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Diffstat (limited to 'libjava/classpath/javax/management/openmbean/CompositeDataInvocationHandler.java')
| -rw-r--r-- | libjava/classpath/javax/management/openmbean/CompositeDataInvocationHandler.java | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/libjava/classpath/javax/management/openmbean/CompositeDataInvocationHandler.java b/libjava/classpath/javax/management/openmbean/CompositeDataInvocationHandler.java new file mode 100644 index 00000000000..170ec32c7a9 --- /dev/null +++ b/libjava/classpath/javax/management/openmbean/CompositeDataInvocationHandler.java @@ -0,0 +1,190 @@ +/* CompositeDataInvocationHandler.java - Pseudo-accessors for CompositeData. + Copyright (C) 2007 Free Software Foundation + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package javax.management.openmbean; + +import java.lang.reflect.InvocationHandler; +import java.lang.reflect.Method; +import java.lang.reflect.Proxy; + +/** + * <p> + * Provides an {@link java.lang.reflect.InvocationHandler} which + * implements a series of accessor methods (those beginning with + * {@code "get"} or {@code "is"}) using the content of a + * {@link CompositeData} object. An instance of {@link CompositeData} + * consists of a series of key-value mappings. This handler assumes + * these keys to be the names of attributes, and thus provides + * accessor methods by returning the associated value. + * </p> + * <p> + * As an example, consider the following interface: + * </p> + * <pre> + * public interface Person + * { + * public String getName(); + * public Date getBirthday(); + * } + * </pre> + * <p> + * This specifies two accessor methods for retrieving the attributes, + * {@code name} and {@code birthday}. An implementation of this interface + * can be provided by creating an instance of this class, using a + * {@link CompositeData} object with appropriate key-value mappings + * (e.g. "name" => "Fred", "birthday" => 30/06/1974), and then passing + * that to {@link java.lang.reflect.Proxy#newProxyInstance} along with + * the interface itself. The invocation handler implements the methods + * by calling {@link CompositeData#get(String)} with the appropriate key. + * </p> + * <p> + * The attribute name is derived by taking the remainder of the method + * name following {@code "get"}. If the first letter of this substring + * is uppercase, then two attempts are made to retrieve the attribute + * from the {@link CompositeData} instance: one using the original substring, + * and one with the first letter changed to its lower-case equivalent. + * If the first letter is lowercase, only the exact substring is used. + * </p> + * <p> + * An {@link Object#equals(Object)} implementation is provided. This returns + * true if the argument is a proxy with a {@link CompositeDataInvocationHandler} + * using an equivalent {@link CompositeData} instance. {@link Object#hashCode()} + * is also defined so as to match this implementation and give equivalent instances + * the same hashcode. + * </p> + * + * @author Andrew John Hughes (gnu_andrew@member.fsf.org) + * @since 1.6 + */ +public class CompositeDataInvocationHandler + implements InvocationHandler +{ + + /** + * The {@link CompositeData} providing the key-value mappings. + */ + private CompositeData data; + + /** + * Constructs a new {@link CompositeDataInvocationHandler} + * with the specified {@link CompositeData} instance. + * + * @param data the {@link CompositeData} instance to use. + * @throws IllegalArgumentException if {@code data} is {@code null}. + */ + public CompositeDataInvocationHandler(CompositeData data) + { + if (data == null) + throw new IllegalArgumentException("The CompositeData instance " + + "must be non-null."); + this.data = data; + } + + /** + * Returns the {@link CompositeData} instance which provides + * the key-value mappings for this instance. This is never + * {@code null}. + * + * @return the {@link CompositeData} instance. + */ + public CompositeData getCompositeData() + { + return data; + } + + /** + * Called by the proxy class whenever a method is called. The + * handler only deals with accessor methods (beginning with + * {@code "get"} or {@code "is"}), {@code equals}, and + * {@code "hashCode"}. Accessor methods are implemented by + * returning the appropriate value from the {@link CompositeData} + * instance, while {@code equals} and {@code hashCode} allow + * two proxies with a {@link CompositeDataInvocationHandler} using + * the same {@link CompositeData} instance to be classified + * as equivalent. + * + * @param proxy the proxy on which the method was called. + * @param method the method which was called. + * @param args the arguments supplied to the method. + * @return the return value from the method. + * @throws Throwable if an exception is thrown in the process. + */ + public Object invoke(Object proxy, Method method, Object[] args) + throws Throwable + { + String mName = method.getName(); + if (mName.equals("equals")) + { + if (args[0] instanceof Proxy) + { + InvocationHandler h = Proxy.getInvocationHandler(args[0]); + if (h instanceof CompositeDataInvocationHandler) + return data.equals(((CompositeDataInvocationHandler) + h).getCompositeData()); + } + return false; + } + if (mName.equals("hashCode")) + { + return data.hashCode(); + } + String attrib = null; + if (mName.startsWith("get")) + attrib = mName.substring(3); + else if (mName.startsWith("is")) + attrib = mName.substring(2); + if (attrib == null) + throw new NoSuchMethodException(mName + " is not an accessor."); + if (!data.containsKey(attrib)) + { + if (Character.isLowerCase(attrib.charAt(0))) + throw new NoSuchMethodException("The attribute " + + attrib + " is not available " + + "in the given CompositeData " + + "object"); + attrib = Character.toLowerCase(attrib.charAt(0)) + + attrib.substring(1); + if (!data.containsKey(attrib)) + throw new NoSuchMethodException("The attribute " + + attrib + " is not available " + + "in the given CompositeData " + + "object"); + } + return data.get(attrib); + } + +} |