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.

<?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.

<?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.

<?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.

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.

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.

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