abstractconfiguration.java

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/*
 * AbstractConfiguration.java
 *
 * Created on 2006年7月18日, 下午12:16
 *
 * To change this template, choose Tools | Options and locate the template under
 * the Source Creation and Management node. Right-click the template and choose
 * Open. You can then make changes to the template in the Source Editor.
 */

package tot.xml;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Properties;
import java.util.StringTokenizer;
import java.util.Vector;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Abstract configuration class. Provide basic functionality but does not
 * store any data. If you want to write your own Configuration class
 * then you should implement only abstract methods from this class.
 *
 * @author <a href="mailto:[e-mail]">Konstantin Shaposhnikov</a>
 * @author <a href="mailto:[e-mail]">Oliver Heger</a>
 * @version $Id: AbstractConfiguration.java,v 1.4 2004/06/01 13:25:39 skoehler Exp $
 */
public abstract class AbstractConfiguration implements Configuration
{
    /** how big the initial arraylist for splitting up name value pairs */
    private static final int INITIAL_LIST_SIZE = 2;

    private static Log log = LogFactory.getLog(AbstractConfiguration.class);
    /**
     * stores the configuration key-value pairs
     */
    protected Configuration defaults = null;

    /** start token */
    protected static final String START_TOKEN = "${";
    /** end token */
    protected static final String END_TOKEN = "}";

    /**
     * Empty constructor.
     */
    public AbstractConfiguration()
    {
    }

    /**
     * Creates an empty AbstractConfiguration object with
     * a Super-Object which is queries for every key.
     *
     * @param defaults Configuration defaults to use if key not in file
     */
    public AbstractConfiguration(Configuration defaults)
    {
        this();
        this.defaults = defaults;
    }

    /**
     * Add a property to the configuration. If it already exists then the value
     * stated here will be added to the configuration entry. For example, if
     *
     * resource.loader = file
     *
     * is already present in the configuration and you
     *
     * addProperty("resource.loader", "classpath")
     *
     * Then you will end up with a Vector like the following:
     *
     * ["file", "classpath"]
     *
     * @param key The Key to add the property to.
     * @param token The Value to add.
     */
    public void addProperty(String key, Object token)
    {
        if (token instanceof String)
        {
            for(Iterator it = processString((String) token).iterator();
            it.hasNext();)
            {
                addPropertyDirect(key, it.next());
            }
        }
        else if (token instanceof Collection)
        {
            for (Iterator it = ((Collection) token).iterator(); it.hasNext();)
            {
                addProperty(key, it.next());
            }
        }
        else
        {
            addPropertyDirect(key, token);
        }
    }

    /**
     * Read property. Should return <code>null</code> if the key doesn't
     * map to an existing object.
     *
     * @param key key to use for mapping
     *
     * @return object associated with the given configuration key.
     */
    protected abstract Object getPropertyDirect(String key);

    /**
     * Adds a key/value pair to the Configuration. Override this method to
     * provide write acces to underlying Configuration store.
     *
     * @param key key to use for mapping
     * @param obj object to store
     */
    protected abstract void addPropertyDirect(String key, Object obj);

    /**
     * interpolate key names to handle ${key} stuff
     *
     * @param base string to interpolate
     *
     * @return returns the key name with the ${key} substituted
     */
    protected String interpolate(String base)
    {
        return (interpolateHelper(base, null));
    }

    /**
     * Recursive handler for multple levels of interpolation.
     *
     * When called the first time, priorVariables should be null.
     *
     * @param base string with the ${key} variables
     * @param priorVariables serves two purposes: to allow checking for
     * loops, and creating a meaningful exception message should a loop
     * occur.  It's 0'th element will be set to the value of base from
     * the first call.  All subsequent interpolated variables are added
     * afterward.
     *
     * @return the string with the interpolation taken care of
     */
    protected String interpolateHelper(String base, List priorVariables)
    {
        if (base == null)
        {
            return null;
        }

        // on the first call initialize priorVariables
        // and add base as the first element
        if (priorVariables == null)
        {
            priorVariables = new ArrayList();
            priorVariables.add(base);
        }

        int begin = -1;
        int end = -1;
        int prec = 0 - END_TOKEN.length();
        String variable = null;
        StringBuffer result = new StringBuffer();

