Spring JDBC

0x00 简介

JDBC是Java程序访问数据库的一个接口,它通过调用厂商提供的JDBC Driver来实现对数据库的访问.

但是它操作比较繁琐,先得创建全局DataSource实例=>再从中获取Connection实例=>通过Connection实例创建PreparedStatement实例=>执行SQL语句
而且每次都得用try-finally释放资源...

因此Spring对它进行了封装,加入了注入功能,把DataSource注入到JdbcTemplate中,省略数据源的获取.还加入了事务和异常控制,减少了繁琐的异常判断.

0x01 安装mysql

1. 下载MySQLMySQL :: Download MySQL Community Server
2. 解压到C:webmysql-8.0.26
3. 修改MySQL配置文件
   1. 在C:webmysql-8.0.26文件夹,创建修改my.ini配置文件
   2. 编写配置信息

[client] # 设置mysql客户端默认字符集 
default-character-set=utf8 

[mysqld] 
# 设置3306端口 
port = 3306 
# 设置mysql的安装目录 
basedir=C:webmysql-8.0.26-winx64
# 设置 mysql数据库的数据的存放目录，MySQL 8+ 不需要以下配置，系统自己生成即可，否则有可能报错  
#datadir=C:\web\sqldata 
# 允许最大连接数 
max_connections=20 
# 服务端使用的字符集默认为8比特编码的latin1字符集 
character-set-server=utf8 
# 创建新表时将使用的默认存储引擎 
default-storage-engine=INNODB

• 千万记得修改basedir为当前目录,否则后续步骤无法正常执行

4. 添加/bin路径到环境变量
   

5. 启动MySQL数据库

   1. 以管理员身份打开cmd

   2. 切换到/bin文件夹cd C:webmysql-8.0.26-winx64in

   3. 初始化数据库mysqld --initialize --console

   4. 记录返回的临时密码
      

   5. 安装mysqlmysqld install

   6. 启动mysql服务net start mysql

   7. 登入mysql数据库mysql -u root -p

   8. 更改密码alter user'root'@'localhost' identified by 'pass'
      %%8. 关闭mysql服务net stop mysql%%

0x02 配置数据源

1. 在mysql中创建一个名为spring_db的数据库create database spring_db

0x03 配置SpringJDBC

1. 在idea中创建一个Spring项目
2. 配置pom.xml文件,导入相关依赖

<?xml version="1.0" encoding="UTF-8"?>  
<project xmlns="http://maven.apache.org/POM/4.0.0"  
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">  
    <modelVersion>4.0.0</modelVersion>  
  
    <groupId>org.example</groupId>  
    <artifactId>SSM-bootstrap</artifactId>  
    <packaging>pom</packaging>  
    <version>1.0-SNAPSHOT</version>  
    <modules>  
        <module>MyJdbc</module>  
    </modules>  
  
    <properties>  
        <maven.compiler.source>8</maven.compiler.source>  
        <maven.compiler.target>8</maven.compiler.target>  
    </properties>  
    <dependencies>  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-webmvc</artifactId>  
            <version>5.3.6</version>  
        </dependency>  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-jdbc</artifactId>  
            <version>5.2.16.RELEASE</version>  
        </dependency>  
        <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-tx</artifactId>  
            <version>5.2.16.RELEASE</version>  
        </dependency>  
        <dependency>  
            <groupId>mysql</groupId>  
            <artifactId>mysql-connector-java</artifactId>  
            <version>8.0.26</version>  
			<!-- 版本号必须和数据库相同, 详见参考4-->
        </dependency>  
    </dependencies>  
</project>

3. 编写配置文件applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>  
<beans xmlns="http://www.springframework.org/schema/beans"  
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">  
  
<!-- 配置数据源-->  
 <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">  
<!-- 数据库驱动-->  
 <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>  
<!-- 连接数据库的url-->  
 <property name="url" value="jdbc:mysql://localhost:3306/spring_db"></property>  
<!-- 连接数据库的用户名-->  
 <property name="username" value="root"></property>  
<!-- 连接数据库的密码-->  
 <property name="password" value="pass"></property>  
    </bean>  
  
