Integrating with Apache Struts

Overview

MetaBoss Datatypes usually perform very strict validation at the time when attempt is made to create an instance of the datatype. This validation process will throw exception back to caller if any problem with proposed data is discovered. On the other hand Struts has a declarative form validation mechanism, which allows to define form validation rules in xml document. If Struts validation is used in web application (and this seem to be a popular choice) the form is validated and, in case it has validation errors, all accumulated error messages are automatically displayed back on a source page. All this is happening well before any custom action java code is executed. This means that MetaBoss datatype validation inside operation invocation preparation code in the body of the custom action occurs too late and any validation error encountered at this stage will not be displayed on the form in the way other validation errors are.

In theory it is possible to solve this by simply duplicating MetaBoss datatype validation rules inside Struts form validation declaration files. However this is very hard work. It is challenging, if not impossible, to keep both MetaBoss Datatype validation rules and Struts validation rules in sync and also this does not reuse any of MetaBoss datatype validation code

MetaBoss includes a better solution for this problem. It contains a custom plug-in validator created in accordance with Struts specification. This validator plug-in can be configurred via Struts form validation declaration to validate any form field against any known MetaBoss datatype. Internally this validator delegates actual validation process to the MetaBoss datatype class and returns all validation erros back to Struts validation framework for displaying amongst other validation erros in the standard fashion. The advantage of using the MetaBoss datatypes validator is that field content validation becomes Model Driven and occurs in one place in the Java code. Struts's form validation definition no longer contains any specific attributes of validation (e.g. matching regular expression, max length, min length etc). All it contains (with regards to single field content validation) is the mapping between form fields and their corresponding datatypes !

Brief description of integration process

• Ensure that MetaBossStrutsIntegration.jar is included in your web application distribution. This jar contains MetaBoss datatypes plug-in validator and can be found in ${metaboss_home}/lib/MetaBossStrutsIntegration.jar
• Define MetaBoss data type validator message in ApplicationResources.properties file in your web application:

  # Special MetaBoss datatypes validator message
  # Arg0 - usual (for Struts) form field name
  # Arg1 - reserved for use by some other validators (e.g. minLength, maxLength etc)
  # Arg2 - reserved for use by some other validators (e.g. minLength, maxLength etc)
  # Arg3 - the MetaBoss data type validation message. Supplied by MetaBoss data type validator at run time
  errors.metaboss={0} is not valid. Reason: {3}
  
  
  

• Define MetaBossDatatypeCheck validation in validator-rules.xml in your web application:

  <validator name="MetaBossDatatype"
      classname="com.metaboss.enterprise.xi.apachestruts.MetaBossDatatypeCheck"
      method="validate"
      methodParams="java.lang.Object,
                    org.apache.commons.validator.ValidatorAction,
                    org.apache.commons.validator.Field,
                    org.apache.struts.action.ActionErrors,
                    javax.servlet.http.HttpServletRequest"
      msg="errors.metaboss"/>
  
  

• For each field linked to particular MetaBoss Datatype class define validation mapping in validation.xml in your web application.

  Example below defines firstName field to be mandatory by invoking standard Struts validation and, if value is present, directs Struts to invoke MetaBossDatatype validator against com.hatmaker.crm.types.core.UserName datatype

  <field property="firstName" depends="required,MetaBossDatatype">
      <arg0 key="registrationForm.firstname.displayname" />
      <var>
          <var-name>datatypeclass</var-name>
          <var-value>com.hatmaker.crm.types.core.UserName</var-value>
      </var>
  </field>
  
  

  Another example below links phone field to com.hatmaker.crm.types.PhoneNo datatype

  <field property="phone" depends="MetaBossDatatype">
      <arg0 key="registrationForm.phone.displayname" />
      <var>
          <var-name>datatypeclass</var-name>
          <var-value>com.hatmaker.crm.types.PhoneNo</var-value>
      </var>
   </field>
  
  

Additional Notes

MetaBoss Datatypes validator plug-in will throw ClassNotFound exception if required datatype class is not found. Normally this should not be a problem and presence of the datatype class is not a specific plug-in requirement. This is because datatype classes must be made available to web application so it will be able to invoke operations.

MetaBoss Datatypes validator plug-in outputs some DEBUG level logging messages (via Apache Commons Logging framework) when it loads datatype classes and when it fails field validation.

At the moment MetaBoss Datatypes validator plug-in does not support internationalisation and Java Script validation definition.