babel.content.pages.MetaData.java Source code

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Here is the source code for babel.content.pages.MetaData.java

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/**
 * This file is licensed 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 babel.content.pages;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.XMLStreamWriter;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.nutch.metadata.Metadata;

import babel.util.persistence.XMLPersistable;

/**
 * Stores key-value matadata (allowing for multiple values per key).
 */
public class MetaData implements XMLPersistable, Writable {
    private static final String XML_TAG_METADATA = "MetaData";
    private static final String XML_ATTRIB_TYPE = "Type";

    public MetaData() {
        this(null);
    }

    public MetaData(String typeLabel) {
        m_typeLabel = (typeLabel == null) ? new String() : typeLabel;
        m_metadata = new Metadata();
    }

    public MetaData(String typeLabel, Metadata nutchMeta) {
        this(typeLabel);
        setAll(nutchMeta);
    }

    /**
     * Associates a given value with a given key. Previous value(s) associated
     * with the key are removed. 
     */
    public void set(String key, String value) {
        if (key != null && value != null && key.length() > 0 && value.length() > 0) {
            m_metadata.set(key, value);
        }
    }

    /**
    * Adds a given key / value pair. 
    */
    public void add(String key, String value) {
        if (key != null && value != null && key.length() > 0 && value.length() > 0) {
            m_metadata.add(key, value);
        }
    }

    public void add(String key, String[] values) {
        if (key != null && values != null && key.length() > 0 && values.length > 0) {
            for (String val : values) {
                if (val.length() > 0) {
                    m_metadata.add(key, val);
                }
            }
        }
    }

    /**
     * Removes all values associated with the given key.
     */
    public void remove(String key) {
        m_metadata.remove(key);
    }

    public void clear() {
        m_metadata.clear();
    }

    /**
     * @return all values associated with the given key, or null if none.
     */
    public String[] get(String key) {
        String[] vals = m_metadata.getValues(key);
        return (vals == null || vals.length == 0) ? null : vals;
    }

    /**
    * @return the first value associated with the given key, or null if none.
    */
    public String getFirst(String key) {
        String[] vals = m_metadata.getValues(key);
        return (vals == null || vals.length == 0) ? null : vals[0];
    }

    public void setAll(Metadata nutchMeta) {
        m_metadata.clear();

        String[] keys = nutchMeta.names();
        String[] vals;

        for (int i = 0; i < keys.length; i++) {
            vals = nutchMeta.getValues(keys[i]);

            for (int j = 0; j < vals.length; j++) {
                m_metadata.add(keys[i], vals[j]);
            }
        }
    }

    public boolean hasKey(String key) {
        return (m_metadata.get(key) != null);
    }

    public int numKeys() {
        return m_metadata.size();
    }

    public String[] keys() {
        return m_metadata.names();
    }

    public String toString() {
        StringBuilder strBld = new StringBuilder();

        strBld.append((m_typeLabel.length() > 0) ? m_typeLabel + " " : "");
        strBld.append("MetaData : ");

        strBld.append(m_metadata.toString());

        return strBld.toString();
    }

    public boolean equals(Object obj) {
        boolean same = obj instanceof MetaData;

        if (same) {
            MetaData other = (MetaData) obj;
            same = m_typeLabel.equals(other.m_typeLabel) && m_metadata.equals(other.m_metadata);
        }

        return same;
    }

    /**
     * Persist the object's state.
     */
    public void persist(XMLStreamWriter writer) throws XMLStreamException {
        writer.writeStartElement(XML_TAG_METADATA);

        if (m_typeLabel.length() > 0) {
            writer.writeAttribute(XML_ATTRIB_TYPE, m_typeLabel.toString());
        }

        String[] names = m_metadata.names();
        String[] vals;

        for (String name : names) {
            vals = m_metadata.getValues(name);

            for (String val : vals) {
                writer.writeStartElement(name);
                writer.writeCharacters(val);
                writer.writeEndElement();
            }
        }

        writer.writeEndElement();
    }

    public void unpersist(XMLStreamReader reader) throws XMLStreamException {
        String elemTag;
        String elemVal;

        m_typeLabel = reader.getAttributeValue(0);
        m_metadata.clear();

        while (true) {
            int event = reader.next();
            if (event == XMLStreamConstants.END_ELEMENT && XML_TAG_METADATA.equals(reader.getName().toString())) {
                break;
            }

            if (event == XMLStreamConstants.START_ELEMENT) {
                elemTag = reader.getName().toString();
                elemVal = reader.getElementText();

                add(elemTag, elemVal);
            }
        }
    }

    public void readFields(DataInput in) throws IOException {
        m_typeLabel = Text.readString(in);

        m_metadata.clear();
        m_metadata.readFields(in);
    }

    public void write(DataOutput out) throws IOException {
        Text.writeString(out, m_typeLabel);
        m_metadata.write(out);
    }

    protected String m_typeLabel;
    protected Metadata m_metadata;
}