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 org.apache.log4j.spi.ThrowableRenderer;

import java.io.StringWriter;
import java.io.PrintWriter;
import java.io.LineNumberReader;
import java.io.StringReader;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.ArrayList;

/**
 * Default implementation of ThrowableRenderer using
 * Throwable.printStackTrace.
 *
 * @since 1.2.16
 */
public final class DefaultThrowableRenderer implements ThrowableRenderer {
    /**
     * Construct new instance.
     */
    public DefaultThrowableRenderer() {

    }


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

    /**
     * Render throwable using Throwable.printStackTrace.
     * @param throwable throwable, may not be null.
     * @return string representation.
     */
    public static String[] render(final Throwable throwable) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        try {
            throwable.printStackTrace(pw);
        } catch(RuntimeException ex) {
        }
        pw.flush();
        LineNumberReader reader = new LineNumberReader(
                new StringReader(sw.toString()));
        ArrayList lines = new ArrayList();
        try {
          String line = reader.readLine();
          while(line != null) {
            lines.add(line);
            line = reader.readLine();
          }
        } catch(IOException ex) {
            if (ex instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            lines.add(ex.toString());
        }
        String[] tempRep = new String[lines.size()];
        lines.toArray(tempRep);
        return tempRep;
    }
}