mybatis单表操作实现完全java代码封装

之前在项目中用到mybtis操作数据库时都是手动写sql,对于我这种sql水平不是很好地人来说痛苦死了；动态查询的sql我表示到现在还不会写呀！

还好，利用数据库表反向生成的工具可以帮我解决大部分的sql;(mybatis generator 你懂的)

首先利用反向生成可以帮我们自动生成实体类，dao接口，dao映射文件；

在dao映射文件如下所示：

<?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" >

<mapper namespace="bz.sunlight.dao.UserMapper" >

<resultMap id="BaseResultMap" type="bz.sunlight.entity.User" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

<id column="id" property="id" jdbcType="VARCHAR" />

<result column="name" property="name" jdbcType="VARCHAR" />

<result column="password" property="password" jdbcType="VARCHAR" />

</resultMap>

<sql id="Example_Where_Clause" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

<where >

<foreach collection="oredCriteria" item="criteria" separator="or" >

<if test="criteria.valid" >

<trim prefix="(" suffix=")" prefixOverrides="and" >

<foreach collection="criteria.criteria" item="criterion" >

<choose >

<when test="criterion.noValue" >

and ${criterion.condition}

</when>

<when test="criterion.singleValue" >

and ${criterion.condition} #{criterion.value}

</when>

<when test="criterion.betweenValue" >

and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}

</when>

<when test="criterion.listValue" >

and ${criterion.condition}

<foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >

#{listItem}

</foreach>

</when>

</choose>

</foreach>

</trim>

</if>

</foreach>

</where>

</sql>

<sql id="Update_By_Example_Where_Clause" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

<where >

<foreach collection="example.oredCriteria" item="criteria" separator="or" >

<if test="criteria.valid" >

<trim prefix="(" suffix=")" prefixOverrides="and" >

<foreach collection="criteria.criteria" item="criterion" >

<choose >

<when test="criterion.noValue" >

and ${criterion.condition}

</when>

<when test="criterion.singleValue" >

and ${criterion.condition} #{criterion.value}

</when>

<when test="criterion.betweenValue" >

and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}

</when>

<when test="criterion.listValue" >

and ${criterion.condition}

<foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >

#{listItem}

</foreach>

</when>

</choose>

</foreach>

</trim>

</if>

</foreach>

</where>

</sql>

<sql id="Base_Column_List" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

id, name, password

</sql>

<select id="selectByExample" resultMap="BaseResultMap" parameterType="bz.sunlight.entity.UserExample" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

select

<if test="distinct" >

distinct

</if>

<include refid="Base_Column_List" />

from user

<if test="_parameter != null" >

<include refid="Example_Where_Clause" />

</if>

<if test="orderByClause != null" >

order by ${orderByClause}

</if>

</select>

<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.String" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

select

<include refid="Base_Column_List" />

from user

where id = #{id,jdbcType=VARCHAR}

</select>

<delete id="deleteByPrimaryKey" parameterType="java.lang.String" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

delete from user

where id = #{id,jdbcType=VARCHAR}

</delete>

<delete id="deleteByExample" parameterType="bz.sunlight.entity.UserExample" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

delete from user

<if test="_parameter != null" >

<include refid="Example_Where_Clause" />

</if>

</delete>

<insert id="insert" parameterType="bz.sunlight.entity.User" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

insert into user (id, name, password

)

values (#{id,jdbcType=VARCHAR}, #{name,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR}

)

</insert>

<insert id="insertSelective" parameterType="bz.sunlight.entity.User" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

insert into user

<trim prefix="(" suffix=")" suffixOverrides="," >

<if test="id != null" >

id,

</if>

<if test="name != null" >

name,

</if>

<if test="password != null" >

password,

</if>

</trim>

<trim prefix="values (" suffix=")" suffixOverrides="," >

<if test="id != null" >

#{id,jdbcType=VARCHAR},

</if>

<if test="name != null" >

#{name,jdbcType=VARCHAR},

</if>

<if test="password != null" >

#{password,jdbcType=VARCHAR},

</if>

</trim>

</insert>

<select id="countByExample" parameterType="bz.sunlight.entity.UserExample" resultType="java.lang.Integer" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

select count(*) from user

<if test="_parameter != null" >

<include refid="Example_Where_Clause" />

</if>

</select>

<update id="updateByExampleSelective" parameterType="map" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

update user

<set >

<if test="record.id != null" >

id = #{record.id,jdbcType=VARCHAR},

</if>

<if test="record.name != null" >

name = #{record.name,jdbcType=VARCHAR},

</if>

<if test="record.password != null" >

password = #{record.password,jdbcType=VARCHAR},

</if>

</set>

<if test="_parameter != null" >

<include refid="Update_By_Example_Where_Clause" />

</if>

</update>

<update id="updateByExample" parameterType="map" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

update user

set id = #{record.id,jdbcType=VARCHAR},

name = #{record.name,jdbcType=VARCHAR},

password = #{record.password,jdbcType=VARCHAR}

<if test="_parameter != null" >

<include refid="Update_By_Example_Where_Clause" />

</if>

</update>

<update id="updateByPrimaryKeySelective" parameterType="bz.sunlight.entity.User" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

update user

<set >

<if test="name != null" >

name = #{name,jdbcType=VARCHAR},

</if>

<if test="password != null" >

password = #{password,jdbcType=VARCHAR},

</if>

</set>

where id = #{id,jdbcType=VARCHAR}

</update>

<update id="updateByPrimaryKey" parameterType="bz.sunlight.entity.User" >

<!--

WARNING - @mbggenerated

This element is automatically generated by MyBatis Generator, do not modify.

This element was generated on Sat Aug 27 23:42:15 CST 2016.

-->

update user

set name = #{name,jdbcType=VARCHAR},

password = #{password,jdbcType=VARCHAR}

where id = #{id,jdbcType=VARCHAR}

</update>

</mapper>

用这些生成的sql语句基本上可以解决我们单表查询中的所有情景；而不必我们再去手写sql(太操蛋了)，是不是有点回到另外一个大框架中了呀;

例如：

我要新增客户：

那么在service层的代码就可以这么写：

@Override

public void saveUser(User record) {

userMapper.insert(record);

}

直接用反向生成的insert方法来进行插入；

你可能会觉得没什么太多意思：这种sql语句太容易写了；

那么查询呢？根据条件查询，条件比较多得情况下呢？更新，需要动态更新呢？

查询：

@Override

public List<User> queryUserByName(String name) {

UserExample example=new UserExample();

example.createCriteria().andNameEqualTo(name);   //我只需要在这里添加查询条件即可，添加的查询条件有很多可供选择的；Criteria这个对象是不是很熟悉呀！

List<User> users = userMapper.selectByExample(example);

return users;

}

这样就将根据姓名查询的服务写好了，还可以有like,between等多种方法可以供选择；

更新：

有时候表单提交上来的数据不是很完整，更新需要写动态sql以防止数据库的数据被更新成null;

现在我们可以这样操作：

@Override

public void updateById(User user,String id) {

UserExample example=new UserExample();

example.createCriteria().andIdEqualTo(id);

userMapper.updateByExampleSelective(user, example);

}

动态sql已经反向生成好了，我们只需要将需要更新的条件封装到example类中即可；

当然，多表关联暂时还无法这么使用，关于多表关联可以关注我的另外一篇博文；

这样，是不是mybatis也实现了全封装的操作；