Why Dozer Framework (Bean Manipulation)

Why Dozer ?

Let us think about a situation that you have a source bean which contains lot of fields and the source bean belongs to a different project or module. Now you want to expose the bean to 

the outside world as a part of your web service REST service development. It is not advisable to do it. There may be the following reasons.

• The source bean is not serialized and a final class.
• The source system does not allow doing it because of security breach.
• The source bean is very heavy and contains lot of nested beans.
• The source bean has fields of different types which may not be required for other system.
• The source bean has lot of fields; some of them are not required.

Scenario to use Dozer

Suppose You want to make a REST call or web service call to get the minimal account details of a person. But the source system has a bean called “Acc0untBean” which contains many sensitive information like person’s internet banking passw0rd, PAN no or social security number, total balance etc. You want to develop an application where you want to expose only account’s address details, name and home branch of the bank. This is a required situation where you want to have your custom defined bean which should be exposed to outside based upon the account number. In this case you have to copy the original bean to your custom defined bean. To achieve this functionality you can do it in the following ways : 

• Use java Reflection or Introspection utility to copy from source to destination bean.
• Write code to manually copy the contents of the source bean to destination bean.
• Use an available framework which does the copy automatically.

In This scenario we can use framework called 'Dozer'. Dozer Framework can be used for : 

• Copy collections
• Copy source Plain/Flat bean to destination Plain/Flat bean
• Copy flat bean to nested bean and vice versa
• Bi-directional bean copy
• Copy bean with custom conversion.

Lets Understand By Code 

Source POJO class : 

package com.snjv.dozer.src;

public class User {

private String name;

private int age;

private Address adrs;

// All getter and setters methods below 

}

package com.snjv.dozer.dst;

public class User {

private String name1;

private int age1;

private Address1 adrs1;

// All getter and setters methods below 

}

Dozer mapping file called "dozerMapping.xml"

<?xml version="1.0" encoding="UTF-8"?>

<mappings xmlns="http://dozer.sourceforge.net" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">

<mapping map-id="a">

<class-a>com.snjv.dozer.src.User</class-a>

<class-b>com.snjv.dozer.dst.User1</class-b>

<field>

<a>name</a>

<b>name1</b>

</field>

<field>

<a>age</a>

<b>age1</b>

</field>

<field>

<a>adrs.doorNo</a>

<b>adrs1.doorNo1</b>

</field>

<field>

<a>adrs.stName</a>

<b>adrs1.stName1</b>

</field>

</mapping>

</mappings>

The above xml configuration file <class-a > refers to source bean and < class-b> refers to destination bean. The other field <a> refers to the property of source bean and <b> refers to the property of the destination bean.

It's done, it looks very simple and provides many powerful Features. Following few things for bean copy using "Dozer" framework need to take care.

• Source bean
• Destination bean
• Dozer mapping file configuration
• Mapping configuration should contain source POJO class with proper package name
• Mapping configuration should contain destination POJO class with proper package name
• Mapping configuration should have proper exact property name what you have defined in         the java class

Copy Custom Data Type  :

package com.snjv.dozer.collection.src;

public class Address {

        private String name;

private String doorNo;

private String stName;

private String countryName;

}

package com.snjv.dozer.collection.src;

public class AddressList {

/** The address list. */

private List<Address> adrsList;

public List<Address> getAdrsList() {

return adrsList;

}

public void setAdrsList(List<Address> adrsList) {

this.adrsList = adrsList;

}

}

In Above class the list contains list of Address type objects. Let us learn how to achieve.

First of all create a mapping between Address objects from source to destination and then create a mapping between source list to destination list. 

Let us see the mapping configuration file

<?xml version="1.0" encoding="UTF-8"?>

<mappings xmlns="http://dozer.sourceforge.net"

      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

      xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">

      

      <mapping map-id="k">

<class-a>com.snjv.dozer.collection.src.Address</class-a>

<class-b>com.snjv.dozer.collection.dst.AddressBean</class-b>

<field>

<a>name</a>

<b>name</b>

</field>

<field >

<a>id</a>

<b>id</b>

</field>

</mapping>

<mapping map-id="q1" type="one-way" relationship-type="non-cumulative">

<class-a>com.snjv.dozer.collection.src.AddressList</class-a>

<class-b>com.snjv.dozer.collection.dst.AddressBeanList</class-b>

<field map-id="k">

<a>adrsList</a>

<b>adrsList</b>

</field>

</mapping>

      

</mappings>

To copy the list object, you can use the same code above.

Copy flat bean to nested bean and vice versa. Lets see the changed required in configuration file

<?xml version="1.0" encoding="UTF-8"?>

<mappings xmlns="http://dozer.sourceforge.net"

      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

      xsi:schemaLocation="http://dozer.sourceforge.net http://dozer.sourceforge.net/schema/beanmapping.xsd">

      

      <mapping map-id="a">

<class-a>com.snjv.dozer.src.User</class-a>

<class-b>com.snjv.dozer.dst.User1</class-b>

<!-- Other field info -->

<field>

<a>doorNo</a>

<b>adrs1.doorNo1</b>

</field>

<field>

<a>stName</a>

<b>adrs1.stName1</b>

</field>

<field>

<a>cname</a>

<b>countryName</b>

</field>

</mapping>

      

</mappings>

Configuration based mapping provides the following benefits.

• You can add the property in the java class as and when required.
• You can change the property name as and when required and it does not require to build the application.
• You can edit and remove the mapping as and when required.
• You can have one or many property files for specific requirements.
• You can also configure the mapping in Spring application ie spring configuration file.

I hope you have enjoyed this small post on DOZER Framework.

Enjoy !!!!!!