bradleyross.j2ee.servlets

Class CsvWriter

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

bradleyross.j2ee.servlets.CsvWriter

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public abstract class CsvWriter
extends HttpServlet

Serves as a template for writing servlets that display the contains of a java.sql.ResultSet object as a CSV (comma separated values) page.

The methods getResultSet and makeConnection are abstract and will need to be overridden before this class can be used. The user may also wish to override several of the methods for formatting information.

This code needs to be changed since many of the fields that belong to the instance must be moved within the service method since there can be multiple copies of the service method running at the same time.

Author:

Bradley Ross

See Also:

getResultSet(HttpServletRequest, DatabaseProperties), Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	CsvWriter.Instance Encapsulates methods and properties for a given instance of the service method.

Field Summary

Fields

Modifier and Type	Field and Description
protected ServletConfig	config ServletConfig object as passed to the init method.
private static long	serialVersionUID Provided for compliance with Serializable interface.

Constructor Summary

Constructors

Constructor and Description
CsvWriter()

Method Summary

Methods

Modifier and Type	Method and Description
void	destroy() Called by the servlet container when the servlet object is being taken out of service.
protected String	formatDateTime(Date valueIn) Alternate calling sequence, leaving out the column number
protected String	formatDateTime(Date valueIn, int column) Formatter for values involving date and time.
protected String	formatDouble(double valueIn) Alternate calling sequence, leaving out the column number.
protected String	formatDouble(double valueIn, int column) Formatter for floating point numbers.
protected String	formatInteger(int valueIn) Alternate calling sequence, omitting the column number.
protected String	formatInteger(int valueIn, int column) Formatter for integer values.
protected String	formatString(String valueIn) Method of calling formatString when it doesn't depend on the column in the result set.
protected String	formatString(String valueIn, int column) Double up on all double quotes in string and surround the string with double quotes so that it will be in the proper format for the CSV file.
protected abstract ResultSet	getResultSet(HttpServletRequest req, DatabaseProperties data) Will be overridden with the method for obtaining the SQL result set.
void	init(ServletConfig configIn) Called by the servlet container when the servlet object is first placed in service.
protected abstract DatabaseProperties	makeConnection() Obtain the database connection information.
protected void	printHeader(CsvWriter.Instance instance) Will print header line for CSV file.
protected void	printLine(CsvWriter.Instance instance) Will print one line of CSV file.
void	service(HttpServletRequest req, HttpServletResponse res) Called by servlet container when an HTTP transaction requests a response from the server.
protected void	setValues(CsvWriter.Instance instance) Sets values in Instance object.

Methods inherited from class javax.servlet.http.HttpServlet

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

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

Provided for compliance with Serializable interface.

See Also:

Constant Field Values

config

protected ServletConfig config

ServletConfig object as passed to the init method.

Must be moved to inner class

Constructor Detail

CsvWriter

public CsvWriter()

Method Detail

init

public void init(ServletConfig configIn)
          throws ServletException

Called by the servlet container when the servlet object is first placed in service.

Specified by:

init in interface Servlet

Overrides:

init in class GenericServlet

Throws:

ServletException

destroy

public void destroy()

Called by the servlet container when the servlet object is being taken out of service.

Specified by:

destroy in interface Servlet

Overrides:

destroy in class GenericServlet

service

public void service(HttpServletRequest req,
           HttpServletResponse res)
             throws IOException

Called by servlet container when an HTTP transaction requests a response from the server.

Overrides:

service in class HttpServlet

Parameters:

req - Object containing request information

res - Object containing response information

Throws:

IOException

makeConnection

protected abstract DatabaseProperties makeConnection()
                                              throws IOException

Obtain the database connection information.

Throws:

IOException

getResultSet

protected abstract ResultSet getResultSet(HttpServletRequest req,
                     DatabaseProperties data)
                                   throws IOException

Will be overridden with the method for obtaining the SQL result set.

This should be kept separate from the getResultSet method within the Instance class. The CsvWriter.Instance.getResultSet() method returns the ResultSet object stored in the Instance object. This method actually generates the ResultSet object. The service method then stores the result of this method in the Instance object.

Parameters:

req - Request information

Returns:

Result set

Throws:

IOException

See Also:

CsvWriter.Instance.message, CsvWriter.Instance.outputFilename

setValues

protected void setValues(CsvWriter.Instance instance)
                  throws IOException

Sets values in Instance object.

This must be overridden in a subclass in order to set parameters.

Parameters:

instance - Instance object being affected

Throws:

IOException

printHeader

protected void printHeader(CsvWriter.Instance instance)
                    throws IOException

Will print header line for CSV file.

Throws:

IOException

printLine

protected void printLine(CsvWriter.Instance instance)
                  throws IOException

Will print one line of CSV file.

This method will be changed at a later time to allow the specification of overriding methods for formatting timestamps, integers, floating point numbers, character strings, etc.

Throws:

IOException

formatString

protected final String formatString(String valueIn)

Method of calling formatString when it doesn't depend on the column in the result set.

Parameters:

valueIn - String to be processed

Returns:

Processed string

formatString

protected String formatString(String valueIn,
                  int column)

Double up on all double quotes in string and surround the string with double quotes so that it will be in the proper format for the CSV file.

Parameters:

valueIn - String to be processed

column - Column number of item - This will allow different formatting to be used for each column. This parameter is not used unless the method is overridden.

Returns:

Processed string

formatDouble

protected final String formatDouble(double valueIn)

Alternate calling sequence, leaving out the column number.

Parameters:

valueIn - Floating point number to be formatted

Returns:

Formatted string

formatDouble

protected String formatDouble(double valueIn,
                  int column)

Formatter for floating point numbers.

This method can be overridden to control printing of the values in the CSV file.

Parameters:

valueIn - Floating point number to be processed

column - Column number - This will allow different formatting to be used for each column. This parameter is not used unless the method is overridden.

Returns:

Formatted string

formatInteger

protected final String formatInteger(int valueIn)

Alternate calling sequence, omitting the column number.

Parameters:

valueIn - Integer value to be formatted

Returns:

Formatted string

formatInteger

protected String formatInteger(int valueIn,
                   int column)

Formatter for integer values.

This method can be overridden to control printing of the values in the CSV file.

Parameters:

valueIn - Integer to be formatted

column - Column number - This will allow different formatting to be used for each column. This parameter is not used unless the method is overridden.

Returns:

Formatted string

formatDateTime

protected final String formatDateTime(Date valueIn)

Alternate calling sequence, leaving out the column number

Parameters:

valueIn - java.util.Date object containing date and time

Returns:

Formatted string

formatDateTime

protected String formatDateTime(Date valueIn,
                    int column)

Formatter for values involving date and time.

This method can be overridden to control printing of the values in the CSV file.

Parameters:

valueIn - java.util.Date object containing date and time

column - Column number - This will allow different formatting to be used for each column. This parameter is not used unless the method is overridden.

Returns:

Formatted string