Java tutorial
/* * Copyright 2010-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/apache2.0 * * or in the "license" file accompanying this file. This file 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 com.amazonaws.hal.client; import com.amazonaws.hal.Link; import com.amazonaws.hal.ResourceInfo; import com.amazonaws.hal.UriValue; import com.amazonaws.hal.UriVariable; import com.damnhandy.uri.template.MalformedUriTemplateException; import com.damnhandy.uri.template.UriTemplate; import com.damnhandy.uri.template.VariableExpansionException; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.lang.annotation.Annotation; import java.lang.reflect.InvocationHandler; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.lang.reflect.Type; import java.util.List; import java.util.Map; import static com.amazonaws.hal.client.ConversionUtil.convert; import static com.amazonaws.hal.client.ConversionUtil.getCollectionType; import static com.amazonaws.hal.client.ConversionUtil.getPropertyName; class HalResourceInvocationHandler implements InvocationHandler { //------------------------------------------------------------- // Variables - Private //------------------------------------------------------------- private HalResource halResource; private String resourcePath; private HalClient halClient; private static Log log = LogFactory.getLog(HalResourceInvocationHandler.class); private static final Object[] EMPTY_ARGS = new Object[0]; //------------------------------------------------------------- // Constructors //------------------------------------------------------------- HalResourceInvocationHandler(HalResource halResource, String resourcePath, HalClient halClient) { this.halResource = halResource; this.resourcePath = resourcePath; this.halClient = halClient; } //------------------------------------------------------------- // Implementation - InvocationHandler //------------------------------------------------------------- /** */ public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if (halResource == null || !halResource.isDefined()) { halResource = halClient.getHalResource(resourcePath); } try { Method resourceInfoMethod = ResourceInfo.class.getMethod(method.getName(), method.getParameterTypes()); return resourceInfoMethod.invoke(halResource, args); } catch (NoSuchMethodException ignore) { // If the method is not defined in ResourceInfo, we handle it below } catch (InvocationTargetException e) { throw e.getTargetException(); } Link link; if ((link = method.getAnnotation(Link.class)) != null) { switch (link.method()) { case GET: if (List.class.isAssignableFrom(method.getReturnType())) { //noinspection unchecked return new HalLinkList(halResource, link.relation(), (Class) getCollectionType(method.getGenericReturnType(), 0, ResourceInfo.class), halClient); } else if (Map.class.isAssignableFrom(method.getReturnType())) { //noinspection unchecked return new HalLinkMap(halResource, link.relation(), link.keyField(), (Class) getCollectionType(method.getGenericReturnType(), 1, ResourceInfo.class), halClient); } else { return halClient.getResource(halResource, method.getReturnType(), getRelationHref(link, args == null ? EMPTY_ARGS : args, method.getParameterAnnotations()), false); } case POST: if (args == null) { throw new IllegalArgumentException("POST operations require a representation argument."); } return halClient.postResource(method.getReturnType(), getRelationHref(link, args, method.getParameterAnnotations()), args[0]); case PUT: if (args == null) { throw new IllegalArgumentException("PUT operations require a representation argument."); } return halClient.putResource(method.getReturnType(), getRelationHref(link, args, method.getParameterAnnotations()), args[0]); case DELETE: return halClient.deleteResource(method.getReturnType(), getRelationHref(link, args == null ? EMPTY_ARGS : args, method.getParameterAnnotations())); default: throw new UnsupportedOperationException("Unexpected HTTP method: " + link.method()); } } else if (method.getName().startsWith("get")) { String propertyName = getPropertyName(method.getName()); Object property = halResource.getProperty(propertyName); Type returnType = method.getGenericReturnType(); // When a value is accessed, it's intended type can either be a // class or some other type (like a ParameterizedType). // // If the target type is a class and the value is of that type, // we return it. If the value is not of that type, we convert // it and store the converted value (trusting it was converted // properly) back to the backing store. // // If the target type is not a class, it may be ParameterizedType // like List<T> or Map<K, V>. We check if the value is already // a converting type and if so, we return it. If the value is // not, we convert it and if it's now a converting type, we store // the new value in the backing store. if (returnType instanceof Class) { if (!((Class) returnType).isInstance(property)) { property = convert(returnType, property); //noinspection unchecked halResource.addProperty(propertyName, property); } } else { if (!(property instanceof ConvertingMap) && !(property instanceof ConvertingList)) { property = convert(returnType, property); if (property instanceof ConvertingMap || property instanceof ConvertingList) { //noinspection unchecked halResource.addProperty(propertyName, property); } } } return property; } else if (method.getName().equals("toString") && args == null) { return resourcePath; } else if (method.getName().equals("equals") && args != null && args.length == 1) { HalResourceInvocationHandler other; try { other = (HalResourceInvocationHandler) Proxy.getInvocationHandler(args[0]); } catch (IllegalArgumentException e) { // argument is not a proxy return false; } catch (ClassCastException e) { // argument is the wrong type of proxy return false; } return resourcePath.equals(other.resourcePath); } else if (method.getName().equals("hashCode") && args == null) { return resourcePath.hashCode(); } throw new UnsupportedOperationException("Don't know how to handle '" + method.getName() + "'"); } //------------------------------------------------------------- // Methods - Package //------------------------------------------------------------- /** * The resource this InvocationHandler manages has been updated or deemed stale. * * @param halResource The new HalResource or null if the resource was stale and the new value is not yet known. */ void resourceUpdated(HalResource halResource) { this.halResource = halResource; } //------------------------------------------------------------- // Methods - Private //------------------------------------------------------------- private String getRelationHref(Link link, Object[] args, Annotation[][] parameterAnnotations) { HalLink halLink = halResource.getLink(link.relation()); if (halLink == null) { throw new UnsupportedOperationException(link.relation()); } if (halLink.getDeprecation() != null) { log.warn("Link '" + link + "' has been deprecated: " + halLink.getDeprecation()); } String href; if (halLink.isTemplated()) { try { UriTemplate uriTemplate = UriTemplate.fromTemplate(halLink.getHref()); for (int i = 0; i < args.length; i++) { for (Annotation annotation : parameterAnnotations[i]) { if (annotation.annotationType() == UriVariable.class) { UriVariable uriVariable = (UriVariable) annotation; assignTemplateValue(uriTemplate, uriVariable.name(), args[i]); } } } for (int i = 0; i < link.uriValues().length; i++) { UriValue uriValue = link.uriValues()[i]; assignTemplateValue(uriTemplate, uriValue.name(), uriValue.value()); } href = uriTemplate.expand(); } catch (MalformedUriTemplateException | VariableExpansionException e) { throw new RuntimeException(e); } } else { href = halLink.getHref(); } return href; } private void assignTemplateValue(UriTemplate uriTemplate, String variableName, Object value) { if (uriTemplate.hasVariable(variableName)) { log.warn(String.format("Duplicate assignment to variable %s. Current = '%s', skipping new value '%s'.", variableName, uriTemplate.get(variableName), value)); return; } uriTemplate.set(variableName, value); } }