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java.lang.Object
|
+--javax.servlet.GenericServlet
|
+--javax.servlet.http.HttpServlet
|
+--com.opmath.util.http.HttpServlet
Provides an abstract class for a servlet.
The structure and functionality of this class enriches the standard
javax.servlet.http.HttpServlet class, with methods that handle parameter
parsing, default responses, and configuration using resource .conf
files.
NOTE: This class carries some static and instance variables that are used in support of user authentication and user sessions. Refer to the immediate subclasses of this class, in order to understand the use of these variables.
WARNING: It is up to the programmer to ensure that the use of the HttpSession
instance variable (or any other instance variable) is thread safe.
Copyright: (c) 2002 The Open Math Company Limited
The Terms of Distribution of this software are stipulated in the javadoc Overview for this project.
HttpSessionServlet,
HttpLogOnServlet,
HttpLogOffServlet,
HttpProtectedServlet,
Serialized Form| Field Summary | |
protected static String |
EOL
The end-of-line character(s) for the server. |
protected static String |
LOGON_ID
The HttpSession attribute used to specify that the requester
has logged on successfully, normally used to hold the unique ID of the user. |
protected static String |
LOGON_TARGET
The HttpSession attribute used to specify the URI of the
target of a request. |
| Constructor Summary | |
HttpServlet()
|
|
| Method Summary | |
void |
doGet(HttpServletRequest req,
HttpServletResponse rsp)
Handles an HTTP GET request. |
protected String |
doGetDispatch(HttpServletRequest req)
Services an HTTP GET request, as caught by the doGet(HttpServletRequest, HttpServletResponse) method on this
class. |
void |
doPost(HttpServletRequest req,
HttpServletResponse rsp)
Handles an HTTP POST request. |
protected String |
doPostDispatch(HttpServletRequest req)
Handles an HTTP POST request. |
int |
getIndex(String paramName,
String paramValue)
Returns the int index associated with the paramName / paramValue pair,
as established by registerIndex(String, String, int). |
int |
getParamIndex(String paramName,
HttpServletRequest req)
Returns the int index of the parameter value found in the HttpServletRequest
whose name is paramName and whose value is found in the HttpServletRequest. |
String |
getServletInfo()
Returns a String carrying some information about the servlet. |
int |
getValueCount(String paramName)
Returns the number of parameter values registered against paramName. |
Enumeration |
paramIndices(String paramName)
Returns an Enumeration of the parameter indices for the values registered
against paramName. |
Enumeration |
paramMappings()
Returns an Enumeration of the parameter (value => index) mappings known to the registry. |
Enumeration |
paramNames()
Returns an Enumeration of the parameter names known to the registry. |
Enumeration |
paramValues(String paramName)
Returns an Enumeration of the parameter values registered against paramName. |
void |
registerIndex(String paramName,
String paramValue,
int paramValueIndex)
Associates the value of a servlet parameter with an int index. |
void |
registerIndices(String paramName,
String[] paramValues)
Associates a number of values of a servlet parameter with successive indices. |
String |
report(HttpServletRequest req,
String message)
Provides a general-purpose failure reporting mechanism, intended to be triggered within a servlet doGet(HttpServletRequest, HttpServletResponse) or
doPost(HttpServletRequest, HttpServletResponse) method. |
void |
setConfig()
Sets static variables, based on the contents of a ServletName.conf file. |
void |
setConfig(String resourceName)
Sets static variables, based on the contents of the named configuration file. |
| Methods inherited from class javax.servlet.http.HttpServlet |
doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service |
| Methods inherited from class javax.servlet.GenericServlet |
destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, 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 |
protected static final String LOGON_TARGET
The HttpSession attribute used to specify the URI of the
target of a request.
HttpLogOnServlet.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
HttpProtectedServlet.doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
HttpProtectedServlet.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
Constant Field Valuesprotected static final String LOGON_ID
The HttpSession attribute used to specify that the requester
has logged on successfully, normally used to hold the unique ID of the user.
