如何在为过滤器编写的单元测试中为 J2EE 过滤器中的模拟请求设置属性

Question

我有一个名为SomeFilter 的过滤器类，它实现了javax.servlet.Filter。 在 doFilter 方法中，我使用键“key”和值“result”设置了属性“someResult”。

我有一个名为TestSomeFilter 的单元测试类，它调用SomeFilter 的doFilter。现在的问题是我在过滤器中设置的请求属性“someResult”没有被设置。这仅在我进行单元测试（在本地）时发生，即请求是模拟请求。如果我在 websphere 应用程序服务器（本地）上部署过滤器，则属性设置正确。此外，当我在调试模式下运行单元测试时，MockedRequestWrapper 的 setAttribute 不会被调用。

代码如下。

如果有人能帮助我解决我的问题或至少为我指明正确的方向，我将不胜感激。

提前致谢！

代码：

public class SomeFilter implements javax.servlet.Filter {

    public void doFilter(ServletRequest req, 
                   ServletResponse res, FilterChain chain) 
    throws ServletException {

    //do some stuff

    HttpServletRequest request = (HttpServletRequest) req;

    Map<String,String> map = new HashMap<String,String>();
    map.put("key","result");

    request.setAttribute("someResult",map);
    chain.doFilter(request, res);
    }
}

public class TestSomeFilter {

    @org.junit.Test
    public void testSomeFilter {
        HttpServletRequest mockRequest = null;
        HttpServletResponse mockResponse = null;
        HttpSession mockSession = null;
        MockedRequestWrapper mrw = null;

        org.easymock.EasyMock.replay(mockSession);
        org.easymock.EasyMock.replay(mockRequest);
        org.easymock.EasyMock.replay(mockResponse);

        mrw = new MockedRequestWrapper(mockRequest);

        filter.doFilter(mrw, mockResponse, mockFilterChain);

        HashMap<String,String> map = (HashMap<String,String>) mrw        
                                         .getAttribute(("someResult");

        String value = map.get("key");

        org.junit.Assert.assertEquals(
            "The output should be result.", 
            "result", value);
    }

    @org.junit.Before
    public void setUp() throws Exception {
        mockRequest = createNiceMock(HttpServletRequest.class);
        mockResponse = createNiceMock(HttpServletResponse.class);
        mockSession = createNiceMock(HttpSession.class);
    }

    @org.junit.After
    public void tearDown() throws Exception {}

    public class MockedFilterChain implements FilterChain {

        public void doFilter(ServletRequest request, 
                        ServletResponse response) 
                    throws ServletException {}
    }
}

public class MockedRequestWrapper extends HttpServletRequestWrapper {

    private Map<String,Object> m = null;
    public MockedRequestWrapper(HttpServletRequest httpServletRequest) {
            super(httpServletRequest);
    }

    public void setAttribute(String name, Object o){            
        m = new HashMap<String,Object>();
        m.put(name, o);         
    }

    public Object getAttribute(String name){
        return m.get(name);//<<<< PROBLEM: This map is always null causing NPE
    }
}

Answer 1

我找到了解决方案。包装类需要这样修改：

public class MockedRequestWrapper extends HttpServletRequestWrapper {

    private Map<String,Object> m = null;
    private HttpServletRequest origReq = null;

    public MockedRequestWrapper(HttpServletRequest httpServletRequest) 
        throws IOException, ServletException {
        super(httpServletRequest);
        origReq = httpServletRequest;
    }

    @Override
    public void setAttribute(String name, Object o){            
        m = new HashMap<String,Object>();
        m.put(name, o);
        super.setAttribute(name, o);
        origReq.setAttribute(name, o);
    }

    @Override
    public Object getAttribute(String name){
        if(m != null){
            return m.get(name);
        } else if(origReq.getAttribute(name) != null){
            return origReq.getAttribute(name);
        } else {
            return super.getAttribute(name);
        }
    }
}