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 Spring > Expression Language > List Selection

List Selection 

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 selection operator (?[selectionExpression]). It filters the collection and returns a new collection containing a subset of the original elements. The selection criteria is evaluated against each individual element in the list.

File Name  :  
com/bethecoder/tutorials/spring3/tests/spel/ListSelectionTest.java 
Author  :  Sudhakar KV
Email  :  kvenkatasudhakar@gmail.com
   
package com.bethecoder.tutorials.spring3.tests.spel;

import java.util.ArrayList;
import java.util.List;

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 ListSelectionTest {

  /**
   @param args
   */
  public static void main(String[] args) {

    StandardEvaluationContext stdContext = new StandardEvaluationContext();
    List<Employee> employees = new ArrayList<Employee>();
    employees.add(new Employee(1"ONE"1111));
    employees.add(new Employee(2"TWO"2222));
    employees.add(new Employee(3"THREE"3333));
    employees.add(new Employee(4"FOUR"4444));
    employees.add(new Employee(5"FIVE"5555));
    employees.add(new Employee(6"SIX"6666));
    
    stdContext.setVariable("emps", employees);
    
    /**
     * Employees having salary greater than 4000
     */
    ExpressionParser parser = new SpelExpressionParser();
    List<Employee> subSet = (List<Employee>parser.parseExpression(
        "#emps.?[salary > 4000]").getValue(stdContext);
    System.out.println(subSet)

    /**
     * Employees having salary less than 4000
     */
    subSet = (List<Employee>parser.parseExpression(
        "#emps.?[salary < 4000]").getValue(stdContext);
    System.out.println(subSet);
  }

}
   

It gives the following output,
[Employee[4, FOUR, 4444.0], Employee[5, FIVE, 5555.0], Employee[6, SIX, 6666.0]]
[Employee[1, ONE, 1111.0], Employee[2, TWO, 2222.0], Employee[3, THREE, 3333.0]]


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