001// Copyright 2006, 2007, 2008, 2011 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.ioc.internal.services;
016
017import org.apache.tapestry5.ioc.services.ExceptionTracker;
018import org.apache.tapestry5.plastic.MethodInvocation;
019import org.slf4j.Logger;
020
021import java.util.Iterator;
022
023import static java.lang.String.format;
024
025/**
026 * Used by {@link org.apache.tapestry5.ioc.internal.services.LoggingDecoratorImpl} to delegate out logging behavior to a
027 * separate object.
028 */
029public final class MethodLogger
030{
031    private static final int BUFFER_SIZE = 200;
032
033    private static final String ENTER = "ENTER";
034
035    private static final String EXIT = " EXIT";
036
037    private static final String FAIL = " FAIL";
038
039    private final Logger logger;
040
041    private final ExceptionTracker exceptionTracker;
042
043    public MethodLogger(Logger logger, ExceptionTracker exceptionTracker)
044    {
045        this.logger = logger;
046        this.exceptionTracker = exceptionTracker;
047    }
048
049    public boolean isDebugEnabled()
050    {
051        return logger.isDebugEnabled();
052    }
053
054    /**
055     * Invoked when a method is first entered
056     *
057     * @param invocation identifies method invoked as well as parameters passed to method
058     */
059    public void entry(MethodInvocation invocation)
060    {
061        StringBuilder buffer = new StringBuilder(BUFFER_SIZE);
062
063        buffer.append(format("[%s] %s(", ENTER, invocation.getMethod().getName()));
064
065        for (int i = 0; i < invocation.getMethod().getParameterTypes().length; i++)
066        {
067            if (i > 0) buffer.append(", ");
068
069            convert(buffer, invocation.getParameter(i));
070        }
071
072        buffer.append(")");
073
074        logger.debug(buffer.toString());
075    }
076
077    private void convert(StringBuilder buffer, Object object)
078    {
079        if (object == null)
080        {
081            buffer.append("null");
082            return;
083        }
084
085        // Minimal, alas: Doesn't handle embedded quotes and other
086        // characters. Really want to convert the string back to what it
087        // would look like as source code.
088
089        if (object instanceof String)
090        {
091            buffer.append("\"");
092            buffer.append(object.toString());
093            buffer.append("\"");
094            return;
095        }
096
097        if (object instanceof Object[])
098        {
099            Object[] values = (Object[]) object;
100            buffer.append('{');
101
102            for (int i = 0; i < values.length; i++)
103            {
104                if (i > 0) buffer.append(", ");
105
106                convert(buffer, values[i]);
107            }
108
109            buffer.append('}');
110            return;
111        }
112
113        if (object instanceof Iterable)
114        {
115            Iterable itr = (Iterable) object;
116            boolean first = true;
117
118            buffer.append('[');
119            Iterator i = itr.iterator();
120            while (i.hasNext())
121            {
122                if (!first) buffer.append(", ");
123
124                convert(buffer, i.next());
125                first = false;
126            }
127            buffer.append(']');
128            return;
129        }
130
131        // Might need to add a few more, for things like character values ...
132
133        buffer.append(object.toString());
134    }
135
136    /**
137     * Invoked when a method exits (possibly returning a value).
138     *
139     * @param invocation identifies method invocation and  result value
140     */
141    public void exit(MethodInvocation invocation)
142    {
143        StringBuilder buffer = new StringBuilder(BUFFER_SIZE);
144
145        buffer.append(format("[%s] %s", EXIT, invocation.getMethod().getName()));
146
147        if (invocation.getMethod().getReturnType() != void.class)
148        {
149            buffer.append(" [");
150            convert(buffer, invocation.getReturnValue());
151            buffer.append(']');
152        }
153
154        logger.debug(buffer.toString());
155    }
156
157    /**
158     * Invoked when method invocation instead throws an exception.
159     *
160     * @param invocation identifies method invocation which failed
161     * @param t          exception throws by method invocation
162     */
163    public void fail(MethodInvocation invocation, Throwable t)
164    {
165        logger.debug(
166                format("[%s] %s -- %s", FAIL,
167                        invocation.getMethod().getName(),
168                        t.getClass().getName()),
169                exceptionTracker.exceptionLogged(t) ? null : t);
170    }
171}