今天把原来的一个查询接口的业务代码进行了优化，减少了十几行冗余的代码。
原来的代码
ChongwuServiceImpl.java
/**
* @author heyunlin
* @version 1.0
*/
@Slf4j
@Service
public class ChongwuServiceImpl implements ChongwuService {
@Override
public JsonResult<JsonPage<Chongwu>> selectByPage(ChongwuPager pager) {
List<Integer> skillIds = pager.getSkillIds();
if (CollectionUtils.isNotEmpty(skillIds)) {
int size = skillIds.size();
// 得到order by语句
String statement = Pager.getOrderByStatement(pager);
List<Chongwu> rows = chongwuMapper.selectBySkills(pager, skillIds, size, statement);
long total = chongwuMapper.selectCountBySkills(pager, skillIds, size);
return JsonResult.restPage(total, rows);
} else {
Page<Chongwu> page = new Page<>(pager.getPage(), pager.getRows());
QueryWrapper<Chongwu> wrapper = new QueryWrapper<>();
wrapper.eq(
pager.getCategoryId() != null,
"category_id", pager.getCategoryId()
);
wrapper.eq(
StringUtils.isNotEmpty(pager.getRoleId()),
"role_id", pager.getRoleId()
);
wrapper.eq(
StringUtils.isNotEmpty(pager.getZuoqiId()),
"zuoqi_id", pager.getZuoqiId()
);
// 得到order by语句
String statement = Pager.getOrderByStatement(pager);
wrapper.last(statement);
Page<Chongwu> result = chongwuMapper.selectPage(page, wrapper);
return JsonResult.restPage(result);
}
}
}ChongwuMapper.java
@Repository
public interface ChongwuMapper extends BaseMapper<Chongwu> {
/**
* 查询已学习指定技能的宠物数量
* @param pager 分页参数
* @param skillIds 宠物技能类型id列表
* @param total 总技能数
* @return int
*/
long selectCountBySkills(
@Param("pager") ChongwuPager pager,
@Param("skillIds") List<Integer> skillIds,
@Param("total") int total
);
/**
* 查询已学习指定技能的宠物
* @param pager 分页参数
* @param skillIds 宠物技能类型id列表
* @param total 总技能数
* @param statement order by后面的语句
* @return List<Chongwu>
*/
List<Chongwu> selectBySkills(
@Param("pager") ChongwuPager pager,
@Param("skillIds") List<Integer> skillIds,
@Param("total") int total,
@Param("statement") String statement
);
}ChongwuMapper.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">
<mapper namespace="cn.edu.sgu.www.mhxysy.mapper.chongwu.ChongwuMapper">
<resultMap id="resultMap" type="cn.edu.sgu.www.mhxysy.entity.chongwu.Chongwu">
<result column = "role_id" property = "roleId" />
<result column = "zuoqi_id" property = "zuoqiId" />
<result column = "zizhi_id" property = "zizhiId" />
<result column = "ty_status" property = "tyStatus" />
<result column = "category_id" property = "categoryId" />
<result column = "attribute_id" property = "attributeId" />
</resultMap>
<select id="selectCountBySkills" resultType="long">
select count(*) from chongwu where id in (
select cs.chongwu_id from (
select chongwu_id from chongwu_skill where skill_id in (
<foreach item='skillId' collection='skillIds' separator=','>
#{skillId}
</foreach>
)
) as cs
group by cs.chongwu_id
having count(cs.chongwu_id) >= #{total}
)
<if test='pager.zuoqiId != null and pager.zuoqiId != ""'>
and zuoqi_id = #{pager.zuoqiId}
</if>
<if test='pager.roleId != null and pager.roleId != ""'>
and role_id = #{pager.roleId}
</if>
<if test='pager.categoryId != null'>
and category_id = #{pager.categoryId}
</if>
</select>
<select id="selectBySkills" resultMap="resultMap">
select * from chongwu where id in (
select cs.chongwu_id from (
select chongwu_id from chongwu_skill where skill_id in (
<foreach item='skillId' collection='skillIds' separator=','>
#{skillId}
</foreach>
)
) as cs
group by cs.chongwu_id
having count(cs.chongwu_id) >= #{total}
)
<if test='pager.zuoqiId != null and pager.zuoqiId != ""'>
and zuoqi_id = #{pager.zuoqiId}
</if>
<if test='pager.roleId != null and pager.roleId != ""'>
and role_id = #{pager.roleId}
</if>
<if test='pager.categoryId != null'>
and category_id = #{pager.categoryId}
</if>
order by role_id, #{statement}
</select>
</mapper>重构后的代码
ChongwuServiceImpl.java
/**
* @author heyunlin
* @version 1.0
*/
@Slf4j
@Service
