package com.validate;

import org.apache.commons.validator.Field;
import org.apache.commons.validator.GenericValidator;
import org.apache.commons.validator.util.ValidatorUtils;

public class ValidatorWrapper
{
    /**
     * Check whether a field in the user form has an empty value or is not present.
     * 
     * @param bean user data represented as a JavaBean
     * @param field the Validator components's representation of the field
     *              in the user data that is to be validated.
     * @return true if the value is not null or zero length, false otherwise.
     */
    public static boolean doRequired(Object bean, Field field)
    {
        //
        //Get the value of the field as String. The Validator API only
        //accepts String values for its built-in validators.
        //
        String value = ValidatorUtils.getValueAsString(bean, field.getProperty());
        
        //
        //examines the String passed in 
        //
        //
        return !GenericValidator.isBlankOrNull(value);
    }
}

package com.bean;

/**
 * This is the JavaBean to validate and act as our user data,
 * we need to create the targeted set of validation rules that
 * will be applied to this JavaBean.
 */
public class SimpleJavaBeanV1
{
    private String firstName;
    private String lastName;
    
    public SimpleJavaBeanV1()
    {
    }
    
    public String getFirstName()
    {
        return firstName;
    }
    
    public void setFirstName(String firstName)
    {
        this.firstName = firstName;
    }
    
    public String getLastName()
    {
        return lastName;
    }
    
    public void setLastName(String lastName)
    {
        this.lastName = lastName;
    }
}

package com.validator;

import java.io.FileInputStream;

import org.apache.commons.validator.Validator;
import org.apache.commons.validator.ValidatorResources;
import org.apache.commons.validator.ValidatorResult;
import org.apache.commons.validator.ValidatorResults;

import com.bean.SimpleJavaBean;

public class VSimpleJavaBean
{
    public static void main(String[] args) throws Exception
    {
        //1. load targeted rules.
        //This class loads tge rules and uses the Digester component to parse them.
        String currentWorkingDirectory = System.getProperty("user.dir");
        ValidatorResources resources = new ValidatorResources(
                new FileInputStream(currentWorkingDirectory + "\\conf\\validation\\SimpleJavaBean.xml"));
        
        //2. accept user data
        Object userData = simulateUserData();
        
        //3. create and initialize new Validator instance
        /*
         * "simpleJavaBean" is the name of the <form> element in the
         * XML file to be processed.
         * The same XML file can be used to define the processing of
         * several forms.
         */
        Validator validator = new Validator(resources, "simpleJavaBean");
        
        /*
         * Notice that, if you're doing multiple validations, and each piece
         * of user data is represented by a different Javabean instance,
         * you'll need to reset this parameter. 
         */
        validator.setParameter(Validator.BEAN_PARAM, userData);
        
        //4. perform validation
        ValidatorResults results = validator.validate();
        
        //5. return results for each field
        ValidatorResult result1 = results.getValidatorResult("firstName");
        ValidatorResult result2 = results.getValidatorResult("lastName");
        
        //6. Print results for each field's validation
        //   passed in each field name
        System.err.println("First Name: " + result1.isValid("required"));
        System.err.println("Last Name: " + result2.isValid("required"));
        

    }
    
    private static Object simulateUserData()
    {
        SimpleJavaBean bean = new SimpleJavaBean();
        bean.setLastName("Zhou");
        return bean;
    }
}