config/src/main/java/org/springframework/security/config/annotation/web/builders/WebSecurity.java
public WebSecurity expressionHandler(
			SecurityExpressionHandler<FilterInvocation> expressionHandler) {
		Assert.notNull(expressionHandler, "expressionHandler cannot be null");
		this.expressionHandler = expressionHandler;
		return this;
	}
public WebSecurity expressionHandler(
			SecurityExpressionHandler<FilterInvocation> expressionHandler) {
		Assert.notNull(expressionHandler, "expressionHandler cannot be null");
		this.expressionHandler = expressionHandler;
		return this;
	}
Set the {@link SecurityExpressionHandler} to be used. If this is null, then a
{@link DefaultWebSecurityExpressionHandler} will be used.

@param expressionHandler the {@link SecurityExpressionHandler} to use
@return the {@link WebSecurity} for further customizations