JAVA EE: p-namespace

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Wednesday, 1 August 2018

How to inject dependent object using Spring’s p namespace in XML configuration

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Introduction

In the Spring Framework, configuring bean properties using traditional nested <property> and <ref bean="..."/> tags can make your XML configuration files lengthy and cluttered. To streamline this, Spring provides the p-namespace, which allows you to define bean properties and wire dependent objects directly as XML attributes.

Why Use Spring's 'p' Namespace for Object References?

Cleaner, Concise Syntax: Eliminates nested child tags, condensing multi-line property definitions into concise single-line bean declarations.
Special '-ref' Suffix: By appending -ref to any property name (e.g., p:address-ref="addressBean"), Spring automatically recognizes that you are wiring an object reference rather than a literal value.
No XSD Schema Location Required: The p namespace does not require an explicit XSD file definition in your schema location, making the XML header lightweight.

Step-by-Step Configuration Example

First, declare the xmlns:p namespace inside your root <beans> tag:

xmlns:p="http://www.springframework.org/schema/p"

1. Wiring Dependent Objects via p-namespace

Notice how simple it is to wire the dependent address bean into employee using p:address-ref:

<!-- Dependent Bean -->
<bean id="addressBean" class="com.ram.model.Address"
      p:city="Chennai"
      p:state="Tamil Nadu"
      p:country="India" />

<!-- Enclosing Bean with Object Reference -->
<bean id="employee" class="com.ram.model.Employee"
      p:id="101"
      p:name="Ram"
      p:address-ref="addressBean" />

2. Loading the Beans in Java

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

Employee emp = (Employee) context.getBean("employee");
emp.displayEmployeeInfo();

Key Takeaway

Using Spring's p namespace together with the -ref suffix gives you the best of both worlds: full setter-based dependency injection capabilities with significantly cleaner and more readable XML declarations.

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How to inject dependent object using Spring’s p namespace in XML configuration

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0%20http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.2.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

Address.java

package com.ram.model;

public class Address

{

    private String city;

    private String state;

    public String getCity()

    {

        return city;

    }

    public void setCity(String city)

    {

        this.city = city;

    }

    public String getState()

    {

        return state;

    }

    public void setState(String state)

    {

        this.state = state;

    }

    @Override

    public String toString()

    {

        return "Address [city=" + city + ", state=" + state + "]";

    }

}

Employee.java

package com.ram.model;

public class Employee

{

    private int id;

    private String name;

    private Address address;

    public int getId()

    {

        return id;

    }

    public void setId(int id)

    {

        this.id = id;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

    public Address getAddress()

    {

        return address;

    }

    public void setAddress(Address address)

    {

        this.address = address;

    }

    @Override

    public String toString()

    {

        return "Employee [id=" + id + ", name=" + name + ", address=" + address

                + "]";

    }

}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"

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

    xmlns:p="http://www.springframework.org/schema/p"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <bean id="address" class="com.ram.model.Address">

        <property name="city" value="TamilNadu"></property>

        <property name="state" value="Chennai"></property>

    </bean>

    <bean id="employee" class="com.ram.model.Employee" p:id="100"

        p:name="Peter" p:address-ref="address">

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.model.Employee;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        System.out.println("---------------------------------------");

        Employee employee = (Employee) context.getBean("employee");

        System.out.println(

                "Got employee object from the ApplicationContext(Spring Container)");

        System.out.println(employee);

    }

}

Output

Jul 08, 2018 8:18:36 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Sun Jul 08 08:18:36 IST 2018]; root of context hierarchy

Jul 08, 2018 8:18:36 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

---------------------------------------

Got employee object from the ApplicationContext(Spring Container)

Employee [id=100, name=Peter, address=Address [city=TamilNadu, state=Chennai]]

Click the below link to download the code:
https://sites.google.com/site/ramj2eev2/java_basics/SpringDemo_p_namespace_dependentObject.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/javaee/tree/master/Spring_2018/SpringDemo_p_namespace_dependentObject

Bitbucket Link:
https://bitbucket.org/ramram43210/spring/src/764179f1702395ebc0d4ce50fe5125258c342eb8/Spring_2018/SpringDemo_p_namespace_dependentObject/?at=master

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What is Spring’s p namespace in XML configuration

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Introduction

In standard Spring XML configurations, setting properties typically requires nested <property name="..." value="..."/> tags. When a bean has many attributes, your XML files can quickly become verbose and difficult to navigate. The p-namespace in Spring provides a streamlined, elegant alternative that allows you to configure property values directly as XML bean tag attributes.

Why Use the 'p' Namespace?

Eliminate Boilerplate: Convert multiple lines of nested <property> elements into compact, clean single-line bean definitions.
Zero Schema Location Overhead: The p namespace does not require a formal XSD schema location declaration in the XML header.
Seamless Setter Injection: Under the hood, Spring continues to use standard setter methods, ensuring full compatibility with your existing Java classes.

Step-by-Step Configuration Example

To start using the p namespace, simply include its namespace declaration in the root <beans> element:

xmlns:p="http://www.springframework.org/schema/p"

1. Traditional Configuration vs. p-namespace

Here is how a bean looks using traditional property tags:

<bean id="user" class="com.ram.model.User">
    <property name="id" value="101"/>
    <property name="name" value="Ram"/>
    <property name="email" value="ram@example.com"/>
</bean>

With the p-namespace, the configuration is concise and clean:

<bean id="user" class="com.ram.model.User"
      p:id="101"
      p:name="Ram"
      p:email="ram@example.com" />

2. Loading the Bean in Java

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

User user = (User) context.getBean("user");
System.out.println("User ID: " + user.getId() + ", Name: " + user.getName());