Spring SpEL - Variables


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SpEL expression allows to create and use variables specific to expression using #variable-name syntax. A variable is set using setVariable on EvaluationContext. There are two types of inbuilt variables as well, #this and #root. #this variable always refers to current evaluation object where as #root variable refers to the root object of the evaluation context.

Syntax

context.setVariable("newName", "Mahesh Kumar");

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 application to run and test.

Here is the content of Employee.java file −

package com.tutorialspoint;

public class Employee {
   private String name;
   private String country;

   public Employee(String name, String country) {
      this.name = name;
      this.country = country;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getCountry() {
      return country;
   }
   public void setCountry(String country) {
      this.country = country;
   }
   public String toString() {
      return "[" +name+ ", "+country + "]";
   }
}

Here is the content of MainApp.java file −

package com.tutorialspoint;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
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("Mahesh", "INDIA");

      EvaluationContext context = new StandardEvaluationContext(employee);
      context.setVariable("newName", "Mahesh Parashar");
      parser.parseExpression("Name = #newName").getValue(context);

      // Evaluate to "Mahesh Parashar"
      System.out.println(employee.getName());
      List<Integer> primes = new ArrayList<Integer>();
      primes.addAll(Arrays.asList(2,3,5,7,11,13,17));

      context.setVariable("primes",primes);

      List<Integer> filteredList =
      (List<Integer>) parser.parseExpression("#primes.?[#this>10]").getValue(context);

      // Evaluate to [11, 13, 17], prime numbers greater than 10
      System.out.println(filteredList);
   }
}

Output

Mahesh Parashar
[11, 13, 17]
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