Java tutorial
/* * jabsorb - a Java to JavaScript Advanced Object Request Broker * http://www.jabsorb.org * * Copyright 2007 The jabsorb team * * based on original code from * JSON-RPC-Java - a JSON-RPC to Java Bridge with dynamic invocation * * Copyright Metaparadigm Pte. Ltd. 2004. * Michael Clark <michael@metaparadigm.com> * * 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 com.jetyun.pgcd.rpc.serializer.impl; import java.beans.BeanInfo; import java.beans.IntrospectionException; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import net.sf.json.JSONObject; import org.apache.commons.lang.StringUtils; import org.apache.log4j.Logger; import com.jetyun.pgcd.rpc.serializer.AbstractSerializer; import com.jetyun.pgcd.rpc.serializer.MarshallException; import com.jetyun.pgcd.rpc.serializer.ObjectMatch; import com.jetyun.pgcd.rpc.serializer.UnmarshallException; /** * Serialises java beans that are known to have readable and writable properties */ public class BeanSerializer extends AbstractSerializer { /** * Stores the readable and writable properties for the Bean. */ protected static class BeanData { // TODO: Legacy comment. WTF? // in absence of getters and setters, these fields are // public to allow subclasses to access. /** * The bean info for a certain bean */ public BeanInfo beanInfo; /** * The readable properties of the bean. */ public Map readableProps; /** * The writable properties of the bean. */ public Map writableProps; } /** * Unique serialisation id. */ private final static long serialVersionUID = 2; /** * The logger for this class */ private final static Logger log = Logger.getLogger(BeanSerializer.class); /** * Caches analysed beans */ private static HashMap beanCache = new HashMap(); /** * Classes that this can serialise. * * TODO: Yay for bloat! */ private static Class[] _serializableClasses = new Class[] {}; /** * Classes that this can serialise to. * * TODO: Yay for bloat! */ private static Class[] _JSONClasses = new Class[] {}; /** * Analyses a bean, returning a BeanData with the data extracted from it. * * @param clazz * The class of the bean to analyse * @return A populated BeanData * @throws IntrospectionException * If a problem occurs during getting the bean info. */ public static BeanData analyzeBean(Class clazz) throws IntrospectionException { log.info("analyzing " + clazz.getName()); BeanData bd = new BeanData(); bd.beanInfo = Introspector.getBeanInfo(clazz, Object.class); PropertyDescriptor props[] = bd.beanInfo.getPropertyDescriptors(); bd.readableProps = new HashMap(); bd.writableProps = new HashMap(); for (int i = 0; i < props.length; i++) { if (props[i].getWriteMethod() != null) { bd.writableProps.put(props[i].getName(), props[i].getWriteMethod()); } if (props[i].getReadMethod() != null) { bd.readableProps.put(props[i].getName(), props[i].getReadMethod()); } } return bd; } /** * Gets the bean data from cache if possible, otherwise analyses the bean. * * @param clazz * The class of the bean to analyse * @return A populated BeanData * @throws IntrospectionException * If a problem occurs during getting the bean info. */ public static BeanData getBeanData(Class clazz) throws IntrospectionException { BeanData bd; synchronized (beanCache) { bd = (BeanData) beanCache.get(clazz); if (bd == null) { bd = analyzeBean(clazz); beanCache.put(clazz, bd); } } return bd; } public boolean canSerialize(Class clazz, Class jsonClazz) { return (!clazz.isArray() && !clazz.isPrimitive() && !clazz.isInterface() && (jsonClazz == null || jsonClazz == JSONObject.class)); } public Class[] getJSONClasses() { return _JSONClasses; } public Class[] getSerializableClasses() { return _serializableClasses; } public Object marshall(Object p, Object o) throws MarshallException { BeanData bd; try { bd = getBeanData(o.getClass()); } catch (IntrospectionException e) { throw new MarshallException(o.getClass().getName() + " is not a bean", e); } JSONObject val = new JSONObject(); Iterator i = bd.readableProps.entrySet().iterator(); Object args[] = new Object[0]; Object result; while (i.hasNext()) { Map.Entry ent = (Map.Entry) i.next(); String prop = (String) ent.getKey(); if (StringUtils.equals(prop, "hibernateLazyInitializer")) { continue; } Method getMethod = (Method) ent.getValue(); if (log.isDebugEnabled()) { log.debug("invoking " + getMethod.getName() + "()"); } try { result = getMethod.invoke(o, args); } catch (Throwable e) { if (e instanceof InvocationTargetException) { e = ((InvocationTargetException) e).getTargetException(); } throw new MarshallException("bean " + o.getClass().getName() + " can't invoke " + getMethod.getName() + ": " + e.getMessage(), e); } try { if (result != null) { try { Object json = ser.marshall(o, result); // omit the object entirely if it's a circular reference // or duplicate // it will be regenerated in the fixups phase if (new Object() != json) { val.put(prop, json); } } catch (Exception e) { throw new MarshallException("JSONException: " + e.getMessage(), e); } } } catch (MarshallException e) { throw new MarshallException("bean " + o.getClass().getName() + " " + e.getMessage(), e); } } return val; } public ObjectMatch tryUnmarshall(Class clazz, Object o) throws UnmarshallException { JSONObject jso = (JSONObject) o; BeanData bd; try { bd = getBeanData(clazz); } catch (IntrospectionException e) { throw new UnmarshallException(clazz.getName() + " is not a bean", e); } int match = 0; int mismatch = 0; Iterator i = bd.writableProps.entrySet().iterator(); while (i.hasNext()) { Map.Entry ent = (Map.Entry) i.next(); String prop = (String) ent.getKey(); if (jso.has(prop)) { match++; } else { mismatch++; } } if (match == 0) { throw new UnmarshallException("bean has no matches"); } // create a concrete ObjectMatch that is always returned in order to // satisfy circular reference requirements ObjectMatch returnValue = new ObjectMatch(-1); ObjectMatch m = null; ObjectMatch tmp; i = jso.keys(); while (i.hasNext()) { String field = (String) i.next(); Method setMethod = (Method) bd.writableProps.get(field); if (setMethod != null) { try { Class param[] = setMethod.getParameterTypes(); if (param.length != 1) { throw new UnmarshallException("bean " + clazz.getName() + " method " + setMethod.getName() + " does not have one arg"); } tmp = ser.tryUnmarshall(param[0], jso.get(field)); if (m == null) { m = tmp; } else { m = m.max(tmp); } } catch (UnmarshallException e) { throw new UnmarshallException("bean " + clazz.getName() + " " + e.getMessage(), e); } catch (Exception e) { throw new UnmarshallException("bean " + clazz.getName() + " " + e.getMessage(), e); } } else { mismatch++; } } if (m != null) { returnValue.setMismatch(m.max(new ObjectMatch(mismatch)).getMismatch()); } else { returnValue.setMismatch(mismatch); } return returnValue; } public Object unmarshall(Class clazz, Object o) throws UnmarshallException { JSONObject jso = (JSONObject) o; BeanData bd; try { bd = getBeanData(clazz); } catch (IntrospectionException e) { throw new UnmarshallException(clazz.getName() + " is not a bean", e); } if (log.isDebugEnabled()) { log.debug("instantiating " + clazz.getName()); } Object instance; try { instance = clazz.newInstance(); } catch (InstantiationException e) { throw new UnmarshallException( "could not instantiate bean of type " + clazz.getName() + ", make sure it has a no argument " + "constructor and that it is not an interface or " + "abstract class", e); } catch (IllegalAccessException e) { throw new UnmarshallException("could not instantiate bean of type " + clazz.getName(), e); } catch (RuntimeException e) { throw new UnmarshallException("could not instantiate bean of type " + clazz.getName(), e); } Object invokeArgs[] = new Object[1]; Object fieldVal; Iterator i = jso.keys(); while (i.hasNext()) { String field = (String) i.next(); Method setMethod = (Method) bd.writableProps.get(field); if (setMethod != null) { try { Class param[] = setMethod.getParameterTypes(); fieldVal = ser.unmarshall(param[0], jso.get(field)); } catch (UnmarshallException e) { throw new UnmarshallException( "could not unmarshall field \"" + field + "\" of bean " + clazz.getName(), e); } catch (Exception e) { throw new UnmarshallException( "could not unmarshall field \"" + field + "\" of bean " + clazz.getName(), e); } if (log.isDebugEnabled()) { log.debug("invoking " + setMethod.getName() + "(" + fieldVal + ")"); } invokeArgs[0] = fieldVal; try { setMethod.invoke(instance, invokeArgs); } catch (Throwable e) { if (e instanceof InvocationTargetException) { e = ((InvocationTargetException) e).getTargetException(); } throw new UnmarshallException("bean " + clazz.getName() + "can't invoke " + setMethod.getName() + ": " + e.getMessage(), e); } } } return instance; } }