springmvc踩坑-jackson与spring的版本兼容问题

一开始 springmvc  4.3.9版本中，用控制器 handler 返回 json 时，用了 2.1.5 的jackson包，发现还是报错 找不到 类方法。

Jul 15, 2018 1:31:48 PM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter HttpPutFormContentFilter
java.lang.NoClassDefFoundError: com/fasterxml/jackson/core/util/DefaultIndenter
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.init(AbstractJackson2HttpMessageConverter.java:97)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.<init>(AbstractJackson2HttpMessageConverter.java:90)
	at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.<init>(MappingJackson2HttpMessageConverter.java:66)
	at org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.<init>(MappingJackson2HttpMessageConverter.java:57)
	at org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter.<init>(AllEncompassingFormHttpMessageConverter.java:61)
	at org.springframework.web.filter.HttpPutFormContentFilter.<init>(HttpPutFormContentFilter.java:63)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at java.lang.Class.newInstance(Class.java:442)
	at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:119)
	at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:258)
	at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
	at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4689)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5329)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1407)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1397)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.core.util.DefaultIndenter
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1332)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
	... 23 more

于是改用 jackson 2.9.6的包时，发现成功了，不再报错。

原因是Spring 3.x 和4.X处理JSON的一个类不一样

spring3.x是org.springframework.http.converter.json.MappingJacksonHttpMessageConverter

spring4.x是org.springframework.http.converter.json.MappingJackson2HttpMessageConverter