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.camel.component.bean; import java.lang.annotation.Annotation; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.lang.reflect.Proxy; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.Comparator; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import org.apache.camel.Attachments; import org.apache.camel.Body; import org.apache.camel.CamelContext; import org.apache.camel.Exchange; import org.apache.camel.ExchangeException; import org.apache.camel.Expression; import org.apache.camel.Handler; import org.apache.camel.Header; import org.apache.camel.Headers; import org.apache.camel.Message; import org.apache.camel.OutHeaders; import org.apache.camel.Properties; import org.apache.camel.Property; import org.apache.camel.builder.ExpressionBuilder; import org.apache.camel.language.LanguageAnnotation; import org.apache.camel.spi.Registry; import org.apache.camel.util.CastUtils; import org.apache.camel.util.IntrospectionSupport; import org.apache.camel.util.ObjectHelper; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import static org.apache.camel.util.ExchangeHelper.convertToType; /** * Represents the metadata about a bean type created via a combination of * introspection and annotations together with some useful sensible defaults * * @version $Revision$ */ public class BeanInfo { private static final transient Log LOG = LogFactory.getLog(BeanInfo.class); private static final String CGLIB_CLASS_SEPARATOR = "$$"; private static final List<Method> EXCLUDED_METHODS = new ArrayList<Method>(); private final CamelContext camelContext; private final Class<?> type; private final ParameterMappingStrategy strategy; private final Map<String, List<MethodInfo>> operations = new ConcurrentHashMap<String, List<MethodInfo>>(); private final List<MethodInfo> operationsWithBody = new ArrayList<MethodInfo>(); private final List<MethodInfo> operationsWithCustomAnnotation = new ArrayList<MethodInfo>(); private final List<MethodInfo> operationsWithHandlerAnnotation = new ArrayList<MethodInfo>(); private final Map<Method, MethodInfo> methodMap = new ConcurrentHashMap<Method, MethodInfo>(); private MethodInfo defaultMethod; private BeanInfo superBeanInfo; static { // exclude all java.lang.Object methods as we dont want to invoke them EXCLUDED_METHODS.addAll(Arrays.asList(Object.class.getMethods())); // exclude all java.lang.reflect.Proxy methods as we dont want to invoke them EXCLUDED_METHODS.addAll(Arrays.asList(Proxy.class.getMethods())); } public BeanInfo(CamelContext camelContext, Class<?> type) { this(camelContext, type, createParameterMappingStrategy(camelContext)); } public BeanInfo(CamelContext camelContext, Class<?> type, ParameterMappingStrategy strategy) { this.camelContext = camelContext; this.type = type; this.strategy = strategy; introspect(getType()); // if there are only 1 method with 1 operation then select it as a default/fallback method if (operations.size() == 1) { List<MethodInfo> methods = operations.values().iterator().next(); if (methods.size() == 1) { defaultMethod = methods.get(0); } } } public Class<?> getType() { return type; } public CamelContext getCamelContext() { return camelContext; } public static ParameterMappingStrategy createParameterMappingStrategy(CamelContext camelContext) { // lookup in registry first if there is a user define strategy Registry registry = camelContext.getRegistry(); ParameterMappingStrategy answer = registry.lookup(BeanConstants.BEAN_PARAMETER_MAPPING_STRATEGY, ParameterMappingStrategy.class); if (answer == null) { // no then use the default one answer = new DefaultParameterMappingStrategy(); } return answer; } public MethodInvocation createInvocation(Method method, Object pojo, Exchange exchange) { MethodInfo methodInfo = introspect(type, method); if (methodInfo != null) { return methodInfo.createMethodInvocation(pojo, exchange); } return null; } public MethodInvocation createInvocation(Object pojo, Exchange exchange) throws AmbiguousMethodCallException, MethodNotFoundException { MethodInfo methodInfo = null; String name = exchange.getIn().getHeader(Exchange.BEAN_METHOD_NAME, String.class); if (name != null) { if (hasMethod(name)) { List<MethodInfo> methods = getOperations(name); if (methods != null && methods.size() == 1) { // only one method then choose it methodInfo = methods.get(0); } else { // there are more methods with that name so we cannot decide which to use // but first lets try to choose a method and see if that comply with the name methodInfo = chooseMethod(pojo, exchange, name); if (methodInfo == null || !name.equals(methodInfo.getMethod().getName())) { throw new AmbiguousMethodCallException(exchange, methods); } } } else { // a specific method was given to invoke but not found throw new MethodNotFoundException(exchange, pojo, name); } } if (methodInfo == null) { // no name or type methodInfo = chooseMethod(pojo, exchange, null); } if (methodInfo == null) { methodInfo = defaultMethod; } if (methodInfo != null) { if (LOG.isTraceEnabled()) { LOG.trace("Chosen method to invoke: " + methodInfo + " on bean: " + pojo); } return methodInfo.createMethodInvocation(pojo, exchange); } if (LOG.isDebugEnabled()) { LOG.debug("Cannot find suitable method to invoke on bean: " + pojo); } return null; } /** * Introspects the given class * * @param clazz the class */ protected void introspect(Class<?> clazz) { // get the target clazz as it could potentially have been enhanced by CGLIB etc. clazz = getTargetClass(clazz); if (LOG.isTraceEnabled()) { LOG.trace("Introspecting class: " + clazz); } Method[] methods = clazz.getDeclaredMethods(); for (Method method : methods) { boolean valid = isValidMethod(clazz, method); if (LOG.isTraceEnabled()) { LOG.trace("Method: " + method + " is valid: " + valid); } if (valid) { introspect(clazz, method); } } Class<?> superclass = clazz.getSuperclass(); if (superclass != null && !superclass.equals(Object.class)) { introspect(superclass); } } /** * Introspects the given method * * @param clazz the class * @param method the method * @return the method info, is newer <tt>null</tt> */ protected MethodInfo introspect(Class<?> clazz, Method method) { if (LOG.isTraceEnabled()) { LOG.trace("Introspecting class: " + clazz + ", method: " + method); } String opName = method.getName(); MethodInfo methodInfo = createMethodInfo(clazz, method); // methods already registered should be preferred to use instead of super classes of existing methods // we want to us the method from the sub class over super classes, so if we have already registered // the method then use it (we are traversing upwards: sub (child) -> super (farther) ) MethodInfo existingMethodInfo = overridesExistingMethod(methodInfo); if (existingMethodInfo != null) { if (LOG.isTraceEnabled()) { LOG.trace( "This method is already overridden in a subclass, so the method from the sub class is preferred: " + existingMethodInfo); } return existingMethodInfo; } if (LOG.isTraceEnabled()) { LOG.trace("Adding operation: " + opName + " for method: " + methodInfo); } if (hasMethod(opName)) { // we have an overloaded method so add the method info to the same key List<MethodInfo> existing = getOperations(opName); existing.add(methodInfo); } else { // its a new method we have not seen before so wrap it in a list and add it List<MethodInfo> methods = new ArrayList<MethodInfo>(); methods.add(methodInfo); operations.put(opName, methods); } if (methodInfo.hasCustomAnnotation()) { operationsWithCustomAnnotation.add(methodInfo); } else if (methodInfo.hasBodyParameter()) { operationsWithBody.add(methodInfo); } if (methodInfo.hasHandlerAnnotation()) { operationsWithHandlerAnnotation.add(methodInfo); } // must add to method map last otherwise we break stuff methodMap.put(method, methodInfo); return methodInfo; } /** * Returns the {@link MethodInfo} for the given method if it exists or null * if there is no metadata available for the given method */ public MethodInfo getMethodInfo(Method method) { MethodInfo answer = methodMap.get(method); if (answer == null) { // maybe the method is defined on a base class? if (superBeanInfo == null && type != Object.class) { Class<?