Spring @Conditional Annotation

Last modified on August 11th, 2015 by Joe.

This Spring tutorial is to learn about @Conditional annotation that was introduced in Spring 4.0 We shall see about what @Conditional annotation is, in what scenarios it can be used, difference between @Conditional vs @Profile annotations and an example Spring application using @Conditional annotation.

• Prerequisites
• Introduction to @Conditional
• Difference between @Conditional and @Profile annotations
• Spring 4.0 Conditional Annotation in detail
• Spring Condition Interface
• Spring @Conditional Examples

Prerequisites

We need to have some basic knowledge of the following concepts before leaning @Conditional annotation.

• Spring’s Java-based Configuration
• Spring Profiles

Please go through “Spring @Profile Annotation” topic to get knowledge on Spring’s Java-based Configuration and Spring Profiles.

Introduction to @Conditional Annotation

Spring 4.0 has introduced a new annotation @Conditional. It is used to develop an “If-Then-Else” type of conditional checking for bean registration.
Till Spring 3.x Framework something similar to @Conditional annotation are,

Spring 4.0 @Conditional annotation is at more higher level when compared to @Profile annotation. @Profile annotation should be used for loading application configuration based on conditional logic.
@Profile annotation is restricted to write conditional checking based on predefined properties. @Conditional annotation does not have this restriction.

Difference between @Conditional and @Profile Annotations

Both Spring @Profiles and @Conditional annotations are used to develop an “If-Then-Else” conditional checking. However, Spring 4 @Conditional  is more generalized version of @Profile annotation.

• Spring 3.1 @Profiles is used to write conditional checking based on Environment variables only. Profiles can be used for loading application configuration based on environments.
• Spring 4 @Conditional annotation allows Developers to define user-defined strategies for conditional checking. @Conditional can be used for conditional bean registrations.

Spring @Conditional Annotation

Spring Boot module makes heavy use of @Conditional annotation.
We can use Spring @Conditional annotation for the following scenarios:

• Condition whether a property is available or not using Environment variables, irrespective of its value.
• Like Profiles, Condition whether a property value is available or not using Environment variables.
• Conditions based on a Bean definition are present in Spring Application context.
• Conditions based on a Bean object are present in Spring Application context.
• Conditions based on some or all Bean properties values.
• Conditions based on some Resources are present in current Spring Application Context or not.
• Conditions based on Bean’s Annotations
• Conditions Bean’s Method’s Annotations.
• Conditions based on Bean’s Annotation’s parameter values
• Conditions based on  Bean’s Method’s Annotation’s parameter values.

This list is just a set of examples.

Spring Condition Interface

We need to have a class implementing an interface named Condition provided by Spring. It has a method matches and our conditional logic should go inside this method. Then we can use the class we have defined in the @Conditional annotation to check for a condition. Following the Condition interface that we need to implement in our custom condition class.

public interface Condition {
	boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);
}

Spring @Conditional Annotation Example 1

In this example let us see how we can use @Conditional annotation to check a property value is dev or prod from environment. For learning we will use Java based configurations in this example.

• Create a Spring Maven based project in Spring STS Suite
• Update the pom.xml with following content.

<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.javapapers.spring4</groupId>
  <artifactId>Spring4.0Conditional</artifactId>
  <version>1.0.0</version>
  
  <properties>
		<spring-framework.version>4.0.9.RELEASE</spring-framework.version>
		<junit.version>4.11</junit.version>
	</properties>	
		
	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring-framework.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-test</artifactId>
			<version>${spring-framework.version}</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>${junit.version}</version>
			<scope>test</scope>
		</dependency>
	</dependencies>	
</project>

• CreateEmployee Domain class with id, name and sal properties with getters only as shown below.

package com.javapapers.spring4.domain;

public class Employee {

	private int id;
	private String name;
	private double sal;
	
	public Employee(int id,String name,double sal) {
		this.id = id;
		this.name = name;
		this.sal = sal;
	}

	public int getId() {
		return id;
	}

	public String getName() {
		return name;
	}

	public double getSal() {
		return sal;
	}		
}

Create Utility classes to represent in-memory Databases. For simplicity, we are not interacting with Databases and also are using our DataSource interface rather than javax.sql.DataSource. DevDatabaseUtil class represents DEV database and ProductionDatabaseUtil class represents PROD database with some data.

