Mybatis分页插件 - PageHelpe http://git.oschina.net/free/Mybatis_PageHelper

极其方便的使用Mybatis单表的增删改查 http://git.oschina.net/free/Mapper

Mybatis示例 http://blog.csdn.net/column/details/mybatis-sample.html

MyBatis官方文档 http://mybatis.github.io/mybatis-3/zh/dynamic-sql.html

##第一种方案

DAO层的函数方法

public User selectUser(String name,String area);

对应的Mapper.xml

<select id="selectUser" resultMap="BaseResultMap">
    select  *  from user_user_t   where user_name = #{0} and user_area=#{1}
</select>

其中，#{0}代表接收的是dao层中的第一个参数，#{1}代表dao层中第二参数，更多参数一致往后加即可。

##第二种方案 此方法采用Map传多参数.

Dao层的函数方法

public User selectUser(Map paramMap);

对应的Mapper.xml

<select id="selectUser" resultMap="BaseResultMap">
   select * from user_user_t where user_name = #{userName，jdbcType=VARCHAR} and user_area=#{userArea,jdbcType=VARCHAR}
</select>

Service层调用

private User xxxSelectUser(){
    Map paramMap=new hashMap();
    paramMap.put(“userName”,”对应具体的参数值”);
    paramMap.put(“userArea”,”对应具体的参数值”);
    User user=xxx. selectUser(paramMap);
}

个人认为此方法不够直观，见到接口方法不能直接的知道要传的参数是什么。

##第三种方案

Dao层的函数方法

public User selectUser(@param(“userName”)String name,@param(“userArea”)String area);

对应的Mapper.xml

<select id="selectUser" resultMap="BaseResultMap">
   select * from user_user_t  where user_name = #{userName，jdbcType=VARCHAR} and user_area=#{userArea,jdbcType=VARCHAR}
</select> 

个人觉得这种方法比较好，能让开发者看到dao层方法就知道该传什么样的参数，比较直观，个人推荐用此种方案。

##mybatis if标签判断的问题

细节可以参考XML代码：

<?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="com.lypaydb.mapper.Order_DayMapper">
    <resultMap type="com.lypaydb.pojo.Order_Day" id="odMap">
      <id property="id" column="id" />
      <result property="date" column="date" />
      <result property="total" column="total" />
      <result property="aisle" column="aisle" />
      <result property="operators" column="operators" />
      <result property="channelid" column="channelid" />
      <result property="appid" column="appid" />
      <result property="paycnt" column="paycnt" />
    </resultMap>
   
  <!-- /*sql -->
  <select id="findod" parameterType="java.util.Map" resultMap="odMap">
      select * from order_day where 1 = 1 
      <if test="${start} != null and ${start != ''}">
        and   date >= #{start} 
      </if>
      <if test="${end} != null and ${end} != ''">
        and #{end} > date  
      </if>
      <if test="appid != null and appid != ''">
        and  appid=${appid}
      </if>
      <if test="operators != null and operators != ''">
        and operators=${operators}  
      </if>
      limit ${Page.startPos},${Page.pageSize};
  </select>
   
  <select id="getAllCount" parameterType="java.util.Map" resultType="java.lang.Integer">
     select count(*)  from order_day where 1=1 
      <if test="${start} != null and ${start != ''}">
        and   date >= #{start} 
      </if>
      <if test="${end} != null and ${end} != ''">
        and #{end} > date  
      </if>
      <if test="appid != null and appid != ''">
        and  appid=${appid}
      </if>
      <if test="operators != null and operators != ''">
        and operators=${operators}  
      </if>
  </select>
  <!-- sql*/ -->
</mapper>

这里是正确的写法：POJO

<select id="findod" parameterType="map" resultMap="odMap">
    select * from order_day where 1 = 1 
    <if test="start != null and start != ''">
    and   date >= #{start} 
    </if>
    <if test="end != null and end != ''">
    and #{end} > date  
    </if>
    <if test="appid != null and appid != ''">
    and  appid=${appid}
    </if>
    <if test="operators != null and operators != ''">
    and operators=${operators}  
    </if>
    limit ${Page.startPos},${Page.pageSize};
</select>

MyBatis，数据库映射这一块。 and #{end} > date 参数是你方法里面传过来参数的实体解析，或者键值对的解析。parameterType是参数类型。可以是map，也可以是你的实体类（完整的包名）

##foreach的使用

<insert id="insertUserList">
  INSERT INTO user(username,password)
  VALUES
  <foreach collection="userList" item="user" separator=",">
    (#{user.username},#{user.password})
  </foreach>
</insert>

对应的接口：

int insertUserList(@Param("userList")List<User> list);