Mybatis通过Mapper代理连接数据库的方法

1.在数据库中创建表和相应字段，如下图我创建了三个字段分别为fromname,message,toname，类型为varchar

2.创建对应的pojo实体类，注意类型要和数据库创建类型一致，如varchar()对应的是java.lang.String 

 3.在resource路径下配置config.xml，配置Mybatis的运行环境3306/后面加上自己的数据库schema名字，数据库username和password输入自己的账号和密码,而在下方mapper则是用于注册我们待会要写的xml文件，路径用/ 写上xml的全名称。

<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<!DOCTYPE configuration PUBLIC \"-//mybatis.org//DTD Config 3.0//EN\"
        \"http://mybatis.org/dtd/mybatis-3-config.dtd\">
<configuration>
    <!--配置Mybatis运行环境-->
    <environments default=\"development\"><!--default命名-->
        <environment id=\"development\"><!--和上面的一致-->
            <transactionManager type=\"JDBC\"></transactionManager><!--事务管理 交给JDBC-->
            <!-- 数据源 -->
            <dataSource type=\"POOLED\">
                <property name=\"driver\" value=\"com.mysql.cj.jdbc.Driver\"/>
                <property name=\"url\" value=\"jdbc:mysql://localhost:3306/bjpower?
        useUnicode=true&amp;characterEncoding=UTF-8\"/>
                <property name=\"username\" value=\"root\"/>
                <property name=\"password\" value=\"xxxx\"/>
            </dataSource>
        </environment>
    </environments>
 
    <mappers>
<!--        <mapper resource=\"com/yyj/repository/msgdataRepository.xml\"></mapper>-->
        <mapper resource=\"com/yyj/repository/msgdatanewRepository.xml\"></mapper>
    </mappers>
</configuration>

4.自定义接口，在repository包下自定义接口，待会在xml中实现即可

5.在repository中建立对应的xml文件，如我取的名称为MsgdatanewReposiotory,名字可自定义，注意mapper注册和改名字一样即可，然后编写sql语句          

statement 的 id 为接⼝中对应的⽅法名

<?xml version=\"1.0\" encoding=\"UTF-8\" ?>
<!DOCTYPE mapper PUBLIC \"-//mybatis.org//DTD Mapper 3.0//EN\"
        \"http://mybatis.org/dtd/mybatis-3-mapper.dtd\">
<mapper namespace=\"com.yyj.repository.MsgdatanewRepository\"><!--接口全类名-->
    <insert id=\"save1\" parameterType=\"com.yyj.pojo.MessageData\">
        <!--parameterType为传入的参数类型，是刚刚设置的pojo类-->
        insert into msgdatanew(fromname,message,toname) values (#{fromName},#{message},#{toName})
    </insert>
    
    <!--resultType为返回值类型-->
    <select id=\"findByName1\" parameterType=\"java.lang.String\"
            resultType=\"com.yyj.pojo.MessageData\">
        select * from msgdatanew where toname = #{toName}
    </select>
</mapper>

6.调用测试类即可，注意要添加commit事务才能提交成功，数据库才有变化

package com.yyj.Test;
 
import com.yyj.pojo.MessageData;
import com.yyj.repository.MsgdatanewRepository;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 
import java.io.InputStream;
 
public class Test2 {
//    public void add(String toName,String message,String fromName){
public static void main(String[] args) {
    InputStream inputStream = Test2.class.getClassLoader().getResourceAsStream(\"config.xml\");
    SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    MsgdatanewRepository msgdatanewRepository = sqlSession.getMapper(MsgdatanewRepository.class);
    MessageData messageData=new MessageData();
    messageData.setMessage(\"nihaoyayay\");
    messageData.setFromName(\"lisi\");
    int save = msgdatanewRepository.save1(messageData);
    System.out.println(save);
    sqlSession.commit();
}
}

 7.效果展示 

8.附上pom.xml文件

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd\">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.demo</groupId>
    <artifactId>websocket-chatroom</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>websocket-chatroom</name>
    <description>WebSocket示例工程</description>
 
    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.3.7.RELEASE</spring-boot.version>
    </properties>
 
    <dependencies>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.27</version>
        </dependency>
 
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>
 
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
<!--            &lt;!&ndash; ehcache &ndash;&gt;-->
<!--            <dependency>-->
<!--                <groupId>net.sf.ehcache</groupId>-->
<!--                <artifactId>ehcache-core</artifactId>-->
<!--                <version>2.4.3</version>-->
<!--            </dependency> <dependency>-->
<!--            <groupId>org.mybatis</groupId>-->
<!--            <artifactId>mybatis-ehcache</artifactId>-->
<!--            <version>1.0.0</version>-->
<!--        </dependency>-->
        </dependencies>
 
 
    </dependencyManagement>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.3.7.RELEASE</version>
                <configuration>
                    <mainClass>com.yyj.WebsocketChatroomApplication</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
 
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
        </resources>
    </build>
 
 
</project>