package com.javapapers.spring4.util;

import java.util.List;
import com.javapapers.spring4.domain.Employee;

public interface DataSource {
	List<Employee> getEmployeeDetails();
}

package com.javapapers.spring4.util;

import java.util.ArrayList;
import java.util.List;
import com.javapapers.spring4.domain.Employee;

public class DevDatabaseUtil implements DataSource {

	@Override
	public List<Employee> getEmployeeDetails(){
		List<Employee> empDetails = new ArrayList<>();
		Employee emp1 = new Employee(111,"Abc",11000);
		Employee emp2 = new Employee(222,"Xyz",22000);
		empDetails.add(emp1);
		empDetails.add(emp2);
		
		return empDetails;
	}
}

package com.javapapers.spring4.util;

import java.util.ArrayList;
import java.util.List;
import com.javapapers.spring4.domain.Employee;

public class ProductionDatabaseUtil implements DataSource {

	@Override
	public List<Employee> getEmployeeDetails(){
		List<Employee> empDetails = new ArrayList<>();
		Employee emp1 = new Employee(9001,"Ramu",45000);
		Employee emp2 = new Employee(9002,"Charan",35000);
		Employee emp3 = new Employee(9003,"Joe",55000);
		empDetails.add(emp1);
		empDetails.add(emp2);
		empDetails.add(emp3);
		
		return empDetails;
	}
}

Create a EmployeeDAO class to represent DAO Layer.

package com.javapapers.spring4.dao;

import java.util.List;
import com.javapapers.spring4.domain.Employee;
import com.javapapers.spring4.util.DataSource;

public class EmployeeDAO {

	private DataSource dataSource;
	public EmployeeDAO(DataSource dataSource) {
		this.dataSource = dataSource;
	}
	
	public List<Employee> getEmployeeDetails() {
		return dataSource.getEmployeeDetails();
	}

}

Create a EmployeeService class to represent Service layer. It interacts with DAO Layer class to get Employee Details data.

package com.javapapers.spring4.service;

import java.util.List;
import com.javapapers.spring4.dao.EmployeeDAO;
import com.javapapers.spring4.domain.Employee;

public class EmployeeService {
	
	private EmployeeDAO employeeDAO;
	public EmployeeService(EmployeeDAO employeeDAO) {
		this.employeeDAO = employeeDAO;
	}
	
	public List<Employee> getEmployeeDetails(){
		return employeeDAO.getEmployeeDetails();
	}

}

Condition Classes

Now it’s time to implement Spring 4 Conditional checking by using @Conditional annotation. Both condition checking classes implements Spring’s Condition interface matches() method. Both Conditional classes checks for “database.name” from Environement. If this values is “dev”, then DevDataSourceCondition’s matches() method returns true. Otherwise false. In the same way, if this property value is “prod”, then ProdDataSourceCondition’s matches() method returns true. Otherwise false.

package com.javapapers.spring4.condition;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class DevDataSourceCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		String dbname = context.getEnvironment().getProperty("database.name");
		return dbname.equalsIgnoreCase("dev");
	}

}

package com.javapapers.spring4.condition;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class ProdDataSourceCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		String dbname = context.getEnvironment().getProperty("database.name");
		return dbname.equalsIgnoreCase("prod");
	}

}

Create Spring’s Java-based configuration classes

getDevDataSource() defines @Conditional annotation with DevDataSourceCondition class. That means if DevDataSourceCondition’s matches() method returns true, then EmployeeDataSourceConfig creates DataSource object to refer to DEV Database.

In the same way, getProdDataSource() defines @Conditional annotation with ProdDataSourceCondition class. That means if ProdDataSourceCondition’s matches() method returns true, then EmployeeDataSourceConfig creates DataSource object to refer to PRDO Database.

EmployeeConfig class configures other beans except DataSource related beans.

package com.javapapers.spring4.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.javapapers.spring4.dao.EmployeeDAO;
import com.javapapers.spring4.service.EmployeeService;
import com.javapapers.spring4.util.DataSource;

@Configuration
public class EmployeeConfig{
	  @Autowired
	  private DataSource dataSource;
	  
	  @Bean
	  public EmployeeService employeeService() {
		  return new EmployeeService(employeeDAO());
	  }
	  
	  @Bean
	  public EmployeeDAO employeeDAO() {
		  System.out.println("EmployeeDAO employeeDAO()" + dataSource);
		  return new EmployeeDAO(dataSource);
	  }

