GZIPInputStream - 损坏的GZIP拖车

Question

我有一个静态辅助方法，负责从我们的 Rails 应用程序中获取压缩的 JSON 字符串，并在返回String表示之前解压缩数据。

我编写了两个 JUnit 测试，一个测试JSON 是否正确解析，另一个更基本的测试确定是否从服务器返回长度大于零的字符串。

问题：当我运行测试套件时，第一个测试方法成功，另一个失败，并显示IOException和消息"GZIP 拖车损坏"（请参阅下面的代码）。我已经确定失败的不是测试本身，因为当我使测试以相反的顺序运行时，"成功"测试就会被颠倒（换句话说，无论如何，总是第二个测试失败，无论两个测试中的哪一个是第二个运行第二个）。

这是帮助程序方法：

public static String doHTTPGet(String urlString) throws IOException{
    URL weatherAPI = new URL(urlString);
    HttpURLConnection apiConnection = (HttpURLConnection) weatherAPI.openConnection();
    apiConnection.setRequestMethod("GET");
    apiConnection.setRequestProperty("Accept-Encoding", "gzip");
    apiConnection.connect();
    BufferedInputStream bufferedInputStream = new BufferedInputStream(apiConnection.getInputStream());
    byte[] inputByteBuffer = new byte[10 * 1024];
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream(10 * 1024); // initialize the output stream with at least one buffer's worth of bytes
    while(bufferedInputStream.read(inputByteBuffer)  > -1){
        outputStream.write(inputByteBuffer);
    }
    outputStream.close();
    bufferedInputStream.close();
    apiConnection.disconnect();
    ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(outputStream.toByteArray());
    byteArrayInputStream.close();
    GZIPInputStream gis = new GZIPInputStream(byteArrayInputStream);
    InputStreamReader inputStreamReader = new InputStreamReader(gis, "UTF-8");
    BufferedReader reader = new BufferedReader(inputStreamReader);
    String decompressedResponse = "";
    String line;
    // readLine() is generating the IOException on the second pass.
    while((line = reader.readLine()) != null){
        decompressedResponse += line;
    }
    reader.close();
    inputStreamReader.close();
    gis.close();
    return decompressedResponse;
}

错误发生在帮助程序方法的底部，在行while((line = reader.readLine()) != null)... 上。具体来说，错误发生在reader.readLine()上。

以及两种测试方法：

@Test
public void testHttpGet(){
    try {
        // FILTERED_API_URL_WITH_TOKEN is merely the URL with an auth token
        String apiResponse = HTTPHelper.doHTTPGet(GlobalConstants.FILTERED_API_URL_WITH_TOKEN);
        assertNotNull(apiResponse);
        assertTrue("The size of the API response should be greater than zero. It is an empty string.", apiResponse.length() > 0);
    } catch (IOException e) {
        e.printStackTrace();
        assertTrue("An exception occured while trying to perform the HTTP Get to the api at URL " + GlobalConstants.FILTERED_API_URL_WITH_TOKEN, false);
    }
}
@Test
public void testAPIContent(){
    try {
        // the getAPIJson() method basically does the same as the testHttpGet
        // method, but converts the string to a json
        JSONObject jsonObject = XMLProducerFromAPI.getAPIJson();
        System.out.println(jsonObject);
        assertNotNull(jsonObject);
    } catch (IOException e) {
        e.printStackTrace();
        assertTrue("An IOException occured. See stack trace", false);
    } catch (JSONException e) {
        e.printStackTrace();
        assertTrue("A JSONException occured. See stack trace", false);
    }
}

我已经通读了这个问题和答案，但我不相信它适用，（或者可能是它，我误解了，如果是这样，请告诉我），我尝试了他们的方法，只收到了相同的消息。

由于doHTTPGet方法是静态的，并且创建的对象是在方法主体中完成的，因此不应重用任何内容（流、连接对象等）。坦率地说，我被难住了。

问：我是否在帮助程序代码中做错了什么，或者我误解了某些对象的某些用法，从而产生"损坏的 GZIP 拖车"消息？简而言之，在我的方案中，什么会导致此错误？

与往常一样，如果我遗漏了这个问题中的任何内容，请告诉我。

编辑

这是堆栈跟踪：

java.io.IOException: Corrupt GZIP trailer
    at java.util.zip.GZIPInputStream.readTrailer(GZIPInputStream.java:200)
    at java.util.zip.GZIPInputStream.read(GZIPInputStream.java:92)
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
    at java.io.InputStreamReader.read(InputStreamReader.java:167)
    at java.io.BufferedReader.fill(BufferedReader.java:136)
    at java.io.BufferedReader.readLine(BufferedReader.java:299)
    at java.io.BufferedReader.readLine(BufferedReader.java:362)
    at com.weathertx.xmlserver.support.HTTPHelper.doHTTPGet(HTTPHelper.java:60)
    at com.weathertx.xmlserver.tests.HttpHelperTest.getAPIResponse(HttpHelperTest.java:47)
    at com.weathertx.xmlserver.tests.HttpHelperTest.testHttpGet(HttpHelperTest.java:21)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Answer 1

问题已解决。坦率地说，我不太明白为什么它最初不起作用，或者它有什么问题（除了显然过于复杂和不必要的复杂）。多亏了这个解决方案，我不知何故错过了我的第一次搜索，我能够通过基本上完全实现他们所做的来解决问题。这是我的最终代码：

public static String doHTTPGet(String urlString) throws IOException{
    URL weatherAPI = new URL(urlString);
    HttpURLConnection apiConnection = (HttpURLConnection) weatherAPI.openConnection();
    apiConnection.setRequestMethod("GET");
    apiConnection.setRequestProperty("Accept-Encoding", "gzip");
    apiConnection.connect();
    InputStream gzippedResponse = apiConnection.getInputStream();
    InputStream decompressedResponse = new GZIPInputStream(gzippedResponse);
    Reader reader = new InputStreamReader(decompressedResponse, "UTF-8");
    StringWriter writer = new StringWriter();
    char[] buffer = new char[10240];
    for(int length = 0; (length = reader.read(buffer)) > 0;){
        writer.write(buffer, 0, length);
    }
    writer.close();
    reader.close();
    decompressedResponse.close();
    gzippedResponse.close();
    apiConnection.disconnect();
    return writer.toString();
}

因此，最终，我不需要通过字节数组流和到处传递数据。除了我原来的方法令人费解之外，如果有人确切知道为什么我的原始算法在第一次调用此方法后产生"损坏的GZIP拖车"错误消息，请务必告诉我。