Mybatis --- 创建方法、全局配置

<!DOCTYPE configuration  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"  
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
      <properties resource="jdbc.properties"/>

      <environments default="development">
            <environment id="development">
                  <transactionManager type="JDBC" />
                  <dataSource type="POOLED">
                        <property name="driver" value="${jdbc.driver}" />
                        <property name="url" value="${jdbc.url}" />
                        <property name="username" value="${jdbc.username}" />
                        <property name="password" value="${jdbc.password}" />
                  </dataSource>
            </environment>
      </environments>

      <mappers>
            <mapper resource="com/neuedu/mapper/EmployeeMapper.xml" />
      </mappers>
</configuration>

public class TestMyBatis {
      @Test
      public void test() {
            String resource = "mybatis-config.xml";
            InputStream inputStream = null;
            try {
                  inputStream = Resources.getResourceAsStream(resource);//从配置文件中读取一个流
            } catch (IOException e) {
                  e.printStackTrace();
            }
            //利用这个流创建一个sqlSessionFactory对象，也就是总控文件创建了这个对象
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            //和数据库建立的一次会话，通过openSession，创建一个sqlsession对象
            SqlSession sqlsession = sqlSessionFactory.openSession();
            try {
                  //selectOne查询一条记录，第一个参数时sql语句的唯一标识，第二个参数时sql要用的参数
                  //为了确保唯一标识唯一，所以在前面写上namespace，因为namesapce唯一
                  //如果第二个参数"4"在数据库中找不到的话，不会报错，返回null
                  Object selectOne = sqlsession.selectOne("com.neuedu.MyBatis.EmployeeMapper.selectStudentById",4 );
                  System.out.println(selectOne);
            } finally {
                  sqlsession.close();
            }
      }
}

<mapper namespace="com.neuedu.MyBatis.EmployeeMapper">
<!--
      namespace：名称空间，随便起一个名，但是要唯一
      id：sql 语句的唯一标识
      #{id}：接收参数传递过来的id值
      resultType：将 sql语句返回成什么对象
 -->
      <select id="selectStudentById" resultType="com.neuedu.entity.Employee">
            select * from student where id = #{id}
      </select>
</mapper>

public interface EmployeeMapper {
      /*
       * 增删改查方法
       * */
      public Employee getEmployeeById(Integer id);

}

<mapper namespace="com.neuedu.mapper.EmployeeMapper">
<!--
      namespace：将sql映射文件和Mapper接口进行关联
      id：要和相对应的mapper接口的方法名保持一致
      #{id}：从参数中获取id
      resultType：将 sql语句返回成什么对象
 -->

      <!-- public Employee getEmployeeById(Integer id); -->
      <select id="getEmployeeById" resultType="com.neuedu.entity.Employee">
            select * from student where id = #{id}
      </select>

</mapper>

private SqlSessionFactory getSqlSessionFactory(){
     String resource = "mybatis-config.xml";
     InputStream inputStream = null;
     try {
           inputStream = Resources.getResourceAsStream(resource);//从配置文件中读取一个流
     } catch (IOException e) {
           e.printStackTrace();
     }
     //利用这个流创建一个sqlSessionFactory对象
     SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

     return sqlSessionFactory;
}

@Test
public void test01(){
      //1.获取sqlSessionFactory对象
      SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
      //2.利用sqlSessionFactory创建一个session对象，表示和数据库的一次会话
      SqlSession session = sqlSessionFactory.openSession();
      //3.用session对象获取mapper接口的代理对象
      //因为sql映射文件给相应的接口创建了一个代理对象，所以mapper接口类不需要实现类
      EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
      //通过mapper接口的代理对象就可以对数据库进行增删改查操作
      Employee employee = mapper.getEmployeeById(4);
      System.out.println(employee);
      session.close();
}

<!--将接口与xml文件进行绑定 -->
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);

<!-- settings标签可以设置多个属性值 -->
<settings>
      <!-- setting标签负责每一个属性的设置 -->
      <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>

public interface EmployeeMapper {
      /*
       * 增删改查方法
       * */
      @Select("select * from student where id = #{id}")
      public Employee getEmployeeById(Integer id);

}

<environments default="development">
      <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="com.neuedu.datasource.C3P0DateSource">
                  <property name="driverClass" value="${jdbc.driver}" />
                  <property name="jdbcUrl" value="${jdbc.url}" />
                  <property name="user" value="${jdbc.username}" />
                  <property name="password" value="${jdbc.password}" />
            </dataSource>
      </environment>
</environments>