問題背景:
在Dao中使用MyBatis進行查詢操作,參數是傳的一個List:studentNameList,但是在執行查詢的時候報錯,具體日誌如下:
com.chenzhou.base.mybatis.IbatisSystemException: SqlSession operation; nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.apache.ibatis.binding.BindingException: Parameter 'studentNameList' not found. Available parameters are [list]
### Cause: org.apache.ibatis.binding.BindingException: Parameter 'studentNameList' not found. Available parameters are [list]
at com.chenzhou.base.mybatis.SqlSessionTemplate.wrapException(SqlSessionTemplate.java:341)
at com.chenzhou.base.mybatis.SqlSessionTemplate.execute(SqlSessionTemplate.java:127)
at com.chenzhou.base.mybatis.SqlSessionTemplate.execute(SqlSessionTemplate.java:106)
at com.chenzhou.base.mybatis.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:138)
at com.chenzhou.dao.GenericMybatisDao.count(GenericMybatisDao.java:306)
at com.chenzhou.cds.ps.dao.impl.StudentDao.getStudentCount(StudentDao.java:42)
at com.chenzhou.cds.ps.dao.impl.StudentDao$$FastClassByCGLIB$$8819e766.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:191)
at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:689)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80)
at com.chenzhou.util.LogUtil.doMethodInfo(LogUtil.java:85)
at com.chenzhou.util.LogUtil.doDebugMethodLog(LogUtil.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:622)
at com.chenzhou.cds.ps.dao.impl.StudentDao$$EnhancerByCGLIB$$d4fcf513.getStudentCount(<generated>)
at com.chenzhou.ps.dao.StudentDaoTest.testgetStudentCount(StudentDaoTest.java:44)
……
單元測試用例代碼如下:
@Test
public void testgetStudentCount(){
List<String> studentNameList = new ArrayList<String>();
studentNameList.add("chenzhou");
studentNameList.add("zhangsan");
studentNameList.add("lisi");
int count = studentDao.getStudentCount(studentNameList);
System.out.println(count);
}
studentDao中的getStudentCount方法代碼如下:
public int getStudentCount(List<String> studentNameList){
return super.count("getStudentCount", studentNameList);
}
MyBatis mapper.xml定義如下:
<!-- 查詢學生數量 -->
<select id="Student.getStudentCount" parameterType="java.util.List" resultType="java.lang.Integer">
<![CDATA[
SELECT
COUNT(*)
FROM
t_student WHERE 1=1
]]>
<if test="studentNameList != null">
AND student_name in
<foreach collection="studentNameList" item="item" open="(" separator="," close=")">
#{item}
</foreach>
</if>
</select>
根據報錯日誌分析,是MyBatis在解析xml時找不到其中聲明的studentNameList,但是在Dao中明明傳的參數就是studentNameList,怎麼會報錯呢?
查詢了一下MyBatis官方的說明文檔,終於找到了原因,在http://mybatis.github.io/mybatis-3/zh/dynamic-sql.html#foreach裏有一段說明:
因爲我傳的參數只有一個,而且傳入的是一個List集合,所以mybatis會自動封裝成Map<"list",studentNameList>。在解析的時候會通過“list”作爲Map的key值去尋找。但是我在xml中卻聲明成studentNameList了,所以自然會報錯找不到。
解決辦法:
第一種就是修改mapper.xml中foreach標籤內容,把studentNameList修改爲list
<if test="list != null">
AND student_name in
<foreach collection="list" item="item" open="(" separator="," close=")">
#{item}
</foreach>
</if>
不過這種方式我個人不太建議,因爲以後如果要擴展該方法,增加集合參數的時候,還得修改xml中的內容。
第二種方式,修改dao中的參數傳入方式,手動封裝成map,然後把map當參數傳進去
Dao方法修改爲:
public int getStudentCount(List<String> studentNameList){
//把參數手動封裝在Map中
Map<String, Object> map = new HashMap<String, Object>();
map.put("studentNameList", studentNameList);
return super.count("getStudentCount", map);
}
然後修改mapper.xml中的parameterType類型爲Map
<!--注意下面的parameterType類型必須修改爲Map類型,foreach中引用的List名稱不用改變-->
<select id="Student.getStudentCount" parameterType="java.util.Map" resultType="java.lang.Integer">
<![CDATA[
SELECT
COUNT(*)
FROM
t_student WHERE 1=1
]]>
<if test="studentNameList != null">
AND student_name in
<foreach collection="studentNameList" item="item" open="(" separator="," close=")">
#{item}
</foreach>
</if>
</select>
修改完後,重新執行了一下測試用例,測試通過。