From 591e7f1f725d20ed84388efb4e55bed3aa50ff7c Mon Sep 17 00:00:00 2001
From: Juergen Hoeller <jhoeller@pivotal.io>
Date: Mon, 5 Nov 2018 12:26:35 +0100
Subject: [PATCH] StandardEvaluationContext supports concurrent variable
 modification

Issue: SPR-17448

(cherry picked from commit 59fa647e2d57392b3a43af2c107a237948a92b12)
---
 .../spel/support/StandardEvaluationContext.java | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java b/spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java
index c8cbac7ef0d..de0a8c781cc 100644
--- a/spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java
+++ b/spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java
@@ -18,9 +18,9 @@ package org.springframework.expression.spel.support;
 
 import java.lang.reflect.Method;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.expression.BeanResolver;
@@ -88,7 +88,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 
 	private OperatorOverloader operatorOverloader = new StandardOperatorOverloader();
 
-	private final Map<String, Object> variables = new HashMap<>();
+	private final Map<String, Object> variables = new ConcurrentHashMap<>();
 
 
 	/**
@@ -203,7 +203,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 	@Override
 	public TypeConverter getTypeConverter() {
 		if (this.typeConverter == null) {
-			 this.typeConverter = new StandardTypeConverter();
+			this.typeConverter = new StandardTypeConverter();
 		}
 		return this.typeConverter;
 	}
@@ -230,11 +230,16 @@ public class StandardEvaluationContext implements EvaluationContext {
 
 	@Override
 	public void setVariable(String name, @Nullable Object value) {
-		this.variables.put(name, value);
+		if (value != null) {
+			this.variables.put(name, value);
+		}
+		else {
+			this.variables.remove(name);
+		}
 	}
 
-	public void setVariables(Map<String,Object> variables) {
-		this.variables.putAll(variables);
+	public void setVariables(Map<String, Object> variables) {
+		variables.forEach(this::setVariable);
 	}
 
 	public void registerFunction(String name, Method method) {