java - 如何测试 resp.getOutputStream()

Question

我有一个想要测试的servlet。我想测试 Mockito 的 doGet。在来自 srvlet 的主代码信息中，通过 PrintWriter 转到页面/json。在我的测试中，我想要一个包含测试信息的文件。而且我无法测试 PrintWriter (我不明白如何测试)

在测试中我尝试使用 PrintWriter 而不是

StringWriter sw = new StringWriter();
PrintWriter pw  =new PrintWriter(sw);
when(new PrintWriter(resp.getOutputStream())).thenReturn(pw);

这是我的 Servlet doGEt

 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/json");
        PrintWriter writer = new PrintWriter(resp.getOutputStream());
        ObjectMapper mapper = new ObjectMapper();
        String jsonString = mapper.writeValueAsString(list);
        writer.append(jsonString);
        writer.flush();
    }

这是我的测试，不起作用

@Test
    public void whenShouldCheckJsonSrevlet() throws ServletException, IOException {
        String fileWay = "D:\\CODE_WORK\\JAVA\\java-a-to-z\\lesson8Aplication\\src\\main\\java\\persistent\\test.txt";
        final JSONControllers servlet = new JSONControllers();
        HttpServletRequest req = mock(HttpServletRequest.class);
        HttpServletResponse resp = mock(HttpServletResponse.class);
        PrintWriter writer = new PrintWriter(new FileWriter(fileWay));
        BufferedReader reader = new BufferedReader(new FileReader(fileWay));
        when(new PrintWriter(resp.getOutputStream())).thenReturn(writer);
        when(req.getReader()).thenReturn(reader);
        servlet.doGet(req,resp);
        servlet.doPost(req,resp);
    }

java.lang.NullPointerException
    at java.io.Writer.<init>(Writer.java:88)
    at java.io.OutputStreamWriter.<init>(OutputStreamWriter.java:109)
    at java.io.PrintWriter.<init>(PrintWriter.java:148)
    at java.io.PrintWriter.<init>(PrintWriter.java:131)
    at servlets.JSONControllersTest.whenShouldCheckJsonSrevlet(JSONControllersTest.java:62)

Answer 1

您传入映射器的 writeValueAsString 的对象“列表”是什么？ JSONControllersTest.java 的第 62 行是哪一行？