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>

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