在Eclipse插件中使用Reflections库时无法工作

Question

我使用Reflections库开发了一个应用程序，用于查询具有特定注释的所有类。在我决定从我的应用程序创建一个Eclipse插件之前，一切都非常顺利。然后Reflections停止工作

考虑到我的应用程序在不作为Eclipse插件的一部分时运行良好，我认为这应该是一个类加载器问题。因此，我向Reflections类添加了插件激活器类的类加载器、上下文类加载器和所有我能想到的其他类加载器，但没有成功。这是我的代码的简化版本:

ConfigurationBuilder config = new ConfigurationBuilder();
config.addClassLoaders(thePluginActivatorClassLoader);
config.addClassLoaders(ClasspathHelper.getContextClassLoader());
config.addClassLoaders("all the classloaders I could imagine");
config.filterInputsBy(new FilterBuilder().include("package I want to analyze"));
Reflections reflections = new Reflections(config);
Set<Class<?>> classes = reflections.getTypesAnnotatedWith(MyAnnotation.class); //this Set is empty

我还尝试添加类的url，我想加载到ConfigurationBuilder类，但它没有帮助。

有人能告诉我是否有一种方法使Reflections作为Eclipse插件的一部分工作?或者我应该更好地寻找另一个替代方案?非常感谢，我真的很困惑。

Answer 1

我假设你已经知道如何创建包(否则，检查这个)。

在对Reflections API进行了一些调试和探索之后，我意识到问题在于Reflections无法读取OSGi url (bundlerresource://…)，从而导致异常:

org.reflections.ReflectionsException: could not create Vfs.Dir from url, 
no matching UrlType was found [bundleresource://1009.fwk651584550/]

和这个建议:

either use fromURL(final URL url, final List<UrlType> urlTypes) 
or use the static setDefaultURLTypes(final List<UrlType> urlTypes) 
or addDefaultURLTypes(UrlType urlType) with your specialized UrlType.

所以我相信实现一个UrlType OSGi(例如class BundleUrlType implements UrlType {...})，并注册它像这样:

Vfs.addDefaultURLTypes(new BundleUrlType());

应该使Reflections API可以从bundle内部使用。reflection依赖项应该像这里所描述的那样添加到Eclipse Plugin项目中。

这就是我的示例MANIFEST。添加所需jar后MF的样子:

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: ReflectivePlugin
Bundle-SymbolicName: ReflectivePlugin
Bundle-Version: 1.0.0.qualifier
Bundle-Activator: reflectiveplugin.Activator
Bundle-ActivationPolicy: lazy
Bundle-RequiredExecutionEnvironment: JavaSE-1.6
Import-Package: javax.annotation;version="1.0.0",
 org.osgi.framework;version="1.3.0",
 org.osgi.service.log;version="1.3",
 org.osgi.util.tracker;version="1.3.1"
Bundle-ClassPath: .,
 lib/dom4j-1.6.1.jar,
 lib/guava-r08.jar,
 lib/javassist-3.12.1.GA.jar,
 lib/reflections-0.9.5.jar,
 lib/slf4j-api-1.6.1.jar,
 lib/xml-apis-1.0.b2.jar
Export-Package: reflectiveplugin, 
 reflectiveplugin.data

注意:Used Reflections v. 0.9.5

下面是一个UrlType实现示例:

package reflectiveplugin;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.Iterator;
import org.osgi.framework.Bundle;
import org.reflections.vfs.Vfs;
import org.reflections.vfs.Vfs.Dir;
import org.reflections.vfs.Vfs.File;
import org.reflections.vfs.Vfs.UrlType;
import com.google.common.collect.AbstractIterator;
public class BundleUrlType implements UrlType {
    public static final String BUNDLE_PROTOCOL = "bundleresource";
    private final Bundle bundle;
    public BundleUrlType(Bundle bundle) {
        this.bundle = bundle;
    }
    @Override
    public boolean matches(URL url) {
        return BUNDLE_PROTOCOL.equals(url.getProtocol());
    }
    @Override
    public Dir createDir(URL url) {
        return new BundleDir(bundle, url);
    }
    public class BundleDir implements Dir {
        private String path;
        private final Bundle bundle;
        public BundleDir(Bundle bundle, URL url) {
            this(bundle, url.getPath());
        }
        public BundleDir(Bundle bundle, String p) {
            this.bundle = bundle;
            this.path = p;
            if (path.startsWith(BUNDLE_PROTOCOL + ":")) { 
                path = path.substring((BUNDLE_PROTOCOL + ":").length()); 
            }
        }
        @Override
        public String getPath() {
            return path;
        }
        @Override
        public Iterable<File> getFiles() {
            return new Iterable<Vfs.File>() {
                public Iterator<Vfs.File> iterator() {
                    return new AbstractIterator<Vfs.File>() {
                        final Enumeration<URL> entries = bundle.findEntries(path, "*.class", true);
                        protected Vfs.File computeNext() {
                            return entries.hasMoreElements() ? new BundleFile(BundleDir.this, entries.nextElement()) : endOfData();
                        }
                    };
                }
            };
        }
        @Override
        public void close() { }
    }
    public class BundleFile implements File {
        private final BundleDir dir;
        private final String name;
        private final URL url;
        public BundleFile(BundleDir dir, URL url) {
            this.dir = dir;
            this.url = url;
            String path = url.getFile();
            this.name = path.substring(path.lastIndexOf("/") + 1);
        }
        @Override
        public String getName() {
            return name;
        }
        @Override
        public String getRelativePath() {
            return getFullPath().substring(dir.getPath().length());
        }
        @Override
        public String getFullPath() {
            return url.getFile();
        }
        @Override
        public InputStream openInputStream() throws IOException {
            return url.openStream();
        }
    }
}

