How to get response body in Zuul post filter?

Question

How it is possible to read a response body while using Zuul as a proxy in post filter?

I am trying to call the code like this:

@Component
public class PostFilter extends ZuulFilter {

    private static final Logger log = LoggerFactory.getLogger(PostFilter.class);

    @Override
    public String filterType() {
        return "post";
    }

    @Override
    public int filterOrder() {
        return 2000;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() {
        RequestContext ctx = RequestContext.getCurrentContext();
        ctx.getResponseBody(); // null

        // cant't do this, cause input stream is used later in other filters and I got InputStream Closed exception
        // GZIPInputStream gzipInputStream = new GZIPInputStream(stream);
        return null;
    }

}

score 13 · Accepted Answer · answered Feb 12 '16 at 16:58

13

I've managed to overcome this. The solution consists of 4 steps:

Read ctx.getResponseDataStream() into a ByteArrayOutputStream
Copy OutputStream to 2 InputStreams.
Use one of it for your custom purposes.
Use the second to reassign to context: context.setResponseBody(inputStream)
- reading stream from point 1 would cause that the stream cannot be read again, so this way you're passing a new fresh stream that wasn't read yet

answered Feb 12 '16 at 16:58

Dariusz Mydlarz

2,940
6
31
59

Don't remember exactly, but probably yes. Did you copied inputstream? – Dariusz Mydlarz Jan 16 '17 at 21:24
1

Copying the `InputStream` worked great, but I had to set my filter order before `org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter`. Using anything greater than 1000 leads to an "InputStream already closed" error because the response body has already been read and returned. – Michael Técourt Jan 17 '17 at 13:59
Ok, good. The number I used in example was probably not so important for my question ;) – Dariusz Mydlarz Jan 17 '17 at 14:17
1

@MichaelTecourt the filter number should be part of the response. I was trying for hours, just changed the filter number to 10 and it worked – Pedro Romão May 12 '17 at 14:43

score 11 · Answer 2 · answered May 09 '18 at 14:40

11

If someone is struggling with compressed answer, here's the solution I used:

// Read the compressed response
RequestContext ctx = RequestContext.getCurrentContext();
InputStream compressedResponseDataStream = ctx.getResponseDataStream();
try {
    // Uncompress and transform the response
    InputStream responseDataStream = new GZIPInputStream(compressedResponseDataStream);
    String responseAsString = StreamUtils.copyToString(responseDataStream, Charset.forName("UTF-8"));
    // Do want you want with your String response
    ...
    // Replace the response with the modified object
    ctx.setResponseBody(responseAsString);
} catch (IOException e) {
    logger.warn("Error reading body", e);
}

answered May 09 '18 at 14:40

VincentS

602
1
10
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Man i missed this comment and spent 6 hrs on it – Cshah Nov 13 '18 at 09:25
@Cshah Never try to solve a problem before searching if this problem exists in SO! ;) Seriously, glad it helped! – VincentS Nov 14 '18 at 12:26
if you using gzip as html compress process – withoutOne Jan 13 '21 at 10:19

score 4 · Answer 3 · answered Dec 29 '16 at 22:14

4

Thanks for suggestion, this is the code I used that works.

try (final InputStream responseDataStream = ctx.getResponseDataStream()) {
   final String responseData = CharStreams.toString(new InputStreamReader(responseDataStream, "UTF-8"));
   ctx.setResponseBody(responseData);
} catch (IOException e) {
   logger.warn("Error reading body",e);
}

answered Dec 29 '16 at 22:14

codesalsa

882
5
18

2

Nice use of Java 7's try-with-resources syntax here. In case someone is worried about `CharStreams.toString()` being `@Beta` (IntelliJ warns about it), one could also use Spring's `StreamUtils.copyToString()` if it's a dependency. This way, one can also omit the `InputStreamReader` instance. Also, imho it's a bit cleaner to use `StandardCharsets.UTF_8` instead of `"UTF-8"`. – Daniel K Nov 12 '18 at 15:17

score 3 · Answer 4 · answered Feb 12 '16 at 11:56

3

As you can see in this example, you have two methods available to extract the response body:

