MyBatis是什么以及为什么需要ORM框架、快速搭建

MyBatis是什么

MyBatis的前身是Ibatis，本质是一款半自动化的ORM框架，除了能对POJO进行ORM映射之外，还可以编写SQL脚本语句。主要是为了解决我们平时开发中经常写的JDBC代码，将繁琐的JDBC代码封装起来，化繁为简。

MyBatis映射文件 四要素：
1.SQL语句
2.映射规则
3.POJO
4.Mapper接口

为什么需要 ORM 框架？**
传统的 JDBC 编程存在的弊端：
1.工作量大，操作数据库至少要 5 步；
2.业务代码和技术代码耦合；
3.连接资源手动关闭，带来了隐患；

MyBatis 快速入门
步骤如下：

  1. 加入 mybatis 的依赖，版本 3.5.x
	<dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>5.1.18</version>
	</dependency>


	<!-- mybatis相关依赖 -->
	<dependency>
		<groupId>org.mybatis</groupId>
		<artifactId>mybatis</artifactId>
		<version>3.5.0-SNAPSHOT</version>
		<!-- <version>3.4.1</version> -->
	</dependency>

	<dependency>
		<groupId>com.github.pagehelper</groupId>
		<artifactId>pagehelper</artifactId>
		<version>5.1.4</version>
	</dependency>
	
	<dependency>
		<groupId>com.fasterxml.jackson.core</groupId>
		<artifactId>jackson-databind</artifactId>
		<version>2.9.5</version>
	</dependency>
  1. 添加 mybatis 的配置文件，包括 MyBatis 核心文件和 mapper.xml 文件
<properties resource="db.properties" />

<settings>

	<!-- 设置自动驼峰转换		 -->
	<setting name="mapUnderscoreToCamelCase" value="true" />

	<!-- 开启懒加载 -->		
	 <!-- 当启用时，有延迟加载属性的对象在被调用时将会完全加载任意属性。否则，每种属性将会按需要加载。默认：true -->
  <setting name="aggressiveLazyLoading" value="false" />

</settings>

<!-- 别名定义 -->

<typeAliases>
	<package name="com.enjoylearning.mybatis.entity" />
</typeAliases>


<!--配置environment环境 -->
<environments default="development">
	<!-- 环境配置1，每个SqlSessionFactory对应一个环境 -->
	<environment id="development">
		<transactionManager type="JDBC" />
		<dataSource type="UNPOOLED">
			<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>

<!-- 映射文件，mapper的配置文件 -->
<mappers>
	<!--直接映射到相应的mapper文件 -->
	<mapper resource="sqlmapper/TUserMapper.xml" />
</mappers>

  1. 场景介绍：基于 t_user 表单数据查询、多数据查询；

  2. 编写实体类、mapper 接口以及 mapper xml 文件；

一、Mapper.xml

<select id="selectByPrimaryKey" resultType="TUser">
	select
	id, userName, realName, sex, mobile, email, note
	from t_user
	where id = #{id,jdbcType=INTEGER}
</select>

<select id="selectAll" resultType="TUser">
	select
	id, userName, realName, sex, mobile, email, note
	from t_user
</select>

<resultMap id="UserResultMap" type="TUser" autoMapping="true">
	<id column="id" property="id" />
    <result column="userName" property="userName"/>
	<result column="realName" property="realName" />
	<result column="sex" property="sex" />
	<result column="mobile" property="mobile" />
	<result column="email" property="email" />
	<result column="note" property="note" />
	<association property="position" javaType="TPosition" columnPrefix="post_">
		<id column="id" property="id"/>
		<result column="name" property="postName"/>
		<result column="note" property="note"/>
	</association>
</resultMap>

<select id="selectTestResultMap" resultMap="UserResultMap" >
	select
	    a.id, 
	    userName,
		realName,
		sex,
		mobile,
		email,
		a.note,
		b.id  post_id,
		b.post_name,
		b.note post_note
	from t_user a,
		t_position b
	where a.position_id = b.id

