com.microdeveloper.servlets.io
Class DbFileDriver

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          com.microdeveloper.servlets.io.DbFileDriver

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public abstract class DbFileDriver
extends HttpServlet
implements Servlet

Abstract servlet for SQL output as download responses in the form of a file download. Extend this class as the basis for taking SQL queries and sending the formatted results back to the client in the form of a file download. The type sent is controlled by the response header which is defined in the returnFile method. The connection to the database is managed by the db package and referenced in this class. The connection criteria is derived from the environment by locating the session variables, validated, userId, password, and dbUrlPrefix. If the user is not validated, the standard response is to redirect to the site index.

Version:

1.0

Author:

Gregg Lagnese

See Also:

Serialized Form

Field Summary

protected String[]	credentials Full database credential string
protected String	CRLF Field CRLF
protected String	ERRAUTHORIZED Error response given when the user attempts to run a report for which they have no authorization
protected String	ERRDBCONN Error response when the database connection fails
protected String	ERRHEADING Error response heading
protected String	ERRINITPARM Error response given when an invalid open parameter is processed
protected String	ERRNODATA Error response when no data is found that match the report criteria
protected String	ERRNOPARMS Error response when no parameters are given and parameters are expected
protected String	ERRSQL Error response given when the SQL instruction fails
protected String	ERRVALIDATED Error response when the user is not validated.
protected String	outFile Fully qualified filename of the desired output file
protected String	parameterForm URL to the parameter form if any
protected HashMap	parameterMap Parameter map for a given report
protected String	reportName Name of the report
protected HttpSession	session HTTP session variable
protected String	TITLE Report title

Constructor Summary

DbFileDriver()

Method Summary

void	destroy() Destroys the servlet.
protected void	doGet(HttpServletRequest request, HttpServletResponse response) Handles the HTTP GET method.
protected void	doPost(HttpServletRequest request, HttpServletResponse response) Handles the HTTP POST method.
HashMap	getParameterMap(HttpServletRequest request, HttpServletResponse response) Returns the parameter map for the servlet
String	getParameterValue(Object key) Returns the value for a given parameter.
String	getServletInfo() Returns a short description of the servlet.
void	init(ServletConfig config) Initializes the servlet.
boolean	isAuthorized(String reportName) Determines if the user is authorized to run the report or not
boolean	isKeyInMap(Object key) Determines if the parameter object key exists in the parameter map or not
void	parameterPage(HttpServletRequest request, HttpServletResponse response) Returns the parameter page for the give report servlet.
protected void	processRequest(HttpServletRequest request, HttpServletResponse response) Processes requests for both HTTP GET and POST methods.
void	returnError(String message, HttpServletRequest request, HttpServletResponse response) Returns the error response using a standard HTML response template.
abstract void	returnFile(Connection conn, HttpServletRequest request, HttpServletResponse response) Returns the result of the SQL query as a file download.
void	writeOutput(PreparedStatement stmt, HttpServletRequest request, HttpServletResponse response) Writes the output to the response writer.

Methods inherited from class javax.servlet.http.HttpServlet

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

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface javax.servlet.Servlet

getServletConfig, service

Field Detail

parameterMap

protected HashMap parameterMap

Parameter map for a given report

TITLE

protected final String TITLE

Report title

See Also:

Constant Field Values

ERRHEADING

protected final String ERRHEADING

Error response heading

See Also:

Constant Field Values

ERRDBCONN

protected final String ERRDBCONN

Error response when the database connection fails

See Also:

Constant Field Values

ERRNOPARMS

protected final String ERRNOPARMS

Error response when no parameters are given and parameters are expected

See Also:

Constant Field Values

ERRNODATA

protected final String ERRNODATA

Error response when no data is found that match the report criteria

See Also:

Constant Field Values

ERRSQL

protected final String ERRSQL

Error response given when the SQL instruction fails

See Also:

Constant Field Values

ERRINITPARM

protected final String ERRINITPARM

Error response given when an invalid open parameter is processed

See Also:

Constant Field Values

ERRVALIDATED

protected final String ERRVALIDATED

Error response when the user is not validated. This occurs if the session variables cannot be read which can happen if the servlet session times out or the user tried to invoke the report with logging in.