        // FIXME: we should probably allow the escaping of the start token
        while (((begin = base.indexOf(START_TOKEN, prec + END_TOKEN.length()))
            > -1)
            && ((end = base.indexOf(END_TOKEN, begin)) > -1))
        {
            result.append(base.substring(prec + END_TOKEN.length(), begin));
            variable = base.substring(begin + START_TOKEN.length(), end);

            // if we've got a loop, create a useful exception message and throw
            if (priorVariables.contains(variable))
            {
                String initialBase = priorVariables.remove(0).toString();
                priorVariables.add(variable);
                StringBuffer priorVariableSb = new StringBuffer();

                // create a nice trace of interpolated variables like so:
                // var1->var2->var3
                for (Iterator it = priorVariables.iterator(); it.hasNext();)
                {
                    priorVariableSb.append(it.next());
                    if (it.hasNext())
                    {
                        priorVariableSb.append("->");
                    }
                }

                throw new IllegalStateException(
                    "infinite loop in property interpolation of "
                        + initialBase
                        + ": "
                        + priorVariableSb.toString());
            }
            // otherwise, add this variable to the interpolation list.
            else
            {
                priorVariables.add(variable);
            }

            //QUESTION: getProperty or getPropertyDirect
            Object value = getProperty(variable);
            if (value != null)
            {
                result.append(interpolateHelper(value.toString(),
                    priorVariables));

                // pop the interpolated variable off the stack
                // this maintains priorVariables correctness for
                // properties with multiple interpolations, e.g.
                // prop.name=${some.other.prop1}/blahblah/${some.other.prop2}
                priorVariables.remove(priorVariables.size() - 1);
            }
            else if (defaults != null && defaults.getString(variable,
                null) != null)
            {
                result.append(defaults.getString(variable));
            }
            else
            {
                //variable not defined - so put it back in the value
                result.append(START_TOKEN).append(variable).append(END_TOKEN);
            }
            prec = end;
        }
        result.append(base.substring(prec + END_TOKEN.length(), base.length()));

        return result.toString();
    }

    /**
     * Returns a Vector of Strings built from the supplied
     * String. Splits up CSV lists. If no commas are in the
     * String, simply returns a Vector with the String as its
     * first element
     *
     * @param token The String to tokenize
     *
     * @return A List of Strings
     */
    protected List processString(String token)
    {
        List retList = new ArrayList(INITIAL_LIST_SIZE);

        if (token.indexOf(PropertiesTokenizer.DELIMITER) > 0)
        {
            PropertiesTokenizer tokenizer =
                new PropertiesTokenizer(token);

            while (tokenizer.hasMoreTokens())
            {
                String value = tokenizer.nextToken();
                retList.add(value);
            }
        }
        else
        {
            retList.add(token);
        }

        //
        // We keep the sequence of the keys here and
        // we also keep it in the Container. So the
        // Keys are added to the store in the sequence that
        // is given in the properties
        return retList;
    }


    /**
     * Test whether the string represent by value maps to a boolean
     * value or not. We will allow <code>true</code>, <code>on</code>,
     * and <code>yes</code> for a <code>true</code> boolean value, and
     * <code>false</code>, <code>off</code>, and <code>no</code> for
     * <code>false</code> boolean values. Case of value to test for
     * boolean status is ignored.
     *
     * @param value The value to test for boolean state.
     * @return <code>true</code> or <code>false</code> if the supplied
     * text maps to a boolean value, or <code>null</code> otherwise.
     */
    protected final Boolean testBoolean(String value)
    {
        String s = value.toLowerCase();

        if (s.equals("true") || s.equals("on") || s.equals("yes"))
        {
            return Boolean.TRUE;
        }
        else if (s.equals("false") || s.equals("off") || s.equals("no"))
        {
            return Boolean.FALSE;
        }
        else
        {
            return null;
        }
    }

    /**
     * Create an BaseConfiguration object that is a subset
     * of this one.
     *
     * @param prefix prefix string for keys
     *
     * @return subset of configuration if there is keys, that match
     * given prefix, or <code>null</code> if there is no such keys.
     */
    public Configuration subset(String prefix)
    {
        BaseConfiguration c = new BaseConfiguration();
        Iterator keys = this.getKeys();
        boolean validSubset = false;

        while (keys.hasNext())
        {
            Object key = keys.next();

            if (key instanceof String && ((String) key).startsWith(prefix))
            {
                if (!validSubset)
                {
                    validSubset = true;
                }

