");//getSex()
Date borndate = set.getDate("borndate");
String phone = set.getString("phone");
//把得到的resultset 的记录,封装到 Actor对象,放入到list集合
list.add(new Actor(id, name, sex, borndate, phone));
}
System.out.println("list集合数据=" + list);
for(Actor actor : list) {
System.out.println("id=" + actor.getId() + "\t" + actor.getName());
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
System.out.println("关闭资源" );
JDBCUtilsByDruid.close(set, preparedStatement, connection);
}
//因为ArrayList 和 connection 没有任何关联,所以该集合可以复用.
}
}
12. Apache—DBUtils
先分析一个问题
用自己的土方法来解决
如果有返回值则 junit 不管用
public class JDBCUtilsByDruid_OLD {
public static void main(String[] args) {
testSelectToArrayList();
}
//使用老师的土方法来解决ResultSet =封装=> Arraylist
@Test
public static ArrayList<Actor> testSelectToArrayList() {
System.out.println("使用 druid方式完成");
//1. 得到连接
Connection connection = null;
//2. 组织一个sql
String sql = "select * from actor where id >= ?";
PreparedStatement preparedStatement = null;
ResultSet set = null;
ArrayList<Actor> list = new ArrayList<>();//创建ArrayList对象,存放actor对象
//3. 创建PreparedStatement 对象
try {
connection = JDBCUtilsByDruid.getConnection();
//连接
System.out.println(connection.getClass());//运行类型 com.alibaba.druid.pool.DruidPooledConnection
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, 1);//给?号赋值
//执行, 得到结果集
set = preparedStatement.executeQuery();
//遍历该结果集
while (set.next()) {
int id = set.getInt("id");
String name = set.getString("name");//getName()
String sex = set.getString("sex");//getSex()
Date borndate = set.getDate("borndate");
String phone = set.getString("phone");
//把得到的resultset 的记录,封装到 Actor对象,放入到list集合
list.add(new Actor(id, name, sex, borndate, phone));
}
System.out.println("list集合数据=" + list);
for(Actor actor : list) {
System.out.println("id=" + actor.getId() + "\t" + actor.getName());
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
//关闭资源
System.out.println("关闭资源" );
JDBCUtilsByDruid.close(set, preparedStatement, connection);
}
//因为ArrayList 和 connection 没有任何关联,所以该集合可以复用.
return list;
}
}
基本介绍
应用实例
使用apache-DBUtils 工具类 + druid 完成对表的crud操作
//使用apache-DBUtils 工具类 + druid 完成对表的crud操作
@Test
public void testQueryMany() throws SQLException { //返回结果是多行的情况
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回ArrayList 结果集
//String sql = "select * from actor where id >= ?";
// 注意: sql 语句也可以查询部分列
String sql = "select id, name from actor where id >= ?";
// 老韩解读
//(1) query 方法就是执行sql 语句,得到resultset ---封装到 --> ArrayList 集合中
//(2) 返回集合
//(3) connection: 连接
//(4) sql : 执行的sql语句
//(5) new BeanListHandler<>(Actor.class): 在将resultset -> Actor 对象 -> 封装到 ArrayList
// 底层使用反射机制 去获取Actor 类的属性,然后进行封装
//(6) 1 就是给 sql 语句中的? 赋值,可以有多个值,因为是可变参数Object... params
//(7) 底层得到的resultset ,会在query 关闭, 关闭PreparedStatment
/**
* 分析 queryRunner.query方法:
* public <T> T query(Connection conn, String sql, ResultSetHandler<T> rsh, Object... params) throws SQLException {
* PreparedStatement stmt = null;//定义PreparedStatement
* ResultSet rs = null;//接收返回的 ResultSet
* Object result = null;//返回ArrayList
*
* try {
* stmt = this.prepareStatement(conn, sql);//创建PreparedStatement
* this.fillStatement(stmt, params);//对sql 进行 ? 赋值
* rs = this.wrap(stmt.executeQuery());//执行sql,返回resultset
* result = rsh.handle(rs);//返回的resultset --> arrayList[result] [使用到反射,对传入class对象处理]
* } catch (SQLException var33) {
* this.rethrow(var33, sql, params);
* } finally {
* try {
* this.close(rs);//关闭resultset
* } finally {
* this.close((Statement)stmt);//关闭preparedstatement对象
* }
* }
*
* return result;
* }
*/
List<Actor> list =
queryRunner.query(connection, sql, new BeanListHandler<>(Actor.class), 1);
System.out.println("输出集合的信息");
for (Actor actor : list) {
System.out.print(actor);
}
//释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
apache-dbutils + druid 完成 返回的结果是单行记录(单个对象)
//演示 apache-dbutils + druid 完成 返回的结果是单行记录(单个对象)
@Test
public void testQuerySingle() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回单个对象
String sql = "select * from actor where id = ?";
// 老韩解读
// 因为我们返回的单行记录<--->单个对象 , 使用的Hander 是 BeanHandler
Actor actor = queryRunner.query(connection, sql, new BeanHandler<>(Actor.class), 10);
System.out.println(actor);
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
apache-dbutils + druid 完成查询结果是单行单列-返回的就是object
//演示apache-dbutils + druid 完成查询结果是单行单列-返回的就是object
@Test