}

package com.javapapers.spring4.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import com.javapapers.spring4.condition.DevDataSourceCondition;
import com.javapapers.spring4.condition.ProdDataSourceCondition;
import com.javapapers.spring4.util.DataSource;
import com.javapapers.spring4.util.DevDatabaseUtil;
import com.javapapers.spring4.util.ProductionDatabaseUtil;

@Configuration
public class EmployeeDataSourceConfig {
	

	  @Bean(name="dataSource")
	  @Conditional(value=DevDataSourceCondition.class)
	  public DataSource getDevDataSource() {
		  return new DevDatabaseUtil();
	  }

	  @Bean(name="dataSource")
	  @Conditional(ProdDataSourceCondition.class)
	  public DataSource getProdDataSource() {
		  return new ProductionDatabaseUtil();
	  }
}

Now it’s time to write JUnits to test Spring’s @Conditional classes.

import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;
import com.javapapers.spring4.config.EmployeeConfig;
import com.javapapers.spring4.config.EmployeeDataSourceConfig;
import com.javapapers.spring4.domain.Employee;
import com.javapapers.spring4.service.EmployeeService;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes= {EmployeeConfig.class,EmployeeDataSourceConfig.class},loader=AnnotationConfigContextLoader.class)
public class Spring4DevConditionalTest {

	@Autowired
	private ApplicationContext applicationContext;
	  
	  @Test	 
	  public void testDevDataSource() {
		  EmployeeService service = (EmployeeService)applicationContext.getBean("employeeService");
		  assertNotNull(service);
		  List<Employee> employeeDetails = service.getEmployeeDetails();
		  assertEquals(2, employeeDetails.size());
		  assertEquals("Abc", employeeDetails.get(0).getName());
		  assertEquals("Xyz", employeeDetails.get(1).getName());
	  }
}

import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;
import com.javapapers.spring4.config.EmployeeConfig;
import com.javapapers.spring4.config.EmployeeDataSourceConfig;
import com.javapapers.spring4.domain.Employee;
import com.javapapers.spring4.service.EmployeeService;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes= {EmployeeConfig.class,EmployeeDataSourceConfig.class},loader=AnnotationConfigContextLoader.class)
public class Spring4ProdConditionalTest {

	@Autowired
	private ApplicationContext applicationContext;

	  @Test	  
	  public void testProdDataSource() {
		  EmployeeService service = (EmployeeService)applicationContext.getBean("employeeService");
		  assertNotNull(service);
		  List<Employee> employeeDetails = service.getEmployeeDetails();
		  assertEquals(3, employeeDetails.size());
		  assertEquals("Ramu", employeeDetails.get(0).getName());
		  assertEquals("Charan", employeeDetails.get(1).getName());
		  assertEquals("Joe", employeeDetails.get(2).getName());
	  }
}

Now the project structure looks as below

Run the Example @Conditional Project

To run this class in Eclipse or Spring STS IDE, please set some Junit Run Configuration as shown below -Ddatabase.name=dev

Similarly you can do for “prod”.

Spring @Conditional Annotation Example 2

In this example, we will write a Spring’s @Conditional checking based on whether a Bean object is present or not in Spring Application Context.

We are going to use same Example-1 project files with some minor changes.

Create a new Spring 4 Condition to check a bean is available in Application Context or not. If bean is available, BeanPresennceCondition’s matches() method return true. Otherwise, it throws NoSuchBeanDefinitionException exception. Just for testing purpose, use a catch block to handle this exception and continue the control flow to end of the matches() method and return false as shown below.

package com.javapapers.spring4.condition;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
import com.javapapers.spring4.config.EmployeeBeanConfig;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;

public class BeanPresennceCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		EmployeeBeanConfig employeeBeanConfig = null;
		try {
			employeeBeanConfig = (EmployeeBeanConfig)context.getBeanFactory().getBean("employeeBeanConfig");	
		}catch(NoSuchBeanDefinitionException ex) {
			
		}
		return employeeBeanConfig != null;
	}

}

Create a new Java-based Configuration class. It defines an Employee bean with some data. This bean configuration is using BeanPresennceCondition. If this condition returns true, then only it configures this bean. Otherwise no bean is created.

package com.javapapers.spring4.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import com.javapapers.spring4.condition.BeanPresennceCondition;
import com.javapapers.spring4.domain.Employee;

@Configuration
public class EmployeeBeanConfig{
 
	  @Bean
	  @Conditional(BeanPresennceCondition.class)
	  public Employee employee() {
		  return new Employee(222,"Popeye",55000);
	  }
}

