Spring expression language - referencing variables - spring-el

Question

I am able to do the following :-
ExpressionParser parser = new SpelExpressionParser();
Expression exp = parser.parseExpression("'hi'.equals('hi')");
it evaluates to true.
Im failing at using variables in the expression ? for example:
If i want to :
Case 1 : use local variables
String str1 = "hi";
String str2 = "hi";
Expression exp = parser.parseExpression("str1.equals(str2)");
and Case2 : use field from a pojo :
Expression exp = parser.parseExpression("pojo1.getName().equals(pojo2.getName())");
How do i achieve case1 and 2 ? The above 2 examples are failing for me.. Case 1 evaluates to false and Case 2 throws an exception

Answer 1

You could do it like this:
Case 1:
String str1 = "hi";
String str2 = "hi";
StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
evaluationContext.setVariable("str1", str1);
evaluationContext.setVariable("str2", str2);
ExpressionParser parser = new SpelExpressionParser();
boolean result = parser.parseExpression("#str1 eq #str2").getValue(evaluationContext, Boolean.class);
// result will be true
// also "#str1 == #str2" can be used
Case 2:
StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
evaluationContext.setVariable("pojo1Name", pojo1.getName());
evaluationContext.setVariable("pojo2Name", pojo2.getName());
ExpressionParser parser = new SpelExpressionParser();
boolean result = parser.parseExpression("#pojo1Name eq #pojo2Name").getValue(evaluationContext, Boolean.class);

Answer 2

Case 1.
You have to register variables with evaluation context, then use #str1 in the expression.
/**
* Set a named variable within this evaluation context to a specified value.
* #param name the name of the variable to set
* #param value the value to be placed in the variable
*/
void setVariable(String name, #Nullable Object value);
Case 2:
Use a BeanExpressionResolver wired up with the bean factory. If you implement BeanFactoryAware, use
#Override
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
if (beanFactory instanceof ConfigurableListableBeanFactory) {
this.resolver = ((ConfigurableListableBeanFactory) beanFactory).getBeanExpressionResolver();
this.expressionContext = new BeanExpressionContext((ConfigurableListableBeanFactory) beanFactory, null);
}
}
then call evaluate.
Beans are referenced with # - #someBean.someMethod().