Java tutorial
/* * Copyright 2008,2009 Tim Jansen * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package sg.atom.core.actor.internal.codegenerator; import java.lang.reflect.GenericArrayType; import java.lang.reflect.Method; import java.lang.reflect.ParameterizedType; import java.lang.reflect.TypeVariable; import java.lang.reflect.WildcardType; import org.objectweb.asm.Type; import org.objectweb.asm.signature.SignatureWriter; /** * Helpers for extracting signatures from generic types. */ public class GenericTypeHelper { /** * Writes the signature of the given type to the SignatureWriter. * * @param sw the signature writer to use * @param type the Type to analyze */ @SuppressWarnings("unchecked") public static void writeSignature(SignatureWriter sw, java.lang.reflect.Type type) { if (type instanceof Class) { Class c = (Class) type; if (c.isPrimitive()) { sw.visitBaseType(Type.getDescriptor(c).charAt(0)); } else { if (c.getDeclaringClass() != null) { sw.visitInnerClassType(Type.getInternalName(c.getDeclaringClass())); } sw.visitClassType(Type.getInternalName(c)); } } else if (type instanceof GenericArrayType) { GenericArrayType gat = (GenericArrayType) type; sw.visitArrayType(); writeSignature(sw, gat.getGenericComponentType()); } else if (type instanceof ParameterizedType) { ParameterizedType pt = (ParameterizedType) type; writeSignature(sw, pt.getRawType()); for (java.lang.reflect.Type t : pt.getActualTypeArguments()) { sw.visitTypeArgument(); writeSignature(sw, t); } } else if (type instanceof TypeVariable) { TypeVariable<?> tv = (TypeVariable<?>) type; sw.visitTypeVariable(tv.getName()); } else if (type instanceof WildcardType) { if (((WildcardType) type).getLowerBounds().length + ((WildcardType) type).getUpperBounds().length == 0) { sw.visitTypeArgument(); } else { for (java.lang.reflect.Type t : ((WildcardType) type).getLowerBounds()) { sw.visitTypeArgument('+'); writeSignature(sw, t); } for (java.lang.reflect.Type t : ((WildcardType) type).getUpperBounds()) { sw.visitTypeArgument('-'); writeSignature(sw, t); } } } else { throw new RuntimeException("Unsupported type " + type); } sw.visitEnd(); } /** * Converts the given Type into a JVM signature. * * @param type the Type to analyze * @return the resulting signature */ public static String getSignature(java.lang.reflect.Type type) { SignatureWriter sw = new SignatureWriter(); writeSignature(sw, type); return sw.toString(); } /** * Converts the given Type into a JVM signature if it is a generic type. * Otherwise it returns null. * * @param type the Type to analyze * @return the resulting signature, or null if not generic */ public static String getSignatureIfGeneric(java.lang.reflect.Type type) { if (type instanceof Class) { return null; } return getSignature(type); } /** * Converts the given Method into a JVM signature. * * @param method the method to analyze * @return the resulting signature */ public static String getSignature(Method method) { StringBuilder sb = new StringBuilder(); sb.append('('); for (java.lang.reflect.Type t : method.getGenericParameterTypes()) { sb.append(getSignature(t)); } sb.append(')'); sb.append(getSignature(method.getGenericReturnType())); return sb.toString(); } }