Spring SpEL - Safe Navigation Operator

SpEL expression supports Safe Navigation operator which is used to avoid NullPointerException.

int length = parser.parseExpression("name?.length").getValue(context, Integer.class);

Here if name is null, then expression will not throw null pointer exception.

Following example shows the various use cases.

Example - Usage of Safe Navigation Operator in SpEL

Let's update the project created in Spring SpEL - Create Project chapter. We're updating following files −

• Employee.java − Employee Class.

• MainApp.java − Main application to run and test.

Employee.java

Here is the content of Employee.java file −

package com.tutorialspoint;

public class Employee {
   private String name;

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

MainApp.java

Here is the content of MainApp.java file −

package com.tutorialspoint;

import java.text.ParseException;

import org.springframework.expression.EvaluationContext;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

public class MainApp {
   public static void main(String[] args) throws ParseException {
      ExpressionParser parser = new SpelExpressionParser();
      Employee employee = new Employee();   
      EvaluationContext employeeContext = new StandardEvaluationContext(employee);

      // Evaluates to null but will not throw null pointer exception during parseExpression
      String result = parser.parseExpression("name?.strip()").getValue(employeeContext, String.class);
      System.out.println(result);
      employee.setName("   Mahesh   ");

      // Evaluates to "Mahesh"
      result = parser.parseExpression("name?.strip()").getValue(employeeContext, String.class);
      System.out.println(result);	   
   }
}

Output

Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message −

null
Mahesh