mondrian.spi.impl.FilterDynamicSchemaProcessor.java Source code

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Here is the source code for mondrian.spi.impl.FilterDynamicSchemaProcessor.java

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/*
// $Id: //open/mondrian/src/main/mondrian/spi/impl/FilterDynamicSchemaProcessor.java#5 $
// This software is subject to the terms of the Eclipse Public License v1.0
// Agreement, available at the following URL:
// http://www.eclipse.org/legal/epl-v10.html.
// Copyright (C) 2007-2009 Julian Hyde
// All Rights Reserved.
// You must accept the terms of that agreement to use this software.
 */
package mondrian.spi.impl;

import mondrian.spi.DynamicSchemaProcessor;
import mondrian.olap.Util;
import org.apache.commons.vfs.FileObject;
import org.apache.commons.vfs.FileContent;

import java.io.File;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;

/**
 * Implementation of {@link DynamicSchemaProcessor} which allows a derived class
 * to easily process a schema file.
 * 
 * <p>
 * Mondrian's default mechanism for loading schema files, if no
 * DynamicSchemaProcessor is specified, is to use Apache VFS (virtual file
 * system) to resolve the URL to a stream, and to read the contents of the
 * stream into a string.
 * 
 * <p>
 * FilterDynamicSchemaProcessor implements exactly the same mechanism, but makes
 * it easy for a derived class to override the mechanism. For example:
 * <ul>
 * 
 * <li>To redirect to a different URL, override the
 * {@link #processSchema(String, mondrian.olap.Util.PropertyList)} method.
 * 
 * <li>To process the contents of the URL, override the
 * {@link #filter(String, mondrian.olap.Util.PropertyList, java.io.InputStream)}
 * method.
 * 
 * </ul>
 * 
 * @author jhyde
 * @version $Id:
 *          //open/mondrian/src/main/mondrian/spi/impl/FilterDynamicSchemaProcessor
 *          .java#5 $
 * @since Mar 30, 2007
 */
public class FilterDynamicSchemaProcessor implements DynamicSchemaProcessor {

    /**
     * {@inheritDoc}
     * 
     * <p>
     * FilterDynamicSchemaProcessor's implementation of this method reads from the
     * URL supplied (that is, it does not perform URL translation) and passes it
     * through the {@link #filter} method.
     */
    public String processSchema(String schemaUrl, Util.PropertyList connectInfo) throws Exception {
        InputStream in = Util.readVirtualFile(schemaUrl);
        return filter(schemaUrl, connectInfo, in);
    }

    /**
     * Reads the contents of a schema as a stream and returns the result as a
     * string.
     * 
     * <p>
     * The default implementation returns the contents of the schema unchanged.
     * 
     * @param schemaUrl
     *          the URL of the catalog
     * @param connectInfo
     *          Connection properties
     * @param stream
     *          Schema contents represented as a stream
     * @return the modified schema
     * @throws Exception
     *           if an error occurs
     */
    protected String filter(String schemaUrl, Util.PropertyList connectInfo, InputStream stream) throws Exception {
        BufferedReader in = new BufferedReader(new InputStreamReader(stream));
        try {
            StringBuilder builder = new StringBuilder();
            char[] buf = new char[2048];
            int readCount;
            while ((readCount = in.read(buf, 0, buf.length)) >= 0) {
                builder.append(buf, 0, readCount);
            }
            return builder.toString();
        } finally {
            in.close();
        }
    }
}

// End FilterDynamicSchemaProcessor.java