</select>

<resultMap id="BaseResultMap" type="TUser">

	<!-- <constructor> <idArg column="id" javaType="int"/> <arg column="userName" 
		javaType="String"/> </constructor> -->
	<id column="id" property="id" />
	<result column="userName" property="userName" />
	<result column="realName" property="realName" />
	<result column="sex" property="sex" />
	<result column="mobile" property="mobile" />
	<result column="email" property="email" />
	<result column="note" property="note" />
</resultMap>

<sql id="Base_Column_List">
	id, userName, realName, sex, mobile, email, note,
	position_id
</sql>

<resultMap id="userAndPosition1" extends="BaseResultMap" type="TUser">
	<association property="position" javaType="TPosition" columnPrefix="post_">
		<id column="id" property="id"/>
		<result column="name" property="postName"/>
		<result column="note" property="note"/>
	</association>
</resultMap>

<resultMap id="userAndPosition2" extends="BaseResultMap" type="TUser">
	<association property="position" fetchType="lazy"  column="position_id" select="com.enjoylearning.mybatis.mapper.TPositionMapper.selectByPrimaryKey" />
</resultMap>

<select id="selectUserPosition1" resultMap="userAndPosition1" >
	select
	    a.id, 
	    userName,
		realName,
		sex,
		mobile,
		email,
		a.note,
		b.id post_id,
		b.post_name,
		b.note post_note
	from t_user a,
		t_position b
	where a.position_id = b.id

</select>

<select id="selectUserPosition2" resultMap="userAndPosition2" >
	select
	a.id,
	a.userName,
	a.realName,
	a.sex,
	a.mobile,
	a.position_id
	from t_user a
</select>


<resultMap id="userAndJobs1" extends="BaseResultMap" type="TUser">
	<collection property="jobs"
		ofType="com.enjoylearning.mybatis.entity.TJobHistory" >
		<result column="comp_name" property="compName" jdbcType="VARCHAR" />
		<result column="years" property="years" jdbcType="INTEGER" />
		<result column="title" property="title" jdbcType="VARCHAR" />
	</collection>
</resultMap>

<resultMap id="userAndJobs2" extends="BaseResultMap" type="TUser">
	<collection property="jobs" fetchType="lazy" column="id"
		select="com.enjoylearning.mybatis.mapper.TJobHistoryMapper.selectByUserId" />
</resultMap>

<select id="selectUserJobs1" resultMap="userAndJobs1">
	select
	a.id,
	a.userName,
	a.realName,
	a.sex,
	a.mobile,
	b.comp_name,
	b.years,
	b.title
	from t_user a,
	t_job_history b
	where a.id = b.user_id

</select>

<select id="selectUserJobs2" resultMap="userAndJobs2">
	select
	a.id,
	a.userName,
	a.realName,
	a.sex,
	a.mobile
	from t_user a
</select>


<resultMap id="userAndHealthReportMale" extends="userAndHealthReport" type="TUser">
	<collection property="healthReports" column="id"
		select= "com.enjoylearning.mybatis.mapper.THealthReportMaleMapper.selectByUserId"></collection>
</resultMap>

<resultMap id="userAndHealthReportFemale" extends="userAndHealthReport" type="TUser">
	<collection property="healthReports" column="id"
		select= "com.enjoylearning.mybatis.mapper.THealthReportFemaleMapper.selectByUserId"></collection>
</resultMap>

<resultMap id="userAndHealthReport" extends="BaseResultMap" type="TUser">
			 
	<discriminator column="sex"  javaType="int">
		<case value="1" resultMap="userAndHealthReportMale"/>
		<case value="2" resultMap="userAndHealthReportFemale"/>
	</discriminator>
</resultMap>


<select id="selectUserHealthReport" resultMap="userAndHealthReport">
	select
	<include refid="Base_Column_List" />
	from t_user a
</select>

<resultMap type="TUser" id="userRoleInfo" extends="BaseResultMap">
	<collection property="roles" ofType="TRole" columnPrefix="role_">
		<result column="id" property="id" />
		<result column="Name" property="roleName" />
		<result column="note" property="note" />
	</collection>
</resultMap>


