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Groovy example source code file (TracingInterceptor.java)

This example Groovy source code file (TracingInterceptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

class, class, interceptor, io, ioexception, ioexception, object, object, string, string, stringbuffer, tracinginterceptor, writer

The Groovy TracingInterceptor.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * 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 groovy.lang;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;

/*
 * This {@link Interceptor} traces method calls on the proxied object to a log. 
 * By default, the log is simply <pre>System.out
; however, that can be * changed with the <pre>setWriter(Writer) method.

* * A message will be written to output before a method is invoked and after a method * is invoked. If methods are nested, and invoke one another, then indentation * of two spaces is written. <br/>
* * Here is an example usage on the ArrayList object: <br/> * <pre> * def proxy = ProxyMetaClass.getInstance(ArrayList.class) * proxy.interceptor = new TracingInterceptor() * proxy.use { * def list = [1, 2, 3] * assert 3 == list.size() * assert list.contains(1) * } * </pre> * Running this code produces this output: * <pre> * before java.util.ArrayList.size() * after java.util.ArrayList.size() * before java.util.ArrayList.contains(java.lang.Integer) * after java.util.ArrayList.contains(java.lang.Integer) * </pre> */ public class TracingInterceptor implements Interceptor { protected Writer writer = new PrintWriter(System.out); private int indent = 0; /** * Returns the writer associated with this interceptor. */ public Writer getWriter() { return writer; } /** * Changes the writer associated with this interceptor. */ public void setWriter(Writer writer) { this.writer = writer; } public Object beforeInvoke(Object object, String methodName, Object[] arguments) { write(object, methodName, arguments, "before"); indent++ ; return null; } public Object afterInvoke(Object object, String methodName, Object[] arguments, Object result) { indent--; write(object, methodName, arguments, "after "); return result; } public boolean doInvoke() { return true; } private String indent(){ StringBuffer result = new StringBuffer(); for (int i=0; i<indent;i++){ result.append(" "); } return result.toString(); } protected void write(Object object, String methodName, Object[] arguments, final String origin) { try { writer.write(indent()); writer.write(origin); writer.write(" "); Class theClass = object instanceof Class ? (Class) object: object.getClass(); writeInfo(theClass, methodName, arguments); writer.write("\n"); writer.flush(); } catch (IOException e) { e.printStackTrace(); } } protected void writeInfo(final Class aClass, String methodName, Object[] arguments) throws IOException { writer.write(aClass.getName()); writer.write("."); writer.write(methodName); writer.write("("); for (int i = 0; i < arguments.length; i++) { if (i > 0) writer.write(", "); Object argument = arguments[i]; writer.write(argument.getClass().getName()); } writer.write(")"); } }

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