HttpLogOnServlet.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
HttpProtectedServlet.doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
HttpProtectedServlet.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse),
Constant Field Valuesprotected static final String EOL
| Constructor Detail |
public HttpServlet()
| Method Detail |
public void doGet(HttpServletRequest req,
HttpServletResponse rsp)
throws ServletException,
IOException
Handles an HTTP GET request. This method provides generic i/o and exception handling facilities. Thus, it simplifies the task of writing code to respond to a GET, and makes that code more reliable in practical use.
Subclasses of com.opmath.util.http.HttpServlet need only override
doGetDispatch(HttpServletRequest, HttpServletResponse), unless the default behaviour
of doGet(HttpServletRequest, HttpServletResponse) must be altered.
doGet in class HttpServletServletException - an exception thrown if
the request could not be handled.
IOException - an exception thrown if
an input or output error is detected when the servlet handles the request.doGetDispatch(com.opmath.util.http.HttpServletRequest)
protected String doGetDispatch(HttpServletRequest req)
throws Exception
Services an HTTP GET request, as caught by the
doGet(HttpServletRequest, HttpServletResponse) method on this
class. This method should be overriden by any real-world application.
String carrying the report.
Exception - if a subclass's method encounters any error state.doGet(HttpServletRequest, HttpServletResponse)
public void doPost(HttpServletRequest req,
HttpServletResponse rsp)
throws ServletException,
IOException
Handles an HTTP POST request. This method provides generic i/o and exception handling facilities. Thus, it simplifies the task of writing code to respond to a POST, and makes that code more reliable in practical use.
Subclasses of com.opmath.util.http.HttpServlet need only override
doPostDispatch(HttpServletRequest, HttpServletResponse), unless the default behaviour
of doGet(HttpServletRequest, HttpServletResponse) must be altered.
doPost in class HttpServletServletException - an exception thrown if
the request could not be handled.
IOException - an exception thrown if
an input or output error is detected when the servlet handles the request.doPostDispatch(com.opmath.util.http.HttpServletRequest)
protected String doPostDispatch(HttpServletRequest req)
throws Exception
Handles an HTTP POST request.
This method instantiates the session object of the servlet, then arranges that
the doPostDispatch(com.opmath.util.http.HttpServletRequest) method is invoked.
Exception - if a subclass's method encounters any error state.doPost(HttpServletRequest, HttpServletResponse)
public void setConfig(String resourceName)
throws ServletException
The purpose of setConfig() is to simplify the deployment of servlet-based applications.
It achieves this by allowing the developer to place all the environment-specific properties of a servlet
in a textual configuration file. setConfig() can assign these properties to static
variables; this should normally be done in the servlet's init() or
init(ServletConfig) method.
Although a similar effect can be achieved with parameters passed
to the servlet via its ServletConfig argument, packaging all the parameters in a
configuration file is ofetn the better option.
The resource should be in the same package as the receiver's class, although the package containing the configuration file may be anywhere on the runtime classpath.
Entries in the configuration file are as follows:
NOTE 1: This version of setConfig() only allows for static variables of class String.
NOTE 2: setConfig() issues a warning if the static variable had already been assigned
a value. Under normal circumstances, the variable should not be assigned a value in the servlet code (thus
it would carry the value null.
If setConfig() encounters an error with the configuration file then it throws a
ServletException. In such a case, further processing of the servlet should not proceed.
ServletException - An exception thrown if configuration file could
not be found, the configuration entries were malformed, or
the static variables could not be accessed.
public void setConfig()
throws ServletException
ServletName.conf file.
setConfig() always looks for a resource file named ServletName.conf,
where ServletName is the name of the class of the receiving object. The resource file
should be in the same package as the receiver's class, although the package containing the configuration
file may be anywhere on the runtime classpath.
For further details, see setConfig(String).
ServletException - An exception thrown if configuration file could
not be found, the configuration entries were malformed, or
the static variables could not be accessed.setConfig(String)
public void registerIndex(String paramName,
String paramValue,
int paramValueIndex)
int index.
