BE THE CODER > Spring > Expression Language

The Spring Expression Language (SpEL) is a simple and powerful expression language which helps to query and manipulate objects at runtime. SpEL allows us to perform customized lookup based on bean name. We can configure a bean resolver with evaluation context and perform lookup for all beans with (@) symbol as name prefix.

File Name :	com/bethecoder/tutorials/spring3/tests/spel/BeanReferenceTest.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.spring3.tests.spel;



import java.util.Random;



import org.springframework.expression.AccessException;

import org.springframework.expression.BeanResolver;

import org.springframework.expression.EvaluationContext;

import org.springframework.expression.ExpressionParser;

import org.springframework.expression.spel.standard.SpelExpressionParser;

import org.springframework.expression.spel.support.StandardEvaluationContext;



import com.bethecoder.tutorials.spring3.basic.Employee;



public class BeanReferenceTest {



  /**

   * @param args

   */

  public static void main(String[] args) {



    StandardEvaluationContext stdContext = new StandardEvaluationContext();

    stdContext.setBeanResolver(new SimpleBeanResolver());

    

    ExpressionParser parser = new SpelExpressionParser();

    

    // Invokes resolve(context, "one") on SimpleBeanResolver during evaluation

    Employee emp = parser.parseExpression("@one").getValue(stdContext, Employee.class);

    System.out.println(emp);



    // Invokes resolve(context, "two") on SimpleBeanResolver during evaluation

    emp = parser.parseExpression("@two").getValue(stdContext, Employee.class);

    System.out.println(emp);

    

    // Invokes resolve(context, "three") on SimpleBeanResolver during evaluation

    emp = parser.parseExpression("@three").getValue(stdContext, Employee.class);

    System.out.println(emp);



  }



}



class SimpleBeanResolver implements BeanResolver {



  private static Random RAND = new Random();

  

  @Override

  public Object resolve(

      EvaluationContext context,

      String beanName) throws AccessException {



    int id = Math.abs(RAND.nextInt(100));

    double salary = RAND.nextDouble() * 10000; 

    

    Employee emp = new Employee(id, beanName.toUpperCase(), salary);

    return emp;

  }

  

}

Bean Reference