JAVA EE: Spring expression language ternary operator (if-then-else) example [Annotation]

Monday, 15 October 2018

Spring expression language ternary operator (if-then-else) example [Annotation] | Spring Tutorial

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Overview: Ternary Operator in SpEL

The Spring Expression Language (SpEL) supports inline conditional logic using the classic ternary operator (if-then-else). Rather than writing conditional statements in Java or setting default properties manually, you can evaluate a condition on the fly and inject the appropriate value directly into your beans using the @Value annotation.

In this guide, you will learn how to write ternary expressions using annotation configuration in your Spring applications.

Understanding the Ternary Syntax in SpEL

The ternary operator follows standard Java syntax: Condition ? trueValue : falseValue:

Inline Conditional Logic: Evaluates a boolean condition and selects one of two branches: @Value("#{beanName.score > 50 ? 'Pass' : 'Fail'}").
Dynamic Value Resolution: The values returned can be literals, calculated values, or references to properties on other beans.
Cleaner Code: Eliminates boilerplate initialization methods or factory beans by embedding simple decision logic directly in property injection.

Step-by-Step Configuration

Define the Condition: Formulate the test expression using relational or logical operators (e.g., checking numeric thresholds or boolean flags).
Apply @Value: Place the ternary expression inside @Value("#{...}") above your target field.
Run the Container: During bean creation, Spring evaluates the condition and injects the corresponding true or false branch value.

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Spring expression language ternary operator (if-then-else) example [Annotation] | Spring Tutorial

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>5.0.5.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;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.stereotype.Component;

@Component("address")

public class Address

{

    @Value("A220 Bridge Appartment")

    private String street;

    @Value("Chennai")

    private String city;

    @Value("TamilNadu")

    private String state;

    public String getStreet()

    {

        return street;

    }

    public void setStreet(String street)

    {

        this.street = street;

    }

    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 [street=" + street + ", city=" + city + ", state="

                + state + "]";

    }

}

Employee.java

package com.ram.model;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.stereotype.Component;

@Component("employee")

public class Employee

{

    @Value("100")

    private int id;

    @Value("Peter")

    private String name;

    @Value("#{address.state == 'TamilNadu' ? true : false}")

    private boolean southIndian;

    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 boolean isSouthIndian()

    {

        return southIndian;

    }

    public void setSouthIndian(boolean southIndian)

    {

        this.southIndian = southIndian;

    }

    @Override

    public String toString()

    {

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

                + southIndian + "]";

    }

}

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">

    <context:component-scan base-package="com.ram" />

</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

Sep 11, 2018 9:55:26 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@736e9adb: startup date [Tue Sep 11 09:55:26 IST 2018]; root of context hierarchy

Sep 11, 2018 9:55:26 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, southIndian=true]