Package org.apache.commons.validator

The Validator package provides validation for JavaBeans based on an xml file.

See:
          Description

Class Summary
Arg A default argument or an argument for a specific validator definition (ex: required) can be stored to pass into a message as parameters.
Constant A constant can be used to define a global or locale level constant that can be used to replace values in certain fields.
Field This contains the list of pluggable validators to run on a field and any message information and variables to perform the validations and generate error messages.
Form This contains a set of validation rules for a form/JavaBean.
FormSet Holds a set of Forms stored associated with a Locale based on the country, language, and variant specified.
GenericTypeValidator This class contains basic methods for performing validations that return the correctly typed class based on the validation performed.
GenericValidator This class contains basic methods for performing validations.
Msg An alternative message can be associated with a Field and a pluggable validator instead of using the default message stored in the ValidatorAction (aka pluggable validator).
Validator Validations are processed by the validate method.
ValidatorAction Contains the information to dynamically instantiate and run a validation method.
ValidatorResources General purpose class for storing FormSet objects based on their associated Locale.
ValidatorResourcesInitializer Maps an xml file to ValidatorResources.
ValidatorResult This contains the results of a set of validation rules processed on JavaBean.
ValidatorResults This contains the results of a set of validation rules processed on JavaBean.
ValidatorUtil Basic utility methods.
Var A variable can be associate with a Field for passing in information to a pluggable validator.
 

Exception Summary
ValidatorException Exception for the Validator Framework.
 

Package org.apache.commons.validator Description

The Validator package provides validation for JavaBeans based on an xml file.

[Dependencies] [Introduction] [Overview] [Resources] [Usage Example]

External Dependencies

Introduction

A common issue when receiving data either electronically or from user input is verifying the integrity of the data. This work is repetitive and becomes even more complicated when different sets of validation rules need to be applied to the same set of data based on locale for example. Error messages may also vary by locale. This package attempts to address some of these issues and speed development and maintenance of validation rules.

In order to use the Validator, the following basic steps are required:

Overview

The Commons Validator is a basic validation framework that lets you define validation rules for a JavaBean in an xml file. Validators, the validation definition, can also be defined in the xml file. An example of a validator would be defining what method and class will be called to perform the validation for a required field. Validation rules can be grouped together based on locale and a JavaBean/Form that the rules are associated with. The framework has basic support for user defined constants which can be used in some field attributes.

Validation rules can be defined in an xml file which keeps them abstracted from JavaBean you are validating. The property reference to a field supports nested properties using the Apache Commons BeanUtils (http://commons.apache.org/beanutils.html) package. Error messages and the arguments for error messages can be associated with a fields validation.

Resources

After a Validator instance is created, instances of classes can be added to it to be passed into validation methods by calling the addResource method. Below is a list of reserved keys (class names).

Class Name Validator Contant Description
java.lang.Object Validator.BEAN_KEY JavaBean that is being validated
java.util.Locale Validator.LOCALE_KEY Locale to use when retrieving a FormSet. The default locale will be used if one isn't specified.
org.apache.commons.validator.ValidatorAction Validator.VALIDATOR_ACTION_KEY This is automatically added to a Validator's resources as a validation is being processed. If this class name is used when defining a method signature for a pluggable validator, the current ValidatorAction will be passed into the validation method.
org.apache.commons.validator.Field Validator.FIELD_KEY This is automatically added to a Validator's resources as a validation is being processed. If this class name is used when defining a method signature for a pluggable validator, the current Field will be passed into the validation method.

Usage Example

This is a basic example setting up a required validator for a name bean. This example is a working unit test (reference org.apache.commons.validator.RequiredNameTest and validator-name-required.xml located under validator/src/test).

Create an xml file with your validator and validation rules. Setup your required validator in your xml file.

XML Example
Validator Example
Pluggable Validator Example

XML Example

Definition of a 'required' pluggable validator.

<form-validation>
   <global>
       <validator name="required"
          classname="org.apache.commons.validator.TestValidator"
          method="validateRequired"
          methodParams="java.lang.Object, org.apache.commons.validator.Field"/>
    </global>
    <formset>
    </formset>
</form-validation>

Add validation rules to require a first name and a last name.

<form-validation>
   <global>
       <validator name="required"
          classname="org.apache.commons.validator.TestValidator"
          method="validateRequired"
          methodParams="java.lang.Object, org.apache.commons.validator.Field"/>
    </global>
    <formset>
       <form name="nameForm">
          <field property="firstName" depends="required">
             <arg0 key="nameForm.firstname.displayname"/>
          </field>
          <field property="lastName" depends="required">
             <arg0 key="nameForm.lastname.displayname"/>
          </field>
       </form>
    </formset>
</form-validation>

Validator Example

Excerpts from org.apache.commons.validator.RequiredNameTest

InputStream in = this.getClass().getResourceAsStream("validator-name-required.xml");

// Create an instance of ValidatorResources to
// initialize from an xml file.
ValidatorResources resources = new ValidatorResources();

// Load resources into ValidatorResources passed in
ValidatorResourcesInitializer.initialize(resources, in);

// Create bean to run test on.
Name name = new Name();

// Construct validator based on the loaded resources
// and the form key
Validator validator = new Validator(resources, "nameForm");
// add the name bean to the validator as a resource
// for the validations to be performed on.
validator.addResource(Validator.BEAN_KEY, name);

// Get results of the validation.
Map hResults = null;

// throws ValidatorException,
// but aren't catching for example
hResults = validator.validate();

if (hResults.get("firstName") == null) {
    // no error
} else {
    // number of errors for first name     int errors = ((Integer)hResults.get("firstName")).intValue();
}

Pluggable Validator Example

Validation method defined in the 'required' pluggable validator (excerpt from org.apache.commons.validator.TestValidator).

public static boolean validateRequired(Object bean, Field field) {
    String value = ValidatorUtil.getValueAsString(bean, field.getProperty());
    return GenericValidator.isBlankOrNull(value);
}



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