Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.ode.il; import java.lang.reflect.Array; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import javax.xml.namespace.QName; import javax.xml.stream.XMLStreamException; import javax.xml.stream.XMLStreamReader; import org.apache.axiom.om.OMAbstractFactory; import org.apache.axiom.om.OMElement; import org.apache.axiom.om.OMFactory; import org.apache.axiom.om.OMNamespace; import org.apache.axiom.om.impl.builder.StAXOMBuilder; import org.apache.axiom.om.impl.dom.NamespaceImpl; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.ode.bpel.pmapi.ProcessInfoCustomizer; import org.apache.xmlbeans.XmlObject; import org.w3c.dom.Node; /** * Dynamic invocation handler for XML-based service; uses RPC message format conventions to dispatch * invocation based on top-level element name (e.g. method name) and sub-elements (e.g. parameters). */ public class DynamicService<T> { private final Log __log = LogFactory.getLog(getClass()); static final OMFactory OM = OMAbstractFactory.getOMFactory(); T _service; Class<T> _clazz; @SuppressWarnings("unchecked") public DynamicService(T service) { _clazz = (Class<T>) service.getClass(); _service = service; } public OMElement invoke(String operation, OMElement payload) { if (__log.isDebugEnabled()) __log.debug("Invoke: operation " + operation + " on " + _clazz + ":\n" + payload); String methodName = operation; try { Method invokedMethod = findMethod(methodName); Object[] params = extractParams(invokedMethod, payload); Object result = invokedMethod.invoke(_service, params); OMElement response = null; if (result != null) { if (__log.isDebugEnabled()) __log.debug("Invoke: operation " + operation + " on " + _clazz + ":\n" + payload + "\nOM:" + OM + " namespace:" + payload.getNamespace()); response = OM.createOMElement( new QName((payload.getNamespace() == null ? "" : payload.getNamespace().getNamespaceURI()), methodName + "Response")); OMElement parts = convertToOM(result); parts = stripNamespace(parts); response.addChild(parts); } if (__log.isDebugEnabled()) { __log.debug("Response: operation " + operation + " on " + _clazz + ":\n" + response); } return response; } catch (IllegalAccessException e) { throw new RuntimeException("Couldn't invoke method named " + methodName + " in management interface!", e); } catch (InvocationTargetException e) { throw new RuntimeException("Invocation of method " + methodName + " in management interface failed: " + e.getTargetException().getMessage(), e.getTargetException()); } } @SuppressWarnings("unchecked") private Object[] extractParams(Method method, OMElement omElmt) { Class<?>[] paramTypes = method.getParameterTypes(); Object[] params = new Object[method.getParameterTypes().length]; Iterator<OMElement> omChildren = (Iterator<OMElement>) omElmt.getChildElements(); int paramIdx = 0; for (Class<?> paramClass : paramTypes) { OMElement omchild = (OMElement) omChildren.next(); if (__log.isDebugEnabled()) { __log.debug("Extracting param " + paramClass + " from " + omchild); } params[paramIdx++] = convertFromOM(paramClass, omchild); } return params; } @SuppressWarnings("unchecked") private static Object convertFromOM(Class<?> clazz, OMElement elmt) { // Here comes the nasty code... if (elmt == null || elmt.getText().length() == 0 && !elmt.getChildElements().hasNext()) return null; else if (clazz.equals(String.class)) { return elmt.getText(); } else if (clazz.equals(Boolean.class) || clazz.equals(Boolean.TYPE)) { return (elmt.getText().equals("true") || elmt.getText().equals("yes")) ? Boolean.TRUE : Boolean.FALSE; } else if (clazz.equals(QName.class)) { // The getTextAsQName is buggy, it sometimes return the full text without extracting namespace return OMUtils.getTextAsQName(elmt); } else if (clazz.equals(ProcessInfoCustomizer.class)) { return new ProcessInfoCustomizer(elmt.getText()); } else if (Node.class.isAssignableFrom(clazz)) { return OMUtils.toDOM(elmt.getFirstElement()); } else if (clazz.equals(Long.TYPE) || clazz.equals(Long.class)) { return Long.parseLong(elmt.getText()); } else if (clazz.equals(Integer.TYPE) || clazz.equals(Integer.class)) { return Integer.parseInt(elmt.getText()); } else if (clazz.isArray()) { ArrayList<Object> alist = new ArrayList<Object>(); Iterator<OMElement> children = elmt.getChildElements(); Class<?> targetClazz = clazz.getComponentType(); while (children.hasNext()) alist.add(parseType(targetClazz, ((OMElement) children.next()).getText())); return alist.toArray((Object[]) Array.newInstance(targetClazz, alist.size())); } else if (XmlObject.class.isAssignableFrom(clazz)) { try { Class beanFactory = clazz.forName(clazz.getCanonicalName() + "$Factory"); elmt.setNamespace(elmt.declareDefaultNamespace("")); elmt.setLocalName("xml-fragment"); return beanFactory.getMethod("parse", XMLStreamReader.class).invoke(null, elmt.getXMLStreamReaderWithoutCaching()); } catch (ClassNotFoundException e) { throw new RuntimeException( "Couldn't find class " + clazz.getCanonicalName() + ".Factory to instantiate xml bean", e); } catch (IllegalAccessException e) { throw new RuntimeException( "Couldn't access class " + clazz.getCanonicalName() + ".Factory to instantiate xml bean", e); } catch (InvocationTargetException e) { throw new RuntimeException("Couldn't access xml bean parse method on class " + clazz.getCanonicalName() + ".Factory " + "to instantiate xml bean", e); } catch (NoSuchMethodException e) { throw new RuntimeException("Couldn't find xml bean parse method on class " + clazz.getCanonicalName() + ".Factory " + "to instantiate xml bean", e); } } else throw new RuntimeException( "Couldn't use element " + elmt + " to obtain a management method parameter."); } @SuppressWarnings("unchecked") private static OMElement convertToOM(Object obj) { if (obj instanceof XmlObject) { try { return new StAXOMBuilder(((XmlObject) obj).newInputStream()).getDocumentElement(); } catch (XMLStreamException e) { throw new RuntimeException("Couldn't serialize result to an outgoing messages.", e); } } else if (obj instanceof List) { OMElement listElmt = OM.createOMElement("list", null); for (Object stuff : ((List) obj)) { OMElement stuffElmt = OM.createOMElement("element", null); stuffElmt.setText(stuff.toString()); listElmt.addChild(stuffElmt); } return listElmt; } else throw new RuntimeException("Couldn't convert object " + obj + " into a response element."); } @SuppressWarnings("unchecked") private static OMElement stripNamespace(OMElement element) { OMElement parent = OM.createOMElement(new QName("", element.getLocalName())); Iterator<OMElement> iter = (Iterator<OMElement>) element.getChildElements(); while (iter.hasNext()) { OMElement child = iter.next(); child = child.cloneOMElement(); parent.addChild(child); } return parent; } private Method findMethod(String methodName) { for (Method method : _clazz.getMethods()) { if (method.getName().equals(methodName)) return method; } throw new RuntimeException( "Couldn't find any method named " + methodName + " in interface " + _clazz.getName()); } private static Object parseType(Class<?> clazz, String str) { if (clazz.equals(Integer.class)) return Integer.valueOf(str); if (clazz.equals(Float.class)) return Integer.valueOf(str); if (clazz.equals(String.class)) return str; return null; } }