> superclass = type.getSuperclass(); if (superclass != null && superclass != Object.class) { superBeanInfo = new BeanInfo(camelContext, superclass, strategy); return superBeanInfo.getMethodInfo(method); } } } return answer; } @SuppressWarnings("unchecked") protected MethodInfo createMethodInfo(Class clazz, Method method) { Class[] parameterTypes = method.getParameterTypes(); Annotation[][] parametersAnnotations = method.getParameterAnnotations(); List<ParameterInfo> parameters = new ArrayList<ParameterInfo>(); List<ParameterInfo> bodyParameters = new ArrayList<ParameterInfo>(); boolean hasCustomAnnotation = false; boolean hasHandlerAnnotation = ObjectHelper.hasAnnotation(method.getAnnotations(), Handler.class); int size = parameterTypes.length; if (LOG.isTraceEnabled()) { LOG.trace("Creating MethodInfo for class: " + clazz + " method: " + method + " having " + size + " parameters"); } for (int i = 0; i < size; i++) { Class parameterType = parameterTypes[i]; Annotation[] parameterAnnotations = parametersAnnotations[i]; Expression expression = createParameterUnmarshalExpression(clazz, method, parameterType, parameterAnnotations); hasCustomAnnotation |= expression != null; ParameterInfo parameterInfo = new ParameterInfo(i, parameterType, parameterAnnotations, expression); if (LOG.isTraceEnabled()) { LOG.trace("Parameter #" + i + ": " + parameterInfo); } parameters.add(parameterInfo); if (expression == null) { boolean bodyAnnotation = ObjectHelper.hasAnnotation(parameterAnnotations, Body.class); if (LOG.isTraceEnabled() && bodyAnnotation) { LOG.trace("Parameter #" + i + " has @Body annotation"); } hasCustomAnnotation |= bodyAnnotation; if (bodyParameters.isEmpty()) { // okay we have not yet set the body parameter and we have found // the candidate now to use as body parameter if (Exchange.class.isAssignableFrom(parameterType)) { // use exchange expression = ExpressionBuilder.exchangeExpression(); } else { // lets assume its the body and it must be mandatory convertable to the parameter type // but we allow null bodies in case the message really contains a null body expression = ExpressionBuilder.mandatoryBodyExpression(parameterType, true); } if (LOG.isTraceEnabled()) { LOG.trace("Parameter #" + i + " is the body parameter using expression " + expression); } parameterInfo.setExpression(expression); bodyParameters.add(parameterInfo); } else { // will ignore the expression for parameter evaluation } } if (LOG.isTraceEnabled()) { LOG.trace("Parameter #" + i + " has parameter info: " + parameterInfo); } } // now lets add the method to the repository return new MethodInfo(camelContext, clazz, method, parameters, bodyParameters, hasCustomAnnotation, hasHandlerAnnotation); } /** * Lets try choose one of the available methods to invoke if we can match * the message body to the body parameter * * @param pojo the bean to invoke a method on * @param exchange the message exchange * @param name an optional name of the method that must match, use <tt>null</tt> to indicate all methods * @return the method to invoke or null if no definitive method could be matched * @throws AmbiguousMethodCallException is thrown if cannot chose method due to ambiguous */ protected MethodInfo chooseMethod(Object pojo, Exchange exchange, String name) throws AmbiguousMethodCallException { // @Handler should be select first // then any single method that has a custom @annotation // or any single method that has a match parameter type that matches the Exchange payload // and last then try to select the best among the rest if (name != null) { // filter all lists to only include methods with this name removeNonMatchingMethods(operationsWithHandlerAnnotation, name); removeNonMatchingMethods(operationsWithCustomAnnotation, name); removeNonMatchingMethods(operationsWithBody, name); } else { // remove all getter/setter as we do not want to consider these methods