Android 上的 Jersey 客户端 - NullPointerException [英] Jersey Client on Android - NullPointerException
问题描述
I am trying to create a simple Android client for a web service I have built, but something goes wrong at runtime.
Here is the Client:
public class MyClient extends AsyncTask<EditText, Integer, String> {
private EditText text;
protected String doInBackground(EditText... strings) {
RuntimeDelegate
.setInstance(new com.sun.ws.rs.ext.RuntimeDelegateImpl());
WebResource wbr;
Client client = Client.create();
wbr = client
.resource("http://my.ip:8080/MazeService/rest/service/hello");
String result = wbr.queryParam("number", "10")
.accept(MediaType.APPLICATION_JSON).get(String.class);
text = strings[0];
return result;
}
protected void onProgressUpdate(Integer... progress) {
// setProgressPercent(progress[0]);
}
protected void onPostExecute(String result) {
if (result != null)
this.text.setText(result);
else
Log.d("MyApp", "No Result");
}
}
and the Service:
@Path("/service")
public class AndroidService {
@GET
@Produces(MediaType.APPLICATION_JSON )
@Path("/hello")
public String getJSON(@QueryParam("number") String nr)
{
String s = "Hi there! The number is: "+nr;
return s;
}
}
I get this stacktrace in LogCat:
02-18 16:26:06.446: E/AndroidRuntime(1381): FATAL EXCEPTION: AsyncTask #1
02-18 16:26:06.446: E/AndroidRuntime(1381): java.lang.RuntimeException: An error occured while executing doInBackground()
02-18 16:26:06.446: E/AndroidRuntime(1381): at android.os.AsyncTask$3.done(AsyncTask.java:278)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
02-18 16:26:06.446: E/AndroidRuntime(1381): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.lang.Thread.run(Thread.java:856)
02-18 16:26:06.446: E/AndroidRuntime(1381): Caused by: java.lang.NullPointerException
02-18 16:26:06.446: E/AndroidRuntime(1381): at javax.ws.rs.core.MediaType.valueOf(MediaType.java:119)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.ClientResponse.getType(ClientResponse.java:615)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:532)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:506)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.WebResource.handle(WebResource.java:674)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:503)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.maze.client.MyClient.doInBackground(MyClient.java:25)
02-18 16:26:06.446: E/AndroidRuntime(1381): at com.maze.client.MyClient.doInBackground(MyClient.java:1)
02-18 16:26:06.446: E/AndroidRuntime(1381): at android.os.AsyncTask$2.call(AsyncTask.java:264)
02-18 16:26:06.446: E/AndroidRuntime(1381): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
02-18 16:26:06.446: E/AndroidRuntime(1381): ... 5 more
I do not understand what the problem is, since a similar client works on PC. There is no problem with the IP address, since I can access the server from the Android VirtualDevice.
The Android version is 4.0.3 API version 15. For the client I used Jersey 1.11.
EDIT
I have also tried to remove the whole thing with the EditText, since someone told me it isn't used as it should be. Still, I got the same error. I simply can not understand what am I doing wrong. If I should display any other additional information, please let me know. Also, ANY idea is good. I am new to Android and I might have made some stupid mistakes.
Paul's suggestion is correct. I got a little bit deeper in that subject and found a reason.
Android apk packaging tool (APKBuilder class from sdklib.jar) ignores different folders while it creates the package (source). One of those folders is META-INF - no matter if its in the attached library or in the project's source folder.
Workaround for version 1.8 (and probably other also, but I didn't test it) of Jersey is to provide custom (default one looks up META-INF/services/ which is not present in android apk) implementation for ServiceFinder$ServiceIteratorProvider which has hard coded provider class names. I based my implementation on this implementation proposed by Lucas:
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import android.util.Log;
import com.sun.jersey.spi.service.ServiceFinder.ServiceIteratorProvider;
public class AndroidServiceIteratorProvider<T> extends ServiceIteratorProvider<T> {
private static final String TAG = AndroidServiceIteratorProvider.class.getSimpleName();
private static final String MESSAGE = "Unable to load provider";
private static final HashMap<String, String[]> SERVICES = new HashMap<String, String[]>();
private static final String[] com_sun_jersey_spi_HeaderDelegateProvider = {
"com.sun.jersey.core.impl.provider.header.MediaTypeProvider",
"com.sun.jersey.core.impl.provider.header.StringProvider"
};
private static final String[] com_sun_jersey_spi_inject_InjectableProvider = {
};
private static final String[] javax_ws_rs_ext_MessageBodyReader = {
"com.sun.jersey.core.impl.provider.entity.StringProvider",
"com.sun.jersey.core.impl.provider.entity.ReaderProvider"
};
private static final String[] javax_ws_rs_ext_MessageBodyWriter = {
"com.sun.jersey.core.impl.provider.entity.StringProvider",
"com.sun.jersey.core.impl.provider.entity.ReaderProvider"
};
static {
SERVICES.put("com.sun.jersey.spi.HeaderDelegateProvider",
com_sun_jersey_spi_HeaderDelegateProvider);
SERVICES.put("com.sun.jersey.spi.inject.InjectableProvider",
com_sun_jersey_spi_inject_InjectableProvider);
SERVICES.put("javax.ws.rs.ext.MessageBodyReader",
javax_ws_rs_ext_MessageBodyReader);
SERVICES.put("javax.ws.rs.ext.MessageBodyWriter",
javax_ws_rs_ext_MessageBodyWriter);
SERVICES.put("jersey-client-components", new String[]{});
SERVICES.put("com.sun.jersey.client.proxy.ViewProxyProvider", new String[]{});
}
@SuppressWarnings("unchecked")
@Override
public Iterator<Class<T>> createClassIterator(Class<T> service,
String serviceName, ClassLoader loader,
boolean ignoreOnClassNotFound) {
String[] classesNames = SERVICES.get(serviceName);
int length = classesNames.length;
ArrayList<Class<T>> classes = new ArrayList<Class<T>>(length);
for (int i = 0; i < length; i++) {
try {
classes.add((Class<T>) Class.forName(classesNames[i]));
} catch (ClassNotFoundException e) {
Log.v(TAG, MESSAGE,e);
}
}
return classes.iterator();
}
@Override
public Iterator<T> createIterator(Class<T> service, String serviceName,
ClassLoader loader, boolean ignoreOnClassNotFound) {
String[] classesNames = SERVICES.get(serviceName);
int length = classesNames.length;
ArrayList<T> classes = new ArrayList<T>(length);
for (int i = 0; i < length; i++) {
try {
classes.add(service.cast(Class.forName(classesNames[i])
.newInstance()));
} catch (IllegalAccessException e) {
Log.v(TAG, MESSAGE,e);
} catch (InstantiationException e) {
Log.v(TAG, MESSAGE,e);
} catch (ClassNotFoundException e) {
Log.v(TAG, MESSAGE,e);
}
}
return classes.iterator();
}
}
I removed most of the classes since I didn't use them and also they were causing verification errors on dalvik vm...
NOTE: It means that with this implementation you can use only subset of headers/types supported by Jersey (I needed only String). To support other types you have to add providers located in META-INF/services folder of jersey-client.jar (or from Lucas' implementation) and check if they don't cause verification errors on Android.
The above code should be used as follows:
ServiceFinder.setIteratorProvider(new AndroidServiceIteratorProvider());
Client client = Client.create();
EDIT:
It seems that the problem have been fixed in android-maven-plugin.
mosa...@gmail.com wrote:
The pull request with the fix was merged into master and will be released with 3.2.1:
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