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 Spring > Expression Language > Map Projection

Map Projection 

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  :  kvenkatasudhakar@gmail.com
   
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(1new Employee(1"ONE"1111));
    employees.put(2new Employee(2"TWO"2222));
    employees.put(3new Employee(3"THREE"3333));
    employees.put(4new Employee(4"FOUR"4444));
    employees.put(5new Employee(5"FIVE"5555));
    employees.put(6new 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);
  }

}
   

It gives the following output,
[ONE, TWO, THREE, FOUR, FIVE, SIX]
[10-one, 20-two, 30-three, 40-four, 50-five, 60-six]


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