The main use of the register is to enable switch statements to work over commands handed
to the servlet; to do this, the int must be declared by the servlet as static final.
registerIndex in interface ParamIndexparamName - the String name of the parameter.paramValue - the String value of the parameter.paramValueIndex - the int value associated with the parameter value.ParamTable.registerIndex(String, String, int)
public void registerIndices(String paramName,
String[] paramValues)
The Strings contained in paramValues are associated with indices
starting at 0. If duplicate values occur in paramValues, the last value is
used. Values in paramValues overwrite matching values that are already
present in the register.
paramName - the String name of the parameter.paramValues - the String[] carrying the values of the parameter.ParamTable.registerIndex(String, String, int)
public int getIndex(String paramName,
String paramValue)
int index associated with the paramName / paramValue pair,
as established by registerIndex(String, String, int).
getIndex in interface ParamIndexparamName - the String name of the parameter.paramValue - the String value of the parameter.
int value of the parameter, or the int value
com.opmath.util.http.ParamIndex.PARAM_INDEX_FAIL.ParamTable.getIndex(String, String)
public int getParamIndex(String paramName,
HttpServletRequest req)
int index of the parameter value found in the HttpServletRequest
whose name is paramName and whose value is found in the HttpServletRequest.
getParamIndex in interface ParamIndexparamName - the String name of the parameter.req - the HttpServletRequest containing the parameter.
int value of the parameter, or the int value
com.opmath.util.http.ParamIndex.PARAM_INDEX_FAIL.ParamTable.getParamIndex(String, HttpServletRequest)public int getValueCount(String paramName)
paramName.
getValueCount in interface ParamIndexparamName - the String name of the parameter.
int total number of values held against this name.ParamTable.getValueCount(String)public Enumeration paramNames()
Enumeration of the parameter names known to the registry. Use the
Enumeration methods on the returned object to fetch the keys sequentially. The enumerated
objects can be cast to String.
paramNames in interface ParamIndexEnumeration of parameter names.ParamTable.paramNames()public Enumeration paramMappings()
Enumeration of the parameter (value => index) mappings known to the registry.
Use the Enumeration methods on the returned object to fetch the keys sequentially. The
enumerated objects can be cast to com.opmath.util.dmldoc.OrderedHashTable.
paramMappings in interface ParamIndexEnumeration of parameter (value => index) mappings.ParamTable.paramMappings()public Enumeration paramValues(String paramName)
Enumeration of the parameter values registered against paramName.
Use the Enumeration methods on the returned object to fetch the keys sequentially. The
enumerated objects can be cast to String.
paramValues in interface ParamIndexparamName - the String name of the parameter.
Enumeration of parameter values.ParamTable.paramValues(String)public Enumeration paramIndices(String paramName)
Enumeration of the parameter indices for the values registered
against paramName. Use the Enumeration methods on the returned
object to fetch the keys sequentially. The enumerated objects can be cast to Integer.
paramIndices in interface ParamIndexparamName - the String name of the parameter.
Enumeration of parameter names.ParamTable.paramIndices(String)
public String report(HttpServletRequest req,
String message)
doGet(HttpServletRequest, HttpServletResponse) or
doPost(HttpServletRequest, HttpServletResponse) method.
The advantage of report(HttpServletRequest) is that is give a simple way in which
the doGet(HttpServletRequest, HttpServletResponse) or
doPost(HttpServletRequest, HttpServletResponse) method can always return some valid
HTML.
NOTE: The template resource for this report is held at
com.opmath.util.http.tpl_ServletReport.html. This template may be edited, but all of
its <!-- SUB .. --> commands should remain unaltered.
req - the javax.servlet.http.HttpServletRequest of the calling servlet.message - a descriptive String.
String containing the instantiated com.opmath.util.http.tpl_ServletReport.html template.public String getServletInfo()
String carrying some information about the servlet. This method should be
overridden by the subclass of com.opmath.util.http.HttpServlet
getServletInfo in interface ServletgetServletInfo in class GenericServletString.
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