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. The following example shows using projection operator (![projectionExpression]). It helps to evaluate a sub expression against the given collection and the result is a new collection.

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


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



import java.util.HashMap;

import java.util.List;

import java.util.Map;



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 MapProjectionTest {



  /**

   * @param args

   */

  public static void main(String[] args) {



    StandardEvaluationContext stdContext = new StandardEvaluationContext();

    Map<Integer, Employee> employees = new HashMap<Integer, Employee>();

    employees.put(1, new Employee(1, "ONE", 1111));

    employees.put(2, new Employee(2, "TWO", 2222));

    employees.put(3, new Employee(3, "THREE", 3333));

    employees.put(4, new Employee(4, "FOUR", 4444));

    employees.put(5, new Employee(5, "FIVE", 5555));

    employees.put(6, new Employee(6, "SIX", 6666));

    

    stdContext.setVariable("empMap", employees);

    

    ExpressionParser parser = new SpelExpressionParser();

    List<String> proj = (List<String>) parser.parseExpression(

        "#empMap.![value.name]").getValue(stdContext);

    System.out.println(proj); 



    proj = (List<String>) parser.parseExpression(

        "#empMap.![(key*10) + '-' + value.name.toLowerCase()]").getValue(stdContext);

    System.out.println(proj);

  }



}

Map Projection