JAVA EE: java.util.Properties

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Friday, 6 July 2018

How to Inject java.util.Properties using Spring dependency injection by Setter method?

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Introduction

In Spring Framework applications, configuring key-value pairs using java.util.Properties is a common requirement for managing environment properties, database settings, or connection configurations. Spring provides dedicated XML elements (such as <props> and <prop>) to inject properties collections into beans via setter methods effortlessly.

Why Inject java.util.Properties in Spring?

Key-Value Mapping: Simplifies passing string-based key-value pairs directly to beans without requiring custom parsing.
Native Spring Support: Spring provides built-in support for java.util.Properties via the <props> configuration tag.
Clean Externalization: Allows developers to centralize configuration details inside Spring XML and inject them cleanly via standard setter methods.

Step-by-Step Code Example

Here is an example showing how to inject a java.util.Properties instance into a Java bean via setter injection:

1. The Java Model Class

package com.ram.model;

import java.util.Properties;

public class DatabaseConfig {
    private Properties dbProperties;

    // Setter method for dependency injection
    public void setDbProperties(Properties dbProperties) {
        this.dbProperties = dbProperties;
    }

    public void displayProperties() {
        System.out.println("Database Properties: " + dbProperties);
    }
}

2. Configuring applicationContext.xml

Inside the <property> tag, use <props> and <prop key="..."> to define your key-value pairs:

<bean id="databaseConfig" class="com.ram.model.DatabaseConfig">
    <property name="dbProperties">
        <props>
            <prop key="driverClassName">com.mysql.cj.jdbc.Driver</prop>
            <prop key="url">jdbc:mysql://localhost:3306/mydb</prop>
            <prop key="username">root</prop>
            <prop key="password">password123</prop>
        </props>
    </property>
</bean>

3. Loading and Running in Java

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

DatabaseConfig config = (DatabaseConfig) context.getBean("databaseConfig");
config.displayProperties();

Key Takeaway

Using the <props> tag combined with setter dependency injection makes managing key-value configuration clean and intuitive, eliminating hard-coded values and keeping application components modular.

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How to Inject java.util.Properties using Spring dependency injection by Setter method?

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>

FruitShop.java

package com.ram.core;

import java.util.Properties;

public class FruitShop

{

    private String shopName;

    private Properties availableFruits;

    public String getShopName()

    {

        return shopName;

    }

    public void setShopName(String shopName)

    {

        this.shopName = shopName;

    }

    public Properties getAvailableFruits()

    {

        return availableFruits;

    }

    public void setAvailableFruits(Properties availableFruits)

    {

        this.availableFruits = availableFruits;

    }

    public void displayFruitShopInfo()

    {

        System.out.println("FruitShop [shopName=" + shopName

                + ", availableFruits=" + availableFruits + "]");

    }

}

applicationContext.xml

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

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

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

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

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

    http://www.springframework.org/schema/context

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

    <bean id="fruitShop" class="com.ram.core.FruitShop">

        <property name="shopName" value="Fruit Mart"></property>

        <property name="availableFruits">

            <props>

                <prop key="1">Apple</prop>

                <prop key="2">Grapes</prop>

            </props>

        </property>

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

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

        FruitShop fruitShop = (FruitShop) context.getBean("fruitShop");

        System.out.println(

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

        fruitShop.displayFruitShopInfo();

    }

}

Output

Jun 04, 2018 10:23:42 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Mon Jun 04 10:23:42 IST 2018]; root of context hierarchy

Jun 04, 2018 10:23:42 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

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

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

Got fruitShop object from the ApplicationContext(Spring Container)

FruitShop [shopName=Fruit Mart, availableFruits={2=Grapes, 1=Apple}]