de.kaiserpfalzEdv.commons.jee.servlet.util.ServletContextParamReader.java Source code

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Here is the source code for de.kaiserpfalzEdv.commons.jee.servlet.util.ServletContextParamReader.java

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/*
 * Copyright 2015 Kaiserpfalz EDV-Service Roland Lichti
 *
 * 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 de.kaiserpfalzEdv.commons.jee.servlet.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.ServletContext;

import static com.google.common.base.Preconditions.checkArgument;
import static org.apache.commons.lang3.StringUtils.isNotBlank;

/**
 * Reads configuration from the Servlet Context.
 *
 * @author klenkes
 * @since 2013Q
 */
public class ServletContextParamReader {
    private static final Logger LOG = LoggerFactory.getLogger(ServletContextParamReader.class);

    private ServletContext context;

    /**
     * @param context The application servlet context.
     * @throws IllegalArgumentException If the servlet context is NULL.
     */
    public ServletContextParamReader(ServletContext context) {
        checkArgument(context != null, "Can't read configuration from NULL context.");

        this.context = context;

        //noinspection ConstantConditions
        LOG.info("Loading configuration from context: {}", context.getServletContextName());
    }

    /**
     * @param key          The param name to read from context.
     * @param defaultValue the default to be returned if nothing is configured.
     * @return the value read from servlet context param or the given defaultValue.
     * @throws IllegalArgumentException If the key is NULL, empty or blank.
     */
    public String getParam(String key, String defaultValue) {
        checkArgument(isNotBlank(key), "Can't read configuration for an empty key!");

        String result = context.getInitParameter(key);

        LOG.debug("Configuration load {\"key\": \"{}\", \"value\": \"{}\", \"default\": \"{}\"}", key, result,
                defaultValue);
        return (result != null) ? result : defaultValue;
    }
}