<select id="selectUserRole" resultMap="userRoleInfo">
	select a.id, 
	      a.userName,
	      a.realName,
	      a.sex,
	      a.mobile,
	      a.note,
	      b.role_id,
	      c.role_name,
	      c.note role_note
	from t_user a,
	     t_user_role b,
	     t_role c
	where a.id = b.user_id AND 
	      b.role_id = c.id
 </select>	
 
 
 <select id="selectUserByRoleId" resultMap="userRoleInfo">
    select
	<include refid="Base_Column_List" />
	from t_user a,
	     t_user_role b
	where a.id = b.user_id and
	      b.role_id = #{id}
 </select>	


<select id="selectByEmailAndSex1" resultMap="BaseResultMap"		parameterType="map">
	select
	<include refid="Base_Column_List" />
	from t_user a
	 where a.email like CONCAT('%', #{email}, '%') and
	 a.sex =#{sex} 
</select>

<select id="selectByEmailAndSex2" resultMap="BaseResultMap">
	select
	<include refid="Base_Column_List" />
	from t_user a
	where a.email like CONCAT('%', #{email}, '%') and
	a.sex =	#{sex}
</select>


<select id="selectByEmailAndSex3" resultMap="BaseResultMap"
	parameterType="com.enjoylearning.mybatis.entity.EmailSexBean">
	select
	<include refid="Base_Column_List" />
	from t_user a
	where a.email like CONCAT('%', #{email}, '%') and
	a.sex =	#{sex}
</select>


<select id="selectBySymbol" resultMap="BaseResultMap">
	select
	${inCol}
	from ${tableName} a
	where a.userName = #{userName}
	order by ${orderStr}
</select>



<select id="selectIfOper" resultMap="BaseResultMap">
	select
	<include refid="Base_Column_List" />
	from t_user a
	where   1=1  
	<if test="email != null and email != ''">
		and a.email like CONCAT('%', #{email}, '%') 
	</if>
	<if test="sex != null ">
		and a.sex = #{sex}
	</if>
</select>

<select id="selectIfandWhereOper" resultMap="BaseResultMap">
	select
	<include refid="Base_Column_List" />
	from t_user a
	<where>
		<if test="email != null and email != ''">
			and a.email like CONCAT('%', #{email}, '%')
		</if>
		<if test="sex != null ">
			and a.sex = #{sex}
		</if>
	</where>
</select>

<select id="selectChooseOper" resultMap="BaseResultMap">
	select
	<include refid="Base_Column_List" />
	from t_user a
	<where>
		<choose>
			<when test="email != null and email != ''">
				and a.email like CONCAT('%', #{email}, '%')
			</when>
			<when test="sex != null">
				and a.sex = #{sex}
			</when>
			<otherwise>
				and 1=1
			</otherwise>
		
		
		</choose>
	</where>
</select>

<update id="updateIfOper" parameterType="TUser">
	update t_user
	set
	<if test="userName != null">
		userName = #{userName,jdbcType=VARCHAR},
	</if>
	<if test="realName != null">
		realName = #{realName,jdbcType=VARCHAR},
	</if>
	<if test="sex != null">
		sex = #{sex,jdbcType=TINYINT},
	</if>
	<if test="mobile != null">
		mobile = #{mobile,jdbcType=VARCHAR},
	</if>
	<if test="email != null">
		email = #{email,jdbcType=VARCHAR},
	</if>
	<if test="note != null">
		note = #{note,jdbcType=VARCHAR}
	</if>
	where id = #{id,jdbcType=INTEGER}
</update>

