Question

I am implementing ResponseCache for HttpUrlConnection in android. Everything seems to work. I call

ResponseCache.setDefault(new ResCache());

And the methods in my ResCache class are being used as expected. The only problem I am having is that the Map with request Parameters is empty. If I try this very same code outside of an android environment, I will be able to see the request Header parameter, but inside an activity and all that stuff is not working. Here is the code for the Activity.

package com.httptest;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.CacheRequest;
import java.net.CacheResponse;
import java.net.HttpURLConnection;
import java.net.ResponseCache;
import java.net.URI;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.os.Bundle;

public class HttpTest extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ResponseCache.setDefault(new ResCache());
        HttpURLConnection urlConnection = null;
        try {
        URL url = new URL("http://169.254.198.146//patch/500.php");
        urlConnection = (HttpURLConnection) url
                .openConnection();
        urlConnection.setUseCaches(true);
        urlConnection.setRequestProperty("MY_PROPERTY", "MY_VALUE");
            InputStream in = new BufferedInputStream(
                    urlConnection.getInputStream());
            String aux = readStream(in);
        }catch(Exception e){
            e.printStackTrace();
        }finally {
            urlConnection.disconnect();
        }
    }

    public static String readStream(InputStream in) throws IOException {
        StringBuilder sb = new StringBuilder();
        BufferedReader r = new BufferedReader(new InputStreamReader(in), 1000);
        for (String line = r.readLine(); line != null; line = r.readLine()) {
            sb.append(line);
        }
        in.close();
        return sb.toString();
    }

    public class ResCache extends ResponseCache{

        @Override
        public CacheResponse get(URI arg0, String arg1,
                Map<String, List<String>> arg2) throws IOException {
            System.out.println(arg2);
            return null;
        }

        @Override
        public CacheRequest put(URI uri, URLConnection connection)
                throws IOException {
            return null;
        }
    }
}

In the method ResCache.get(URI, String, Map), the map is always empty. I would like to see the parameters I added to the request. By the way the parameters all well set in the request, as I can read them in the server when performing the request.

Again, this works outside of an android environment.

Any help with this?

Thank you!

Answer 1

I think there is a bug in Android’s HttpURLConnection implementation where the response headers are passed to this method instead of the request headers.

I have solved this problem in my code as below, although I did not google for more details for the bug in android, but I’m pretty convinced android’s implementation for httpurlconnection has some problem, as you can see it works on non-android jvms:

Basically I fixed it by passing a VirenRequestHeadersMap instead of passing URLConnection#getRequestProperies() to be consistent with the values passed from put(…).

@Override
        public CacheRequest put(URI uri, URLConnection connection)
                throws IOException {
            MyPrivateContext context = <>;
            context.setConnection(connection);

            //...
        }

@Override
        public CacheResponse get(URI arg0, String arg1,
                Map<String, List<String>> arg2) throws IOException {
            System.out.println(arg2);

            MyPrivateContext context = <>;
            URLConnection connection = context.getConnection();
            arg2 = new VirenRequestHeadersMap(connection);
            //...
        }

And here is the entire VirenRequestHeadersMap class if you are curious as to how it looks like:

class VirenRequestHeadersMap implements Map<String, List<String>> {

    private final URLConnection mConnection;

    public VirenRequestHeadersMap(URLConnection connection) {
        mConnection = connection;
    }

    public void clear() {
        throw new UnsupportedOperationException();
    }

    public boolean containsKey(Object key) {
        if (key instanceof String) {
            String field = (String) key;
            return mConnection.getRequestProperty(field) != null;
        } else {
            return false;
        }
    }

    public boolean containsValue(Object value) {
        throw new UnsupportedOperationException();
    }

    public Set<Entry<String, List<String>>> entrySet() {
        throw new UnsupportedOperationException();
    }

    public List<String> get(Object key) {
        if (key instanceof String) {
            String field = (String) key;
            String value = mConnection.getRequestProperty(field);
            return value != null ? Collections.singletonList(value) : null;
        } else {
            return null;
        }
    }

    public boolean isEmpty() {
        throw new UnsupportedOperationException();
    }

    public Set<String> keySet() {
        throw new UnsupportedOperationException();
    }

    public List<String> put(String key, List<String> value) {
        throw new UnsupportedOperationException();
    }

    public void putAll(Map<? extends String, ? extends List<String>> value) {
        throw new UnsupportedOperationException();
    }

    public List<String> remove(Object key) {
        throw new UnsupportedOperationException();
    }

    public int size() {
        throw new UnsupportedOperationException();
    }

    public Collection<List<String>> values() {
        throw new UnsupportedOperationException();
    }
}