MyBatis工程搭建&MyBatis实现Mapper配置查询

一、MyMyBatis工程搭建

新建Maven项目：mybatis-demo

准备数据源

 1 # 删除mybatis_demo数据库

 2 drop database if exists mybatis_demo;

 3

 4 # 创建mybatis_demo数据库

 5 create database mybatis_demo;

 6

 7 # 使用mybatis_demo数据库

 8 use mybatis_demo;

 9

10 # 创建account表

11 create table user (

12     id int auto_increment primary key,

13     username varchar(20),

14     age int,

15     score int

16 );

17

18 # 新增数据

19 insert into user (id, username, age, score) values

20 (1,'peter', 18, 100), (2,'pedro', 24, 200),

21 (3,'jerry', 28, 500), (4,'mike', 12, 300),

22 (5,'tom', 27, 1000);

连接数据库

1 <dependencies>

2     <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->

3     <dependency>

4         <groupId>mysql</groupId>

5         <artifactId>mysql-connector-java</artifactId>

6         <version>8.0.23</version>

7     </dependency>

8 </dependencies>

代码结构图：

代码编写：

JDBCDemo.java

 1 import java.sql.Connection;

 2 import java.sql.DriverManager;

 3 import java.sql.PreparedStatement;

 4 import java.sql.ResultSet;

 5

 6 public class JDBCDemo {

 7     public static void main(String[] args) throws Exception {

 8         //1.注册驱动

 9         Class.forName("com.mysql.cj.jdbc.Driver");

10         //2.获取连接

11         Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mybatis_demo", "root", "root");

12         //3.获取Statement对象

13         PreparedStatement preparedStatement = connection.prepareStatement("select * from user WHERE id = ?");

14         preparedStatement.setInt(1, 1);

15         //4.执行SQL语句返回结果集

16         ResultSet resultSet = preparedStatement.executeQuery();

17         //5.遍历结果集

18         while (resultSet.next()) {

19             System.out.println("username: " + resultSet.getString("username"));

20             System.out.println("age: " + resultSet.getString("age"));

21         }

22         //6.释放资源

23         resultSet.close();

24         preparedStatement.close();

25         connection.close();

26     }

27 }

执行结果：

引入MyBatis依赖

 1 <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->

 2 <dependency>

 3     <groupId>org.mybatis</groupId>

 4     <artifactId>mybatis</artifactId>

 5     <version>3.5.6</version>

 6 </dependency>

 7 <!-- https://mvnrepository.com/artifact/ch.qos.logback/logback-classic -->

 8 <dependency>

 9     <groupId>ch.qos.logback</groupId>

10     <artifactId>logback-classic</artifactId>

11     <version>1.3.0-alpha5</version>

12     <scope>test</scope>

13 </dependency>

删除JDBC连接：JDBCDemo.java

新建文件：StartNoXml.java

 1 import org.apache.ibatis.datasource.pooled.PooledDataSource;

 2 import org.apache.ibatis.mapping.Environment;

 3 import org.apache.ibatis.session.Configuration;

 4 import org.apache.ibatis.session.SqlSession;

 5 import org.apache.ibatis.session.SqlSessionFactory;

 6 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 7 import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;

 8

 9 import java.sql.PreparedStatement;

10 import java.sql.ResultSet;

11 import java.sql.SQLException;

12

13 @SuppressWarnings({"SqlResolve", "SqlNoDataSourceInspection", "Duplicates"})

14 public class StartNoXml {

15     public static void main(String[] args) throws SQLException {

16         // 准备jdbc事务类

17         JdbcTransactionFactory jdbcTransactionFactory = new JdbcTransactionFactory();

18         // 配置数据源

19         PooledDataSource dataSource = new PooledDataSource(

20                 "com.mysql.cj.jdbc.Driver",

21                 "jdbc:mysql://localhost:3306/mybatis_demo?useSSL=false",

22                 "root",

23                 "root");

24         // 配置环境，向环境中指定环境id、事务和数据源

25         Environment environment = new Environment.Builder("development")

26                 .transactionFactory(jdbcTransactionFactory)

27                 .dataSource(dataSource).build();

28         // 新建 MyBatis 配置类

29         Configuration configuration = new Configuration(environment);

30         // 得到 SqlSessionFactory 核心类

31         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

32         // 开始一个 sql 会话

33         SqlSession session = sqlSessionFactory.openSession();

34         // 得到 sql 连接并运行 sql 语句

35         PreparedStatement preStatement = session

36                 .getConnection()

37                 .prepareStatement("SELECT * FROM user WHERE id = ?");

38         preStatement.setInt(1, 1);

39         ResultSet result = preStatement.executeQuery();

40         // 验证结果

41         while (result.next()) {

42             System.out.println("username: " + result.getString("username"));

43             System.out.println("age: " + result.getString("age"));

44         }

45         // 关闭会话

46         session.close();

