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mybatis mapper namespace

本文轉載自   查看原文   2016-08-29 00:13   3526    mybatis mapper namespace foreach

http://www.mybatis.org/mybatis-3/zh/sqlmap-xml.html#insert_update_and_delete

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.ibatis.executor.ExecutorException: No constructor found in tk.mybatis.springboot.model.Course matching [java.lang.Integer, java.lang.String]
### The error may exist in mapper/CourseMapper.xml
### The error may involve tk.mybatis.springboot.mapper.CourseMapper.selectAll
### The error occurred while handling results
### SQL: select * from course
### Cause: org.apache.ibatis.executor.ExecutorException: No constructor found in tk.mybatis.springboot.model.Course matching [java.lang.Integer, java.lang.String]
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:122)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:113)
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:122)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:64)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
    at com.sun.proxy.$Proxy6.selectAll(Unknown Source)

 

 

 

org.apache.ibatis.jdbc.RuntimeSqlException: Error executing: create TABLE course (
id INTEGER ,
NAME VARCHAR(20)
)
.  Cause: org.apache.ibatis.jdbc.RuntimeSqlException: Line missing end-of-line terminator (;) => create TABLE course (
id INTEGER ,
NAME VARCHAR(20)
)

    at org.apache.ibatis.jdbc.ScriptRunner.executeLineByLine(ScriptRunner.java:141)
    at org.apache.ibatis.jdbc.ScriptRunner.runScript(ScriptRunner.java:101)

 

 

 

org.apache.ibatis.binding.BindingException: Type interface tk.mybatis.springboot.mapper.CourseMapper is not known to the MapperRegistry.
    at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
    at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:689)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:250)

mybatis中定義行為的接口，需要在xml文件中注冊：

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="tk.mybatis.springboot.mapper.CourseMapper">

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，具體日志如下：

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);
}

 

JstudentDao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>

 

根據報錯日志分析，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，怎么會報錯呢?

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里有一段說明：

寫道
注意 你可以傳遞一個 List 實例或者數組作為參數對象傳給 MyBatis。
當你這么做的時 候,MyBatis 會自動將它包裝在一個 Map 中,用名稱在作為鍵。
List 實例將會以“ list” 作為鍵,
而數組實例將會以“array”作為鍵。

因為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”作為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標簽內容，把studentNameList修改為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，因為以后如果要擴展該方法，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，然后把map當參數傳進去

Dao方法修改為：

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);  
 }

 

然后修改mapper.xml中的parameterType類型為Map

<!--注意下面的parameterType類型必須修改為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>

 

修改完后，重新執行了一下測試用例，測試通過。

 http://www.cnblogs.com/winkey4986/p/3480328.html

 


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