com.bigdata.rdf.sail.webapp

Class BigdataServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

com.bigdata.rdf.sail.webapp.BigdataServlet

All Implemented Interfaces:

IMimeTypes, Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

BigdataRDFServlet, CountersServlet

public abstract class BigdataServlet
extends javax.servlet.http.HttpServlet
implements IMimeTypes

Useful glue for implementing service actions, but does not directly implement any service action/

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	ATTRIBUTE_RDF_CONTEXT The name of the ServletContext attribute whose value is the BigdataRDFContext.
protected static String	charset The character set used for the response (not negotiated).
protected static String	DELETE
protected static String	GET
static int	HTTP_BADREQUEST Some HTTP response status codes
static String	HTTP_HEADER_BIGDATA_READ_ONLY HTTP header may be used to specify that the request is for read only.
static int	HTTP_INTERNALERROR Some HTTP response status codes
static int	HTTP_METHOD_NOT_ALLOWED Some HTTP response status codes
static int	HTTP_NOTFOUND Some HTTP response status codes
static int	HTTP_NOTIMPLEMENTED Some HTTP response status codes
static int	HTTP_OK Some HTTP response status codes
protected static String	POST
protected static String	PUT

Fields inherited from interface com.bigdata.rdf.sail.webapp.client.IMimeTypes

MIME_APPLICATION_JSON, MIME_APPLICATION_URL_ENCODED, MIME_APPLICATION_XML, MIME_DEFAULT_BINARY, MIME_GRAPH_ML, MIME_PROPERTIES_XML, MIME_TEXT_HTML, MIME_TEXT_JAVASCRIPT, MIME_TEXT_PLAIN

Constructor Summary

Constructors

Constructor and Description
BigdataServlet()

Method Summary

Methods

Modifier and Type	Method and Description
static void	buildAndCommitResponse(javax.servlet.http.HttpServletResponse resp, int status, String mimeType, String content, NV... headers) Generate and commit a response having the indicated http status code, mime type, and content.
protected static org.openrdf.model.Resource[]	decodeContexts(javax.servlet.http.HttpServletRequest req, String name) Decode an array of named graph contexts from a request.
protected BigdataRDFContext	getBigdataRDFContext()
protected boolean	getBooleanValue(javax.servlet.http.HttpServletRequest req, String name, boolean defaultValue) Return the effective boolean value of a request parameter.
protected IIndexManager	getIndexManager() The backing IIndexManager.
static IIndexManager	getIndexManager(javax.servlet.ServletContext servletContext) The backing IIndexManager.
static String[]	getServiceURIs(javax.servlet.ServletContext servletContext, javax.servlet.http.HttpServletRequest req) Return the serviceURI(s) for this service (one or more).
protected static String	readFully(Reader reader)
protected <T> FutureTask<T>	submitApiTask(AbstractRestApiTask<T> task) Submit a task, await its Future, flush and commit the servlet resdponse, and then a completed Future for that task.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, 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

Field Detail

ATTRIBUTE_RDF_CONTEXT

public static final transient String ATTRIBUTE_RDF_CONTEXT

The name of the ServletContext attribute whose value is the BigdataRDFContext.

charset

protected static final String charset

The character set used for the response (not negotiated).

See Also:

Constant Field Values

GET

protected static final transient String GET

See Also:

Constant Field Values

POST

protected static final transient String POST

See Also:

Constant Field Values

PUT

protected static final transient String PUT

See Also:

Constant Field Values

DELETE

protected static final transient String DELETE

See Also:

Constant Field Values

HTTP_HEADER_BIGDATA_READ_ONLY

public static final String HTTP_HEADER_BIGDATA_READ_ONLY

HTTP header may be used to specify that the request is for read only.

See Also:

Constant Field Values

HTTP_OK

public static final transient int HTTP_OK

Some HTTP response status codes

See Also:

Constant Field Values

HTTP_NOTFOUND

public static final transient int HTTP_NOTFOUND

Some HTTP response status codes

See Also:

Constant Field Values

HTTP_BADREQUEST

public static final transient int HTTP_BADREQUEST

Some HTTP response status codes

See Also:

Constant Field Values

HTTP_METHOD_NOT_ALLOWED

public static final transient int HTTP_METHOD_NOT_ALLOWED

Some HTTP response status codes

See Also:

Constant Field Values

HTTP_INTERNALERROR

public static final transient int HTTP_INTERNALERROR

Some HTTP response status codes

See Also:

Constant Field Values

HTTP_NOTIMPLEMENTED

public static final transient int HTTP_NOTIMPLEMENTED

Some HTTP response status codes

See Also:

Constant Field Values

Constructor Detail

BigdataServlet

public BigdataServlet()

Method Detail

getBigdataRDFContext

protected final BigdataRDFContext getBigdataRDFContext()

getIndexManager

protected IIndexManager getIndexManager()

The backing IIndexManager.

getIndexManager

public static IIndexManager getIndexManager(javax.servlet.ServletContext servletContext)

The backing IIndexManager.

submitApiTask

protected <T> FutureTask<T> submitApiTask(AbstractRestApiTask<T> task)
                               throws DatasetNotFoundException,
                                      InterruptedException,
                                      ExecutionException,
                                      IOException,
                                      TimeoutException

Submit a task, await its Future, flush and commit the servlet resdponse, and then a completed Future for that task. The task will be run on the appropriate executor service depending on the nature of the backing database and the view required by the task.

The servlet API MUST NOT close the output stream from within the a submitted mutation task. Closing the output stream within the mutation task permits the client to conclude that the operation was finished before the group commit actually occurs which breaks the visibility guarantee of an ACID commit (the change is not yet visible).

This arises because the AbstractApiTask implementation has invoked conn.commit() and hence believes that it was successful, but the AbstractTask itself has not yet been through a checkpoint and the write set for the commit group has not yet been melded into a stable commit point. Instead, the caller MUST allow the servlet container to close the output stream once the submitted task has completed successfully (at which point the group commit will be stable). This provides the necessary and correct visibility barrier for the updates.

CAUTION: Non-success outcomes MUST throw exceptions! Once the flow of control enters an AbstractRestApiTask the task MUST throw out a typed exception that conveys the necessary information to the launderThrowable() code which can then turn it into an appropriate HTTP response. If the task does not throw an exception then it is presumed to be successful and it will join the next group commit. Failure to follow this caution can cause partial write sets to be made durable, thus breaking the ACID semantics of the API.

Parameters:

task - The task.

Returns:

The Future for that task.

Throws:

DatasetNotFoundException

ExecutionException

InterruptedException

IOException

TimeoutException

See Also:

HA doLocalAbort() should interrupt NSS requests and AbstractTasks , Concurrent unisolated operations against multiple KBs , All REST API operations should be cancelable from both REST API and workbench

getServiceURIs

public static String[] getServiceURIs(javax.servlet.ServletContext servletContext,
                      javax.servlet.http.HttpServletRequest req)

Return the serviceURI(s) for this service (one or more).

Parameters:

req - The request.

Returns:

The known serviceURIs for this service.

buildAndCommitResponse

public static void buildAndCommitResponse(javax.servlet.http.HttpServletResponse resp,
                          int status,
                          String mimeType,
                          String content,
                          NV... headers)
                                   throws IOException

Generate and commit a response having the indicated http status code, mime type, and content.

This flushes the response to the client immediately. Therefore this method MUST NOT be invoked before the group commit point! All code paths in the REST API that have actually performed a mutation (vs simply reporting a client or server error before entering into their mutation code path) MUST use submitApiTask(AbstractRestApiTask).

Note: It is NOT safe to invoke this method once you are inside an AbstractRestApiTask EVEN if the purpose is to report a client or server error. The task MUST throw out a typed exception that conveys the necessary information to the launderThrowable() code which can then turn it into an appropriate HTTP response. If the task does not throw an exception then it is presumed to be successful and it will join the next group commit!

Parameters:

resp -

status - The http status code.

mimeType - The MIME type of the response.

content - The content (optional).

headers - Zero or more headers.

Throws:

IOException

getBooleanValue

protected boolean getBooleanValue(javax.servlet.http.HttpServletRequest req,
                      String name,
                      boolean defaultValue)

Return the effective boolean value of a request parameter. The text "true" is recognized. All other values are interpreted as false.

Parameters:

req - The request.

name - The name of the request parameter.

defaultValue - The default value.

Returns:

The effective value.

decodeContexts

protected static org.openrdf.model.Resource[] decodeContexts(javax.servlet.http.HttpServletRequest req,
                                          String name)

Decode an array of named graph contexts from a request.

Parameters:

req - The request.

name - The name of the request parameter to be decoded.

Returns:

An array of decoded resources and never null. If the request parameter does not appear in the request then this method returns Resource[0].

See Also:

BD.NULL_GRAPH, EncodeDecodeValue.decodeContexts(String[]), Resource... contexts not encoded/decoded according to openrdf semantics (REST API)

readFully

protected static String readFully(Reader reader)
                           throws IOException

Throws:

IOException