prajna.servlet

Class RecordAccessorServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

prajna.servlet.RecordAccessorServlet

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

CoordinatorAccessorServlet, FusionAccessorServlet

public abstract class RecordAccessorServlet
extends javax.servlet.http.HttpServlet

Handles server-side semantic accessors. The SemanticAccessorServlet provides the data from a server-based RecordAccessor as textual output in various formats The servlet uses a StructureWriter to specify the format and write out its data. The SemanticAccessorServlet can also serialize the results and send the serialized results to a RecordAccessorClient. The servlet can handle multiple accessors simultaneously, coordinating queries to different accessors with any particular request.

Concrete implementations of this class should initialize the accessor in the servlet init method.

Author:

Edward Swing

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RecordAccessorServlet()

Method Summary

Methods

Modifier and Type	Method and Description
void	doGet(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse res) Handles the servlet GET request.
protected void	generateData(java.lang.String dataName, java.lang.String nodeName, javax.servlet.http.HttpServletResponse res, boolean serial) Generate the data for the named data structure, sending it on the response.
RecordAccessor	getAccessor() Get the data accessor currently used
javax.xml.parsers.DocumentBuilder	getDocBuilder() Get the document builder used to generate XML.
StructureWriter	getSemanticWriter() Get the semantic writer used to format the data structures
javax.xml.transform.Transformer	getTransformer() Get the transformer used to format or transform the XML output.
protected boolean	isDebug() Return whether the servlet is in debug mode for a particular request.
void	setAccessor(RecordAccessor accessor) Set the SemanticAccessor used by this servlet.
protected void	setDebug(boolean debugFlag) Set the debug flag
void	setSemanticWriter(StructureWriter writer) Set the semantic writer used by this servlet.
protected void	writeXml(org.w3c.dom.Document doc, javax.servlet.http.HttpServletResponse res) Write the XML document out to the Servlet Response.

Methods inherited from class javax.servlet.http.HttpServlet

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

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Constructor Detail

RecordAccessorServlet

public RecordAccessorServlet()

Method Detail

doGet

public void doGet(javax.servlet.http.HttpServletRequest req,
         javax.servlet.http.HttpServletResponse res)
           throws javax.servlet.ServletException,
                  java.io.IOException

Handles the servlet GET request. This method accepts several parameters:

• name: the name of the data structure requested. If not specified, the servlet generates a list of the data structure names available instead of the content of a particular data structure.
• node: The name of the node within the data structure. This is used for expanding a graph or tree, and is only valid if the name parameter is also specified
• query: If the name parameter is not set, the query parameter specifies what type of data structure the servlet should generate names for. If neither query nor name are set, all named structures are returned.
• serial: if set to true, the servlet writes the data structure out to a serialized stream, instead of using the SemanticWriter to format the output
• debug: if true, activate debugging for this request

Overrides:

doGet in class javax.servlet.http.HttpServlet

Parameters:

req - the request the client has made of the servlet

res - the response the servlet sends to the client

Throws:

javax.servlet.ServletException - if the request could not be handled

java.io.IOException - if an input or output error is detected when the servlet handles the request

generateData

protected void generateData(java.lang.String dataName,
                java.lang.String nodeName,
                javax.servlet.http.HttpServletResponse res,
                boolean serial)
                     throws java.io.IOException

Generate the data for the named data structure, sending it on the response. This method is available so that subclasses can invoke this method.

Parameters:

dataName - the name of the data structure.

nodeName - the name of a node within the data structure. If set, the semantic accessor will use the name to expand a data structure. If null, the accessor will generate data without regard to any particular node.

res - the servlet response object

serial - whether to serialize the data.

Throws:

java.io.IOException - if there is a problem writing the data

getAccessor

public RecordAccessor getAccessor()

Get the data accessor currently used

Returns:

the dataAccessor

getDocBuilder

public javax.xml.parsers.DocumentBuilder getDocBuilder()

Get the document builder used to generate XML. Initializes the document builder if it has not been initialized yet.

Returns:

the document builder

getSemanticWriter

public StructureWriter getSemanticWriter()

Get the semantic writer used to format the data structures

Returns:

the semantic Writer

getTransformer

public javax.xml.transform.Transformer getTransformer()

Get the transformer used to format or transform the XML output. Initializes the transformer if it has not been initialized.

Returns:

the transformer

isDebug

protected boolean isDebug()

Return whether the servlet is in debug mode for a particular request.

Returns:

the debug flag

setAccessor

public void setAccessor(RecordAccessor accessor)

Set the SemanticAccessor used by this servlet. By default, a DataCoordinator is used to coordinate between multiple accessors.

Parameters:

accessor - the semantic accessor

setDebug

protected void setDebug(boolean debugFlag)

Set the debug flag

Parameters:

debugFlag - the debug flag

setSemanticWriter

public void setSemanticWriter(StructureWriter writer)

Set the semantic writer used by this servlet. If not set, this servlet uses a StructureWriter

Parameters:

writer - the semanticWriter

writeXml

protected void writeXml(org.w3c.dom.Document doc,
            javax.servlet.http.HttpServletResponse res)

Write the XML document out to the Servlet Response. The content type of the response is set using the SemanticWriter.getContentType() method. The document is transformed by the internal transformer, and written to the servlet response object

Parameters:

doc - the XML document

res - the servlet response object