removeAllSetterOrGetterMethods(operationsWithHandlerAnnotation); removeAllSetterOrGetterMethods(operationsWithCustomAnnotation); removeAllSetterOrGetterMethods(operationsWithBody); } if (operationsWithHandlerAnnotation.size() > 1) { // if we have more than 1 @Handler then its ambiguous throw new AmbiguousMethodCallException(exchange, operationsWithHandlerAnnotation); } if (operationsWithHandlerAnnotation.size() == 1) { // methods with handler should be preferred return operationsWithHandlerAnnotation.get(0); } else if (operationsWithCustomAnnotation.size() == 1) { // if there is one method with an annotation then use that one return operationsWithCustomAnnotation.get(0); } else if (operationsWithBody.size() == 1) { // if there is one method with body then use that one return operationsWithBody.get(0); } Collection<MethodInfo> possibleOperations = new ArrayList<MethodInfo>(); possibleOperations.addAll(operationsWithBody); possibleOperations.addAll(operationsWithCustomAnnotation); if (!possibleOperations.isEmpty()) { // multiple possible operations so find the best suited if possible MethodInfo answer = chooseMethodWithMatchingBody(exchange, possibleOperations); if (answer == null) { throw new AmbiguousMethodCallException(exchange, possibleOperations); } else { return answer; } } // not possible to determine return null; } private MethodInfo chooseMethodWithMatchingBody(Exchange exchange, Collection<MethodInfo> operationList) throws AmbiguousMethodCallException { // lets see if we can find a method who's body param type matches the message body Message in = exchange.getIn(); Object body = in.getBody(); if (body != null) { Class bodyType = body.getClass(); if (LOG.isTraceEnabled()) { LOG.trace("Matching for method with a single parameter that matches type: " + bodyType.getCanonicalName()); } List<MethodInfo> possibles = new ArrayList<MethodInfo>(); List<MethodInfo> possiblesWithException = new ArrayList<MethodInfo>(); for (MethodInfo methodInfo : operationList) { // test for MEP pattern matching boolean out = exchange.getPattern().isOutCapable(); if (out && methodInfo.isReturnTypeVoid()) { // skip this method as the MEP is Out so the method must return something continue; } // try to match the arguments if (methodInfo.bodyParameterMatches(bodyType)) { if (LOG.isTraceEnabled()) { LOG.trace("Found a possible method: " + methodInfo); } if (methodInfo.hasExceptionParameter()) { // methods with accepts exceptions possiblesWithException.add(methodInfo); } else { // regular methods with no exceptions possibles.add(methodInfo); } } } // find best suited method to use return chooseBestPossibleMethodInfo(exchange, operationList, body, possibles, possiblesWithException); } // no match so return null return null; } private MethodInfo chooseBestPossibleMethodInfo(Exchange exchange, Collection<MethodInfo> operationList, Object body, List<MethodInfo> possibles, List<MethodInfo> possiblesWithException) throws AmbiguousMethodCallException { Exception exception = ExpressionBuilder.exchangeExceptionExpression().evaluate(exchange, Exception.class); if (exception != null && possiblesWithException.size() == 1) { if (LOG.isTraceEnabled()) { LOG.trace("Exchange has exception set so we prefer method that also has exception as parameter"); } // prefer the method that accepts exception in case we have an exception also return possiblesWithException.get(0); } else if (possibles.size() == 1) { return possibles.get(0); } else if (possibles.isEmpty()) { if (LOG.isTraceEnabled()) { LOG.trace("No possible methods so now trying to convert body to parameter types"); } // lets try converting Object newBody = null; MethodInfo matched = null; int matchCounter = 0; for (MethodInfo methodInfo : operationList) { if (methodInfo.getBodyParameterType().isInstance(body)) { return methodInfo; } Object value = convertToType(exchange, methodInfo.getBodyParameterType(), body); if (value != null) { if (LOG.isTraceEnabled()) { LOG.trace("Converted body from: " + body.getClass().getCanonicalName() + "to: " + methodInfo.getBodyParameterType().getCanonicalName()); } matchCounter++; newBody = value; matched = methodInfo; } } if (matchCounter > 1) { throw new AmbiguousMethodCallException(exchange, Arrays.asList(matched, matched)); } if (matched != null) { if (LOG.isTraceEnabled()) { LOG.trace("Setting converted body: " + body); } Message in = exchange.getIn(); in.setBody(newBody); return matched; } } else { // if we only have a single method with custom annotations, lets use that one if (operationsWithCustomAnnotation.size() == 1) { MethodInfo answer = operationsWithCustomAnnotation.get(0); if (LOG.isTraceEnabled()) { LOG.trace("There are only one method with annotations so we choose it: " + answer); } return answer; } // phew try to choose among multiple methods with annotations return chooseMethodWithCustomAnnotations(exchange, possibles); } // cannot find a good method to use return null; } /** * Validates whether the given method is a valid candidate for Camel Bean Binding. * * @param clazz the class * @param method the method * @return true if valid, false to skip the method */ protected boolean isValidMethod(Class<?> clazz, Method method) { // must not be in the excluded list for (Method excluded : EXCLUDED_METHODS) { if (ObjectHelper.isOverridingMethod(excluded, method)) { // the method is overriding an excluded method so its not valid return false; } } // must be a public method if (!Modifier.isPublic(method.getModifiers())) { return false; } // return type must not be an Exchange and it should not be a bridge method if ((method.getReturnType() != null && Exchange.class.isAssignableFrom(method.getReturnType())) || method.isBridge()) { return false; } return true; } /** * Does the given method info override an existing method registered before (from a subclass) * * @param methodInfo the method to test * @return the already registered method to use, null if not overriding any */ private MethodInfo overridesExistingMethod(MethodInfo methodInfo) { for (MethodInfo info : methodMap.values()) { Method source = info.getMethod(); Method target = methodInfo.getMethod(); boolean override = ObjectHelper.isOverridingMethod(source, target); if (override) { // same name, same parameters, then its overrides an existing class return info; } } return null; } private MethodInfo chooseMethodWithCustomAnnotations(Exchange exchange, Collection<MethodInfo> possibles) throws AmbiguousMethodCallException { // if we have only one method with custom annotations lets choose that MethodInfo chosen = null; for (MethodInfo possible : possibles) { if (possible.hasCustomAnnotation()) { if (chosen != null) { chosen = null; break; } else { chosen = possible; } } } if (chosen != null) { return chosen; } throw new AmbiguousMethodCallException(exchange, possibles); } /** * Creates an expression for the given parameter type if the parameter can * be mapped automatically or null if the parameter cannot be mapped due to * insufficient annotations or not fitting with the default type * conventions. */ private Expression createParameterUnmarshalExpression(Class<?> clazz, Method method, Class<?> parameterType, Annotation[] parameterAnnotation) { // look for a parameter annotation that converts into an expression for (Annotation annotation : parameterAnnotation) { Expression answer = createParameterUnmarshalExpressionForAnnotation(clazz, method, parameterType, annotation); if (answer != null) { return answer; } } // no annotations then try the default parameter mappings return strategy.getDefaultParameterTypeExpression(parameterType); } private Expression createParameterUnmarshalExpressionForAnnotation(Class<?> clazz, Method method, Class<?