org.apache.hadoop.hive.conf.SystemVariables.java Source code

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Here is the source code for org.apache.hadoop.hive.conf.SystemVariables.java

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/**
 * 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.hadoop.hive.conf;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;

public class SystemVariables {

    private static final Log l4j = LogFactory.getLog(SystemVariables.class);
    protected static Pattern varPat = Pattern.compile("\\$\\{[^\\}\\$\u0020]+\\}");

    public static final String ENV_PREFIX = "env:";
    public static final String SYSTEM_PREFIX = "system:";
    public static final String HIVECONF_PREFIX = "hiveconf:";
    public static final String HIVEVAR_PREFIX = "hivevar:";
    public static final String METACONF_PREFIX = "metaconf:";
    public static final String SET_COLUMN_NAME = "set";

    protected String getSubstitute(Configuration conf, String var) {
        String val = null;
        try {
            if (var.startsWith(SYSTEM_PREFIX)) {
                val = System.getProperty(var.substring(SYSTEM_PREFIX.length()));
            }
        } catch (SecurityException se) {
            l4j.warn("Unexpected SecurityException in Configuration", se);
        }
        if (val == null && var.startsWith(ENV_PREFIX)) {
            val = System.getenv(var.substring(ENV_PREFIX.length()));
        }
        if (val == null && conf != null && var.startsWith(HIVECONF_PREFIX)) {
            val = conf.get(var.substring(HIVECONF_PREFIX.length()));
        }
        return val;
    }

    public static boolean containsVar(String expr) {
        return expr != null && varPat.matcher(expr).find();
    }

    static String substitute(String expr) {
        return expr == null ? null : new SystemVariables().substitute(null, expr, 1);
    }

    static String substitute(Configuration conf, String expr) {
        return expr == null ? null : new SystemVariables().substitute(conf, expr, 1);
    }

    protected final String substitute(Configuration conf, String expr, int depth) {
        Matcher match = varPat.matcher("");
        String eval = expr;
        StringBuilder builder = new StringBuilder();
        int s = 0;
        for (; s <= depth; s++) {
            match.reset(eval);
            builder.setLength(0);
            int prev = 0;
            boolean found = false;
            while (match.find(prev)) {
                String group = match.group();
                String var = group.substring(2, group.length() - 1); // remove ${ .. }
                String substitute = getSubstitute(conf, var);
                if (substitute == null) {
                    substitute = group; // append as-is
                } else {
                    found = true;
                }
                builder.append(eval.substring(prev, match.start())).append(substitute);
                prev = match.end();
            }
            if (!found) {
                return eval;
            }
            builder.append(eval.substring(prev));
            eval = builder.toString();
        }
        if (s > depth) {
            throw new IllegalStateException(
                    "Variable substitution depth is deeper than " + depth + " for expression " + expr);
        }
        return eval;
    }
}