public void testScalar() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 就可以执行相关的方法,返回单行单列 , 返回的就是Object
String sql = "select name from actor where id = ?";
//老师解读: 因为返回的是一个对象, 使用的handler 就是 ScalarHandler
Object obj = queryRunner.query(connection, sql, new ScalarHandler(), 4);
System.out.println(obj);
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
apache-dbutils + druid 完成 dml (update, insert ,delete)
//演示apache-dbutils + druid 完成 dml (update, insert ,delete)
@Test
public void testDML() throws SQLException {
//1. 得到 连接 (druid)
Connection connection = JDBCUtilsByDruid.getConnection();
//2. 使用 DBUtils 类和接口 , 先引入DBUtils 相关的jar , 加入到本Project
//3. 创建 QueryRunner
QueryRunner queryRunner = new QueryRunner();
//4. 这里组织sql 完成 update, insert delete
//String sql = "update actor set name = ? where id = ?";
//String sql = "insert into actor values(null, ?, ?, ?, ?)";
String sql = "delete from actor where id = ?";
//老韩解读
//(1) 执行dml 操作是 queryRunner.update()
//(2) 返回的值是受影响的行数 (affected: 受影响)
//int affectedRow = queryRunner.update(connection, sql, "林青霞", "女", "1966-10-10", "116");
int affectedRow = queryRunner.update(connection, sql, 1000 );
System.out.println(affectedRow > 0 ? "执行成功" : "执行没有影响到表");
// 释放资源
JDBCUtilsByDruid.close(null, null, connection);
}
表和 JavaBean 的类型映射关系
13. DAO 和增删改查通用方法-BasicDao
先分析一个问题
分层
底层数据库(具体数据的存储)——> dao(实现从表中读数据)——> domain(讲表与实体进行关联,进行实体的定义,set,get方法的定义)——> service(逻辑的实现,进行数据关联,方便底层取数据)——> controller(方便为前段提供数据)。
基本说明
BasicDAO 应用实例
ActorDAO
public class ActorDAO extends BasicDAO<Actor> {
//1. 就有 BasicDAO 的方法
//2. 根据业务需求,可以编写特有的方法.
}
BasicDAO
public class BasicDAO<T> { //泛型指定具体类型
private QueryRunner qr = new QueryRunner();
//开发通用的dml方法, 针对任意的表
public int update(String sql, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
int update = qr.update(connection, sql, parameters);
return update;
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//返回多个对象(即查询的结果是多行), 针对任意表
/**
*
* @param sql sql 语句,可以有 ?
* @param clazz 传入一个类的Class对象 比如 Actor.class
* @param parameters 传入 ? 的具体的值,可以是多个
* @return 根据Actor.class 返回对应的 ArrayList 集合
*/
public List<T> queryMulti(String sql, Class<T> clazz, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//查询单行结果 的通用方法
public T querySingle(String sql, Class<T> clazz, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new BeanHandler<T>(clazz), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
//查询单行单列的方法,即返回单值的方法
public Object queryScalar(String sql, Object... parameters) {
Connection connection = null;
try {
connection = JDBCUtilsByDruid.getConnection();
return qr.query(connection, sql, new ScalarHandler(), parameters);
} catch (SQLException e) {
throw new RuntimeException(e); //将编译异常->运行异常 ,抛出
} finally {
JDBCUtilsByDruid.close(null, null, connection);
}
}
}
Actor
public class Actor { //Javabean, POJO, Domain对象
private Integer id;
private String name;
private String sex;
private Date borndate;
private String phone;
public Actor() { //一定要给一个无参构造器[反射需要]
}
public Actor(Integer id, String name, String sex, Date borndate, String phone) {
this.id = id;
this.name = name;
this.sex = sex;
this.borndate = borndate;
this.phone = phone;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBorndate() {
return borndate;
}
public void setBorndate(Date borndate) {
this.borndate = borndate;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
@Override
public String toString() {
return "\nActor{" +
"id=" + id +
", name='" + name + '\'' +
", sex='" + sex + '\'' +
", borndate=" + borndate +
", phone='" + phone + '\'' +
'}';
}
}
TestDAO
public class TestDAO {
//测试ActorDAO 对actor表crud操作
@Test
public void testActorDAO() {
ActorDAO actorDAO = new ActorDAO();
//1. 查询
List<Actor> actors = actorDAO.queryMulti("select * from actor where id >= ?", Actor.class, 1);
System.out.println("===查询结果===");
for (Actor actor : actors) {
System.out.println(actor);
}
//2. 查询单行记录
Actor actor = actorDAO.querySingle("select * from actor where id = ?", Actor.class, 6);
System.out.println("====查询单行结果====");
System.out.println(actor);
//3. 查询单行单列
Object o = actorDAO.queryScalar("select name from actor where id = ?", 6);
System.out.println("====查询单行单列值===");
System.out.println(o);
//4. dml操作 insert ,update, delete
int update = actorDAO.update("insert into actor values(null, ?, ?, ?, ?)", "张无忌", "男", "2000-11-11", "999");
System.out.println(update > 0 ? "执行成功" : "执行没有影响表");
}
}