Java tutorial
package bboss.org.apache.velocity.runtime.parser.node; /* * 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. */ import java.lang.reflect.InvocationTargetException; import org.apache.commons.lang.ArrayUtils; import org.apache.commons.lang.StringUtils; import bboss.org.apache.velocity.app.event.EventHandlerUtil; import bboss.org.apache.velocity.context.InternalContextAdapter; import bboss.org.apache.velocity.exception.MethodInvocationException; import bboss.org.apache.velocity.exception.TemplateInitException; import bboss.org.apache.velocity.exception.VelocityException; import bboss.org.apache.velocity.runtime.RuntimeConstants; import bboss.org.apache.velocity.runtime.directive.StopCommand; import bboss.org.apache.velocity.runtime.parser.Parser; import bboss.org.apache.velocity.util.ClassUtils; import bboss.org.apache.velocity.util.introspection.Info; import bboss.org.apache.velocity.util.introspection.VelMethod; /** * ASTMethod.java * * Method support for references : $foo.method() * * NOTE : * * introspection is now done at render time. * * Please look at the Parser.jjt file which is * what controls the generation of this class. * * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> * @version $Id: ASTMethod.java 898032 2010-01-11 19:51:03Z nbubna $ */ public class ASTMethod extends SimpleNode { private String methodName = ""; private int paramCount = 0; protected Info uberInfo; /** * Indicates if we are running in strict reference mode. */ protected boolean strictRef = false; /** * @param id */ public ASTMethod(int id) { super(id); } /** * @param p * @param id */ public ASTMethod(Parser p, int id) { super(p, id); } /** * @see bboss.org.apache.velocity.runtime.parser.node.SimpleNode#jjtAccept(bboss.org.apache.velocity.runtime.parser.node.ParserVisitor, java.lang.Object) */ public Object jjtAccept(ParserVisitor visitor, Object data) { return visitor.visit(this, data); } /** * simple init - init our subtree and get what we can from * the AST * @param context * @param data * @return The init result * @throws TemplateInitException */ public Object init(InternalContextAdapter context, Object data) throws TemplateInitException { super.init(context, data); /* * make an uberinfo - saves new's later on */ uberInfo = new Info(getTemplateName(), getLine(), getColumn()); /* * this is about all we can do */ methodName = getFirstToken().image; paramCount = jjtGetNumChildren() - 1; strictRef = rsvc.getBoolean(RuntimeConstants.RUNTIME_REFERENCES_STRICT, false); return data; } /** * invokes the method. Returns null if a problem, the * actual return if the method returns something, or * an empty string "" if the method returns void * @param o * @param context * @return Result or null. * @throws MethodInvocationException */ public Object execute(Object o, InternalContextAdapter context) throws MethodInvocationException { /* * new strategy (strategery!) for introspection. Since we want * to be thread- as well as context-safe, we *must* do it now, * at execution time. There can be no in-node caching, * but if we are careful, we can do it in the context. */ Object[] params = new Object[paramCount]; /* * sadly, we do need recalc the values of the args, as this can * change from visit to visit */ final Class[] paramClasses = paramCount > 0 ? new Class[paramCount] : ArrayUtils.EMPTY_CLASS_ARRAY; for (int j = 0; j < paramCount; j++) { params[j] = jjtGetChild(j + 1).value(context); if (params[j] != null) { paramClasses[j] = params[j].getClass(); } } VelMethod method = ClassUtils.getMethod(methodName, params, paramClasses, o, context, this, strictRef); if (method == null) return null; try { /* * get the returned object. It may be null, and that is * valid for something declared with a void return type. * Since the caller is expecting something to be returned, * as long as things are peachy, we can return an empty * String so ASTReference() correctly figures out that * all is well. */ Object obj = method.invoke(o, params); if (obj == null) { if (method.getReturnType() == Void.TYPE) { return ""; } } return obj; } catch (InvocationTargetException ite) { return handleInvocationException(o, context, ite.getTargetException()); } /** Can also be thrown by method invocation **/ catch (IllegalArgumentException t) { return handleInvocationException(o, context, t); } /** * pass through application level runtime exceptions */ catch (RuntimeException e) { throw e; } catch (Exception e) { String msg = "ASTMethod.execute() : exception invoking method '" + methodName + "' in " + o.getClass(); log.error(msg, e); throw new VelocityException(msg, e); } } private Object handleInvocationException(Object o, InternalContextAdapter context, Throwable t) { /* * We let StopCommands go up to the directive they are for/from */ if (t instanceof StopCommand) { throw (StopCommand) t; } /* * In the event that the invocation of the method * itself throws an exception, we want to catch that * wrap it, and throw. We don't log here as we want to figure * out which reference threw the exception, so do that * above */ else if (t instanceof Exception) { try { return EventHandlerUtil.methodException(rsvc, context, o.getClass(), methodName, (Exception) t); } /** * If the event handler throws an exception, then wrap it * in a MethodInvocationException. Don't pass through RuntimeExceptions like other * similar catchall code blocks. */ catch (Exception e) { throw new MethodInvocationException("Invocation of method '" + methodName + "' in " + o.getClass() + " threw exception " + e.toString(), e, methodName, getTemplateName(), this.getLine(), this.getColumn()); } } /* * let non-Exception Throwables go... */ else { /* * no event cartridge to override. Just throw */ throw new MethodInvocationException("Invocation of method '" + methodName + "' in " + o.getClass() + " threw exception " + t.toString(), t, methodName, getTemplateName(), this.getLine(), this.getColumn()); } } /** * Internal class used as key for method cache. Combines * ASTMethod fields with array of parameter classes. Has * public access (and complete constructor) for unit test * purposes. * @since 1.5 */ public static class MethodCacheKey { private final String methodName; private final Class[] params; public MethodCacheKey(String methodName, Class[] params) { /** * Should never be initialized with nulls, but to be safe we refuse * to accept them. */ this.methodName = (methodName != null) ? methodName : StringUtils.EMPTY; this.params = (params != null) ? params : ArrayUtils.EMPTY_CLASS_ARRAY; } /** * @see java.lang.Object#equals(java.lang.Object) */ public boolean equals(Object o) { /** * note we skip the null test for methodName and params * due to the earlier test in the constructor */ if (o instanceof MethodCacheKey) { final MethodCacheKey other = (MethodCacheKey) o; if (params.length == other.params.length && methodName.equals(other.methodName)) { for (int i = 0; i < params.length; ++i) { if (params[i] == null) { if (params[i] != other.params[i]) { return false; } } else if (!params[i].equals(other.params[i])) { return false; } } return true; } } return false; } /** * @see java.lang.Object#hashCode() */ public int hashCode() { int result = 17; /** * note we skip the null test for methodName and params * due to the earlier test in the constructor */ for (int i = 0; i < params.length; ++i) { final Class param = params[i]; if (param != null) { result = result * 37 + param.hashCode(); } } result = result * 37 + methodName.hashCode(); return result; } } /** * @return Returns the methodName. * @since 1.5 */ public String getMethodName() { return methodName; } }