Create Junit test class to test this. Here we are trying to test “employee” bean data. If BeanPresennceCondition returns true, then only this bean is created.

import org.junit.Test;
import org.junit.runner.RunWith;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;
import com.javapapers.spring4.config.EmployeeBeanConfig;
import com.javapapers.spring4.domain.Employee;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes= {EmployeeBeanConfig.class},loader=AnnotationConfigContextLoader.class)
public class Spring4DevBeanPresenceConditionalTest {

	@Autowired
	private ApplicationContext applicationContext;
	  
	  @Test	 
	  public void testDevDataSource() {
		  Employee emp = (Employee)applicationContext.getBean("employee");
		  assertNotNull(emp);
		  assertEquals(222, emp.getId());
		  assertEquals("Popeye", emp.getName());
	  }
}

Now change BeanPresennceCondition class matches() method logic as show below to check the failure case of the Condition.

package com.javapapers.spring4.condition;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
import com.javapapers.spring4.config.EmployeeBeanConfig;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;

public class BeanPresennceCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		EmployeeBeanConfig employeeBeanConfig = null;
		try {
			employeeBeanConfig = (EmployeeBeanConfig)context.getBeanFactory().getBean("employeeBeanConfig2");	
		}catch(NoSuchBeanDefinitionException ex) {
			
		}
		return employeeBeanConfig != null;
	}

}

Here we are checking for “employeeBeanConfig2” bean instead of “employeeBeanConfig”. It will definitely fail because our application does not have this bean configuration. When BeanPresennceCondition fails, it returns false value to EmployeeBeanConfig’s employee() method where we are using @Conditional annotation. When this condition fails (that is ELSE block in “IF-ELSE” conditional checking), Spring IOC Container does not load “employee” bean into Spring Application Context.

When we run our Junit now, we will get Junit RED bar showing that failed status with the following error. org.springframework. beans.factory.NoSuchBeanDefinitionException: No bean named 'employee' is defined.

Download the example Project Spring4.0Conditional

Spring 4 @Profile Annotation Updates

In the previous tutorial on Spring, we learnt about @Profile annotation. Now let us see how @Profile annotation is updated using @Conditional annotation.

Spring 3.x @Profile annotation declaration:

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE })
@Documented
public @interface Profile {
	String[] value();
}

Spring 4.0 @Profile annotation declaration:

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
@Documented
@Conditional(ProfileCondition.class)
public @interface Profile {
	String[] value();
}

If we observe both declaration, we can find the following changes to @Profile definition.

• In Spring 3.x, we can use the @Profile annotation only at the class level. We cannot use at method level.
• From Spring 4.0 onwards, we can use @Profile annotation at the class level and the method level.
• @Profile annotation is refactored to use @Conditional annotation.

• There are four types of conditional sentences.
• It’s important to use the correct structure for each of these different conditional sentences because they express varying meanings.
• Pay attention to verb tense when using different conditional modes.
• Use a comma after the if-clause when the if-clause precedes the main clause.

Conditional sentences are statements discussing known factors or hypothetical situations and their consequences. Complete conditional sentences contain a conditional clause (often referred to as the if-clause) and the consequence. Consider the following sentences:

If a certain condition is true, then a particular result happens.

I would travel around the world if I won the lottery.

When water reaches 100 degrees, it boils.

What Are the Different Types of Conditional Sentences?

There are four different types of conditional sentences in English. Each expresses a different degree of probability that a situation will occur or would have occurred under certain circumstances.

• Zero Conditional Sentences
• First Conditional Sentences
• Second Conditional Sentences
• Third Conditional Sentences

Let’s look at each of these different types of conditional sentences in more detail.

How to Use Zero Conditional Sentences

Zero conditional sentences express general truths—situations in which one thing always causes another. When you use a zero conditional, you’re talking about a general truth rather than a specific instance of something. Consider the following examples:

If you don’t brush your teeth, you get cavities.

When people smoke cigarettes, their health suffers.

There are a couple of things to take note of in the above sentences in which the zero conditional is used. First, when using the zero conditional, the correct tense to use in both clauses is the simple present tense. A common mistake is to use the simple future tense.

When people smoke cigarettes, their health will suffer
.

Secondly, notice that the words if and when can be used interchangeably in these zero conditional sentences. This is because the outcome will always be the same, so it doesn’t matter “if” or “when” it happens.

