Struts 2.0 + Hibernate Validator

                                            Struts 2.0 + Hibernate Validation

 

As long as you are feeling lazy to write code…you are on the right track.

                 -Vamshi.Somanchi

 

Objectives:

 

• Struts2.0 validation?

• Hibernate validator?

• POJO class?

• How to write them as a Frame Work?

• Why should you appreciate me???

 

 

                                                                Struts 2.0 Validation

 

Struts 2 supports manual validation via the validate method and the XWork Validation framework. The Xwork Validation Framework supports chaining validation into sub-properties using the validations defined for the properties class type and the validation context.

 

Telling you in simple terms Struts 2.0 have inbuilt functionalities to validate the Parameters.

 

The Struts 2 validation framework uses xml based configuration file. The file name should be <Your action class> -validation.xml. Lets say our action class name is Login.java, so our validation configuration file will be Login-validation.xml.

  

<?xml version=”1.0″ encoding=”UTF-8″?><!DOCTYPE validators PUBLIC ”-//OpenSymphony Group//XWork Validator 1.0.2//EN”  “http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd“><validators>  <field name=”username”> <field-validator type=”requiredstring”>  <param name=”trim”>true</param> <message>Login name is required</message> </field-validator> </field> <field name=”password”> <field-validator type=”requiredstring”>  <param name=”trim”>true</param> <message>Password is required</message> </field-validator> </field> </validators>

 

There are two functions which are provided by the Action class they are catching the “action errors” and “field errors”.

Action errors are Server side validation.

Field errors are client side validation.

Thing to be observed here is if you have some set of forms we need to write same number of validator.xml files in order to handle them.

 

 

                                                                                Hibernate

 

Hibernate is a solution for object relational mapping and a persistence management solution or persistent layer. This is probably not understandable for anybody learning Hibernate.

 

What you can imagine is probably that you have your application with some functions (business logic) and you want to save data in a database. When you use Java all the business logic normally works with objects of different class types. Your database tables are not at all objects.

 

Hibernate provides a solution to map database tables to a class. It copies the database data to a class. In the other direction it supports to save objects to the database. In this process the object is transformed to one or more tables.

 

Saving data to storage is called persistence. And the copying of tables to objects and vice versa is called object relational mapping.

 

 

                                                               Hibernate Validator

 

Following the DRY (Don’t Repeat Yourself) principle, Hibernate Validator let’s you express your domain constraints once (and only once) and ensure their compliance at various level of your system automatically.

Hibernate Validator comes bundled with a set of common validations (@NotNull, @Email, @Max, and so on), and you can build you own validation rules very easily

                                                                                 POJO

POJO is an acronym for Plain Old Java Object, and is favored by advocates of the idea that the simpler the design, the better. The name is used to emphasize that the object in question is an ordinary Java Object, not a special object, and in particular not an Enterprise Java Bean(especially before EJB 3).

These are the brief descriptions.

Integrating all these as a Frame Work.

Web-based application is developed Using a Struts 2.0 Frame work now …. Now what is this I am going to integrate?

Hibernate validation what we have discussed above has to be integrated into our application.

Hidden secret of this document is very simple … we can avoid JavaScript for basic validations.

Integration is not complicated understand each and every point in that…..

Step 1:

