com.opengamma.collect.io.PropertiesFile.java Source code

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Here is the source code for com.opengamma.collect.io.PropertiesFile.java

Source

/**
 * Copyright (C) 2014 - present by OpenGamma Inc. and the OpenGamma group of companies
 * 
 * Please see distribution for license.
 */
package com.opengamma.collect.io;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Map;
import java.util.Properties;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Multimap;
import com.google.common.io.CharSource;
import com.opengamma.collect.ArgChecker;

/**
 * A properties file.
 * <p>
 * Represents a properties file together with the ability to parse it from a {@link CharSource}.
 * This is similar to {@link Properties} but with a simpler format and without extending {@link Map}.
 * Duplicate keys are allowed and handled.
 * <p>
 * The properties file format used here is deliberately simple.
 * There is only one element - key-value pairs.
 * <p>
 * The key is separated from the value using the '=' symbol.
 * Duplicate keys are allowed.
 * For example 'key = value'.
 * <p>
 * Keys and values are trimmed.
 * Blank lines are ignored.
 * Whole line comments begin with hash '#' or semicolon ';'.
 * No escape format is available.
 * Lookup is case sensitive.
 * <p>
 * This example explains the format:
 * <pre>
 *  # line comment
 *  key = value
 *  month = January
 * </pre>
 * <p>
 * The aim of this class is to parse the basic format.
 * Interpolation of variables is not supported.
 */
public final class PropertiesFile {

    /**
     * The key-value pairs.
     */
    private final PropertySet keyValueMap;

    //-------------------------------------------------------------------------
    /**
     * Parses the specified source as a properties file.
     * <p>
     * This parses the specified character source expecting a properties file format.
     * The resulting instance can be queried for each key and value.
     * 
     * @param source  the properties file resource, not null
     * @return the properties file, not null
     */
    public static PropertiesFile of(CharSource source) {
        ArgChecker.notNull(source, "source");
        try {
            PropertySet keyValues = parse(source);
            return new PropertiesFile(keyValues);
        } catch (IOException ex) {
            throw new UncheckedIOException(ex);
        }
    }

    // parses the properties file format
    private static PropertySet parse(CharSource source) throws IOException {
        ImmutableList<String> lines = source.readLines();
        Multimap<String, String> parsed = ArrayListMultimap.create();
        int lineNum = 0;
        for (String line : lines) {
            lineNum++;
            line = line.trim();
            if (line.length() == 0 || line.startsWith("#") || line.startsWith(";")) {
                continue;
            }
            int equalsPosition = line.indexOf('=');
            if (equalsPosition < 0) {
                throw new IllegalArgumentException(
                        "Invalid properties file, expected key=value property, line " + lineNum);
            }
            String key = line.substring(0, equalsPosition).trim();
            String value = line.substring(equalsPosition + 1).trim();
            if (key.length() == 0) {
                throw new IllegalArgumentException("Invalid properties file, empty key, line " + lineNum);
            }
            parsed.put(key, value);
        }
        return PropertySet.of(parsed);
    }

    //-------------------------------------------------------------------------
    /**
     * Restricted constructor.
     * 
     * @param keyValueMap  the values
     */
    private PropertiesFile(PropertySet keyValueMap) {
        this.keyValueMap = keyValueMap;
    }

    //-------------------------------------------------------------------------
    /**
     * Gets all the key-value properties of this file.
     * <p>
     * The map of key-value properties is exposed by this method.
     * 
     * @return the key-value properties
     */
    public PropertySet getProperties() {
        return keyValueMap;
    }

    //-------------------------------------------------------------------------
    /**
     * Checks if this file equals another.
     * <p>
     * The comparison checks the content.
     * 
     * @param obj  the other section, null returns false
     * @return true if equal
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj instanceof PropertiesFile) {
            return keyValueMap.equals(((PropertiesFile) obj).keyValueMap);
        }
        return false;
    }

    /**
     * Returns a suitable hash code for the file.
     * 
     * @return the hash code
     */
    @Override
    public int hashCode() {
        return keyValueMap.hashCode();
    }

    /**
     * Returns a string describing the file.
     * 
     * @return the descriptive string
     */
    @Override
    public String toString() {
        return keyValueMap.toString();
    }

}