<update id="updateIfAndSetOper" parameterType="TUser">

    update t_user
	<set>
		<if test="userName != null">
			userName = #{userName,jdbcType=VARCHAR},
		</if>
		<if test="realName != null">
			realName = #{realName,jdbcType=VARCHAR},
		</if>
		<if test="sex != null">
			sex = #{sex,jdbcType=TINYINT},
		</if>
		<if test="mobile != null">
			mobile = #{mobile,jdbcType=VARCHAR},
		</if>
		<if test="email != null">
			email = #{email,jdbcType=VARCHAR},
		</if>
		<if test="note != null">
			note = #{note,jdbcType=VARCHAR},
		</if>
	</set>
	where id = #{id,jdbcType=INTEGER} 
</update>


<insert id="insertIfOper" parameterType="TUser">
	insert into t_user (
	<if test="id != null">
		id,
	</if>
	<if test="userName != null">
		userName,
	</if>
	<if test="realName != null">
		realName,
	</if>
	<if test="sex != null">
		sex,
	</if>
	<if test="mobile != null">
		mobile,
	</if>
	<if test="email != null">
		email,
	</if>
	<if test="note != null">
		note
	</if>
	)
	values(
	<if test="id != null">
		#{id,jdbcType=INTEGER},
	</if>
	<if test="userName != null">
		#{userName,jdbcType=VARCHAR},
	</if>
	<if test="realName != null">
		#{realName,jdbcType=VARCHAR},
	</if>
	<if test="sex != null">
		#{sex,jdbcType=TINYINT},
	</if>
	<if test="mobile != null">
		#{mobile,jdbcType=VARCHAR},
	</if>
	<if test="email != null">
		#{email,jdbcType=VARCHAR},
	</if>
	<if test="note != null">
		#{note,jdbcType=VARCHAR}
	</if>
	)
</insert>


<select id="selectForeach4In" resultMap="BaseResultMap">
	select
	<include refid="Base_Column_List" />
	from t_user a
	where a.userName in
	<foreach collection="array" open="(" close=")" item="userName" separator=",">
		#{userName}
	</foreach> 
</select>

<insert id="insertForeach4Batch" useGeneratedKeys="true"		keyProperty="id">
	insert into t_user (userName, realName,
	sex, mobile,email,note,
	position_id)
	values
	<foreach collection="list" separator="," item="user">
		(
		#{user.userName,jdbcType=VARCHAR},
		#{user.realName,jdbcType=VARCHAR},
		#{user.sex,jdbcType=TINYINT},
		#{user.mobile,jdbcType=VARCHAR},
		#{user.email,jdbcType=VARCHAR},
		#{user.note,jdbcType=VARCHAR},
		#{user.position.id,jdbcType=INTEGER}
		)
	</foreach>

</insert>


<delete id="deleteByPrimaryKey" parameterType="java.lang.Integer">
	delete from t_user
	where id = #{id,jdbcType=INTEGER}
</delete>

<insert id="insert1" parameterType="TUser" useGeneratedKeys="true"	keyProperty="id">
	insert into t_user (id, userName, realName,
	sex, mobile,
	email,
	note, position_id)
	values (#{id,jdbcType=INTEGER},
	#{userName,jdbcType=VARCHAR},
	#{realName,jdbcType=VARCHAR},
	#{sex,jdbcType=TINYINT}, #{mobile,jdbcType=VARCHAR},
	#{email,jdbcType=VARCHAR},
	#{note,jdbcType=VARCHAR},
	#{position.id,jdbcType=INTEGER})
</insert>

<insert id="insert2" parameterType="TUser">

	<selectKey keyProperty="id" order="AFTER" resultType="int">
		select
		LAST_INSERT_ID()
	</selectKey>
	insert into t_user (id, userName, realName,
	sex, mobile,
	email,
	note,
	position_id)
	values (#{id,jdbcType=INTEGER},
	#{userName,jdbcType=VARCHAR},
	#{realName,jdbcType=VARCHAR},
	#{sex,jdbcType=TINYINT}, #{mobile,jdbcType=VARCHAR},
	#{email,jdbcType=VARCHAR},
	#{note,jdbcType=VARCHAR},
	#{position.id,jdbcType=INTEGER})
</insert>

