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

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

Employee.java − Employee class.

MainApp.java − Main apppcation to run and test.

Here is the content of Employee.java file −

package com.tutorialspoint;

pubpc class Employee {
   private String name;
   pubpc String getName() {
      return name;
   }
   pubpc void setName(String name) {
      this.name = name;
   }
}

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;

pubpc class MainApp {
   pubpc 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

null
Mahesh