Mybatis连接操作数据库的四种方式

第一种：

配置sqlMapConfig.xml(mybatis核心配置文件)

<!-- 配置数据源，事务 -->
<environment id="test">
            <!-- 事务：JDBC/MANAGED-自己管理去 -->
            <transactionManager type="JDBC"/>
            <!-- 数据源：POOLED/UNPOOLED/JNDI -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatisdb?charsetEncoding=utf8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>

<!-- 映射文件mapper -->
    <mappers>
        <mapper resource="cn/itcast/mapper/PersonMapper.xml"/>
    </mappers>

创建mapper.xml

<!-- 自定义命名空间-->
<mapper namespace="cn.itcast.mapper.PersonMapper">
     <!-- 查询一个，按id查询 -->
    <select id="get" parameterType="int" resultType="cn.itcast.domain.Person">
        select * from person
        where id = #{pid}
    </select>
</mapper>

在测试类中使用：

private SqlSessionFactory factory;
@Before //最先执行，初始化SessionFactory
    public void init() throws IOException{
        String resource = "sqlMapConfig.xml";
        InputStream is = Resources.getResourceAsStream(resource);
        factory = new SqlSessionFactoryBuilder().build(is);
    }

@Test   //查询一条
    public void testGet(){
        SqlSession session = factory.openSession();
        Person p = session.selectOne("cn.itcast.mapper.PersonMapper.get", 1);
        //cn.itcast.mapper.PersonMapper：mapper.xml中定义的命名空间
        // get：各种操作定义的id
        System.out.println(p);
    }

后面是三种都是结合spring，且动态生成mapper代理。
程序员只需要编写mapper接口(相当于dao接口)，不需要编写 mapper接口的实现类，mybatis提供根据mapper接口和mapper.xml（映射文件）生成mapper接口动态代理对象(mapper接口的实现)。
具备什么规则生成mapper代理对象：
Mapper.xml中的namespace等于mapper接口的地址。
Mapper.xml中定义的sql的id（mapped statement的id）等于mapper.java中方法名
Mapper.xml中定义的statement的parametertype等于mapper.java中方法的形参类型。
Mapper.xml中定义的statement的resultType等于mapper.java中方法的返回值类型。

第二种 ：

sqlMapConfig.xml核心配置文件不需要再配置xxxmapper.xml

applicationContext.xml：spring核心配置文件

<!-- 1.jdbc.properties属性配置文件 -->
    <context:property-placeholder location="classpath:jdbc.properties"/>
    
    <!-- 2.数据源 DataSource -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${jdbc.driverclass}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>
    
    <!-- 3.SqlSessionFactory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- spring和mybatis整合 -->
        <!-- 1）引入mybatis核心配置文件 -->
        <property name="configLocation" value="classpath:sqlMapConfig.xml"/>
        
        <!-- 2）扫描指定目录下的所有Mapper.xml -->
        <property name="mapperLocations" value="classpath:cn/itcast/ssm/mapper/*.xml"/>
    </bean>

创建mapper.xml：personMapper.xml

<!-- 自定义命名空间-->
<mapper namespace="cn.itcast.mapper.PersonMapper">
     <!-- 带条件查询 -->
    <select id="find" parameterType="map" resultMap="personRM">
        select * from person
        where 1=1
        <if test="name!=null"> and user_name like #{name}</if>
        <if test="ageStart!=null"> and age>#{ageStart}</if>
        <if test="ageEnd!=null"><![CDATA[ and age<=#{ageEnd}]]></if>
    </select>
    
    <!-- 查询某人的书籍 -->
    <select id="findPersonBook" parameterType="int" resultMap="personBookRM">
SELECT
    p.id,p.user_name,p.age,p.remark,
    b.id AS book_id,b.name,b.money
FROM
    (SELECT * FROM person
        WHERE id = #{id}
    ) p
LEFT JOIN
    (SELECT * FROM book
        WHERE person_id = #{id}
    ) b
ON p.id=b.person_id
    </select>
    
    <!-- 新增 -->
    <insert id="insert" parameterType="cn.itcast.ssm.domain.Person">
        insert into person
        (user_name,age,remark)
        values
        (   
            #{name, jdbcType=VARCHAR},
            #{age, jdbcType=INTEGER},
            #{remark, jdbcType=VARCHAR}
        )
    </insert>
</mapper>

创建PersonMapper接口文件，接口文件路径一定要和xxxmapper.xml文件namespace名称一致。

public interface PersonMapper {
    public List<Person> find(Map map);
    public void insert(Person person);
    public Person findPersonBook(Integer id);
        // 需要注意的是方法中的参数要和mapper.xml中定义的参数类型一致
}

编写dao层

@Repository
public class PersonDaoImpl extends SqlSessionDaoSupport implements PersonDao {
    
