mybatis mapper namespace

时间：2023-03-10 00:00:56
mybatis mapper namespace

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中定义行为的接口，需要在xml文件中注册：

<!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">

问题背景：

在Dao中使用MyBatis进行查询操作，参数是传的一个List：studentNameList，但是在执行查询的时候报错，具体日志如下：

  1. com.chenzhou.base.mybatis.IbatisSystemException: SqlSession operation; nested exception is org.apache.ibatis.exceptions.PersistenceException:
  2. ### Error querying database. Cause: org.apache.ibatis.binding.BindingException: Parameter 'studentNameList' not found. Available parameters are [list]
  3. ### Cause: org.apache.ibatis.binding.BindingException: Parameter 'studentNameList' not found. Available parameters are [list]
  4. at com.chenzhou.base.mybatis.SqlSessionTemplate.wrapException(SqlSessionTemplate.java:341)
  5. at com.chenzhou.base.mybatis.SqlSessionTemplate.execute(SqlSessionTemplate.java:127)
  6. at com.chenzhou.base.mybatis.SqlSessionTemplate.execute(SqlSessionTemplate.java:106)
  7. at com.chenzhou.base.mybatis.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:138)
  8. at com.chenzhou.dao.GenericMybatisDao.count(GenericMybatisDao.java:306)
  9. at com.chenzhou.cds.ps.dao.impl.StudentDao.getStudentCount(StudentDao.java:42)
  10. at com.chenzhou.cds.ps.dao.impl.StudentDao$$FastClassByCGLIB$$8819e766.invoke(<generated>)
  11. at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:191)
  12. at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:689)
  13. at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
  14. at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:80)
  15. at com.chenzhou.util.LogUtil.doMethodInfo(LogUtil.java:85)
  16. at com.chenzhou.util.LogUtil.doDebugMethodLog(LogUtil.java:36)
  17. at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  18. at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  19. at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  20. at java.lang.reflect.Method.invoke(Method.java:597)
  21. at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
  22. at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
  23. at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65)
  24. at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
  25. at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55)
  26. at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
  27. at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
  28. at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
  29. at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
  30. at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
  31. at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:622)
  32. at com.chenzhou.cds.ps.dao.impl.StudentDao$$EnhancerByCGLIB$$d4fcf513.getStudentCount(<generated>)
  33. at com.chenzhou.ps.dao.StudentDaoTest.testgetStudentCount(StudentDaoTest.java:44)
  34. ……

单元测试用例代码如下：

  1. @Test
  2. public void testgetStudentCount(){
  3. List<String> studentNameList = new ArrayList<String>();
  4. studentNameList.add("chenzhou");
  5. studentNameList.add("zhangsan");
  6. studentNameList.add("lisi");
  7. int count = studentDao.getStudentCount(studentNameList);
  8. System.out.println(count);
  9. }

studentDao中的getStudentCount方法代码如下：

  1. public int getStudentCount(List<String> studentNameList){
  2. return super.count("getStudentCount", studentNameList);
  3. }

MyBatis mapper.xml定义如下：

<!-- 查询学生数量  -->

<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>

根据报错日志分析，是MyBatis在解析xml时找不到其中声明的studentNameList，但是在Dao中明明传的参数就是studentNameList，怎么会报错呢?

查询了一下MyBatis官方的说明文档，终于找到了原因，在http://mybatis.github.io/mybatis-3/zh/dynamic-sql.html#foreach里有一段说明：

写道
注意 你可以传递一个 List 实例或者数组作为参数对象传给 MyBatis。
当你这么做的时 候,MyBatis 会自动将它包装在一个 Map 中,用名称在作为键。
List 实例将会以“list” 作为键,
而数组实例将会以“array”作为键。

因为我传的参数只有一个，而且传入的是一个List集合，所以mybatis会自动封装成Map<"list",studentNameList>。在解析的时候会通过“list”作为Map的key值去寻找。但是我在xml中却声明成studentNameList了，所以自然会报错找不到。

解决办法：

第一种就是修改mapper.xml中foreach标签内容，把studentNameList修改为list

<if test="list != null">

    AND student_name in

    <foreach collection="list" item="item" open="(" separator="," close=")">

        #{item}

    </foreach>

</if>

不过这种方式我个人不太建议，因为以后如果要扩展该方法，增加集合参数的时候，还得修改xml中的内容。

第二种方式，修改dao中的参数传入方式，手动封装成map，然后把map当参数传进去

Dao方法修改为：

public int getStudentCount(List<String> studentNameList){

     //把参数手动封装在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类型为Map

<!--注意下面的parameterType类型必须修改为Map类型,foreach中引用的List名称不用改变-->

<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，重新执行了一下测试用例，测试通过。

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

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