Jersey客户端在Android上 - NullPointerException异常 [英] Jersey Client on Android - NullPointerException

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问题描述

我想创建一个简单的Andr​​oid客户端的web服务，我已经建立，但不顺心的事在运行时。

I am trying to create a simple Android client for a web service I have built, but something goes wrong at runtime.

下面是客户端：

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");
}

}

和服务：

@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;
}
}

我得到这个堆栈跟踪在LogCat中：

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

我不明白是什么问题，因为类似的客户端适用于PC。没有与IP地址没有问题，因为我可以从Android VirtualDevice访问服务器。

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.

而Android版本是4.0.3 API版本15.我用球衣1.11客户端

The Android version is 4.0.3 API version 15. For the client I used Jersey 1.11.

修改

我还试图删除整个事情与EditText上，因为有人告诉我，它不使用，因为它应该是。不过，我得到了同样的错误。我根本无法理解我在做什么错。如果我要显示任何其他附加信息，请让我知道。此外，任何想法是好的。我是新来的Andr​​oid，我可能已经取得了一些愚蠢的错误。

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.

推荐答案

保罗的建议是正确的。我有一点点这个主题更深，找了个理由。

Paul's suggestion is correct. I got a little bit deeper in that subject and found a reason.

安卓APK打包工具（从sdklib.jar APKBuilder类）忽略不同的文件夹，而在创建程序包（的来源）。其中一个文件夹是META-INF - 无论其在连接库，或在项目的源文件夹中。

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.

解决方法对于1.8版本的泽西（可能其他的还可以，但我没有测试它）是提供自定义（默认的查找META-INF /服务/这不是present在安卓APK）实施为<一个href="http://java.net/projects/jersey/sources/svn/content/trunk/jersey/jersey-core/src/main/java/com/sun/jersey/spi/service/ServiceFinder.java?rev=5709"相对=nofollow> ServiceFinder $ ServiceIteratorProvider 有硬codeD供应商的类名。我根据我的实现上<一个href="http://jersey.576304.n2.nabble.com/java-lang-NullPointerException-on-Android-tt4212447.html#a5459910"相对=nofollow>这个中提出的卢卡斯实现：

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 &lt; 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();
    }
}

我删除了大部分的类，因为我没有用他们，还他们造成的Dalvik虚拟机验证错误...

I removed most of the classes since I didn't use them and also they were causing verification errors on dalvik vm...

注：这意味着，这个实现，你可以使用由新泽西支持页眉/类型的唯一子集（我只需要字符串）。为了支持其他类型，你必须添加位于泽西-client.jar中的META-INF / services文件夹供应商（或从卢卡斯的实现），并检查它们不会引起对Android的验证错误。

以上code，应使用如下：

The above code should be used as follows:

ServiceFinder.setIteratorProvider(new AndroidServiceIteratorProvider());
Client client = Client.create();

编辑：

看来，问题已经在Android的Maven的插件固定。

MOSA ... @ gmail.com写道：的

与修复拉请求被合并到主会发布3.2.1：

The pull request with the fix was merged into master and will be released with 3.2.1:

这篇关于Jersey客户端在Android上 - NullPointerException异常的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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