log4j-1.2-api/src/main/java/org/apache/log4j/DefaultThrowableRenderer.java

/*
 * 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.log4j;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.LineNumberReader;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import org.apache.log4j.spi.ThrowableRenderer;

/**
 * Default implementation of {@link ThrowableRenderer} using {@link Throwable#printStackTrace(PrintWriter)}.
 *
 * @since 1.2.16
 */
public final class DefaultThrowableRenderer implements ThrowableRenderer {

    /**
     * Render throwable using Throwable.printStackTrace.
     *
     * @param throwable throwable, may not be null.
     * @return string representation.
     */
    @SuppressFBWarnings(
            value = "INFORMATION_EXPOSURE_THROUGH_AN_ERROR_MESSAGE",
            justification = "The throwable is formatted into a log file, which should be private.")
    public static String[] render(final Throwable throwable) {
        final StringWriter sw = new StringWriter();
        final PrintWriter pw = new PrintWriter(sw);
        try {
            throwable.printStackTrace(pw);
        } catch (final RuntimeException ex) {
            // ignore
        }
        pw.flush();
        final LineNumberReader reader = new LineNumberReader(new StringReader(sw.toString()));
        final ArrayList<String> lines = new ArrayList<>();
        try {
            String line = reader.readLine();
            while (line != null) {
                lines.add(line);
                line = reader.readLine();
            }
        } catch (final IOException ex) {
            if (ex instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            lines.add(ex.toString());
        }
        final String[] tempRep = new String[lines.size()];
        lines.toArray(tempRep);
        return tempRep;
    }

    /**
     * Construct new instance.
     */
    public DefaultThrowableRenderer() {
        // empty
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String[] doRender(final Throwable throwable) {
        return render(throwable);
    }
}