1.springmvc:
Handler dispatch failed; nested exception is java.lang.NoSuchMethodError: com.fasterxml.jackson.core.JsonGenerator.writeFieldId(J)V
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:982)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
********************************
Caused by: java.lang.NoSuchMethodError: com.fasterxml.jackson.core.JsonGenerator.writeFieldId(J)V
at com.fasterxml.jackson.databind.ser.std.StdKeySerializers$Default.serialize(StdKeySerializers.java:180)
at com.fasterxml.jackson.databind.ser.std.MapSerializer.serializeFields(MapSerializer.java:707)
at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:639)
at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:33)
*****************************
[Request processing failed; nested exception is java.lang.IllegalStateException: getOutputStream() has already been called for this response] with root cause
java.lang.IllegalStateException: getOutputStream() has already been called for this response
解决：
1)版本 : 与spring相适应
2）加包
提示：如果是多模块开发，或许要install
