xqueryprocessor.java

Web-Harvest是一个Java开源Web数据抽取工具。它能够收集指定的Web页面并从这些页面中提取有用的数据。Web-Harvest主要是运用了像XSLT,XQuery,正则表达式等这些技术来实

/*  Copyright (c) 2006-2007, Vladimir Nikic
    All rights reserved.

    Redistribution and use of this software in source and binary forms,
    with or without modification, are permitted provided that the following
    conditions are met:

    * Redistributions of source code must retain the above
      copyright notice, this list of conditions and the
      following disclaimer.

    * Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the
      following disclaimer in the documentation and/or other
      materials provided with the distribution.

    * The name of Web-Harvest may not be used to endorse or promote
      products derived from this software without specific prior
      written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.

    You can contact Vladimir Nikic by sending e-mail to
    [e-mail]. Please include the word "Web-Harvest" in the
    subject line.
*/
package org.webharvest.runtime.processors;

import net.sf.saxon.Configuration;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.query.*;
import net.sf.saxon.trans.XPathException;
import org.webharvest.definition.XQueryDef;
import org.webharvest.definition.XQueryExternalParamDef;
import org.webharvest.definition.BaseElementDef;
import org.webharvest.exception.ScraperXQueryException;
import org.webharvest.runtime.Scraper;
import org.webharvest.runtime.ScraperContext;
import org.webharvest.runtime.variables.*;
import org.webharvest.utils.CommonUtil;

import javax.xml.transform.stream.StreamSource;
import java.io.StringReader;
import java.util.*;

/**
 * XQuery processor.
 */
public class XQueryProcessor extends BaseProcessor {

    public static Set ALLOWED_PARAM_TYPES = new TreeSet();
    public static String DEFAULT_PARAM_TYPE = "node()";

    // initialize set of allowed parameter types
    static {
        ALLOWED_PARAM_TYPES.add("node()");
        ALLOWED_PARAM_TYPES.add("node()*");
        ALLOWED_PARAM_TYPES.add("integer");
        ALLOWED_PARAM_TYPES.add("integer*");
        ALLOWED_PARAM_TYPES.add("long");
        ALLOWED_PARAM_TYPES.add("long*");
        ALLOWED_PARAM_TYPES.add("float");
        ALLOWED_PARAM_TYPES.add("float*");
        ALLOWED_PARAM_TYPES.add("double");
        ALLOWED_PARAM_TYPES.add("double*");
        ALLOWED_PARAM_TYPES.add("boolean");
        ALLOWED_PARAM_TYPES.add("boolean*");
        ALLOWED_PARAM_TYPES.add("string");
        ALLOWED_PARAM_TYPES.add("string*");
    }

    private XQueryDef xqueryDef;

    public XQueryProcessor(XQueryDef xqueryDef) {
        super(xqueryDef);
        this.xqueryDef = xqueryDef;
    }

    public IVariable execute(Scraper scraper, ScraperContext context) {
        BaseElementDef xqueryElementDef = xqueryDef.getXqDef();
        IVariable xq = getBodyTextContent(xqueryElementDef, scraper, context);
        debug(xqueryElementDef, scraper, xq);

        String xqExpression = xq.toString().trim();
        XQueryExternalParamDef[] externalParamDefs = xqueryDef.getExternalParamDefs();

		final Configuration config = new Configuration();
	    final StaticQueryContext sqc = new StaticQueryContext(config);

	    try {
	        final XQueryExpression exp = sqc.compileQuery(xqExpression);
		    final DynamicQueryContext dynamicContext = new DynamicQueryContext(config);

            // define external parameters
            for (int i = 0; i < externalParamDefs.length; i++) {
                XQueryExternalParamDef externalParamDef = externalParamDefs[i];
                String externalParamType = externalParamDefs[i].getType();
                if (externalParamType == null) {
                    externalParamType = DEFAULT_PARAM_TYPE;
                }

                // check if param type is one of allowed
                if ( !ALLOWED_PARAM_TYPES.contains(externalParamType) ) {
                    throw new ScraperXQueryException("Type " + externalParamType + " is not allowed. Use one of " + ALLOWED_PARAM_TYPES.toString());
                }

                if ( externalParamType.endsWith("*") ) {
                    ListVariable listVar = (ListVariable) getBodyListContent(externalParamDef, scraper, context);
                    debug(externalParamDef, scraper, listVar);
                    
                    Iterator it = listVar.toList().iterator();
                    List paramList = new ArrayList(); 
                    while (it.hasNext()) {
                        IVariable currVar =  (IVariable) it.next();
                        paramList.add( castSimpleValue(externalParamType, currVar, sqc) );
                    }

                    dynamicContext.setParameter(externalParamDef.getName(), paramList);
                } else {
                    IVariable var = getBodyTextContent(externalParamDef, scraper, context);

                    debug(externalParamDef, scraper, var);
                    
                    Object value = castSimpleValue(externalParamType, var, sqc);
                    dynamicContext.setParameter(externalParamDef.getName(), value);
                }
            }

            final SequenceIterator iter = exp.iterator(dynamicContext);
		    
		    ListVariable listVariable = new ListVariable();
		    while (true) {
	            Item item = iter.next();
	            if (item == null) {
	                break;
	            }
	            
	            String value = CommonUtil.serializeItem(item, config);
	            listVariable.addVariable( new NodeVariable(value) );
	        }

	        return listVariable;
	    } catch (XPathException e) {
	    	throw new ScraperXQueryException("Error executing XQuery expression (XQuery = [" + xqExpression + "])!", e);
	    }
    }

    /**
     * For the specified type, value and static query context, returns proper Java typed value. 
     * @param type
     * @param value
     * @param sqc
     * @return
     * @throws XPathException
     */
    private Object castSimpleValue(String type, IVariable value, StaticQueryContext sqc) throws XPathException {
        type = type.toLowerCase();

        if ( type.startsWith("node()") ) {
            StringReader reader = new StringReader(value.toString() );
            return sqc.buildDocument(new StreamSource(reader));
        } else if ( type.startsWith("integer") ) {
            return new Integer( value.toString() );
        } else if ( type.startsWith("long") ) {
            return new Long( value.toString() );
        } else if ( type.startsWith("float") ) {
            return new Float( value.toString() );
        } else if ( type.startsWith("double") ) {
            return new Double( value.toString() );
        } else if ( type.startsWith("boolean") ) {
            return CommonUtil.isBooleanTrue(value.toString()) ? Boolean.TRUE : Boolean.FALSE;
        } else {
            return value.toString();
        }
    }

}