Not able to run sql query with Mybatis

Question

I am trying to run a simple sql query using mybatis but its giving me following exception

java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for com.mycom.myproject.db.mybatis.dao.UserMapper.countByExample
org.apache.ibatis.session.Configuration$StrictMap.get(Configuration.java:660)
org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:495)
org.apache.ibatis.session.Configuration.getMappedStatement(Configuration.java:488)
org.apache.ibatis.binding.MapperMethod.setupCommandType(MapperMethod.java:236)
org.apache.ibatis.binding.MapperMethod.<init>(MapperMethod.java:71)
org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:39)
$Proxy9.countByExample(Unknown Source)
com.mycom.myproject.controller.LoginController.login(LoginController.java:39)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:601)
org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

My UserMapper.xml is

<?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="com.mycom.myproject.db.mybatis.dao.UserMapper" >
<select id="countByExample" resultType="int">
select count(*) from users
</select>
</mapper>

My UserMapper is

public interface UserMapper {
   int countByExample();
}

I am trying to access it in my LoginController

public class LoginController
 {
static final Logger logger = Logger.getLogger(LoginController.class);

@Autowired
private UserMapper userMapper;



@RequestMapping("/login")
public ModelAndView login(@ModelAttribute User userBean, Model model){  

    int count = userMapper.countByExample();

    System.out.println("Count: "+ count);       

    return new ModelAndView("login", "userBean", userBean); 

}
    }

My spring-servlet.xml file is

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.1.xsd
    http://www.springframework.org/schema/mvc
    http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">



<context:annotation-config />   

<context:component-scan
    base-package="com.mycom.myproject" />

<!-- Enable annotation driven controllers, validation etc... -->
<mvc:annotation-driven />

<mvc:resources mapping="/resources/**" location="/resources/" />


<bean id="datasource" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost/mydatabase"/>
    <property name="username" value="root"/>
    <property name="password" value="root"/>
</bean>

<!-- Declare a transaction manager -->

<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
p:dataSource-ref="datasource" />


<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="datasource" />
</bean>

<!-- scan for mappers and will automatically scan the whole classpath for xmls -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    <property name="basePackage" value="com.mycom.myproject.db.mybatis.dao" />
</bean> 


<bean id="viewResolver"
    class="org.springframework.web.servlet.view.UrlBasedViewResolver">
    <property name="viewClass"
        value="org.springframework.web.servlet.view.JstlView" />
    <property name="prefix" value="/WEB-INF/jsp/" />
    <property name="suffix" value=".jsp" />
</bean>

I don't know why this error is coming.

Answer 1

Taking a look to the error

Mapped Statements collection does not contain value for com.mycom.myproject.db.mybatis.dao.UserMapper.countByExample

it looks like myBatis is not finding your query. That is probably becuase it is not finding your xml mapped. It should be in com.mycom.myproject.db.mybatis.dao package according with your configuration:

<!-- scan for mappers and will automatically scan the whole classpath for xmls -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    <property name="basePackage" value="com.mycom.myproject.db.mybatis.dao" />
</bean>

In the project structure, UserMapper.java and UserMapper.xml can be in different folders (if you want to separate xml from java files) but they should be in a package with the same name and they should be combined in the same folder in the war build process because they both should be available in the classpath according with your configuration.