How to Use First Conditional Sentences

First conditional sentences are used to express situations in which the outcome is likely (but not guaranteed) to happen in the future. Look at the examples below:

If you rest, you will feel better.

If you set your mind to a goal, you’ll eventually achieve it.

Note that we use the simple present tense in the if-clause and simple future tense in the main clause—that is, the clause that expresses the likely outcome. This is how we indicate that under a certain condition (as expressed in the if-clause), a specific result will likely happen in the future. Examine some of the common mistakes people make using the first conditional structure:

If you will rest
, you will feel better.

If you rest
, you will feel better.

Explanation: Use the simple present tense in the if-clause.

If you set your mind to a goal, you eventually achieve
 it.

If you set your mind to a goal, you’ll eventually achieve
 it.

Explanation: Use the zero conditional (i.e., simple present + simple present) only when a certain result is guaranteed. If the result is likely, use the first conditional (i.e., simple present + simple future).

How to Use Second Conditional Sentences

Second conditional sentences are useful for expressing outcomes that are completely unrealistic or will not likely happen in the future. Consider the examples below:

If I inherited a billion dollars, I would travel to the moon.

If I owned a zoo, I might let people interact with the animals more.

Notice the correct way to structure second conditional sentences is to use the simple past tense in the if-clause and an auxiliary modal verb (e.g., could, should, would, might) in the main clause (the one that expresses the unrealistic or unlikely outcome). The following sentences illustrate a couple of the common mistakes people make when using the second conditional:

If I inherit
 a billion dollars, I would travel to the moon.

If I inherited
 a billion dollars, I would travel to the moon.

Explanation: When applying the second conditional, use the simple past tense in the if-clause.

If I owned a zoo, I will let
 people interact with the animals more.

If I owned a zoo, I might let
 people interact with the animals more.

Explanation: Use a modal auxiliary verb in the main clause when using the second conditional mood to express the unlikelihood that the result will actually happen.

How to Use Third Conditional Sentences

Third conditional sentences are used to explain that present circumstances would be different if something different had happened in the past. Look at the following examples:

If you had told me you needed a ride, I would have left earlier.

If I had cleaned the house, I could have gone to the movies.

These sentences express a condition that was likely enough, but did not actually happen in the past. The speaker in the first sentence was capable of leaving early, but did not. Along these same lines, the speaker in the second sentence was capable of cleaning the house, but did not. These are all conditions that were likely, but regrettably did not happen.

Note that when using the third conditional, we use the past perfect (i.e., had + past participle) in the if-clause. The modal auxiliary (would, could, should, etc.) + have + past participle in the main clause expresses the theoretical situation that could have happened.

Consider these common mistakes when applying the third conditional:

If you would have told
 me you needed a ride, I would have left earlier.

If you had told
 me you needed a ride, I would have left earlier.

Explanation: With third conditional sentences, do not use a modal auxiliary verb in the if-clause.

If I had cleaned the house, I could go
 to the movies.

If I had cleaned the house, I could have gone
 to the movies.

Explanation: The third conditional mood expresses a situation that could have only happened in the past if a certain condition had been met. That’s why we use the modal auxiliary verb + have + the past participle.

Exceptions and Special Cases When Using Conditional Sentences

As with most topics in the English language, conditional sentences often present special cases in which unique rules must be applied.

Use of the Simple Future in the If-Clause

Generally speaking, the simple future should be used only in the main clause. One exception is when the action in the if-clause will take place after the action in the main clause. For example, consider the following sentence:

If aspirin will ease my headache, I will take a couple tonight.

The action in the if-clause is the aspirin easing the headache, which will take place only after the speaker takes them later that night.

“Were to” in the If-Clause

The verb phrase were to is sometimes used in conditional sentences when the likely or unlikely result is particularly awful or unthinkable. In this case, were to is used to place emphasis on this potential outcome. Consider these sentences:

If I were to
 be sick, I would miss another day of work.

If she were to
 be late again, she would have to have a conference with the manager.

If the rent were to
 have been a penny more, they would not have been able to pay it.

Note that the emphatic “were to” can be used to describe hypothetical scenarios in the present, future, and past.

Punctuating Conditional Sentences

Despite the complex nature of conditional sentences, punctuating them properly is really simple!

Here’s the skinny:

Use a comma after the if-clause when the if-clause precedes the main clause.

If I’d had time, I would have cleaned the house.

If the main clause precedes the if-clause, no punctuation is necessary.

I would have cleaned the house if I’d had time.