title: How to mock HttpServletRequest and HttpServletResponse objects?
body: <p>I have a simple servlet. He forward to <code>jsp</code> page. But when I use mock objects for <code>HttpServletRequest</code> and <code>HttpServletResponse</code> instead original objects in my test, I get <code>NullPointerException</code>. </p>
  
  <pre><code>public class SimpleServlet extends HttpServlet {
      @Override
      protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          req.getRequestDispatcher("WEB-INF/views/AdminMenu.jsp")
                  .forward(req, resp); // In this place I get NPE (16th string.)
      }
  }
  </code></pre>
  
  <p>This is my test which create <code>HttpServletRequest</code> and <code>HttpServletResponse</code>objects and send their into <code>doPost</code> method:</p>
  
  <pre><code>@Test
  public void test() throws ServletException, IOException {
  
      final HttpServletRequest req = mock(HttpServletRequest.class);
      final HttpServletResponse resp = mock(HttpServletResponse.class);
  
  
      final SimpleServlet simpleServlet = new SimpleServlet();
  
      simpleServlet.doPost(req, resp);
  
  }
  </code></pre>
  
  <p>This is my log after running text:</p>
  
  <pre><code>java.lang.NullPointerException
      at ru.pravvich.servlets.SimpleServlet.doPost(SimpleServlet.java:16)
      at ru.pravvich.servlets.SimpleServletTest.test(SimpleServletTest.java:28)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
  </code></pre>
  
  <p>What reason? Help me fix this issue. Thank You.</p>