<!-- 配置JDBC模板-->  
 <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">  
<!-- 引用上面配置的数据源-->  
 <property name="dataSource" ref="dataSource"></property>  
    </bean>  
  
</beans>

4. 编写测试类

import org.springframework.context.ApplicationContext;  
import org.springframework.context.support.ClassPathXmlApplicationContext;  
import org.springframework.jdbc.core.JdbcTemplate;  
  
public class MyJdbcTest {  
    public static void main(String[] args) {  
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");  
        JdbcTemplate jdbcTemplate = (JdbcTemplate) applicationContext.getBean("jdbcTemplate");  
        jdbcTemplate.execute(  
                "create table user("+  
                        "id int primary key auto_increment,"+  
                        "username varchar(40),"+  
                        "password varchar(40))"  
 );  
  
    }  
}

5. 查看测试结果
   

运行测试类后,登入数据库发现新表创建成功,说明JDBC配置成功.

0x04 Spring JdbcTemplate的常用方法

4.1 execute()

利用JdbcTemplate的execute()方法执行sql语句,我们在上面已经用过了,这边不再赘述.

4.2 update() 更新数据

• 编写Userbean

package bean;  
  
public class User {  
    private Integer id;  
    private String username;  
    private String password;  
  
    public Integer getId() {  
        return id;  
    }  
  
    public void setId(Integer id) {  
        this.id = id;  
    }  
  
    public String getUsername() {  
        return username;  
    }  
  
    public void setUsername(String username) {  
        this.username = username;  
    }  
  
    public String getPassword() {  
        return password;  
    }  
  
    public void setPassword(String password) {  
        this.password = password;  
    }  
}

• 编写UserDao和UserDaoImpl

package dao;  
  
import bean.User;  
  
public interface UserDao {  
    public int addUser(User user);  
    public int updateUser(User user);  
    public int deleteUser(int id);  
}

package dao;  
  
import bean.User;  
import org.springframework.jdbc.core.JdbcTemplate;  
  
public class UserDaoImpl implements UserDao{  
    private JdbcTemplate jdbcTemplate;  
  
    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {  
        this.jdbcTemplate = jdbcTemplate;  
    }  
  
    @Override  
 public int addUser(User user) {  
        String sql = "insert into user(username,password) value(?,?)";  
        Object[] obj = new Object[]{  
                user.getUsername(),  
                user.getPassword()  
        };  
        int retVal = this.jdbcTemplate.update(sql,obj);  
        return retVal;  
    }  
  
    @Override  
 public int updateUser(User user) {  
        String sql = "update user set username=?,password=? where id=?";  
        Object[] obj = new Object[]{  
                user.getUsername(),  
                user.getPassword(),  
                user.getId()  
        };  
        int retVal = this.jdbcTemplate.update(sql,obj);  
        return retVal;  
    }  
  
    @Override  
 public int deleteUser(int id) {  
        String sql = "delete from user where id=?";  
        int retVal = this.jdbcTemplate.update(sql,id);  
        return retVal;  
    }  
}

• 注册UserDaoImpl到applicationContext.xml

<bean id="userDao" class="dao.UserDaoImpl">  
    <property name="jdbcTemplate" ref="jdbcTemplate"></property>  
</bean>

• 编写测试类(添加用户)

@Test  
public void addUserTest(){  
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");  
    UserDao userDao = (UserDao) applicationContext.getBean("userDao");  
    User user = new User();  
    user.setUsername("foo");  
    user.setPassword("bar");  
    int retVal = userDao.addUser(user);  
    if(retVal>0){  
        System.out.println("成功插入了" + retVal + "条数据");  
    }else {  
        System.out.println("插入操作执行失败");  
    }  
}

• 调试运行后查看数据库
  

• 编写测试类+调试查看数据库(更新用户)

