it.unimi.di.mg4j.query
Class QueryServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.apache.velocity.tools.view.servlet.VelocityViewServlet
              it.unimi.di.mg4j.query.QueryServlet

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public class QueryServlet
extends VelocityViewServlet

A query servlet.

This class provides a basic servlet for searching a collection. It expects some data (a collection, an index map and a path) in the ServletContext (see the code for init()). It can be used to search in a collection, but it is essentially a worked-out example.

The three parameters are q, the query, m, the maximum number of results to be displayed, and s, the first result to be displayed.

Usually, the URI associated with each result is taken from the collection. Alternatively, each result will point to the /Item path with some query arguments (doc, containing the document pointer, uri, containing the original URI, and m, containing an optional suggested MIME type). See, for instance, GenericItem and InputStreamItem.

The Velocity template used by this servlet can be set using the initialisation parameter template (or using a context attribute with the same name). If you're using this servlet via HttpQueryServer, please read the documentation therein for information about template resolution order.

This servlet is thread safe. Each instance uses its own flyweight copies of the collection and query engine to return the result (in particular, snippets). In a production site it might be more sensible to pool and reuse such classes.

Warning: the loadConfiguration(ServletConfig) method initialises Velocity with some default parameters: in particular, template resolution is performed first on the classpath, then relatively to the current directory, and finally using absolute pathnames. Watch out for template resolution issues.

See Also:

Serialized Form

Field Summary

protected static String	DEFAULT_TEMPLATE The default Velocity template used by this servlet; may be overriden in the context using an attribute named template.
protected DocumentCollection	documentCollection The document collection.
protected Object2ReferenceMap<String,Index>	indexMap A sorted map from index names to indices: the first entry is the default index.
protected QueryEngine	queryEngine The query engine.
protected String	template The actual template used by this servlet (default: DEFAULT_TEMPLATE).
protected List<CharSequence>	titleList An optional title list if the document collection is not present.

Fields inherited from class org.apache.velocity.tools.view.servlet.VelocityViewServlet

CONTENT_TYPE, DEFAULT_CONTENT_TYPE, DEFAULT_OUTPUT_ENCODING, DEFAULT_PROPERTIES_PATH, DEFAULT_TOOLBOX_PATH, DEFAULT_TOOLS_PROPERTIES, INIT_PROPS_KEY, SERVLET_CONTEXT_KEY, TOOLBOX_KEY, toolboxManager

Constructor Summary

QueryServlet()

Method Summary

Template	handleRequest(HttpServletRequest request, HttpServletResponse response, Context context)
void	init()
protected ExtendedProperties	loadConfiguration(ServletConfig config)

Methods inherited from class org.apache.velocity.tools.view.servlet.VelocityViewServlet

createContext, doGet, doPost, doRequest, error, findInitParameter, getResponseWriter, getTemplate, getTemplate, getVelocityEngine, getVelocityProperty, init, initToolbox, initVelocity, mergeTemplate, performMerge, requestCleanup, setContentType, setVelocityEngine

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_TEMPLATE

protected static final String DEFAULT_TEMPLATE

The default Velocity template used by this servlet; may be overriden in the context using an attribute named template.

See Also:

Constant Field Values

template

protected String template

The actual template used by this servlet (default: DEFAULT_TEMPLATE).

queryEngine

protected QueryEngine queryEngine

The query engine.

documentCollection

protected DocumentCollection documentCollection

The document collection.

titleList

protected List<CharSequence> titleList

An optional title list if the document collection is not present.

indexMap

protected Object2ReferenceMap<String,Index> indexMap

A sorted map from index names to indices: the first entry is the default index.

Constructor Detail

QueryServlet

public QueryServlet()

Method Detail

loadConfiguration

protected ExtendedProperties loadConfiguration(ServletConfig config)
                                        throws FileNotFoundException,
                                               IOException

Overrides:

loadConfiguration in class VelocityViewServlet

Throws:

FileNotFoundException

IOException

init

public void init()
          throws ServletException

Overrides:

init in class GenericServlet

Throws:

ServletException

handleRequest

public Template handleRequest(HttpServletRequest request,
                              HttpServletResponse response,
                              Context context)

Overrides:

handleRequest in class VelocityViewServlet