Our POJO class parameters has to be defined with the hibernate validations

Like this…

import org.hibernate.validator.AssertTrue; import org.hibernate.validator.Email; import org.hibernate.validator.Length; import org.hibernate.validator.NotEmpty; import org.hibernate.validator.NotNull; import org.hibernate.validator.Pattern;     public class EbookUsers implements Serializable {   private Integer userId;   @NotEmpty(message = “{ebookUsers.firstName}”) @Pattern(regex=“[A-Za-z]+”,message=“{ebookUsers.firstName}”) @Length(min = 3 , max = 25 ,message= “{ebookUsers.firstName}”)   private String firstName;     @NotEmpty(message = “{ebookUsers.lastName}”) @Pattern(regex=“[A-Za-z]+”,message=“{ebookUsers.lastName}”) @Length(min = 3 , max = 25 ,message= “{ebookUsers.lastName}”)   private String lastName;   @NotEmpty(message = “{ebookUsers.loginName}”) @Pattern(regex=“[0-9a-zA-Z]+”,message=“{ebookUsers.loginName}”) @Length(min = 6, max = 25, message = “{ebookUsers.loginName}”)   private String loginName;   @NotEmpty(message = “{ebookUsers.passWord}”) @Length(min = 6, max = 10, message = “{ebookUsers.passWord}”)   private String passWord;   private String street;   private String city;   private String state;   private String country;   @Pattern(regex=“^([0-9a-zA-Z]([-\\.\\w]*[0-9a-zA-Z])*@(([0-9a-zA-Z])+([-\\w]*[0-9a-zA-Z])*\\.)+[a-zA-Z]{2,9})$”,message=“{ebookUsers.email}”) @NotEmpty(message = “{ebookUsers.email}”)   private String email;   @NotEmpty(message = “{ebookUsers.phone}”) @Pattern(regex=“[0-9]+”,message=“{ebookUsers.phone}”) @Length(min = 10, max = 10, message = “{ebookUsers.phone}”) private String phone;   @NotEmpty(message = “{ebookUsers.mobile}”) @Length(min = 10, max = 10, message = “{ebookUsers.mobile}”) @Pattern(regex=“[0-9]+”,message=“{ebookUsers.mobile}”) private String mobile;   private int failedAttempts;   @Length(min = 5 , max = 5 , message = “{ebookUsers.zip}”) @Pattern(regex=“[0-9]+”,message=“{ebookUsers.zip}”) private String zip; } //powered by vamshi.somanchi

 

The above class have a User Information.

I have used those what I need total annotations available are listed below.

Annotation	Apply on	Runtime checking	Hibernate Metadata impact
@Length(min=, max=)	property (String)	check if the string length match the range	Column length will be set to max
@Max(value=)	property (numeric or string representation of a numeric)	check if the value is less than or equals to max	Add a check constraint on the column
@Min(value=)	property (numeric or string representation of a numeric)	check if the value is more than or equals to min	Add a check constraint on the column
@NotNull	property	check if the value is not null	Column(s) are not null
@NotEmpty	property	check if the string is not null nor empty. Check if the connection is not null nor empty	Column(s) are not null (for String)
@Past	property (date or calendar)	check if the date is in the past	Add a check constraint on the column
@Future	property (date or calendar)	check if the date is in the future	none
@Pattern(regex=”regexp”, flag=) or @Patterns( {@Pattern(…)} )	property (string)	check if the property match the regular expression given a match flag (see java.util.regex.Pattern )	none
@Range(min=, max=)	property (numeric or string representation of a numeric)	check if the value is between min and max (included)	Add a check constraint on the column
@Size(min=, max=)	property (array, collection, map)	check if the element size is between min and max (included)	none
@AssertFalse	property	check that the method evaluates to false (useful for constraints expressed in code rather than annotations)	none
@AssertTrue	property	check that the method evaluates to true (useful for constraints expressed in code rather than annotations)	none
@Valid	property (object)	perform validation recursively on the associated object. If the object is a Collection or an array, the elements are validated recursively. If the object is a Map, the value elements are validated recursively.	none
@Email	property (String)	check whether the string is conform to the email address specification	none
@CreditCardNumber	property (String)	check whether the string is a well formated credit card number (derivative of the Luhn algorithm)	none
@Digits	property (numeric or string representation of a numeric)	check whether the property is a number having up to integerDigits integer digits and fractionalDigits fractonal digits	define column precision and scale
@EAN	property (string)	check whether the string is a properly formated EAN or UPC-A code	none
@Digits	property (numeric or string representation of a numeric)	check whether the property is a number having up to integerDigits integer digits and fractionalDigits fractonal digits	define column precision and scale

Each and every annotation is designed with a requirement this will be very clear if you observe the Coloum Apply On.

There is one special annotation named @Pattern this will allow the developer to add the “Regular expression”. Example can be seen in EbookUsers class.

These annotations hold the properties of the parameters throughout the application, and can be crosschecked where ever necessary.