@Test  
public void updateUserTest(){  
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");  
    UserDao userDao = (UserDao) applicationContext.getBean("userDao");  
    User user = new User();  
    user.setId(1);  
    user.setUsername("fooo");  
    user.setPassword("barr");  
    int retVal = userDao.updateUser(user);  
    if(retVal>0){  
        System.out.println("成功更新了" + retVal + "条数据");  
    }else {  
        System.out.println("更新操作执行失败");  
    }  
}

• 编写测试类+调试查看数据库(删除用户)

@Test  
public void deleteUserTest(){  
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");  
    UserDao userDao = (UserDao) applicationContext.getBean("userDao");  
    int retVal = userDao.deleteUser(1);  
    if(retVal>0){  
        System.out.println("成功删除了" + retVal + "条数据");  
    }else {  
        System.out.println("删除操作执行失败");  
    }  
}

4.3 query() 查询数据

• 修改UserDao

public interface UserDao {  
    public int addUser(User user);  
    public int updateUser(User user);  
    public int deleteUser(int id);  
    public User findUserById(int id);  
    public List<User> findAllUser();  
}

• 修改UserDaoImpl

@Override  
public User findUserById(int id) {  
    String sql = "select * from user where id=?";  
    RowMapper<User> rowMapper = new BeanPropertyRowMapper<User>(User.class);  
    return this.jdbcTemplate.queryForObject(sql,rowMapper);  
}  
  
@Override  
public List<User> findAllUser() {  
    String sql = "select * from user";  
    RowMapper<User> rowMapper = new BeanPropertyRowMapper<User>(User.class);  
    return this.jdbcTemplate.queryForObject(sql,rowMapper,id);
}

• 编写测试类

@Test  
public void findUserById(){  
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");  
    UserDao userDao = (UserDao) applicationContext.getBean("userDao");  
    User user = userDao.findUserById(2);  
    System.out.println(user);  
}  
  
@Test  
public void findAllUser(){  
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");  
    UserDao userDao = (UserDao) applicationContext.getBean("userDao");  
    List<User> userList = userDao.findAllUser();  
    for (User user:userList){  
        System.out.println(user);  
    }  
}

• 测试
  先用之前的addUserTest测试函数,往数据库添加几个User.
  添加成功后开始测试刚写的两个测试方法.
  

0x05 Spring JdbcTemplat的解析

大致翻译下文档写的介绍.
JdbcTemplate是JDBC核心包的中心类.它简化了JDBC的使用,避免了常见错误.它能够执行JDBC核心工作流,使程序代码能够通过提供SQL语句来获取结果.这个类通过ResultSets执行SQL查询/更新/初始化迭代器,截取JDBC异常并把它们转译成org.springframework.dao 包中定义的通用的、信息更丰富的异常层次结构.

参考资料

1. MySQL 安装 | 菜鸟教程 (runoob.com)
2. MySQL8.0.21安装教程（Windows系统） - 华为云 (huaweicloud.com)
3. mysql5.7初始化密码报错 ERROR 1820 (HY000): You must reset your password using ALTER USER statement before - 开始认识 - 博客园 (cnblogs.com)
4. java - MySQLNonTransientConnectionException: Client does not support authentication protocol requested by server; consider upgrading MySQL client - Stack Overflow
5. java - Could not load JDBC driver class [com.mysql.jdbc.Driver] - Stack Overflow
6. 使用Maven构建spring JdbcTemplate项目_1号帅比的博客-CSDN博客_jdbctemplate maven
7. Spring - applicationContext.xml cannot be opened because it does not exist - Stack Overflow
8. 138 张图带你 MySQL 入门 (juejin.cn)
9. Spring入门(十五)：使用Spring JDBC操作数据库 (juejin.cn)
10. JDBC 框架概述 - Spring 教程 - 极客学院Wiki (jikexueyuan.com)
11. 使用JDBC - 廖雪峰的官方网站 (liaoxuefeng.com)
12. JDBC简介 - 廖雪峰的官方网站 (liaoxuefeng.com)