com.hp.util

Class AbstractValidator

java.lang.Object

com.hp.util.AbstractValidator

Direct Known Subclasses:

AbstractResourceValidator

public abstract class AbstractValidator
extends Object

This class forms the basis for validators that want to report multiple warnings and errors.

Here's a pattern we want to avoid:

• There are multiple issues with an implementation
• The first issue detected (#1) is reported
• The developer fixes that issue
• The first issue detected (#2) is reported
• The developer fixes that issue
• ...

We want to discover and report all the issues at one time, allowing the developer to fix them all in one go.

A typical pattern for concrete subclasses is:

 public class MyValidator extends AbstractValidator {
     // no instantiation outside the class
     private MyValidator() { }

     private void validate(SomeInterface someImplementation) {

         if ( ... some problem ... ) {
             addError(" detail message ");
         } else if ( ... some other problem ... ) {
             addError(" other detail message ");
         }
         throwExceptionIfMessages();
     }

     /** Validates an implementation of ...
      * If all is well, this method silently returns. If issues are found, a
      * ValidationException is thrown, with details of the discovered issues.
      *
      * @throws ValidationException if issues were found
      * @throws NullPointerException if parameter is null
      */
     public static void validateImplementation(SomeInterface someImplementation) {
         new MyValidator().validate(someImplementation);
     }
 }
 

Production code would then use the public API:

 SomeInterface myImplementation = ...
 MyValidator.validateImplementation(myImplementation);
 

Author:

Simon Hunt

Constructor Summary

Constructors

Constructor and Description
AbstractValidator()

Method Summary

Methods

Modifier and Type	Method and Description
protected void	addError(String message) Add a message prefixed with "Error: "
protected void	addInfo(String message) Add a message prefixed with "Info: "
protected void	addVerbatim(String message) Add a message verbatim.
protected void	addWarning(String message) Add a message prefixed with "Warning: "
List<String>	getMessages() Returns the list of messages.
String	getMessagesAsString() Returns the messages as a string (newlines after each individual message).
protected boolean	nullOrEmpty(String s) This predicate returns true if the supplied string is null, or if (once trimmed of whitespace) its length is zero.
protected int	numberOfMessages() Returns the number of messages stored.
protected void	throwException() This method throws an exception to terminate the validation.
protected void	throwException(String message) This method can be used when the validator finds an unrecoverable error and wants to terminate the validation.
protected void	throwException(String message, Throwable cause) This method can be used when the validator finds an unrecoverable error and wants to terminate the validation.
protected void	throwExceptionIfMessages() This method will throw a default exception if the message buffer is not empty.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractValidator

public AbstractValidator()

Method Detail

getMessages

public List<String> getMessages()

Returns the list of messages.

Returns:

the list of messages

getMessagesAsString

public String getMessagesAsString()

Returns the messages as a string (newlines after each individual message).

Returns:

the messages as a string

nullOrEmpty

protected boolean nullOrEmpty(String s)

This predicate returns true if the supplied string is null, or if (once trimmed of whitespace) its length is zero.

Parameters:

s - the string

Returns:

true if the string is null or just whitespace

numberOfMessages

protected int numberOfMessages()

Returns the number of messages stored.

Returns:

the number of messages

addInfo

protected void addInfo(String message)

Add a message prefixed with "Info: "

Parameters:

message - the message

addWarning

protected void addWarning(String message)

Add a message prefixed with "Warning: "

Parameters:

message - the message

addError

protected void addError(String message)

Add a message prefixed with "Error: "

Parameters:

message - the message

addVerbatim

protected void addVerbatim(String message)

Add a message verbatim.

Parameters:

message - the message

throwExceptionIfMessages

protected void throwExceptionIfMessages()

This method will throw a default exception if the message buffer is not empty.

Throws:

ValidationException - thrown if any messages are pending

throwException

protected void throwException()

This method throws an exception to terminate the validation. It uses a default exception message of "Validation Failed".

Throws:

ValidationException - thrown using the default message

throwException

protected void throwException(String message)

This method can be used when the validator finds an unrecoverable error and wants to terminate the validation.

Parameters:

message - the exception message

Throws:

ValidationException - thrown using the specified message

throwException

protected void throwException(String message,
                  Throwable cause)

This method can be used when the validator finds an unrecoverable error and wants to terminate the validation.

Parameters:

message - the exception message

cause - an underlying cause

Throws:

ValidationException - thrown using the specified message and cause