web项目引用Java项目，连接报错error HTTP Status 500

错误信息

项目背景：

一个web项目引用一个java Project，项目中添加了引用，但是打开页面访问，总报500错误。提示：servlet初始化错误。

环境：Eclipse luna

JDK: 1.7

Tomcat: 8.0

HTTP Status 500 - Servlet execution threw an exception

type Exception report

message Servlet execution threw an exception

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Servlet execution threw an exception
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause

java.lang.NoClassDefFoundError: org/codehaus/jackson/map/ObjectMapper
	com.founder.xap.maserver.actionstruct.ActionStructParser.fromJson(ActionStructParser.java:20)
	com.founder.xap.maserver.servlet.MAServlet.processRequest(MAServlet.java:63)
	com.founder.xap.maserver.servlet.MAServlet.doGet(MAServlet.java:42)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause

java.lang.ClassNotFoundException: org.codehaus.jackson.map.ObjectMapper
	org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1305)
	org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
	com.founder.xap.maserver.actionstruct.ActionStructParser.fromJson(ActionStructParser.java:20)
	com.founder.xap.maserver.servlet.MAServlet.processRequest(MAServlet.java:63)
	com.founder.xap.maserver.servlet.MAServlet.doGet(MAServlet.java:42)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/8.0.21 logs.

解决方案：

1、项目属性，java build path --》projects，添加所需的java项目

2、项目属性--》 Java build Path --》 Order and Export勾选java项目

3、项目属性--》Deployment Assemby 添加所依赖的Java项目