一、问题
eclipse启动时报下面的错误：
Caused by: java.lang.IllegalArgumentException: Caches collection already contains value for com.crm.dao.PaperUserMapper
at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:782) ~[mybatis-3.2.7.jar:3.2.7]
at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:754) ~[mybatis-3.2.7.jar:3.2.7]
at org.apache.ibatis.session.Configuration.addCache(Configuration.java:516) ~[mybatis-3.2.7.jar:3.2.7]
at org.apache.ibatis.builder.MapperBuilderAssistant.useNewCache(MapperBuilderAssistant.java:132) ~[mybatis-3.2.7.jar:3.2.7]
at org.apache.ibatis.builder.xml.XMLMapperBuilder.cacheElement(XMLMapperBuilder.java:209) ~[mybatis-3.2.7.jar:3.2.7]
at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:114) ~[mybatis-3.2.7.jar:3.2.7]
... 82 common frames omitted
二、解决
a.检查命名空间、别名是否正确
b.检查mapper.xml和mapper.java中是否有重复的
我这里是因为项目mapper.xml中出现重复的，修改后问题成功解决。小建议：把insert、select这些标签折起来，然后看看id属性是不是有重复的。
三、参考文献
https://blog.csdn.net/prader/article/details/80547010
https://blog.csdn.net/zengdeqing2012/article/details/46340357