org.wso2.carbon.dataservices.core.engine.DSOMDataSource.java Source code

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Here is the source code for org.wso2.carbon.dataservices.core.engine.DSOMDataSource.java

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/*
 *  Copyright (c) 2005-2010, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 *  WSO2 Inc. 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.wso2.carbon.dataservices.core.engine;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.OutputStream;
import java.io.Writer;
import java.util.Map;

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

import org.apache.axiom.om.OMDataSource;
import org.apache.axiom.om.OMOutputFormat;
import org.apache.commons.io.output.NullOutputStream;
import org.wso2.carbon.dataservices.core.DBUtils;
import org.wso2.carbon.dataservices.core.DataServiceFault;

/**
 * This class represents the data source for an OMElement,
 * where the generation of data is encapsulated in this object,
 * and it is used in on-demand data retrieval, and effectively
 * streaming data.
 */
public class DSOMDataSource implements OMDataSource {

    private static final int XMLREADER_DEFAULT_MESSAGE_SIZE = 1024;

    private DataService dataService;

    private String opName;

    private Map<String, ParamValue> params;

    public DSOMDataSource(DataService dataService, String opName, Map<String, ParamValue> params) {
        this.dataService = dataService;
        this.opName = opName;
        this.params = params;
    }

    public DataService getDataService() {
        return dataService;
    }

    public String getOpName() {
        return opName;
    }

    public Map<String, ParamValue> getParams() {
        return params;
    }

    /**
     * This method is called when the current request is a in-only operations,
     * so a result is not expected.
     */
    public void executeInOnly() throws XMLStreamException {
        /* in case there is a result, write it to /dev/null */
        XMLStreamWriter xmlWriter = DBUtils.getXMLOutputFactory().createXMLStreamWriter(new NullOutputStream());
        this.serialize(xmlWriter);
    }

    public void serialize(OutputStream output, OMOutputFormat format) throws XMLStreamException {
        XMLStreamWriter xmlWriter = DBUtils.getXMLOutputFactory().createXMLStreamWriter(output);
        this.serialize(xmlWriter);
    }

    public void serialize(Writer writer, OMOutputFormat format) throws XMLStreamException {
        XMLStreamWriter xmlWriter = DBUtils.getXMLOutputFactory().createXMLStreamWriter(writer);
        this.serialize(xmlWriter);
    }

    public void execute(XMLStreamWriter xmlWriter) throws XMLStreamException {
        try {
            this.getDataService().invoke(xmlWriter, this.getOpName(), this.getParams());
            /* flush the stream, if there's a result */
            if (xmlWriter != null) {
                xmlWriter.flush();
            }
        } catch (DataServiceFault e) {
            throw new XMLStreamException(e.getMessage(), e);
        }
    }

    public void serialize(XMLStreamWriter xmlWriter) throws XMLStreamException {
        this.execute(xmlWriter);
    }

    public XMLStreamReader getReader() throws XMLStreamException {
        ByteArrayOutputStream byteOut = new ByteArrayOutputStream(XMLREADER_DEFAULT_MESSAGE_SIZE);
        XMLStreamWriter xmlWriter = DBUtils.getXMLOutputFactory().createXMLStreamWriter(byteOut);
        this.serialize(xmlWriter);
        xmlWriter.close();
        ByteArrayInputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());
        return DBUtils.getXMLInputFactory().createXMLStreamReader(byteIn);
    }

}