<insert id="insertSelective" parameterType="TUser" useGeneratedKeys="true"		keyProperty="id">
	insert into t_user
	<trim prefix="(" suffix=")" suffixOverrides="," >
		<if test="id != null">
			id,
		</if>
		<if test="userName != null">
			userName,
		</if>
		<if test="realName != null">
			realName,
		</if>
		<if test="sex != null">
			sex,
		</if>
		<if test="mobile != null">
			mobile,
		</if>
		<if test="email != null">
			email,
		</if>
		<if test="note != null">
			note,
		</if>
	</trim>
	<trim prefix="values (" suffix=")" suffixOverrides=",">
		<if test="id != null">
			#{id,jdbcType=INTEGER},
		</if>
		<if test="userName != null">
			#{userName,jdbcType=VARCHAR},
		</if>
		<if test="realName != null">
			#{realName,jdbcType=VARCHAR},
		</if>
		<if test="sex != null">
			#{sex,jdbcType=TINYINT},
		</if>
		<if test="mobile != null">
			#{mobile,jdbcType=VARCHAR},
		</if>
		<if test="email != null">
			#{email,jdbcType=VARCHAR},
		</if>
		<if test="note != null">
			#{note,jdbcType=VARCHAR},
		</if>
	</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="TUser">
	update t_user
	<set>
		<if test="userName != null">
			userName = #{userName,jdbcType=VARCHAR},
		</if>
		<if test="realName != null">
			realName = #{realName,jdbcType=VARCHAR},
		</if>
		<if test="sex != null">
			sex = #{sex,jdbcType=TINYINT},
		</if>
		<if test="mobile != null">
			mobile = #{mobile,jdbcType=VARCHAR},
		</if>
		<if test="email != null">
			email = #{email,jdbcType=VARCHAR},
		</if>
		<if test="note != null">
			note = #{note,jdbcType=VARCHAR},
		</if>
		<if test="position != null">
			position_id = #{position.id,jdbcType=INTEGER},
		</if>
	</set>
	where id = #{id,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKey" parameterType="TUser">
	update t_user
	set
	userName = #{userName,jdbcType=VARCHAR},
	realName =
	#{realName,jdbcType=VARCHAR},
	sex = #{sex,jdbcType=TINYINT},
	mobile =
	#{mobile,jdbcType=VARCHAR},
	email = #{email,jdbcType=VARCHAR},
	note =
	#{note,jdbcType=VARCHAR},
	position_id = #{position.id,jdbcType=INTEGER}
	where id = #{id,jdbcType=INTEGER}
</update>

二、实体类
package com.enjoylearning.mybatis.entity;

import java.io.Serializable;
import java.util.List;

import org.apache.ibatis.annotations.Param;

import com.mysql.jdbc.Blob;

public class TUser implements Serializable{

private Integer id;

private String userName;

private String realName;

private Byte sex;

private String mobile;

private String email;

private String note;

private TPosition position;

private List<TJobHistory> jobs ;

private List<HealthReport> healthReports;


private List<TRole> roles;

@Override
public String toString() {
	String positionId=  (position == null ? "" : String.valueOf(position.getId()));
	return "TUser [id=" + id + ", userName=" + userName + ", realName="
			+ realName + ", sex=" + sex + ", mobile=" + mobile + ", email="
			+ email + ", note=" + note + ", positionId=" + positionId + "]";
}

public Integer getId() {
	return id;
}

public void setId(Integer id) {
	this.id = id;
}

public String getUserName() {
	return userName;
}

public void setUserName(String userName) {
	this.userName = userName;
}

public String getRealName() {
	return realName;
}

public void setRealName(String realName) {
	this.realName = realName;
}

public Byte getSex() {
	return sex;
}

public void setSex(Byte sex) {
	this.sex = sex;
}

public String getMobile() {
	return mobile;
}

public void setMobile(String mobile) {
	this.mobile = mobile;
}

public String getEmail() {
	return email;
}

public void setEmail(String email) {
	this.email = email;
}

public String getNote() {
	return note;
}

public void setNote(String note) {
	this.note = note;
}

public TPosition getPosition() {
	return position;
}

public void setPosition(TPosition position) {
	this.position = position;
}

public List<TJobHistory> getJobs() {
	return jobs;
}

public void setJobs(List<TJobHistory> jobs) {
	this.jobs = jobs;
}

public List<HealthReport> getHealthReports() {
	return healthReports;
}

public void setHealthReports(List<HealthReport> healthReports) {
	this.healthReports = healthReports;
}

