title: MyBatis - Mapped Statements collection already contains value for
body: <p>I had the following error messages thrown when registering the mapper classes on my server startup,</p>
  
  <pre><code>[artifact:mvn] 2016-05-07 11:39:21,708 [ERROR] org.mybatis.spring.mapper.MapperFactoryBean - Error while adding the mapper 'interface com.sample.mappers.UserMapper' to configuration.
  [artifact:mvn] java.lang.IllegalArgumentException: Mapped Statements collection already contains value for com.sample.mappers.UserMapper.getAllUsers
  [artifact:mvn]  at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:802)
  [artifact:mvn]  at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:774)
  [artifact:mvn]  at org.apache.ibatis.session.Configuration.addMappedStatement(Configuration.java:598)
  [artifact:mvn]  at org.apache.ibatis.builder.MapperBuilderAssistant.addMappedStatement(MapperBuilderAssistant.java:300)
  [artifact:mvn]  at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.parseStatement(MapperAnnotationBuilder.java:313)
  [artifact:mvn]  at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.parse(MapperAnnotationBuilder.java:128)
  [artifact:mvn]  at org.apache.ibatis.binding.MapperRegistry.addMapper(MapperRegistry.java:72)
  [artifact:mvn]  at org.apache.ibatis.session.Configuration.addMapper(Configuration.java:671)
  [artifact:mvn]  at org.mybatis.spring.mapper.MapperFactoryBean.checkDaoConfig(MapperFactoryBean.java:81)
  [artifact:mvn]  at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:44)
  </code></pre>
  
  <p>I used annotations for my mapper interfaces and there's no xml configuration.  </p>
  
  <p>Below is my UserMapper interface,</p>
  
  <pre><code>public interface UserMapper {
  
    @Select("SELECT  * FROM customer")
    List&lt;User&gt; getAllUsers();
  
    @Select("SELECT * FROM customer where userId = #{userId} ")
    List&lt;User&gt; getAllUsers(Long userId);
  
  }
  </code></pre>