web项目整合MongoDb出现No converter found capable of converting from org.bson.types.ObjectId to type Long异常

Spring、SpringMVC、MyBatis框架整合 MongoDb ，启动web项目时出现异常，项目不能运行，查看原因是出现如下异常：

with root cause org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type org.bson.types.ObjectId to type java.lang.Long

异常堆栈如下：

org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [springMvcDispatcherServlet] in context with path [/conference] threw exception [Request processing failed; nested exception is org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type org.bson.types.ObjectId to type java.lang.Long] with root cause
org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type org.bson.types.ObjectId to type java.lang.Long

解决方法：

Spring使用MongoDb帮助文档

在MongoDb里要求每个文档都需要有_id 字段，java类中有如下情况会被映射为_id字段

• 如果1个字段加上了 @Id (org.springframework.data.annotation.Id)注解，那么将bean保存到数据库时就会把该字段映射为文档中的_id字段
• 如果java对象中没有 @Id 注解，名字为id 的字段将会被映射为文档中的_id字段