> parameterType, Annotation annotation) { if (annotation instanceof Attachments) { return ExpressionBuilder.attachmentsExpression(); } else if (annotation instanceof Property) { Property propertyAnnotation = (Property) annotation; return ExpressionBuilder.propertyExpression(propertyAnnotation.value()); } else if (annotation instanceof Properties) { return ExpressionBuilder.propertiesExpression(); } else if (annotation instanceof Header) { Header headerAnnotation = (Header) annotation; return ExpressionBuilder.headerExpression(headerAnnotation.value()); } else if (annotation instanceof Headers) { return ExpressionBuilder.headersExpression(); } else if (annotation instanceof OutHeaders) { return ExpressionBuilder.outHeadersExpression(); } else if (annotation instanceof ExchangeException) { return ExpressionBuilder.exchangeExceptionExpression(CastUtils.cast(parameterType, Exception.class)); } else { LanguageAnnotation languageAnnotation = annotation.annotationType() .getAnnotation(LanguageAnnotation.class); if (languageAnnotation != null) { Class<?> type = languageAnnotation.factory(); Object object = camelContext.getInjector().newInstance(type); if (object instanceof AnnotationExpressionFactory) { AnnotationExpressionFactory expressionFactory = (AnnotationExpressionFactory) object; return expressionFactory.createExpression(camelContext, annotation, languageAnnotation, parameterType); } else { LOG.warn("Ignoring bad annotation: " + languageAnnotation + "on method: " + method + " which declares a factory: " + type.getName() + " which does not implement " + AnnotationExpressionFactory.class.getName()); } } } return null; } private static void removeAllSetterOrGetterMethods(List<MethodInfo> methods) { Iterator<MethodInfo> it = methods.iterator(); while (it.hasNext()) { MethodInfo info = it.next(); if (IntrospectionSupport.isGetter(info.getMethod())) { // skip getters it.remove(); } else if (IntrospectionSupport.isSetter(info.getMethod())) { // skip setters it.remove(); } } } private static void removeNonMatchingMethods(List<MethodInfo> methods, String name) { Iterator<MethodInfo> it = methods.iterator(); while (it.hasNext()) { MethodInfo info = it.next(); if (!name.equals(info.getMethod().getName())) { // name does not match so remove it it.remove(); } } } private static Class<?> getTargetClass(Class<?> clazz) { if (clazz != null && clazz.getName().contains(CGLIB_CLASS_SEPARATOR)) { Class<?> superClass = clazz.getSuperclass(); if (superClass != null && !Object.class.equals(superClass)) { return superClass; } } return clazz; } /** * Do we have a method with the given name. * <p/> * Shorthand method names for getters is supported, so you can pass in eg 'name' and Camel * will can find the real 'getName' method instead. * * @param methodName the method name * @return <tt>true</tt> if we have such a method. */ public boolean hasMethod(String methodName) { return getOperations(methodName) != null; } /** * Gets the list of methods sorted by A..Z method name. * * @return the methods. */ @SuppressWarnings("unchecked") public List<MethodInfo> getMethods() { if (operations.isEmpty()) { return Collections.EMPTY_LIST; } List<MethodInfo> methods = new ArrayList<MethodInfo>(); for (Collection<MethodInfo> col : operations.values()) { methods.addAll(col); } // sort the methods by name A..Z Collections.sort(methods, new Comparator<MethodInfo>() { public int compare(MethodInfo o1, MethodInfo o2) { return o1.getMethod().getName().compareTo(o2.getMethod().getName()); } }); return methods; } /** * Get the operation(s) with the given name. We can have multiple when methods is overloaded. * <p/> * Shorthand method names for getters is supported, so you can pass in eg 'name' and Camel * will can find the real 'getName' method instead. * * @param methodName the method name * @return the found method, or <tt>null</tt> if not found */ private List<MethodInfo> getOperations(String methodName) { List<MethodInfo> answer = operations.get(methodName); if (answer != null) { return answer; } // now try all getters to see if any of those matched the methodName for (Method method : methodMap.keySet()) { if (IntrospectionSupport.isGetter(method)) { String shorthandMethodName = IntrospectionSupport.getGetterShorthandName(method); // if the two names matches then see if we can find it using that name if (methodName.equals(shorthandMethodName)) { return operations.get(method.getName()); } } } return null; } }