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. Often while traversing object graphs its required to check whether a particular property is non null and then dig further. The SpEL Safe Navigation Operator (?.) is very useful to navigate object graphs.

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


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



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 SafeNavigationOperatorTest {



  /**

   * @param args

   */

  public static void main(String[] args) {



    StandardEvaluationContext stdContext = new StandardEvaluationContext();

    Employee employee = new Employee(1, "BTC", 9999);

    stdContext.setVariable("emp", employee);

    

    ExpressionParser parser = new SpelExpressionParser();

    String value = parser.parseExpression(

        "#emp?.name").getValue(stdContext, String.class);

    System.out.println(value);   //BTC



    stdContext.setVariable("emp", null);

    value = parser.parseExpression("#emp?.name").getValue(stdContext, String.class);

    System.out.println(value);    //null



    

    stdContext.setVariable("emp", employee);

    value = parser.parseExpression(

        "#emp?.name?.toLowerCase()").getValue(stdContext, String.class);

    System.out.println(value);    //btc

    

    

    stdContext.setVariable("emp", null);

    value = parser.parseExpression(

        "#emp?.name?.toLowerCase()").getValue(stdContext, String.class);

    System.out.println(value);    //null

    

  }



}