shared
Class HelperBaseCh4

java.lang.Object
  shared.HelperBaseCh4

Direct Known Subclasses:

ControllerHelper, HelperBaseCh5

public abstract class HelperBaseCh4
extends java.lang.Object

HelperBase class that is used in Chapter 4. It is also the super class for all the other helper base classes.

Nested Class Summary

protected static class

HelperBaseCh4.SessionData Enumeration to describe if the data should be read from the session.

Field Summary

protected org.apache.log4j.Logger	logger Member variable for the logger object
protected javax.servlet.http.HttpServletRequest	request Member variable for the request object
protected javax.servlet.http.HttpServletResponse	response Member variable for the response object

Constructor Summary

HelperBaseCh4(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
Initialise the request, response and logger.

Method Summary

void	addHelperToSession(java.lang.String name, boolean checkSession) Overridden method that accepts a boolean value.
void	addHelperToSession(java.lang.String name, HelperBaseCh4.SessionData state) Test if the old helper data should be retrieved.
protected abstract void	copyFromSession(java.lang.Object helper) Abstract method that must be defined in the controller helper.
protected void	doGet() Default doGet method that prints a warning message, if called.
protected void	doPost() Default doPost method that prints a warning message, if called.
protected java.lang.String	executeButtonMethod() Find the method associated with a button name.
protected java.lang.String	executeButtonMethod(java.lang.Class clazz, boolean searchForDefault) Overridden method that accepts the parent class of the class heirarchy for the current object.
void	fillBeanFromRequest(java.lang.Object data) Copy the request data to the bean.
protected java.lang.String	invokeButtonMethod(java.lang.reflect.Method buttonMethod) Execute the found method.
static void	writeError(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, java.lang.String title, java.lang.Exception ex) Write an error page, instead of calling a JSP.

Methods inherited from class java.lang.Object

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

Field Detail

request

protected javax.servlet.http.HttpServletRequest request

Member variable for the request object

response

protected javax.servlet.http.HttpServletResponse response

Member variable for the response object

logger

protected org.apache.log4j.Logger logger

Member variable for the logger object

Constructor Detail

HelperBaseCh4

public HelperBaseCh4(javax.servlet.http.HttpServletRequest request,
                     javax.servlet.http.HttpServletResponse response)

Initialise the request, response and logger.

Parameters:

request - Request information encapsulated in a Java object

response - Response information encapsulated in a Java object

Method Detail

doGet

protected void doGet()
              throws javax.servlet.ServletException,
                     java.io.IOException

Default doGet method that prints a warning message, if called.

Throws:

javax.servlet.ServletException

java.io.IOException

doPost

protected void doPost()
               throws javax.servlet.ServletException,
                      java.io.IOException

Default doPost method that prints a warning message, if called.

Throws:

javax.servlet.ServletException

java.io.IOException

copyFromSession

protected abstract void copyFromSession(java.lang.Object helper)

Abstract method that must be defined in the controller helper. The base class calls this method when it needs to know how to copy the old helper data that is in the session into the current helper.

Parameters:

helper - The old helper from the session

addHelperToSession

public void addHelperToSession(java.lang.String name,
                               HelperBaseCh4.SessionData state)

Test if the old helper data should be retrieved. If so, then try to get the old helper from the session; if there is data, then call the abstract copyFromSession method. Always adds the current helper to the session, releasing the previous helper from the session.

Parameters:

name - The name to use to store the helper in the session

state - Whether to read the old data or to ignore it

addHelperToSession

public void addHelperToSession(java.lang.String name,
                               boolean checkSession)

Overridden method that accepts a boolean value.

Parameters:

name - The name to use to store the helper in the session

checkSession - Whether to read the old data or to ignore it. True means read, false means ignore

executeButtonMethod

protected java.lang.String executeButtonMethod()
                                        throws javax.servlet.ServletException,
                                               java.io.IOException

Find the method associated with a button name.

Returns:

Throws:

javax.servlet.ServletException

java.io.IOException

executeButtonMethod

protected java.lang.String executeButtonMethod(java.lang.Class clazz,
                                               boolean searchForDefault)
                                        throws java.lang.IllegalAccessException,
                                               java.lang.reflect.InvocationTargetException

Overridden method that accepts the parent class of the class heirarchy for the current object.

Parameters:

clazz - The most extended class for this object.

searchForDefault - If the default method has not been found, continue to search for it.

Returns:

The address of the next JSP.

Throws:

java.lang.IllegalAccessException

java.lang.reflect.InvocationTargetException

invokeButtonMethod

protected java.lang.String invokeButtonMethod(java.lang.reflect.Method buttonMethod)
                                       throws java.lang.IllegalAccessException,
                                              java.lang.reflect.InvocationTargetException

Execute the found method. Log all errors.

Parameters:

buttonMethod - The method to execute

Returns:

Address of the next JSP.

Throws:

java.lang.IllegalAccessException

java.lang.reflect.InvocationTargetException

fillBeanFromRequest

public void fillBeanFromRequest(java.lang.Object data)

Copy the request data to the bean. Catch errors and log them.

Parameters:

data - The bean to fill.

writeError

public static void writeError(javax.servlet.http.HttpServletRequest request,
                              javax.servlet.http.HttpServletResponse response,
                              java.lang.String title,
                              java.lang.Exception ex)
                       throws java.io.IOException,
                              javax.servlet.ServletException

Write an error page, instead of calling a JSP.

Parameters:

request - Request information encapsulated in a Java object

response - Response information encapsulated in a Java object

title - The title of the generated page

ex - The exception that caused the error

Throws:

java.io.IOException

javax.servlet.ServletException