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Ant example source code file (ChainReaderHelper.java)

This example Ant source code file (ChainReaderHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Ant tags/keywords

antfilterreader, basefilterreader, buildexception, buildexception, chainablereader, default_buffer_size, filterchain, io, project, project, reader, reader, reflection, string, util, vector, vector

The ChainReaderHelper.java source code

/*
 *  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.tools.ant.filters.util;

import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.Vector;
import org.apache.tools.ant.AntClassLoader;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.filters.BaseFilterReader;
import org.apache.tools.ant.filters.ChainableReader;
import org.apache.tools.ant.types.AntFilterReader;
import org.apache.tools.ant.types.FilterChain;
import org.apache.tools.ant.types.Parameter;
import org.apache.tools.ant.types.Parameterizable;
import org.apache.tools.ant.types.Path;
import org.apache.tools.ant.util.FileUtils;

/**
 * Process a FilterReader chain.
 *
 */
public final class ChainReaderHelper {

    // default buffer size
    private static final int DEFAULT_BUFFER_SIZE = 8192;
    // CheckStyle:VisibilityModifier OFF - bc
    /**
     * The primary reader to which the reader chain is to be attached.
     */
    public Reader primaryReader;

    /**
     * The size of the buffer to be used.
     */
    public int bufferSize = DEFAULT_BUFFER_SIZE;

    /**
     * Chain of filters
     */
    public Vector filterChains = new Vector();

    /** The Ant project */
    private Project project = null;

    // CheckStyle:VisibilityModifier ON

    /**
     * Sets the primary reader
     * @param rdr the reader object
     */
    public void setPrimaryReader(Reader rdr) {
        primaryReader = rdr;
    }

    /**
     * Set the project to work with
     * @param project the current project
     */
    public void setProject(final Project project) {
        this.project = project;
    }

    /**
     * Get the project
     *
     * @return the current project
     */
    public Project getProject() {
        return project;
    }

    /**
     * Sets the buffer size to be used.  Defaults to 8192,
     * if this method is not invoked.
     * @param size the buffer size to use
     */
    public void setBufferSize(int size) {
        bufferSize = size;
    }

    /**
     * Sets the collection of filter reader sets
     *
     * @param fchain the filter chains collection
     */
    public void setFilterChains(Vector fchain) {
        filterChains = fchain;
    }

    /**
     * Assemble the reader
     * @return the assembled reader
     * @exception BuildException if an error occurs
     */
    public Reader getAssembledReader() throws BuildException {
        if (primaryReader == null) {
            throw new BuildException("primaryReader must not be null.");
        }

        Reader instream = primaryReader;
        final int filterReadersCount = filterChains.size();
        final Vector finalFilters = new Vector();

        for (int i = 0; i < filterReadersCount; i++) {
            final FilterChain filterchain =
                (FilterChain) filterChains.elementAt(i);
            final Vector filterReaders = filterchain.getFilterReaders();
            final int readerCount = filterReaders.size();
            for (int j = 0; j < readerCount; j++) {
                finalFilters.addElement(filterReaders.elementAt(j));
            }
        }

        final int filtersCount = finalFilters.size();

        if (filtersCount > 0) {
            for (int i = 0; i < filtersCount; i++) {
                Object o = finalFilters.elementAt(i);

                if (o instanceof AntFilterReader) {
                    final AntFilterReader filter
                        = (AntFilterReader) finalFilters.elementAt(i);
                    final String className = filter.getClassName();
                    final Path classpath = filter.getClasspath();
                    final Project pro = filter.getProject();
                    if (className != null) {
                        try {
                            Class clazz = null;
                            if (classpath == null) {
                                clazz = Class.forName(className);
                            } else {
                                AntClassLoader al
                                    = pro.createClassLoader(classpath);
                                clazz = Class.forName(className, true, al);
                            }
                            if (clazz != null) {
                                if (!FilterReader.class.isAssignableFrom(clazz)) {
                                    throw new BuildException(className
                                        + " does not extend java.io.FilterReader");
                                }
                                final Constructor[] constructors =
                                    clazz.getConstructors();
                                int j = 0;
                                boolean consPresent = false;
                                for (; j < constructors.length; j++) {
                                    Class[] types = constructors[j]
                                                      .getParameterTypes();
                                    if (types.length == 1
                                        && types[0].isAssignableFrom(Reader.class)) {
                                        consPresent = true;
                                        break;
                                    }
                                }
                                if (!consPresent) {
                                    throw new BuildException(className
                                        + " does not define a public constructor"
                                        + " that takes in a Reader as its "
                                        + "single argument.");
                                }
                                final Reader[] rdr = {instream};
                                instream =
                                    (Reader) constructors[j].newInstance((Object[]) rdr);
                                setProjectOnObject(instream);
                                if (Parameterizable.class.isAssignableFrom(clazz)) {
                                    final Parameter[] params = filter.getParams();
                                    ((Parameterizable)
                                        instream).setParameters(params);
                                }
                            }
                        } catch (final ClassNotFoundException cnfe) {
                            throw new BuildException(cnfe);
                        } catch (final InstantiationException ie) {
                            throw new BuildException(ie);
                        } catch (final IllegalAccessException iae) {
                            throw new BuildException(iae);
                        } catch (final InvocationTargetException ite) {
                            throw new BuildException(ite);
                        }
                    }
                } else if (o instanceof ChainableReader) {
                    setProjectOnObject(o);
                    instream = ((ChainableReader) o).chain(instream);
                    setProjectOnObject(instream);
                }
            }
        }
        return instream;
    }

    /**
     * helper method to set the project on an object.
     * the reflection setProject does not work for anonymous/protected/private
     * classes, even if they have public methods.
     */
    private void setProjectOnObject(Object obj) {
        if (project == null) {
            return;
        }
        if (obj instanceof BaseFilterReader) {
            ((BaseFilterReader) obj).setProject(project);
            return;
        }
        project.setProjectReference(obj);
    }

    /**
     * Read data from the reader and return the
     * contents as a string.
     * @param rdr the reader object
     * @return the contents of the file as a string
     * @exception IOException if an error occurs
     */
    public String readFully(Reader rdr)
        throws IOException {
        return FileUtils.readFully(rdr, bufferSize);
    }
}

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