reactor-spring-core/src/main/java/reactor/spring/selector/ExpressionSelector.java
public static Selector expressionSelector(String expr, EvaluationContext evalCtx, SpelCompilerMode mode) {
        SpelParserConfiguration configuration = new SpelParserConfiguration(mode, null);
        SpelExpressionParser parser = new SpelExpressionParser(configuration);
        return new ExpressionSelector(parser.parseExpression(expr), evalCtx);
    }
public static Selector expressionSelector(String expr, EvaluationContext evalCtx, SpelCompilerMode mode) {
        SpelParserConfiguration configuration = new SpelParserConfiguration(mode, null);
        SpelExpressionParser parser = new SpelExpressionParser(configuration);
        return new ExpressionSelector(parser.parseExpression(expr), evalCtx);
    }
Helper method for creating an {@code ExpressionSelector}.

@param expr
The expression to parse.
@param evalCtx
The {@link org.springframework.expression.EvaluationContext} to use.
@param mode
The {@link org.springframework.expression.spel.SpelCompilerMode} to use.

@return A new {@link reactor.bus.selector.Selector}