public List<TRole> getRoles() {
	return roles;
}

public void setRoles(List<TRole> roles) {
	this.roles = roles;
}

public static void main(String[] args) {
	System.out.println(1<<2);
}

}

三、Mapper接口
package com.enjoylearning.mybatis.mapper;

import java.util.List;
import java.util.Map;

import org.apache.ibatis.annotations.Param;

import com.enjoylearning.mybatis.entity.EmailSexBean;
import com.enjoylearning.mybatis.entity.TJobHistory;
import com.enjoylearning.mybatis.entity.TUser;

public interface TUserMapper {

TUser selectByPrimaryKey(Integer id);


List<TUser> selectAll();

List<TUser> selectTestResultMap();

List<TUser> selectAllTest();


int deleteByPrimaryKey(Integer id);

int insert1(TUser record);

int insert2(TUser record);

int insertSelective(TUser record);


int updateByPrimaryKeySelective(TUser record);

int updateByPrimaryKey(TUser record);


List<TUser> selectUserPosition1();

List<TUser> selectUserPosition2();

List<TUser> selectUserJobs1();

List<TUser> selectUserJobs2();

List<TUser> selectUserHealthReport();

List<TUser> selectUserRole();

List<TUser> selectByEmailAndSex1(Map<String, Object> param);

List<TUser> selectByEmailAndSex2(@Param("email")String email,@Param("sex")Byte sex);

List<TUser> selectByEmailAndSex3(EmailSexBean esb);


List<TUser> selectBySymbol(@Param("tableName")String tableName,
		                   @Param("inCol")String inCol,
		                   @Param("orderStr")String orderStr,
		                   @Param("userName")String userName);

List<TUser> selectIfOper(@Param("email")String email,@Param("sex")Byte sex);


List<TUser> selectIfandWhereOper(@Param("email")String email,@Param("sex")Byte sex);

List<TUser> selectChooseOper(@Param("email")String email,@Param("sex")Byte sex);

int updateIfOper(TUser record);

int updateIfAndSetOper(TUser record);

int insertIfOper(TUser record);

List<TUser> selectForeach4In(String[] names);

int insertForeach4Batch(List<TUser> users);

}

  1. 编写实例代码：com.enjoylearning.mybatis.MybatisDemo. quickStart

public class MybatisDemo {

private SqlSessionFactory sqlSessionFactory;

@Before
public void init() throws IOException {
	//--------------------第一阶段---------------------------
    // 1.读取mybatis配置文件创SqlSessionFactory
	String resource = "mybatis-config.xml";
	InputStream inputStream = Resources.getResourceAsStream(resource);
	// 1.读取mybatis配置文件创SqlSessionFactory
	sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
	inputStream.close();
}

@Test
// 快速入门
public void quickStart() throws IOException {
	//--------------------第二阶段---------------------------
	// 2.获取sqlSession	
	SqlSession sqlSession = sqlSessionFactory.openSession();
	// 3.获取对应mapper
	TUserMapper mapper = sqlSession.getMapper(TUserMapper.class);
	
	//--------------------第三阶段---------------------------
	// 4.执行查询语句并返回单条数据
	TUser user = mapper.selectByPrimaryKey(1);
	System.out.println(user);
	
	System.out.println("----------------------------------");
	
	// 5.执行查询语句并返回多条数据
	List<TUser> users = mapper.selectAll();
	for (TUser tUser : users) {
		System.out.println(tUser);
	}
}
posted @   vello  阅读(74)  评论(0)  编辑  收藏  举报
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