Mybatis配置并实现（XML方式）

Mybatis配置并实现（XML方式）

1. idea中创建一个maven项目

2. 在pom文件中导入下面的依赖

   <!--mybatis核心包-->
       <dependency>
         <groupId>org.mybatis</groupId>
         <artifactId>mybatis</artifactId>
         <version>3.4.6</version>
       </dependency>
       <!--mysql数据库驱动包-->
       <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
         <version>8.0.18</version>
       </dependency>
       <!--log4j日志包-->
       <dependency>
         <groupId>log4j</groupId>
         <artifactId>log4j</artifactId>
         <version>1.2.17</version>
       </dependency>
   

3. 创建一个java源文件夹和resources资源文件夹并准备好mybatis配置文件mybaits.xml和数据库文件db.properties

   

mybaits.xml

<?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>
    <!--数据库参数文件-->
    <properties resource="db.properties"></properties>
    <!--别名的配置，可以不用-->
    <typeAliases>
        <package name="cn.cqy.domain"></package>
    </typeAliases>
    <!--配置环境，可以多个，这里要设置一个默认使用的环境-->
    <environments default="dev">
        <!--配置环境名，唯一一个id名称-->
        <environment id="dev">
            <!--事务管理   type:JDBC(支持事务)/MANAGED(什么都不做)-->
            <transactionManager type="JDBC"></transactionManager>
            <!--数据源, 连接池  type(POOLED):MyBatis自带的连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="${driverClassName}"></property>
                <property name="url" value="${url}"></property>
                <property name="username" value="${username}"></property>
                <property name="password" value="${password}"></property>
            </dataSource>
        </environment>
    </environments>

    <!--这个mappers代表的是相应的ORM映射文件 这里先准备好了-->
    <mappers>
        <mapper resource="cn/cqy/mapper/StudentMapper.xml"></mapper>
    </mappers>
</configuration>

db.properties

driverClassName=com.mysql.jdbc.Driver 
url=jdbc:mysql://localhost:3306/prc?userUnicode=true&characterEncoding=utf8&serverTimezone=UTC
username=root
password=root

4. 数据库准备，略。

5. 准备相应的对象

   创建一个Student对象，和数据库的表对应

   public class Student {
       private String s_id;
       private String s_name;
       private String s_birth;
       private String s_sex;
   
       public Student() {}
       
       //getter,setter 方法省略
   ｝
   

6. mapper的准备 ，创建一个mapper文件夹，并在内创建一个StudentMapper接口

   public interface StudentMapper {
   	//查找学生表全部信息
       public List<Student> selectAll();
   	//根据姓名查找学生
       public Student selectByName(String name);
   	//插入一条学生信息
       public void insertOne(Student stu);
   	//根据姓名删除一条学生信息
       public void deleteByName(String name);
   	//根据姓名修改一条学生信息
       public void updateByName(Student stu);
   
   }
   

7. 在resoures资源文件夹下创建和mapper文件夹路径相同的文件夹

   

   然后创建映射文件StudentMapper.xml

   <?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">
   <!--命名空间 必须和所对应接口的全限定名一致-->
   <mapper namespace="cn.cqy.mapper.StudentMapper">
       <!--定义sql的标签的id，需要和对应接口的方法名一致 resultType的类型在没有配置别名的情况下，应该是POJO类的全限定名 如cn.cqy.domain.Student-->
       <select id="selectAll" resultType="Student">
           SELECT s_id,s_name,s_birth,s_sex FROM student
       </select>
       <!--参数类型为自定类型没有别名，输入类型全限定名，为Java类型时输入其对应映射名 如 long:大Long  _long:小long (具体的对应请参见文档)-->
       <select id="selectByName" resultType="Student" parameterType="String">
           SELECT s_id,s_name,s_birth,s_sex FROM student
           WHERE s_name = #{name}
       </select>
   
       <insert id="insertOne" parameterType="Student">
           INSERT INTO student (s_id,s_name,s_birth,s_sex) VALUES (#{s_id},#{s_name},#{s_birth},#{s_sex})
       </insert>
   
       <delete id="deleteByName" parameterType="String">
           DELETE FROM student where s_name = #{s_name}
       </delete>
   
       <update id="updateByName" parameterType="Student" >
           UPDATE student SET s_birth = #{s_birth},s_sex = #{s_sex} WHERE s_name = #{s_name}
       </update>
   </mapper>
   

8. 抽取出一个MybatisUtil工具类

   public class MybatisUtil {
       private static SqlSessionFactory sqlSessionFactory;
   	//静态代码块：在使用的时候先执行，并且执行一次
       static {
           try {
               InputStream is = Resources.getResourceAsStream("mybatis.xml");
               SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
               //创建一个工厂实例（加载了我们的配置文件）
               sqlSessionFactory = builder.build(is);
           } catch (IOException e) {
               e.printStackTrace();
           }
       }
   	/**
   	 *拿到了一个SqlSession对象
   	 */
       public static SqlSession getSqlSession() {
           return sqlSessionFactory.openSession();
       }
   
       public static void closeSqlSession(SqlSession sqlSession) {
           if (sqlSession != null) {
               sqlSession.close();
           }
       }
   }
   

9. 编写测试类

   public class SqlTest {
       @Test
       public void testSelectAll() {
           //通过工具类获得SqlSession对象
           SqlSession sqlSession = MybatisUtil.getSqlSession();
           //获取到绑定到SqlSession的POJO类对应的映射
           StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
           //通过映射调用查询方法
           List<Student> students = studentMapper.selectAll();
           //关闭SqlSession
           sqlSession.close();
           for (Student student : students) {
               System.out.println(student);
           }
       }
   
       @Test
       public void testSelectByName() {
           SqlSession sqlSession = MybatisUtil.getSqlSession();
           StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
           Student stu = studentMapper.selectByName("吴兰");
           sqlSession.close();
           System.out.println(stu);
       }
   
       @Test
       public void testInsertOne() {
           SqlSession sqlSession = MybatisUtil.getSqlSession();
           StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
           Student stu = new Student();
           stu.setS_id("09");
           stu.setS_name("李水");
           stu.setS_birth("1988-08-22");
           stu.setS_sex("男");
           studentMapper.insertOne(stu);
           //增、删、改需要提交事务，否则不会修改
           sqlSession.commit();
           sqlSession.close();
       }
   
       @Test
       public void testDeleteByName() {
           SqlSession sqlSession = MybatisUtil.getSqlSession();
           StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
           studentMapper.deleteByName("李水");
           sqlSession.commit();
           sqlSession.close();
       }
   
       @Test
       public void testUpdateByName() {
           SqlSession sqlSession = MybatisUtil.getSqlSession();
           StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
           Student stu = new Student();
           stu.setS_name("李水");
           stu.setS_birth("1999-01-22");
           stu.setS_sex("女");
           studentMapper.updateByName(stu);
           sqlSession.commit();
           sqlSession.close();
       }
   }
   

10. 测试查询结果