Mybatis如何通过Mapper代理连接数据库

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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

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>

自定义接口，在repository包下自定义接口，待会在xml中实现即可

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>

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 

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>class="lazy" data-src/main/java</directory>                <includes>                    <include>**/*.xml</include>                </includes>            </resource>        </resources>    </build>  </project>

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