    /*
     * mybatis3.0.0+mybatis-psring1.0.0无需，整合包自己注入
     * mybatis3.2.2+mybatis-spring1.2.0 必须自己注入sqlSessionFactory；
     */
    @Resource
    public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
        super.setSqlSessionFactory(sqlSessionFactory);
    }
    
    public List<Person> find(Map map){
        PersonMapper mapper = this.getSqlSession().getMapper(PersonMapper.class);
        return mapper.find(map);
    }
    
    public void insert(Person person){
        PersonMapper mapper = this.getSqlSession().getMapper(PersonMapper.class);
        mapper.insert(person);
    }
    
    public Person findPersonBook(Integer id){
        PersonMapper mapper = this.getSqlSession().getMapper(PersonMapper.class);
        return mapper.findPersonBook(id);
    }
    
}

第三种 ：

sqlMapConfig.xml核心配置文件不需要再配置xxxmapper.xml
注意：mapper.xml和mapper.java同名且在一个目录 ，不需要在SqlMapConfig.xml中加载mapper文件。
applicationContext.xml：spring核心配置文件

<!-- 加载配置文件 -->
<context:property-placeholder location="classpath:db.properties"/>

<!-- 数据库连接池 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" >
       <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <!-- 开发阶段建议最大连接数据尽量少，够用即可 -->
        <property name="maxActive" value="${jdbc.maxActive}"/>
        <property name="maxIdle" value="${jdbc.maxIdle}"/>
</bean>

<!-- 事务管理器 -->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <!-- 数据源 -->
    <property name="dataSource" ref="dataSource"/>
</bean>

<!-- 配置SqlSessionFactory
从spring和mybatis的整合包中获取
 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <!-- 加载数据源 -->
    <property name="dataSource" ref="dataSource"/>
    <!-- 配置SqlMapConfig.xml -->
    <property name="configLocation" value="classpath:mybatis/SqlMapConfig.xml"/>
</bean>

<!-- 使用MapperFactoryBean 生成mapper的代理对象
在mybatis和spring的整合包中
-->

<bean id="sysuserCustomMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
  配置mapper接口
  <property name="mapperInterface" value="yycg.base.dao.mapper.SysuserCustomMapper"/>
  配置sqlSessionFactory
  <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
</bean>

编写xxxmapper.xml文件

 <!-- 带条件查询 -->
    <select id="findSysuserById" parameterType="int" resultType="Sysuser ">
        select * from Sysuser 
        where 1=1
        <if test="name!=null"> and user_name like #{name}</if>
        <if test="ageStart!=null"> and age>#{ageStart}</if>
        <if test="ageEnd!=null"><![CDATA[ and age<=#{ageEnd}]]></if>
    </select>

编写接口文件

public interface SysuserCustomMapper {
    
    public Sysuser findSysuserById(String id) throws Exception;
}

编写test类

public void testFindSysuserById() throws Exception {
        // 获取spring容器
                applicationContext = new ClassPathXmlApplicationContext(new String[] {
                        "spring/applicationContext.xml", "spring/applicationContext-dao.xml"

                });
        SysuserCustomMapper sysuserCustomMapper = (SysuserCustomMapper) applicationContext
                .getBean("sysuserCustomMapper");
        Sysuser sysuser =  sysuserCustomMapper.findSysuserById("286");
        System.out.println(sysuser);
    }

使用MapperFactoryBean需要在spring容器对每个mapper进行配置，麻烦。

第四种 ：

利用代码生成工具(就是一个java工程)

4444444.png

1、将接口文件、mapper.xml、实体类文件拷贝到项目的相应包下即可。
2、在spring中配置mapper自动扫描器

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
   <!-- 配置扫描包路径 ，如果扫描多个包路径，中间使用半角逗号分隔-->
   <property name="basePackage" value="yycg.base.dao.mapper"/>
    <!-- 配置SqlSessionFactory -->
    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
</bean>

3、编写测试类

private ApplicationContext applicationContext;

    protected void setUp() throws Exception {
        // 获取spring容器
        applicationContext = new ClassPathXmlApplicationContext(new String[] {
                "spring/applicationContext.xml", "spring/applicationContext-dao.xml"

        });
    }

    protected void tearDown() throws Exception {

    }
    
    public void testFindSysuserById() throws Exception {
        // 获取spring容器
                applicationContext = new ClassPathXmlApplicationContext(new String[] {
                        "spring/applicationContext.xml", "spring/applicationContext-dao.xml"

                });
        SysuserCustomMapper sysuserCustomMapper = (SysuserCustomMapper) applicationContext
                .getBean("sysuserCustomMapper");
        Sysuser sysuser =  sysuserCustomMapper.findSysuserById("286");
        System.out.println(sysuser);
    }

注意：mapper.xml和mapper.java同名且在一个目录