「最小生成樹計數」題解

阿新 • • 發佈：2021-06-17

Spring整合Mybatis

匯入相關的jar包

<dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.22</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.3</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.2.12.RELEASE</version>
        </dependency>
        <!--Spring操作資料庫的話，還需要一個spring-jdbc-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.2.12.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.6</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.2</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

回憶mybatis

1.編寫實體類

@Data
public class User {
    private int id;
    private String name;
    private String pwd;
}

2.編寫核心配置檔案

<?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核心配置檔案-->
<configuration>
    <!--引入外部配置檔案-->
    <properties resource="db.properties" />
    <typeAliases>
        <package name="com.saxon.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--  每一個mapper.xml都需要在mybatis核心配置檔案中註冊  -->
    <mappers>
        <mapper class="com.saxon.mapper.UserMapper"/>
    </mappers>
</configuration>

db.properties檔案

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/shop?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=Asia/Shanghai
username=root
password=123456

3.編寫介面

public interface UserMapper {
    List<User> selectUser();
}

4.編寫Mapper

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//mapper Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.saxon.mapper.UserMapper">
    <select id="selectUser" resultType="user">
        select * from user;
    </select>
</mapper>

5.測試

public class UserMapperTest extends TestCase {
    @Test
    public void test() throws IOException {
        String resource="mybatis-config.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        SqlSession sqlSession = factory.openSession(true);//開啟自動提交事務
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList =
                mapper.selectUser();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }

}

Mybatis-Spring

步驟：

1.在spring-dao.xml配置中編寫資料來源配置DriverManagerDataSource

使用Spring的資料來源代替Mybatis的配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        https://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        https://www.springframework.org/schema/tx/spring-tx.xsd">
    <!--DataSource:使用Spring的資料來源代替Mybatis的配置 c3p0 dbcp druid
        這裡使用Spring提供的JDBC：org.springframework.jdbc.datasource.DriverManagerDataSource
    -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/shop?useUnicode=true&amp;characterEncoding=UTF-8&amp;useSSL=false&amp;serverTimezone=Asia/Shanghai"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </bean>
    <!--sqlSessionFactory-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!--繫結mybatis配置檔案-->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <property name="mapperLocations" value="classpath:com/saxon/mapper/*.xml"/>
    </bean>
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <!--只能使用構造器注入sqlSessionFactory,因為他沒有set方法-->
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>
</beans>

需要給介面新增實現類

把之前mybatis做的事情交給spring來做

public class UserMapperImpl implements UserMapper{

    //原來我們的所有都是使用SqlSession操作，現在使用SqlSessionTemplate
    private SqlSessionTemplate sqlSession;
    public void setSqlSession(SqlSessionTemplate sqlSession) {
        this.sqlSession = sqlSession;
    }
    public List<User> selectUser() {
        return sqlSession.getMapper(UserMapper.class).selectUser();
    }
}

applicationContext.xml 註冊實現類

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/aop
         http://www.springframework.org/schema/aop/spring-aop.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context.xsd">
    
    <import resource="spring-dao.xml"/>
    <!--註冊UserMapperImpl 注入屬性-->
    <bean id="userMapper" class="com.saxon.mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    </bean>
</beans>

測試

@Test
public void selectUser() throws IOException {
    ApplicationContext context =
        new ClassPathXmlApplicationContext("applicationContext.xml");
    UserMapper userMapper = context.getBean("userMapper", UserMapper.class);
    for (User user : userMapper.selectUser()) {
        System.out.println(user);
    }
}

方式二

實現類繼承了 SqlSessionDaoSupport

public class UserMapperImpl2 extends SqlSessionDaoSupport implements UserMapper{
    public List<User> selectUser() {
        return getSqlSession().getMapper(UserMapper.class).selectUser();
    }
}

配置檔案applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/aop
         http://www.springframework.org/schema/aop/spring-aop.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context.xsd">
    <import resource="spring-dao.xml"/>
   <!-- 注入屬性 sqlSessionFactory -->
    <bean id="userMapper2" class="com.dada.mapper.UserMapperImpl2">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>
</beans>