java.lang.ClassNotFoundException: com.fasterxml.jackson.databind.ObjectMapper的解决方法【IDEA】

报错如下

java.lang.ClassNotFoundException: com.fasterxml.jackson.databind.ObjectMapper
		at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1360)
		at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1182)
		at servlet.jsonServlet.doPost(jsonServlet.java:32)
		at servlet.jsonServlet.doGet(jsonServlet.java:40)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
		at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
		at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:528)
		at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
		at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
		at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
		at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
		at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
		at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798)
		at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
		at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:810)
		at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
		at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
		at java.lang.Thread.run(Thread.java:748)

我是 ObjectMapper objectMapper = new ObjectMapper();这段代码出问题，于是：

解决方法

1.按住ctrl，鼠标左键点ObjectMapper ，打开了依赖的jar包。发现文件最上面出现download…的字样，点击下载。
2.耐心等下载完成。完成后，file选项卡打开project structure…
3.如图：
再跑一遍项目，问题解决。

其他

这个问题折腾得比较久，因为网上的结果大同小异，分为以下几类：
1.jar包未导入（但我导入了）
2.与spring或者maven的jar包冲突（但我没创建这两个东西）
3.jar包版本过低，与spring的比匹配（但我下载了最新的也没用）