                String newKey = null;

                /*
                 * Check to make sure that c.subset(prefix) doesn't blow up when
                 * there is only a single property with the key prefix. This is
                 * not a useful subset but it is a valid subset.
                 */
                if (((String) key).length() == prefix.length())
                {
                    newKey = prefix;
                }
                else
                {
                    newKey = ((String) key).substring(prefix.length() + 1);
                }

                /*
                 * use addPropertyDirect() - this will plug the data as is into
                 * the Map, but will also do the right thing re key accounting
                 *
                 * QUESTION: getProperty or getPropertyDirect
                 */
                Object value = getProperty((String) key);
                if (value instanceof String)
                {
                    c.addPropertyDirect(newKey, interpolate((String) value));
                }
                else
                {
                    c.addProperty(newKey, value);
                }
            }
        }

        if (validSubset)
        {
            return c;
        }
        else
        {
            return null;
        }
    }

    /**
     * Check if the configuration is empty
     *
     * @return <code>true</code> if Configuration is empty,
     * <code>false</code> otherwise.
     */
    public abstract boolean isEmpty();

    /**
     * check if the configuration contains the key
     *
     * @param key the configuration key
     *
     * @return <code>true</code> if Configuration contain given key,
     * <code>false</code> otherwise.
     */
    public abstract boolean containsKey(String key);

    /**
     * Set a property, this will replace any previously
     * set values. Set values is implicitly a call
     * to clearProperty(key), addProperty(key,value).
     *
     * @param key the configuration key
     * @param value the property value
     */
    public void setProperty(String key, Object value)
    {
        clearProperty(key);
        addProperty(key, value); // QUESTION: or addPropertyDirect?
    }

    /**
     * Clear a property in the configuration.
     *
     * @param key the key to remove along with corresponding value.
     */
    public  abstract void clearProperty(String key);

    /**
     * Get the list of the keys contained in the configuration
     * repository.
     *
     * @return An Iterator.
     */
    public abstract Iterator getKeys();

    /**
     * Get the list of the keys contained in the configuration
     * repository that match the specified prefix.
     *
     * @param prefix The prefix to test against.
     *
     * @return An Iterator of keys that match the prefix.
     */
    public Iterator getKeys(String prefix)
    {
        Iterator keys = getKeys();
        ArrayList matchingKeys = new ArrayList();

        while (keys.hasNext())
        {
            Object key = keys.next();

            if (key instanceof String && ((String) key).startsWith(prefix))
            {
                matchingKeys.add(key);
            }
        }
        return matchingKeys.iterator();
    }

    /**
     * Get a list of properties associated with the given
     * configuration key.
     *
     * @param key The configuration key.
     *
     * @return The associated properties if key is found.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a String/Vector.
     * @throws IllegalArgumentException if one of the tokens is
     * malformed (does not contain an equals sign).
     *
     * @see #getProperties(String, Properties)
     */
    public Properties getProperties(String key)
    {
        return getProperties(key, null);
    }

    /**
     * Get a list of properties associated with the given
     * configuration key.
     *
     * @param key The configuration key.
     * @param defaults Any default values for the returned
     * <code>Properties</code> object.  Ignored if <code>null</code>.
     *
     * @return The associated properties if key is found.
     *
     * @throws ClassCastException is thrown if the key maps to an
     * object that is not a String/Vector of Strings.
     * @throws IllegalArgumentException if one of the tokens is
     * malformed (does not contain an equals sign).
     */
    public Properties getProperties(String key, Properties defaults)
    {
        /*
         * Grab an array of the tokens for this key.
         */
        String[] tokens = getStringArray(key);

        /*
         * Each token is of the form 'key=value'.
         */
        Properties props =
            (defaults == null ? new Properties() : new Properties(defaults));
        for (int i = 0; i < tokens.length; i++)
        {
            String token = tokens[i];
            int equalSign = token.indexOf('=');
            if (equalSign > 0)
            {
                String pkey = token.substring(0, equalSign).trim();
                String pvalue = token.substring(equalSign + 1).trim();
                props.put(pkey, pvalue);
            }
            else if (tokens.length == 1 && "".equals(token))
            {
                // Semantically equivalent to an empty Properties
                // object.
                break;
            }
            else
            {