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Diffstat (limited to 'src/core/lombok/core/SpiLoadUtil.java')
-rw-r--r-- | src/core/lombok/core/SpiLoadUtil.java | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/core/lombok/core/SpiLoadUtil.java b/src/core/lombok/core/SpiLoadUtil.java new file mode 100644 index 00000000..0a97af7e --- /dev/null +++ b/src/core/lombok/core/SpiLoadUtil.java @@ -0,0 +1,164 @@ +/* + * Copyright © 2009 Reinier Zwitserloot and Roel Spilker. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ +package lombok.core; + +import java.io.BufferedReader; +import java.io.IOException; +import java.io.InputStream; +import java.io.InputStreamReader; +import java.lang.annotation.Annotation; +import java.lang.reflect.ParameterizedType; +import java.lang.reflect.Type; +import java.net.URL; +import java.util.Collection; +import java.util.Enumeration; +import java.util.Iterator; +import java.util.LinkedHashSet; +import java.util.Set; + +import lombok.Lombok; + +/** + * The java core libraries have a SPI discovery system, but it works only in Java 1.6 and up. For at least Eclipse, + * lombok actually works in java 1.5, so we've rolled our own SPI discovery system. + * + * It is not API compatible with {@code ServiceLoader}. + * + * @see java.util.ServiceLoader + */ +public class SpiLoadUtil { + private SpiLoadUtil() { + //Prevent instantiation + } + + /** + * Returns an iterator of instances that, at least according to the spi discovery file, are implementations + * of the stated class. + * + * Like ServiceLoader, each listed class is turned into an instance by calling the public no-args constructor. + * + * Convenience method that calls the more elaborate {@link #findServices(Class, ClassLoader)} method with + * this {@link java.lang.Thread}'s context class loader as {@code ClassLoader}. + * + * @param target class to find implementations for. + */ + public static <C> Iterable<C> findServices(Class<C> target) throws IOException { + return findServices(target, Thread.currentThread().getContextClassLoader()); + } + + /** + * Returns an iterator of class objects that, at least according to the spi discovery file, are implementations + * of the stated class. + * + * Like ServiceLoader, each listed class is turned into an instance by calling the public no-args constructor. + * + * @param target class to find implementations for. + * @param loader The classloader object to use to both the spi discovery files, as well as the loader to use + * to make the returned instances. + */ + public static <C> Iterable<C> findServices(final Class<C> target, final ClassLoader loader) throws IOException { + Enumeration<URL> resources = loader.getResources("META-INF/services/" + target.getName()); + final Set<String> entries = new LinkedHashSet<String>(); + while (resources.hasMoreElements()) { + URL url = resources.nextElement(); + readServicesFromUrl(entries, url); + } + + final Iterator<String> names = entries.iterator(); + return new Iterable<C> () { + @Override public Iterator<C> iterator() { + return new Iterator<C>() { + @Override public boolean hasNext() { + return names.hasNext(); + } + + @Override public C next() { + try { + return target.cast(Class.forName(names.next(), true, loader).newInstance()); + } catch (Throwable t) { + throw Lombok.sneakyThrow(t); + } + } + + @Override public void remove() { + throw new UnsupportedOperationException(); + } + }; + } + }; + } + + private static void readServicesFromUrl(Collection<String> list, URL url) throws IOException { + InputStream in = url.openStream(); + try { + if (in == null) return; + BufferedReader r = new BufferedReader(new InputStreamReader(in, "UTF-8")); + while (true) { + String line = r.readLine(); + if (line == null) break; + int idx = line.indexOf('#'); + if (idx != -1) line = line.substring(0, idx); + line = line.trim(); + if (line.length() == 0) continue; + list.add(line); + } + } finally { + try { + if (in != null) in.close(); + } catch (Throwable ignore) {} + } + } + + /** + * This method will find the @{code T} in {@code public class Foo extends BaseType<T>}. + * + * It returns an annotation type because it is used exclusively to figure out which annotations are + * being handled by {@link lombok.eclipse.EclipseAnnotationHandler} and {@link lombok.javac.JavacAnnotationHandler}. + */ + @SuppressWarnings("unchecked") + public static Class<? extends Annotation> findAnnotationClass(Class<?> c, Class<?> base) { + if (c == Object.class || c == null) return null; + for (Type iface : c.getGenericInterfaces()) { + if (iface instanceof ParameterizedType) { + ParameterizedType p = (ParameterizedType)iface; + if (!base.equals(p.getRawType())) continue; + Type target = p.getActualTypeArguments()[0]; + if (target instanceof Class<?>) { + if (Annotation.class.isAssignableFrom((Class<?>) target)) { + return (Class<? extends Annotation>) target; + } + } + + throw new ClassCastException("Not an annotation type: " + target); + } + } + + Class<? extends Annotation> potential = findAnnotationClass(c.getSuperclass(), base); + if (potential != null) return potential; + for (Class<?> iface : c.getInterfaces()) { + potential = findAnnotationClass(iface, base); + if (potential != null) return potential; + } + + return null; + } +} |