1- ctx.getResponseBody();

2- ctx.getResponseDataStream();

You have to check which one is not null and use that one.

answered Feb 12 '16 at 11:56

Pablo Valiente

31
1

Thanks, I already did id, but it was a little bit tricky. I'll post some code – Dariusz Mydlarz Feb 12 '16 at 16:54
in my case, ctx.getResponseBody(); return null so i used ctx.getResponseDataStream(); instead – Sal Prima Sep 30 '17 at 10:35
3

just found that `delete` has `ctx.getResponseBody()` but `post` and `put` has `getResponseDataStream()` – Tiina Mar 27 '18 at 06:16

Pedro Romão · Answer 5 · 2020-03-10T18:02:28.347

3

Be careful with the filterNumber

Using anything greater than 1000 leads to an "InputStream already closed" error because the response body has already been read and

I used the number 10 and worked fine

edited Mar 10 '20 at 18:02

answered May 12 '17 at 14:50

Pedro Romão

2,285
28
22

Man, you make my day! Thanks for the answer! – Carlos Cavero Dec 03 '19 at 19:25

Damian · Answer 6 · 2019-03-22T13:01:28.453

None of the answers worked for me. 1) Order of the filter needs to be lower that 1000 (sending response filter)

2) Code:

 private String getResponseData(RequestContext ctx) throws IOException {
    String responseData = null;

    final InputStream responseDataStream = ctx.getResponseDataStream();
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ByteArrayOutputStream copy = new ByteArrayOutputStream();
    int read = 0;
    byte[] buff = new byte[1024];
    while ((read = responseDataStream.read(buff)) != -1) {
        bos.write(buff, 0, read);
        copy.write(buff, 0, read);
    }
    InputStream isFromFirstData = new ByteArrayInputStream(bos.toByteArray());

    boolean responseGZipped = ctx.getResponseGZipped();
    try {
        InputStream zin = null;
        if (responseGZipped) {
            zin = new GZIPInputStream(isFromFirstData);
        } else {
            zin = responseDataStream;
        }
        responseData = CharStreams.toString(new InputStreamReader(zin, "UTF-8"));
        ctx.setResponseDataStream(new ByteArrayInputStream(copy.toByteArray()));

    } catch (IOException e) {
        logger.warn("Error reading body {}", e.getMessage());
    }

    return responseData;
}

score 0 · Answer 7 · answered Aug 09 '21 at 11:33

The simplest solution would be to get an input stream, read it with InputStreamReader, and finally create a new stream based on the read string and set it as a response data stream of context. Also, don't forget to set the order of the filter to number lower then 1000.

final InputStream responseDataStream = ctx.getResponseDataStream();
String response = CharStreams.toString(new InputStreamReader(responseDataStream, StandardCharsets.UTF_8));
InputStream stream = new ByteArrayInputStream(response.getBytes(StandardCharsets.UTF_8));
ctx.setResponseDataStream(stream);

score 0 · Answer 8 · answered Jun 14 '22 at 07:39

//NOTE:filterOrder:999
RequestContext context = getCurrentContext();
InputStream stream = context.getResponseDataStream();
// uncompress
String body = StreamUtils.copyToString(new GZIPInputStream(stream),
    Charset.forName("UTF-8"));

// modify
body = "Modified gzipped response via setResponseBody(): " + body;

// compress again
ByteArrayOutputStream bos = new ByteArrayOutputStream(body.length());
GZIPOutputStream gzip = new GZIPOutputStream(bos);
gzip.write(body.getBytes("UTF-8"));
gzip.close();
byte[] compressed = bos.toByteArray();
bos.close();
context.setResponseDataStream(new ByteArrayInputStream(compressed));

https://github.com/spring-attic/sample-zuul-filters/issues/4

How to get response body in Zuul post filter?

8 Answers8

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