mybatis学习笔记--常见的错误

2022-09-16 10:55:23

昨天刚学了下mybatis,用的是3.2.2的版本,在使用过程中遇到了些小问题,现总结如下,会不断更新.

1.没有在configuration.xml配置对应的sql配置文件

错误:

Error updating database. Cause: java.lang.IllegalArgumentException:
Mapped Statements collection does not contain value for ***Mapper.*** Cause:
java.lang.IllegalArgumentException: Mapped Statements collection does not
contain value for ***Mapper.***
解决方法:

在configuration.xml配置文件中引用对应的sql配置文件

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<mappers>
<mapper resource="esd/db/mapper/ResumeMapper.xml" />
</mappers>

2.同一sql配置文件中id重复

错误:

Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.lang.RuntimeException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Mapped Statements collection already contains value for GeographyMapper.getByCode
两个sql语句的id重复了,就会报这个错.

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<select id="getByCode" resultType="Geography"
parameterType="java.lang.String">
select * from Geography where code = ${code}
</select>
<select id="getByCode" resultType="Geography"
parameterType="java.lang.String">
select * from Geography where fullName = ${fullName}
</select>

解决方法:

修改其中的一个id就ok了.
3.mapper配置文件中为bean类配置的属性没有在对应的bean类中找到对应的字段

错误:

Error updating database. Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'education' in 'class esd.bean.Personal'
Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'education' in 'class esd.bean.Personal'

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<if test="education != null and education != ''">
education = #{education},
</if>

解决方法:

在mapper配置文件中删除多配置的属性/或则在自己的bean类中补全该字段

4.<if>标签中不支持 && 符号

错误:

The entity name must immediately follow the '&' in the entity reference

解析不了 && 是什么东东

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<update id="update" parameterType="Geography">
update Geography
<trim prefix="set" suffixOverrides=",">
<if test="code != null && code !=''">
code=#{code},
</if>
<if test="name != null && name != ''">
name=#{name},
</if>
</trim>
where id= #{id}
</update>

解决方法:使用正确的语法咯,别用&&,用and

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<update id="update" parameterType="Geography">
update Geography
<trim prefix="set" suffixOverrides=",">
<if test="code != null and code !=''">
code=#{code},
</if>
<if test="name != null and name != ''">
name=#{name},
</if>
</trim>
where id= #{id}
</update>

5.返回结果类型写错

由于我的项目配置原因, debug 输出信息中没有报错, 但是项目就是启动不起来, 所以没能截到错误信息提示, 以后遇到会补上

具体说就是: 如果自定义了返回的结果集, 返回的类型一定要是resultMap类型,(下面是错误示例) 如下

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<resultMap id="ResultArea" type="Area">
<id column="a_code" property="code" />
<result column="a_name" property="name" />
<result column="a_pyName" property="pyName" />
<result column="a_abbr" property="abbr" />
<result column="a_mark" property="mark" />
</resultMap>
<resultMap id="ResultParameter" type="Parameter">
<id column="p_id" property="id" />
<result column="p_name" property="name" />
<result column="p_value" property="value" />
<result column="p_type" property="type" />
<result column="p_mark" property="mark" />
<association property="area" javaType="Parameter" resultMap="ResultArea" />
</resultMap>
<select id="getById" resultType="ResultParameter" parameterType="int">
select p.id as p_id, p.name as p_name, p.value as p_value, p.type as p_type, p.mark as p_mark,
a.code as a_code, a.name as a_name, a.pyname as a_pyName, a.abbr as a_abbr, a.mark as a_mark
from parameter as p, area as a
where p.acode = a.code and id = #{id}
</select>

常用在表连接查询中.

如上例中, 我定义了'ResultParameter'的结果集, 那么下面表连接查询的时候,如果返回的是表连接查询结果, 那么一定要使用 resultMap="ResultParameter", 否则万一提示信息中没有显示出来, 要费些时间才能找出来.

6. 标签顺序写错

错误:

The content of element type "resultMap" must match "(constructor?,id*,result*,association*,collection*,discriminator?)".

下午的时候无意中遇到这个错误, 下面是错误代码:

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<resultMap id="ResultMenu" type="com.esd.hesf.model.Menu">
<id column="id" property="id" jdbcType="CHAR" />
<result column="text" property="text" jdbcType="VARCHAR" />
<result column="iconcls" property="iconcls" jdbcType="VARCHAR" />
<association property="permissionType" javaType="com.esd.hesf.model.PermissionType" resultMap="ResultPermissionType"/>
<result column="update_time" property="updateTime" jdbcType="TIMESTAMP" />
</resultMap>

在<resultMap 处画红线, 原因是: 里面的<association />标签, 一定要放在这组标签最下面. 如下:

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<resultMap id="ResultMenu" type="com.esd.hesf.model.Menu">
<id column="id" property="id" jdbcType="CHAR" />
<result column="text" property="text" jdbcType="VARCHAR" />
<result column="iconcls" property="iconcls" jdbcType="VARCHAR" />
<result column="update_time" property="updateTime" jdbcType="TIMESTAMP" />
<association property="permissionType" javaType="com.esd.hesf.model.PermissionType" resultMap="ResultPermissionType"/>
</resultMap>

7.多写了if判断

错误:

org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'year' in 'class java.lang.String'

下面是代码:

dao层方法

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/**
* 查询审核报表情况--按公司类型查
* @return
*/
List<ReportViewModel> retrieveReportByCompanyType(String year);

mapper配置文件

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<select id="retrieveReportByCompanyType" parameterType="java.lang.String" resultMap="ReportViewModel">
select
<include refid="report_column_list"/>
from audit_company_view
<where>
<if test="year != null and year != ''">
au_year = #{year,jdbcType=CHAR}
</if>
</where>
group by t_id
</select>

一般这个错是指参数parameterType类型的字段没有get, set方法, 我只是传个String类型的参数, so 刚遇到这个问题的时候, 有点摸不着头脑, 怎么会报这个错呢? 原来问题出现在配置文件中:

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<if test="year != null and year != ''">

mybatis自动将if判断中的字段默认为传进来的parameterType类型的字段了... so....只要将这个if判断去掉即可.

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<select id="retrieveReportByCompanyType" parameterType="java.lang.String" resultMap="ReportViewModel">
select
<include refid="report_column_list"/>
from audit_company_view
<where>
au_year = #{year,jdbcType=CHAR}
</where>
group by t_id
</select>

那问题出来了, 我怎么判断传进来的单个字符串是否为空值呢? 这是否是mybatis的一个小bug呢? 答案尚在查找中, 有了会第一时间贴上来的.

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