如何通过XML方式配置并实现Mybatis

idea中创建一个maven项目

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>

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

数据库准备

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
｝

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);

}

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>

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();
    }
  }
}

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();
  }
}

测试查询结果

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