47     }

48 }

执行结果：

配置文件：mybatis-config.xml

 1 <?xml version="1.0" encoding="UTF-8" ?>

 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">

 3 <configuration>

 4     <!-- 环境变量 -->

 5     <environments default="development">

 6         <environment id="development">

 7             <!-- 事务管理器 -->

 8             <transactionManager type="JDBC"/>

 9             <!-- 数据源 -->

10             <dataSource type="POOLED">

11                 <property name="driver" value="com.mysql.cj.jdbc.Driver"/>

12                 <property name="url" value="jdbc:mysql://localhost:3306/mybatis_demo?useSSL=false"/>

13                 <property name="username" value="root"/>

14                 <property name="password" value="123456"/>

15             </dataSource>

16         </environment>

17     </environments>

18     <!-- mapper配置 -->

19     <mappers>

20         <mapper class="mapper.UserMapper"/>

21     </mappers>

22 </configuration>

修改StartNoXml.java类名：StartWithXml.java

 1 import org.apache.ibatis.datasource.pooled.PooledDataSource;

 2 import org.apache.ibatis.io.Resources;

 3 import org.apache.ibatis.mapping.Environment;

 4 import org.apache.ibatis.session.Configuration;

 5 import org.apache.ibatis.session.SqlSession;

 6 import org.apache.ibatis.session.SqlSessionFactory;

 7 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 8 import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;

 9

10 import java.io.IOException;

11 import java.io.InputStream;

12 import java.sql.PreparedStatement;

13 import java.sql.ResultSet;

14 import java.sql.SQLException;

15

16 @SuppressWarnings({"SqlResolve", "SqlNoDataSourceInspection", "Duplicates"})

17 public class StartWithXml {

18     public static void main(String[] args) throws SQLException, IOException {

19         // 读取配置文件

20         InputStream configuration = Resources.getResourceAsStream("mybatis-config.xml");

21         // 得到 SqlSessionFactory 核心类

22         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

23         // 开始一个 sql 会话

24         SqlSession session = sqlSessionFactory.openSession();

25         // 得到 sql 连接并运行 sql 语句

26         PreparedStatement preStatement = session

27                 .getConnection()

28                 .prepareStatement("SELECT * FROM user WHERE id = ?");

29         preStatement.setInt(1, 1);

30         ResultSet result = preStatement.executeQuery();

31         // 验证结果

32         while (result.next()) {

33             System.out.println("username: " + result.getString("username"));

34             System.out.println("age: " + result.getString("age"));

35         }

36         // 关闭会话

37         session.close();

38     }

39 }

执行结果：

二、MyBatis实现Mapper配置查询

注解方式使用Mapper

代码编写：

在mybatis-config.xml配置文件中加入mapper配置

1 <!-- mapper配置 -->

2 <mappers>

3     <mapper class="mapper.UserMapper"/>

4 </mappers>

新建mapper包，新建一个UserMapper.java类

UserMapper.java

 1 package mapper;

 2

 3 import entity.User;

 4 import org.apache.ibatis.annotations.Select;

 5

 6 public interface UserMapper {

 7     /**

 8      * 通过用户id查询用户名称

 9      *

10      * @param id 用户id

11      * @return 用户名称

12      */

13     //通过#{**}的方式来查询

14     @Select("SELECT username FROM user WHERE id = #{id}")

15     String selectUsernameById(Integer id);

16     /**

17      * 通过用户id查询用户年龄

18      *

19      * @param id 用户id

20      * @return 用户年龄

21      */

22     Integer selectUserAgeById(Integer id);

23

24     /**

25      * 通过用户id查询用户信息

26      *

27      * @param id

28      * @return

29      */

30     User selectUserById(Integer id);

31

32 }

UserTest.java

 1 import entity.User;

 2 import mapper.UserMapper;

 3 import org.apache.ibatis.io.Resources;

 4 import org.apache.ibatis.session.SqlSession;

 5 import org.apache.ibatis.session.SqlSessionFactory;

 6 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 7

 8 import java.io.IOException;

 9 import java.io.InputStream;

10 import java.sql.SQLException;

11

12 @SuppressWarnings({"SqlResolve", "SqlNoDataSourceInspection", "Duplicates"})

13 public class UserTest {

14     public static void main(String[] args) throws IOException, SQLException {

15         // 读取配置文件

16         InputStream configuration = Resources.getResourceAsStream("mybatis-config.xml");

17         // 得到 SqlSessionFactory 核心类

18         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

19         // 开始一个 sql 会话

20         SqlSession session = sqlSessionFactory.openSession();

21         // 得到 mapper

22         UserMapper mapper = session.getMapper(UserMapper.class);

23         // 调用注解的SQL

24         String username = mapper.selectUsernameById(1);

25         System.out.println("username: " + username);

26         // 调用XML的SQL

27         Integer age = mapper.selectUserAgeById(1);

28         System.out.println("age: " + age);

29

30         // 调用通过用户id查询用户信息的方法

31         User user = mapper.selectUserById(1);

32         System.out.println(user);

33         // 关闭会话

34         session.close();

35     }

36 }

执行结果：

巴特西

MyBatis工程搭建&MyBatis实现Mapper配置查询

一、MyMyBatis工程搭建

二、MyBatis实现Mapper配置查询

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