See Also:

Constant Field Values

ERRAUTHORIZED

protected final String ERRAUTHORIZED

Error response given when the user attempts to run a report for which they have no authorization

See Also:

Constant Field Values

parameterForm

protected String parameterForm

URL to the parameter form if any

credentials

protected String[] credentials

Full database credential string

session

protected HttpSession session

HTTP session variable

reportName

protected String reportName

Name of the report

outFile

protected String outFile

Fully qualified filename of the desired output file

CRLF

protected final String CRLF

Field CRLF

Constructor Detail

DbFileDriver

public DbFileDriver()

Method Detail

init

public void init(ServletConfig config)
          throws ServletException

Initializes the servlet.

Specified by:

init in interface Servlet

Overrides:

init in class GenericServlet

Parameters:

config - Determines where to locate the configuration parameters for a given report

Throws:

ServletException - Thrown when a servlet exception occurs

destroy

public void destroy()

Destroys the servlet.

Specified by:

destroy in interface Servlet

Overrides:

destroy in class GenericServlet

returnFile

public abstract void returnFile(Connection conn,
                                HttpServletRequest request,
                                HttpServletResponse response)
                         throws ServletException,
                                IOException,
                                SQLException

Returns the result of the SQL query as a file download.

Parameters:

conn - the database connection object

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

SQLException

getServletInfo

public String getServletInfo()

Returns a short description of the servlet.

Specified by:

getServletInfo in interface Servlet

Overrides:

getServletInfo in class GenericServlet

Returns:

servlet descriptive information

processRequest

protected void processRequest(HttpServletRequest request,
                              HttpServletResponse response)
                       throws ServletException,
                              IOException

Processes requests for both HTTP GET and POST methods.

Parameters:

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

doGet

protected void doGet(HttpServletRequest request,
                     HttpServletResponse response)
              throws ServletException,
                     IOException

Handles the HTTP GET method.

Overrides:

doGet in class HttpServlet

Parameters:

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

doPost

protected void doPost(HttpServletRequest request,
                      HttpServletResponse response)
               throws ServletException,
                      IOException

Handles the HTTP POST method.

Overrides:

doPost in class HttpServlet

Parameters:

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

returnError

public void returnError(String message,
                        HttpServletRequest request,
                        HttpServletResponse response)
                 throws ServletException,
                        IOException

Returns the error response using a standard HTML response template.

Parameters:

message - the error message or html to return

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

getParameterValue

public String getParameterValue(Object key)

Returns the value for a given parameter.

Parameters:

key - the parameter object name

Returns:

the parameter value

isKeyInMap

public boolean isKeyInMap(Object key)

Determines if the parameter object key exists in the parameter map or not

Parameters:

key - the parameter object name

Returns:

true if the key exists, otherwise false

isAuthorized

public boolean isAuthorized(String reportName)

Determines if the user is authorized to run the report or not

Parameters:

reportName - Name of the report to check authorization for

Returns:

true if authorized, otherwise false

getParameterMap

public HashMap getParameterMap(HttpServletRequest request,
                               HttpServletResponse response)
                        throws ServletException

Returns the parameter map for the servlet

Parameters:

request - servlet request

response - servlet response

Returns:

Hashmap consisting of the parameters for the report

Throws:

ServletException - Thrown when a servlet exception occurs

parameterPage

public void parameterPage(HttpServletRequest request,
                          HttpServletResponse response)
                   throws ServletException,
                          IOException

Returns the parameter page for the give report servlet. If no parameter page is given and this method is invoked, it will return an error page.

Parameters:

request - servlet request

response - servlet response

Throws:

ServletException - Thrown when a servlet exception occurs

IOException

writeOutput

public void writeOutput(PreparedStatement stmt,
                        HttpServletRequest request,
                        HttpServletResponse response)
                 throws ServletException,
                        IOException,
                        SQLException

Writes the output to the response writer.

Parameters:

stmt - an opened but not executed prepared statement (java.sql.PreparedStatement)

request - the HttpServletRequest request

response - the HttpServletResponse response

Throws:

ServletException - if an error occurs reading or writing the request or response

IOException

SQLException