下面是我在Activator类中创建反射的方法:

private Reflections createReflections(Bundle bundle) {
    Vfs.addDefaultURLTypes(new BundleUrlType(bundle));
    Reflections reflections = new Reflections(new Object[] { "reflectiveplugin.data" });
    return reflections;
}

最后一点非常令人困惑，但仍然很重要:如果你在Eclipse(运行/OSGi框架)中运行插件，你必须将你的类输出目录也添加到Reflections路径模式(即。"bin"或"target/classes")。虽然，对于一个已发布的插件来说，它是不需要的(要构建一个插件/包，请执行"Export"->"可部署的插件和片段")。

Answer 2

只是为了记录以防其他人有同样的问题。这里对Vlad的答案做了一个小修改，以避免必须将输出目录添加到Reflections路径模式中。区别只存在于BundleDir类中。在我所有的测试中，它似乎工作得很好:

public class BundleUrlType implements UrlType {
public static final String BUNDLE_PROTOCOL = "bundleresource";
private final Bundle bundle;
public BundleUrlType(Bundle bundle) {
    this.bundle = bundle;
}
@Override
public Dir createDir(URL url) {
    return new BundleDir(bundle, url);
}
@Override
public boolean matches(URL url) {
    return BUNDLE_PROTOCOL.equals(url.getProtocol());
}

public static class BundleDir implements Dir {
    private String path;
    private final Bundle bundle;
    private static String urlPath(Bundle bundle, URL url) {
        try {
            URL resolvedURL = FileLocator.resolve(url);
            String resolvedURLAsfile = resolvedURL.getFile();
            URL bundleRootURL = bundle.getEntry("/");
            URL resolvedBundleRootURL = FileLocator.resolve(bundleRootURL);
            String resolvedBundleRootURLAsfile = resolvedBundleRootURL.getFile();
            return("/"+resolvedURLAsfile.substring(resolvedBundleRootURLAsfile.length()));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    public BundleDir(Bundle bundle, URL url) {
        //this(bundle, url.getPath());
        this(bundle, urlPath(bundle,url));
    }
    public BundleDir(Bundle bundle, String p) {
        this.bundle = bundle;
        this.path = p;
        if (path.startsWith(BUNDLE_PROTOCOL + ":")) { 
            path = path.substring((BUNDLE_PROTOCOL + ":").length()); 
        }
    }
    @Override
    public String getPath() {
        return path;
    }
    @Override
    public Iterable<File> getFiles() {
        return new Iterable<Vfs.File>() {
            public Iterator<Vfs.File> iterator() {
                return new AbstractIterator<Vfs.File>() {
                    final Enumeration<URL> entries = bundle.findEntries(path, "*.class", true);
                    protected Vfs.File computeNext() {
                        return entries.hasMoreElements() ? new BundleFile(BundleDir.this, entries.nextElement()) : endOfData();
                    }
                };
            }
        };
    }
    @Override
    public void close() { }
}

public static class BundleFile implements File {
    private final BundleDir dir;
    private final String name;
    private final URL url;
    public BundleFile(BundleDir dir, URL url) {
        this.dir = dir;
        this.url = url;
        String path = url.getFile();
        this.name = path.substring(path.lastIndexOf("/") + 1);
    }
    @Override
    public String getName() {
        return name;
    }
    @Override
    public String getRelativePath() {
        return getFullPath().substring(dir.getPath().length());
    }
    @Override
    public String getFullPath() {
        return url.getFile();
    }
    @Override
    public InputStream openInputStream() throws IOException {
        return url.openStream();
    }
}
}

Answer 3

Eclipse是建立在OSGi之上的，你要面对OSGi类加载…这不是一场容易取胜的战斗。

看看Neil Bartlett的这篇文章:OSGi就绪-加载类。你也可以谷歌"OSGi伙伴策略"