Apache Commons Lang 3 is the 3rd version of Apache Commons Lang, which provides a host of helper utilities for the java.lang API.

Apache Commons Lang 3 Source Code files are provided in both binary packge (commons-lang3-3.12.0-bin.zip) and source package (commons-lang3-3.12.0-src.zip). You can download them at Apache Commons Lang Website.

Apache Commons Lang 3 Source Code has no dependencies and is compatible with Java 8 and newer versions. You can compile it to generate your own version of Apache Commons Lang 3 JAR file.

You can also browse the source code below:

⏎ org/apache/commons/lang3/exception/DefaultExceptionContext.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.commons.lang3.exception;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.apache.commons.lang3.tuple.Pair;

/**
 * Default implementation of the context storing the label-value pairs for contexted exceptions.
 * <p>
 * This implementation is serializable, however this is dependent on the values that
 * are added also being serializable.
 * </p>
 *
 * @see ContextedException
 * @see ContextedRuntimeException
 * @since 3.0
 */
public class DefaultExceptionContext implements ExceptionContext, Serializable {

    /** The serialization version. */
    private static final long serialVersionUID = 20110706L;

    /** The list storing the label-data pairs. */
    private final List<Pair<String, Object>> contextValues = new ArrayList<>();

    /**
     * {@inheritDoc}
     */
    @Override
    public DefaultExceptionContext addContextValue(final String label, final Object value) {
        contextValues.add(new ImmutablePair<>(label, value));
        return this;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public DefaultExceptionContext setContextValue(final String label, final Object value) {
        contextValues.removeIf(p -> StringUtils.equals(label, p.getKey()));
        addContextValue(label, value);
        return this;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List<Object> getContextValues(final String label) {
        final List<Object> values = new ArrayList<>();
        for (final Pair<String, Object> pair : contextValues) {
            if (StringUtils.equals(label, pair.getKey())) {
                values.add(pair.getValue());
            }
        }
        return values;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Object getFirstContextValue(final String label) {
        for (final Pair<String, Object> pair : contextValues) {
            if (StringUtils.equals(label, pair.getKey())) {
                return pair.getValue();
            }
        }
        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Set<String> getContextLabels() {
        final Set<String> labels = new HashSet<>();
        for (final Pair<String, Object> pair : contextValues) {
            labels.add(pair.getKey());
        }
        return labels;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List<Pair<String, Object>> getContextEntries() {
        return contextValues;
    }

    /**
     * Builds the message containing the contextual information.
     *
     * @param baseMessage  the base exception message <b>without</b> context information appended
     * @return the exception message <b>with</b> context information appended, never null
     */
    @Override
    public String getFormattedExceptionMessage(final String baseMessage) {
        final StringBuilder buffer = new StringBuilder(256);
        if (baseMessage != null) {
            buffer.append(baseMessage);
        }

        if (!contextValues.isEmpty()) {
            if (buffer.length() > 0) {
                buffer.append('\n');
            }
            buffer.append("Exception Context:\n");

            int i = 0;
            for (final Pair<String, Object> pair : contextValues) {
                buffer.append("\t[");
                buffer.append(++i);
                buffer.append(':');
                buffer.append(pair.getKey());
                buffer.append("=");
                final Object value = pair.getValue();
                if (value == null) {
                    buffer.append("null");
                } else {
                    String valueStr;
                    try {
                        valueStr = value.toString();
                    } catch (final Exception e) {
                        valueStr = "Exception thrown on toString(): " + ExceptionUtils.getStackTrace(e);
                    }
                    buffer.append(valueStr);
                }
                buffer.append("]\n");
            }
            buffer.append("---------------------------------");
        }
        return buffer.toString();
    }

}

⏎ org/apache/commons/lang3/exception/DefaultExceptionContext.java

Or download all of them as a single archive file:

File name: commons-lang3-3.12.0-sources.jar
File size: 651724 bytes
Release date: 2020-01-22
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