public class ChongwuServiceImpl implements ChongwuService {
@Override
public Page<Chongwu> selectByPage(ChongwuPager pager) {
List<Integer> skillIds = pager.getSkillIds();
pager.setTotal(skillIds != null ? skillIds.size() : 0);
pager.setStatement(Pager.getStatement(pager));
Page<Chongwu> page = Pager.ofPage(pager);
return chongwuMapper.selectPage(page, pager);
}
}ChongwuMapper.java
@Repository
public interface ChongwuMapper extends BaseMapper<Chongwu> {
/**
* 分页查询宠物列表
* @param page 分页参数
* @param pager 查询条件
* @return List<Chongwu>
*/
Page<Chongwu> selectPage(Page<Chongwu> page, ChongwuPager pager);
}ChongwuMapper.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">
<mapper namespace="cn.edu.sgu.www.mhxysy.mapper.chongwu.ChongwuMapper">
<resultMap id="resultMap" type="cn.edu.sgu.www.mhxysy.entity.chongwu.Chongwu">
<result column = "role_id" property = "roleId" />
<result column = "zuoqi_id" property = "zuoqiId" />
<result column = "zizhi_id" property = "zizhiId" />
<result column = "ty_status" property = "tyStatus" />
<result column = "category_id" property = "categoryId" />
<result column = "attribute_id" property = "attributeId" />
</resultMap>
<select id="selectPage" resultMap="resultMap">
select * from chongwu
<where>
1 = 1
<if test='pager.total > 0'>
and id in (
select cwjnb.chongwu_id from (
select chongwu_id from chongwu_skill where skill_id in (
<foreach item="skillId" collection="pager.skillIds" separator=",">
#{skillId}
</foreach>
)
) as cwjnb
group by cwjnb.chongwu_id
having count(cwjnb.chongwu_id) >= #{pager.total}
)
</if>
<if test="pager.zuoqiId != null and pager.zuoqiId != ''">
and zuoqi_id = #{pager.zuoqiId}
</if>
<if test="pager.roleId != null and pager.roleId != ''">
and role_id = #{pager.roleId}
</if>
<if test='pager.categoryId != null'>
and category_id = #{pager.categoryId}
</if>
</where>
<if test="pager.statement != null and pager.statement != ''">
order by #{pager.statement}
</if>
</select>
</mapper>排序失效问题
修改后引发了前端排序失效问题，点击排序图标触发了重新渲染表格数据的ajax请求，而且控制台打印的SQL语句也没有问题，直接复制到数据库中执行，能查出排序后的数据。
前端排序失效截图
控制台打印的SQL查询语句
直接复制到Navicat中执行，查询到了正确的结果（score列按升序排序）
问题原因分析
遇到这个问题其实仔细一想非常简单，就是${}和#{}的区别，把#{}改为${}即可。
这是把#{}改成${}之后，在控制台的SQL语句，两者有一定的区别：
- 上图的SQL语句：select * from chongwu WHERE 1 = 1 order by role_id , "score desc" LIMIT 10
- 下图的SQL语句：select * from chongwu WHERE 1 = 1 order by role_id , score desc LIMIT 10
纠正后的代码
ChongwuMapper.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">
<mapper namespace="cn.edu.sgu.www.mhxysy.mapper.chongwu.ChongwuMapper">
<resultMap id="resultMap" type="cn.edu.sgu.www.mhxysy.entity.chongwu.Chongwu">
<result column = "role_id" property = "roleId" />
<result column = "zuoqi_id" property = "zuoqiId" />
<result column = "zizhi_id" property = "zizhiId" />
<result column = "ty_status" property = "tyStatus" />
<result column = "category_id" property = "categoryId" />
<result column = "attribute_id" property = "attributeId" />
</resultMap>
<select id="selectPage" resultMap="resultMap">
select * from chongwu
<where>
1 = 1
<if test='pager.total > 0'>
and id in (
select cwjnb.chongwu_id from (
select chongwu_id from chongwu_skill where skill_id in (
<foreach item="skillId" collection="pager.skillIds" separator=",">
#{skillId}
</foreach>
)
) as cwjnb
group by cwjnb.chongwu_id
having count(cwjnb.chongwu_id) >= #{pager.total}
)
</if>
<if test="pager.zuoqiId != null and pager.zuoqiId != ''">
and zuoqi_id = #{pager.zuoqiId}
</if>
<if test="pager.roleId != null and pager.roleId != ''">
and role_id = #{pager.roleId}
</if>
<if test='pager.categoryId != null'>
and category_id = #{pager.categoryId}
</if>
</where>
<if test="pager.statement != null and pager.statement != ''">
order by ${pager.statement}
</if>
</select>
</mapper>重新启动项目之后，问题得以解决，不知道有没有大佬遇到类似的问题，欢迎评论区留言分享~
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