Spring p-namespace tutorial

last modified October 18, 2023

Spring property namespace tutorial shows how to use p-namespace in property-based injection in a Spring application.

Spring is a popular Java application framework for creating enterprise applications.

Spring p-namespace

Spring p-namespace is an XML shortcut and replacement of the <property/> subelement of the <bean/> tag. To enable the p-namespace feature, we need to add the xmlns:p=“http://www.springframework.org/schema/p" into the XML file. Note that this namespace does not have a separate XSD file; therefore, IDEs such as IntelliJ do not recognize it.

Spring p-namespace example

The application contains two HelloMessage beans. One is injected with the older <property/>, the other one with the newer p-namespace attribute.

src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───bean │ │ HelloMessage.java │ └───resources │ logback.xml │ my-beans.xml └───test └───java

This is the project structure.

pom.xml

<?xml version=“1.0” encoding=“UTF-8”?> <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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>

<groupId>com.zetcode</groupId>
<artifactId>cnamespace</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
    <spring-version>5.3.23</spring-version>

</properties>

<dependencies>

    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.4.0</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring-version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring-version}</version>
    </dependency>
    
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>3.1.0</version>
            <configuration>
                <mainClass>com.zetcode.Application</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

</project>

In the pom.xml file, we have basic Spring dependencies spring-core and spring-context and logging logback-classic dependency.

The exec-maven-plugin is used for executing Spring application from the Maven on the command line.

resources/logback.xml

<?xml version=“1.0” encoding=“UTF-8”?> <configuration> <logger name=“org.springframework” level=“ERROR”/> <logger name=“com.zetcode” level=“INFO”/>

<appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n
        </Pattern>
    </encoder>
</appender>

<root>
    <level value="INFO" />
    <appender-ref ref="consoleAppender" />
</root>

</configuration>

The logback.xml is a configuration file for the Logback logging library.

resources/my-beans.xml

<?xml version=“1.0” encoding=“UTF-8”?> <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.xsd">

<bean name="msg1" class="com.zetcode.bean.HelloMessage">
    <property name="message" value="How are you?"/>
</bean>

<bean name="msg2" class="com.zetcode.bean.HelloMessage" p:message="Hello there"/>

</beans>

The my-beans.xml file declares two beans: msg1 and msg2. The msg1 uses <property/> tag to inject its values, while msg2 uses p:message attribute.

com/zetcode/bean/HelloMessage.java

package com.zetcode.bean;

public class HelloMessage {

private String message;

public String getMessage() {
    return message;
}

public void setMessage(String message) {

    this.message = message;
}

}

This is the HelloMessage class that is managed by Spring container. It must contain a setter method because we use property-based injection in our application.

com/zetcode/Application.java

package com.zetcode;

import com.zetcode.bean.HelloMessage; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.context.support.GenericXmlApplicationContext;

public class Application {

private static final Logger logger = LoggerFactory.getLogger(Application.class);

public static void main(String[] args) {

    var ctx = new GenericXmlApplicationContext("my-beans.xml");

    var msg1 = (HelloMessage) ctx.getBean("msg1");
    logger.info("{}", msg1.getMessage());

    var msg2 = (HelloMessage) ctx.getBean("msg2");
    logger.info("{}", msg2.getMessage());

    ctx.close();
}

}

This is the main application class. It retrieves the two HelloMessage beans and prints them to the console.

$ mvn -q exec:java 16:52:11.257 [main] INFO com.zetcode.Application - How are you? 16:52:11.273 [main] INFO com.zetcode.Application - Hello there

We run the application.

In this article we have shown how to use property-based injection with p-namespace.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

List all Spring tutorials.