Step 2:

Write a properties file to define the errors messages. Parameter identification should be done with “POJO class object . Parameter name” (this is just for a good practice)

for example:

@NotEmpty(message = “{ebookUsers.phone})”

Private String phone;

Here I am giving the properties files for the above mentioned POJO class.

EBOOKUSERS START HERE   ebookUsers.firstName=Enter First Name. It should be minimum of ‘3′ characters and maximum of ‘25′ characters. ebookUsers.lastName=Enter Last Name. It should be minimum of ‘3′ characters and maximum of ‘25′ characters. ebookUsers.loginName=Enter User Name. It should be minimum of ‘6′ characters and maximum of ‘25′ characters. ebookUsers.passWord=Enter Password. It should be minimum of ‘6′ characters and maximum of ‘10′ characters. ebookUsers.phone=Enter Phone Number. It should be exactly of ‘10′ Numbers (eg:xxxxxxxxxx) ebookUsers.mobile=Enter Mobile Number. It should be exactly of ‘10′ Numbers (eg:xxxxxxxxxx) ebookUsers.email=Enter proper Email ID (eg:ebook@emantras.com) ebookUsers.zip=Zip should be exactly of ‘5′ numbers. ebookUsers.city=City should be minimum of ‘3′ characters and maximum of ‘25′ characters. ebookUsers.state=State should be minimum of ‘3′ characters and maximum of ‘25′ characters. ebookUsers.country=Country should be minimum of ‘3′ characters and maximum of ‘25′ characters. ebookUsers.street=Street should be minimum of ‘3′ alphanumeric characters and maximum of ‘25′ alphanumeric characters.   EBOOKUSERS END HERE //Powered by vamshisomanchi

Step 3:

We need to write a class which will act like a centralized wire between pojo class and properties file.

This is necessary because we cant load properties file where ever we need that is again a bad practice.

Let’s name this class as EbookValidation.

This class basically loads the messages from properties file based on the class name and the message name and loads that errors in Invalidvalues class we can retrive these errors messages and add them to struts error messges which inturn will display in the JSP page.

This is how we write the Validation.

import java.io.File; import java.io.FileInputStream; import java.util.ArrayList; import java.util.Collection; import java.util.HashSet; import java.util.List; import java.util.Locale; import java.util.MissingResourceException; import java.util.ResourceBundle;   import org.hibernate.validator.ClassValidator; import org.hibernate.validator.InvalidValue;   public class EbookValidation {   Collection errors = null;   public Collection validate(Class clazz, Object obj) {   InvalidValue[] invalidValues = null; try { errors = new HashSet(); ClassValidator classValidator = new ClassValidator(clazz, loadproperties()); invalidValues = classValidator.getInvalidValues(obj); // System.err.println(” invalidValues “+invalidValues); for (int i = 0; i < invalidValues.length; i++) {   errors.add(invalidValues[i].getMessage().trim()); } } catch (Exception e) { e.printStackTrace(); } return errors; }   public ResourceBundle loadproperties() { String baseName = “ebook”; // ebook.properties is properties file name ResourceBundle rb = null; try { // Get the resource bundle for the default locale rb = ResourceBundle.getBundle(baseName); } catch (MissingResourceException e) { // The resource bundle cannot be found or // the key does not exist in the resource bundle } return rb; } } //Powered by Vamshi.Somanchi

Step 4:

This is where we write our controller to do some operations with the POJO class.

Lets say for example I am planning to insert my user values into the database.

public String editUserProfile(){ String pageEditUser=“EditUser”; roles=new Roles(); Collection err = this.getEbookValidation().validate(EbookUsers.class,getEbookUsers());   // this is where we load the properties file using Class   if (err.size() > 0){ //this happens if errors are collected. this.setActionErrors(err); //this line sets the action errors. return Action.ERROR; //returns to the error page } else (xyz bla bla bla){ do the insertion operation. } return Action.SUCCESS;   }

Now values are collected and these collected values will be displayed in JSP with the following strus tags

<%@ taglib prefix=“s” uri=“/struts-tags” %> <html> <head> </head> <body> <!– error will be loaded here with the following tag–> <s:div cssClass=“your wish”><s:actionerror/></s:div>   This is you body page and … .. . </body>   </html>

All the collected error messges will be displayed one after the other.

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