Getting HTTP Status 500 - Servlet execution threw an exception

Question

I Created a Dynamic web project where the input parameters are coming from UI(Index.html) going to servlet.java, but when I am trying to call auth in oAuthBean.java file its giving me an error.

Attached navigation view:

Exception:

Aug 24, 2017 3:18:42 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [clientCredServlet1] in context with path [/Java-Credit-Offers-Example] threw exception [Servlet execution threw an exception] with root cause
java.lang.ClassNotFoundException: org.apache.http.HttpEntity
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1333)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167)
    at controller.clientCredServlet.doPost(clientCredServlet.java:45)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:502)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1132)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1539)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1495)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Answer 1

It looks like your servlet uses Apache http client (that's where org.apache.http.HttpEntity is coming from), but corresponding dependency jar is not present in resulting deployment, most likely because there is a lack of configuration glue between Maven and Eclipse WTP plugin which deploys to and runs your Tomcat from IDE. That lack appeared because it seems that Maven project has been created outside of Eclipse.

Option 1. Leave things as is and do quickfix (worse)

Try executing under your project root folder:

mvn eclipse:eclipse -Dwtpversion=2.0

and reopen Eclipse workspace then

According to Maven Eclipse plugin documentation when the wtpversion flag is explicitly set, maven generates necessary workspace configuration for WTP plugins (including Tomcat one) in order to let them understand how to obtain Maven dependencies during deployments from Eclipse

Option 2. Rely on built-in IDE integration with Maven (best for long term)

Examine following great answer which, at some approximation, describes why, and how to rely on built-in Eclipse Maven support. This approach eliminates the problem with missing dependencies in IDE deployments as well, but requires more effort to migrate project onto, which however is quite minor while your project is at the beginning stage