JAVA EE: Primitive Values

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Tuesday, 26 June 2018

How to Inject primitive value and String using Spring dependency injection by Setter method?

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Introduction

Dependency Injection (DI) is the foundation of the Spring Framework. One of the most fundamental techniques for configuring bean properties is setter-based dependency injection. When dealing with literal values like primitive data types (e.g., int, double, boolean) and String objects, Spring uses the <property> element along with the value attribute to inject configuration values directly into Java objects.

Why Use Setter Injection for Primitives and Strings?

Automatic Type Conversion: Spring’s built-in PropertyEditor system automatically converts XML string values into their corresponding target Java primitive or wrapper types.
Configurability: Literal values are decoupled from the Java source code, enabling configuration updates without recompiling code.
Simplicity & Readability: The <property name="..." value="..."/> syntax provides a clean and clear XML structure.

Step-by-Step Code Example

Here is an example demonstrating how primitive types and strings are injected into an Employee bean via setter methods:

1. The Java Model Class

package com.ram.model;

public class Employee {
    private int id;
    private String name;
    private double salary;

    // Setter methods for dependency injection
    public void setId(int id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public void display() {
        System.out.println("Employee ID: " + id);
        System.out.println("Employee Name: " + name);
        System.out.println("Employee Salary: " + salary);
    }
}

2. Configuring applicationContext.xml

Define the bean in your XML configuration and set the primitive and string values using the value attribute:

<bean id="employee" class="com.ram.model.Employee">
    <property name="id" value="101" />
    <property name="name" value="Ram" />
    <property name="salary" value="75000.50" />
</bean>

3. Loading and Executing with ApplicationContext

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

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

Key Takeaway

Setter injection using <property name="..." value="..."/> is the standard way to supply primitive values and strings in Spring XML configurations. Spring handles type parsing behind the scenes, ensuring the values are converted and injected seamlessly.

Recommended Dependency Injection Tutorials from Ram N Java

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How to Inject primitive value and String 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>

Employee.java

package com.ram.model;

public class Employee

{

    private int id;

    private String name;

    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;

    }

    @Override

    public String toString()

    {

        return "Employee [id=" + id + ", name=" + name + "]";

    }

}

applicationContext.xml

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

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

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

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

    <bean id="employee" class="com.ram.model.Employee">

        <property name="id">

            <value>50</value>

        </property>

        <property name="name">

            <value>Peter</value>

        </property>

    </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.txt

May 09, 2018 9:02:46 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Wed May 09 09:02:46 IST 2018]; root of context hierarchy

May 09, 2018 9:02:46 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=50, name=Peter]